WorldWideScience

Sample records for hii galaxy ii

  1. VizieR Online Data Catalog: Inner/outer HII regions: galaxy sample (Rodriguez-Baras+, 2018)

    Science.gov (United States)

    Rodriguez-Baras, M.; Diaz, A. I.; Rosales-Ortega, F. F.; Sanchez, S. F.

    2017-11-01

    Physical properties for 263 isolated spiral galaxies, observed by the CALIFA survey, are presented. These galaxies compose this work galaxy sample. For each galaxy redshift, morphological type, inclination, distance, effective radius, g and r SDSS magnitudes, absolute B magnitude and total number of HII regions extracted in the galaxy are given. (1 data file).

  2. Giant HII regions as distance indicators

    International Nuclear Information System (INIS)

    Melnick, Jorge; Terlevich, Robert; Moles, Mariano

    1987-01-01

    The correlations between the integrated Hβ luminosities, the velocity widths of the nebular lines and the metallicities of giant HII regions and HII galaxies are demonstrated to provide powerful distance indicators. They are calibrated on a homogeneous sample of giant HII regions with well determined distances and applied to distant HII galaxies to obtain a value of H 0 =95+-10 for the Hubble parameter, consistent with the value obtained by the Tully-Fisher technique. The effect of Malmquist bias and other systematic effects on the HII region method are discussed in detail. (Author)

  3. A Complete Census of the ~7000 Milky Way HII Regions

    Science.gov (United States)

    Armentrout, William Paul; Anderson, Loren Dean; Wenger, Trey; Bania, Thomas; Balser, Dana; Dame, Thomas; Dickey, John M.; Dawson, Joanne; Jordan, Christopher H.; McClure-Griffiths, Naomi M.; Andersen, Morten

    2018-01-01

    HII regions are the archetypical tracers of high-mass star formation. Because of their high luminosities, they can be seen across the entire Galactic disk from mid-infrared to radio wavelengths. A uniformly sensitive survey of Galactic HII regions would allow us to constrain the properties of Galactic structure and star formation. We have cataloged over 8000 HII regions and candidates in the WISE Catalog of Galactic HII Regions (astro.phys.wvu.edu/wise), but only 2000 of these are confirmed HII regions to date.To bring us closer to a complete census of high-mass star formation regions in the Milky Way, we have several ongoing observational campaigns. These efforts include (1) Green Bank Telescope radio recombination line (RRL) observations as part of the HII Region Discovery Survey (HRDS); (2) Australia Telescope Compact Array observations of southern HII region candidates in the Southern HII Region Discovery Survey (SHRDS); (3) Green Bank and Gemini North Telescope observations of star formation regions thought to reside at the edge of the star forming disk in the Outer Scutum-Centaurus Arm (OSC); and (4) Very Large Array continuum observations of the faintest HII region candidates in the second and third Galactic quadrants.Together, these observations will detect the RRL emission from all Galactic HII regions with peak cm-wavelength flux densities > 60mJy, establish the outer edge of Galactic high-mass star formation, and determine the number of HII regions in the Galaxy. The HRDS and SHRDS surveys have more than doubled the known population of Galactic HII regions. We use the OSC observations to determine the properties of high-mass star formation in the extreme outer Galaxy and our VLA observations to determine how many of our faint candidates are indeed HII regions. We combine the completeness limits we obtain through these HII region surveys with an HII region population synthesis model to estimate the total number of Galactic HII regions. From this, we

  4. HII regions in IC 1613: The ISM in a nearby dwarf irregular galaxy

    Science.gov (United States)

    Price, Jill S.; Mason, Stephen F.; Gullixson, Craig A.

    1990-01-01

    IC 1613, a nearby (725 kpc distant) dwarf irregular galaxy, has always been known to contain large, ring-shaped HII regions in its northeast corner. A new H alpha image has been obtained using the Bell Labs Charge Coupled Device (CCD) camera, an RCA 320 X 512 pixel-thinned, back-illuminated CCD, an H alpha filter of central wavelength 6562 A and width (full width half maximum) of 30 A, and the 42 inch telescope at Lowell Observatory. The low resolution images exhibit many new, faint features.

  5. Starbursts and the chemical evolution of HII galaxies: ages of bursts VS local environmental pollution

    International Nuclear Information System (INIS)

    Pagel, B.E.J.

    1987-01-01

    Results previously published for oxygen, nitrogen and helium abundances in HII galaxies are revised to allow for collisional contributions to the helium lines and a few further objects added. The relationships found are similar in general to those found previously, though with fewer objects departing from the dY/dZ relation derived by Peimbert and his colleagues, and are confirmed by a principal component analysis which shows that O/H accounts for about half of the variation in helium but N/H for essentially all of it. These effects are consistent with an additional component of helium and secondary nitrogen, superposed on primary nitrogen, with the additional component either coming from low-mass stars made in very old bursts or resulting from local pollution of the observed HII regions by winds from massive stars within them. Evidence from different regions of POX 4 and NGC 5253 gives some slight support to the latter hypothesis

  6. Vibration test of 1/5 scale H-II launch vehicle

    Science.gov (United States)

    Morino, Yoshiki; Komatsu, Keiji; Sano, Masaaki; Minegishi, Masakatsu; Morita, Toshiyuki; Kohsetsu, Y.

    In order to predict dynamic loads on the newly designed Japanese H-II launch vehicle, the adequacy of prediction methods has been assessed by the dynamic scale model testing. The three-dimensional dynamic model was used in the analysis to express coupling effects among axial, lateral (pitch and yaw) and torsional vibrations. The liquid/tank interaction was considered by use of a boundary element method. The 1/5 scale model of the H-II launch vehicle was designed to simulate stiffness and mass properties of important structural parts, such as core/SRB junctions, first and second stage Lox tanks and engine mount structures. Modal excitation of the test vehicle was accomplished with 100-1000 N shakers which produced random or sinusoidal vibrational forces. The vibrational response of the test vehicle was measured at various locations with accelerometers and pressure sensor. In the lower frequency range, corresmpondence between analysis and experiment was generally good. The basic procedures in analysis seem to be adequate so far, but some improvements in mathematical modeling are suggested by comparison of test and analysis.

  7. Differences in the size-internal velocity relation of galactic and extragalactic HII regions

    International Nuclear Information System (INIS)

    Odell, C.R.

    1990-01-01

    The nature of the size-internal velocity relation in extragalactic HII regions is examined in order to improve their use as distance determinants. The relation between the linear size and the internal velocity was compared for HII regions in the Galaxy and in external galaxies. Data for the former are from the researcher's own studies at high spatial resolution, while the latter have been the subject of spectroscopy that includes almost the entire objects. The Galactic HII regions are corrected to values of the internal velocity that would be observed if they were at extragalactic distances. A very different size-internal velocity relation was found for the two types of objects in the sense that the extragalactic objects are some ten times larger at the same internal velocity. This is interpreted to mean that the extragalactic HII regions are actually complexes of small HII regions comparable in size to their Galactic counterparts

  8. Properties of the HII Regions Derived Using Integral Field Spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Sánchez, Sebastián F.

    2013-01-01

    Roč. 2013, č. 1 (2013), 596501/1-596501/14 ISSN 1687-7969 Grant - others:Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100031241; Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100031201 Program:M Institutional support: RVO:67985815 Keywords : H-II regions * star -foraming galaxies * chemo-spectrophotometric evolution Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.234, year: 2013

  9. Properties of the HII Regions Derived Using Integral Field Spectroscopy

    Directory of Open Access Journals (Sweden)

    Sebastian F. Sánchez

    2013-01-01

    Full Text Available Here we review some of our more recent results on the observed properties of HII regions using Integral Field Spectroscopy. In particular, we illustrate the use of this technique to study in detail the ionization conditions across the nebulae for galactic HII regions (focused on the Orion Nebula and the statistical study of large samples of extragalactic HII regions. We review the reported new scaling relation between the local mass density and the oxygen abundance across the disk galaxies and the recently discovered universal gradient for oxygen abundances. We update our previous results the lack of a dependence of the Mass-Metallicity relation with the starformation rate, including new unpublished data. Finally we discuss on the relation between the ionization conditions in the nebulae and the underlying stellar population. All together our results indicate that disk galaxies present a chemical enrichment dominated by an inside-out growth scenario, with a less evident effect of radial migrations and/or outflows.

  10. On the Nature and History of Blue Amorphous Galaxies

    Science.gov (United States)

    Marlowe, Amanda True

    1998-07-01

    Dwarf galaxies play an important role in our understanding of galaxy formation and evolution. We have embarked on a systematic study of 12 blue amorphous galaxies (BAGs) whose properties suggest that they are dwarf galaxies in a starburst or post-burst state. It seems likely that BAGs are related to other 'starburst' dwarfs such as blue compact dwarfs (BCDs) and HII galaxies. The BAGs in our sample, however, are considerably closer than BCDs and HII galaxies in other samples, and therefore easier to study. These galaxies may offer important insights into dwarf galaxy evolution. In an effort to clarify the role of BAGs in evolutionary scenarios for dwarf galaxies, we present and analyze Hα and UBVI data for our sample. BAGs, like BCDs and HII galaxies, have surface brightness profiles that are exponential in the outer regions but have a predominantly blue central blue excess, suggesting a young burst in an older, redder galaxy. Seven of the galaxies have the bubble or filamentary Hα morphology and double peaked emission lines that are the signature of superbubbles or superwind activity. These galaxies are typically the ones with the strongest central excesses. The starbursting regions are young events compared to the older underlying galaxy, which follow an exponential surface brightness law. Not all of the galaxies develop superwinds: the appearance of superwinds is most sensitive to the concentration and rate of star formation in the starbursting core. The underlying exponential galaxies are very similar to those found in BCDs and HII galaxies, though the 'burst' colors are slightly redder than those found in HII galaxies. BAGs are structurally similar to BCDs and HII galaxies. How BAGs fit into the dwarf galaxy evolutionary debate is less clear. While some compact dIs have properties similar to those of the underlying exponential galaxy in our sample, issues such as mass loss from superwinds, the impact of the starbursting core on the underlying galaxy, and

  11. HRM: HII Region Models

    Science.gov (United States)

    Wenger, Trey V.; Kepley, Amanda K.; Balser, Dana S.

    2017-07-01

    HII Region Models fits HII region models to observed radio recombination line and radio continuum data. The algorithm includes the calculations of departure coefficients to correct for non-LTE effects. HII Region Models has been used to model star formation in the nucleus of IC 342.

  12. The Southern HII Region Discovery Survey

    Science.gov (United States)

    Wenger, Trey; Miller Dickey, John; Jordan, Christopher; Bania, Thomas M.; Balser, Dana S.; Dawson, Joanne; Anderson, Loren D.; Armentrout, William P.; McClure-Griffiths, Naomi

    2016-01-01

    HII regions are zones of ionized gas surrounding recently formed high-mass (OB-type) stars. They are among the brightest objects in the sky at radio wavelengths. HII regions provide a useful tool in constraining the Galactic morphological structure, chemical structure, and star formation rate. We describe the Southern HII Region Discovery Survey (SHRDS), an Australia Telescope Compact Array (ATCA) survey that discovered ~80 new HII regions (so far) in the Galactic longitude range 230 degrees to 360 degrees. This project is an extension of the Green Bank Telescope HII Region Discovery Survey (GBT HRDS), Arecibo HRDS, and GBT Widefield Infrared Survey Explorer (WISE) HRDS, which together discovered ~800 new HII regions in the Galactic longitude range -20 degrees to 270 degrees. Similar to those surveys, candidate HII regions were chosen from 20 micron emission (from WISE) coincident with 10 micron (WISE) and 20 cm (SGPS) emission. By using the ATCA to detect radio continuum and radio recombination line emission from a subset of these candidates, we have added to the population of known Galactic HII regions.

  13. On the Relationship between Star Formation and Activity in Galaxies

    Science.gov (United States)

    Gonzalez Delgado, Rosa M.

    1995-11-01

    This thesis is made of three main parts. In the first one a sample of 55 galaxies with an active nucleus (Seyfert 1, Seyfert2 and LINERs) is analysed; these were observed with the 4.2m WHT and 1m JKT in CCD narrow band H-alpha +[NII] and [OIII] to map the distribution of HII regions and the morphology of the circumnuclear extended emission associated with the active nucleus. The analysis of the extended emission and HII regions is carried out, as a function of the level of activity and of the Hubble type. One third of the sample shows circumnuclear HII regions, but only 9% of these are S1. The number surface density of the star forming sites and the location of the brightest HII region, indicates that in S2 the star formation is more important in the inner disk; however, in S1 the distribution of the star forming sites is more uniform with distance, and the brighest HII regions are farther away from the nucleus than in S2. The luminosity function, size distribution, the relationship between the Ha flux and the size, the emission measure, and the radial distribution of the HII regions in 27 out of the 55 galaxies of the sample are studied. This comprises a statistical analysis of more than 2000 HII regions. In the second part of this thesis the giant extragalactic HII region NGC 2363 and the starburst galaxy NGC 7714 are studied; they were observed in narrow band CCD H-alpha image with the JKT and spectroscopically from 3700 to 9600 A with the WHT. Both objects are experiencing intense star formation activity. Evidence of this comes from the detection of WC and WN emission features in NGC 2363 and in NGC 7714 respectively; this suggests an age of the present burst between 3 and 5 Myr. However, evidence for the existence of a previous burst in NGC 7714 comes from the detection of the infrared CaII triplet in absorption. The physical conditions and chemical composition of the gas are derived. In both cases, the metallicity is low (12+log O/H=7.89 for NGC 2363) and

  14. Galaxy S II

    CERN Document Server

    Gralla, Preston

    2011-01-01

    Unlock the potential of Samsung's outstanding smartphone with this jargon-free guide from technology guru Preston Gralla. You'll quickly learn how to shoot high-res photos and HD video, keep your schedule, stay in touch, and enjoy your favorite media. Every page is packed with illustrations and valuable advice to help you get the most from the smartest phone in town. The important stuff you need to know: Get dialed in. Learn your way around the Galaxy S II's calling and texting features.Go online. Browse the Web, manage email, and download apps with Galaxy S II's 3G/4G network (or create you

  15. H II region-like galaxies

    International Nuclear Information System (INIS)

    French, H.B.

    1979-01-01

    Line fluxes in the region 3700 to 7100A are presented for 14 galaxies with strong, sharp, H II region-like emission lines. Ten of these galaxies are low luminosity objects (M > -17); the others have M approx. < -20. Ratios of the line fluxes are used to derive electron temperatures and densities, and the abundances of helium, oxygen, nitrogen, neon, and sulfur relative to hydrogen. The low luminosity galaxies are generally found to have oxygen abundances about 30% of normal, while the high luminosity ones generally have about 60% of normal. These galaxies are found to be almost certainly photoionized by hot main sequence stars. The velocity dispersion has been measured for one object; the mass of stars derived for it is several times smaller than the mass of neutral hydrogen which has previously been found in an extended halo around this object. The continuum colors of these galaxies are very blue, and are indistinguishable from those of extragalactic H II regions. No older red population has been convincingly detected. Galactic chemical evolution is investigated through a comparison of the relative abundances in these galaxies with their normal values. It is found that: (i) there is a primary contribution to the nitrogen abundance ((N/O)/sub p = 0.019), but that 80% of the nitrogen in the Galaxy today is of secondary origin; (ii) Ne/O appears to be constant for all objects (Ne/O = 0.23); and (iii) S/O decreases with increasing oxygen abundance, implying that most sulfur is produced in the most massive stars

  16. Low surface brightness spiral galaxies

    International Nuclear Information System (INIS)

    Romanishin, W.

    1980-01-01

    This dissertation presents an observational overview of a sample of low surface brightness (LSB) spiral galaxies. The sample galaxies were chosen to have low surface brightness disks and indications of spiral structure visible on the Palomar Sky Survey. They are of sufficient angular size (diameter > 2.5 arcmin), to allow detailed surface photometry using Mayall 4-m prime focus plates. The major findings of this dissertation are: (1) The average disk central surface brightness of the LSB galaxies is 22.88 magnitude/arcsec 2 in the B passband. (2) From broadband color measurements of the old stellar population, we infer a low average stellar metallicity, on the order of 1/5 solar. (3) The spectra and optical colors of the HII regions in the LSB galaxies indicate a lack of hot ionizing stars compared to HII regions in other late-type galaxies. (4) The average surface mass density, measured within the radius containing half the total mass, is less than half that of a sample of normal late-type spirals. (5) The average LSB galaxy neutral hydrogen mass to blue luminosity ratio is about 0.6, significantly higher than in a sample of normal late-type galaxies. (6) We find no conclusive evidence of an abnormal mass-to-light ratio in the LSB galaxies. (7) Some of the LSB galaxies exhibit well-developed density wave patterns. (8) A very crude calculation shows the lower metallicity of the LSB galaxies compared with normal late-type spirals might be explained simply by the deficiency of massive stars in the LSB galaxies

  17. Formation des etoiles massives dans les galaxies spirales

    Science.gov (United States)

    Lelievre, Mario

    Le but de cette thèse est de décrire la formation des étoiles massives dans les galaxies spirales appartenant à divers types morphologiques. L'imagerie Hα profonde combinée à une robuste méthode d'identification des régions HII ont permis de détecter et de mesurer les propriétés (position, taille, luminosité, taux de formation d'étoiles) de plusieurs régions HII situées dans le disque interne (R influencer de façon significative la stabilité des nuages moléculaires face à l'effondrement gravitationnel. D'une part, l'étendue du disque de régions HII pour cinq galaxies de l'échantillon coïncide avec celle de l'hydrogène atomique. D'autre part, en analysant la stabilité des disques galactiques, on conclue qu'en incluant la densité des étoiles vieilles présentes, on arrive à mieux contraindre le rayon à partir duquel aucune formation d'étoiles ne devrait se produire dans les galaxies.

  18. [NEII] Line Velocity Structure of Ultracompact HII Regions

    Science.gov (United States)

    Okamoto, Yoshiko K.; Kataza, Hirokazu; Yamashita, Takuya; Miyata, Takashi; Sako, Shigeyuki; Honda, Mitsuhiko; Onaka, Takashi; Fujiyoshi, Takuya

    Newly formed massive stars are embedded in their natal molecular clouds and are observed as ultracompact HII regions. They emit strong ionic lines such as [NeII] 12.8 micron. Since Ne is ionized by UV photons of E>21.6eV which is higher than the ionization energy of hydrogen atoms the line probes the ionized gas near the ionizing stars. This enables to probe gas motion in the vicinity of recently-formed massive stars. High angular and spectral resolution observations of the [NeII] line will thus provide siginificant information on structures (e.g. disks and outflows) generated through massive star formation. We made [NeII] spectroscopy of ultracompact HII regions using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2m Subaru Telescope in July 2002. Spatial and spectral resolutions were 0.5"" and 10000 respectively. Among the targets G45.12+0.13 shows the largest spatial variation in velocity. The brightest area of G45.12+0.13 has the largest line width in the object. The total velocity deviation amounts to 50km/s (peak to peak value) in the observed area. We report the velocity structure of [NeII] emission of G45.12+0.13 and discuss the gas motion near the ionizing star.

  19. MAGIICAT I. THE Mg II ABSORBER-GALAXY CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, Nikole M.; Churchill, Christopher W. [New Mexico State University, Las Cruces, NM 88003 (United States); Kacprzak, Glenn G.; Murphy, Michael T., E-mail: nnielsen@nmsu.edu [Swinburne University of Technology, Victoria 3122 (Australia)

    2013-10-20

    We describe the Mg II Absorber-Galaxy Catalog, MAGIICAT, a compilation of 182 spectroscopically identified intermediate redshift (0.07 ≤ z ≤ 1.1) galaxies with measurements of Mg II λλ2796, 2803 absorption from their circumgalactic medium within projected distances of 200 kpc from background quasars. In this work, we present 'isolated' galaxies, which are defined as having no spectroscopically identified galaxy within a projected distance of 100 kpc and a line of sight velocity separation of 500 km s{sup –1}. We standardized all galaxy properties to the ΛCDM cosmology and galaxy luminosities, absolute magnitudes, and rest-frame colors to the B- and K-band on the AB system. We present galaxy properties and rest-frame Mg II equivalent width, W{sub r} (2796), versus galaxy redshift. The well-known anti-correlation between W{sub r} (2796) and quasar-galaxy impact parameter, D, is significant to the 8σ level. The mean color of MAGIICAT galaxies is consistent with an Sbc galaxy for all redshifts. We also present B- and K-band luminosity functions for different W{sub r} (2796) and redshift subsamples: 'weak absorbing' [W{sub r} (2796) < 0.3 Å], 'strong absorbing' [W{sub r} (2796) ≥ 0.3 Å], low redshift (z < (z)), and high redshift (z ≥ (z)), where (z) = 0.359 is the median galaxy redshift. Rest-frame color B – K correlates with M{sub K} at the 8σ level for the whole sample but is driven by the strong absorbing, high-redshift subsample (6σ). Using M{sub K} as a proxy for stellar mass and examining the luminosity functions, we infer that in lower stellar mass galaxies, Mg II absorption is preferentially detected in blue galaxies and the absorption is more likely to be weak.

  20. CIFOG: Cosmological Ionization Fields frOm Galaxies

    Science.gov (United States)

    Hutter, Anne

    2018-03-01

    CIFOG is a versatile MPI-parallelised semi-numerical tool to perform simulations of the Epoch of Reionization. From a set of evolving cosmological gas density and ionizing emissivity fields, it computes the time and spatially dependent ionization of neutral hydrogen (HI), neutral (HeI) and singly ionized helium (HeII) in the intergalactic medium (IGM). The code accounts for HII, HeII, HeIII recombinations, and provides different descriptions for the photoionization rate that are used to calculate the residual HI fraction in ionized regions. This tool has been designed to be coupled to semi-analytic galaxy formation models or hydrodynamical simulations. The modular fashion of the code allows the user to easily introduce new descriptions for recombinations and the photoionization rate.

  1. The Southern HII Region Discovery Survey: The Bright Catalog

    Science.gov (United States)

    Wenger, Trey V.; Dickey, John M.; Jordan, Christopher H.; Balser, Dana; Armentrout, William Paul; Anderson, Loren; Bania, Thomas; Dawson, Joanne; McClure-Griffiths, Naomi M.; Shea, Jeanine

    2018-01-01

    HII regions, the zones of ionized gas surrounding recently formed high-mass stars, are the archetypical tracers of Galactic structure. The census of Galactic HII regions in the Southern sky is vastly incomplete due to a lack of sensitive radio recombination line (RRL) surveys. The Southern HII Region Discovery Survey (SHRDS) is a 900-hour Australia Telescope Compact Array cm-wavelength RRL and continuum emission survey of hundreds of third and fourth quadrant Galactic HII region candidates. These candidates are identified in the Widefield Infrared Survey Explorer (WISE) Catalog of Galactic HII Regions based on coincident 10 micron (WISE) and 20 cm (Southern Galactic Plane Survey) emission. The SHRDS is an extension of HII Region Discovery Surveys in the Northern sky with the Green Bank Telescope and Arecibo Telescope which discovered ~800 new HII regions. In the first 500 hours of the SHRDS, we targeted the 249 brightest HII region candidates and 33 previously known HII regions. We discuss the data reduction, analysis, and preliminary results from this first stage of the survey.

  2. GAME: GAlaxy Machine learning for Emission lines

    Science.gov (United States)

    Ucci, G.; Ferrara, A.; Pallottini, A.; Gallerani, S.

    2018-06-01

    We present an updated, optimized version of GAME (GAlaxy Machine learning for Emission lines), a code designed to infer key interstellar medium physical properties from emission line intensities of ultraviolet /optical/far-infrared galaxy spectra. The improvements concern (a) an enlarged spectral library including Pop III stars, (b) the inclusion of spectral noise in the training procedure, and (c) an accurate evaluation of uncertainties. We extensively validate the optimized code and compare its performance against empirical methods and other available emission line codes (PYQZ and HII-CHI-MISTRY) on a sample of 62 SDSS stacked galaxy spectra and 75 observed HII regions. Very good agreement is found for metallicity. However, ionization parameters derived by GAME tend to be higher. We show that this is due to the use of too limited libraries in the other codes. The main advantages of GAME are the simultaneous use of all the measured spectral lines and the extremely short computational times. We finally discuss the code potential and limitations.

  3. GAME: GAlaxy Machine learning for Emission lines

    Science.gov (United States)

    Ucci, G.; Ferrara, A.; Pallottini, A.; Gallerani, S.

    2018-03-01

    We present an updated, optimized version of GAME (GAlaxy Machine learning for Emission lines), a code designed to infer key interstellar medium physical properties from emission line intensities of UV/optical/far infrared galaxy spectra. The improvements concern: (a) an enlarged spectral library including Pop III stars; (b) the inclusion of spectral noise in the training procedure, and (c) an accurate evaluation of uncertainties. We extensively validate the optimized code and compare its performance against empirical methods and other available emission line codes (pyqz and HII-CHI-mistry) on a sample of 62 SDSS stacked galaxy spectra and 75 observed HII regions. Very good agreement is found for metallicity. However, ionization parameters derived by GAME tend to be higher. We show that this is due to the use of too limited libraries in the other codes. The main advantages of GAME are the simultaneous use of all the measured spectral lines, and the extremely short computational times. We finally discuss the code potential and limitations.

  4. Optical observations of the nearby galaxy IC342 with narrow band [SII] and Hα filters. I

    Directory of Open Access Journals (Sweden)

    Vučetić M.M.

    2013-01-01

    Full Text Available We present observations of a portion of the nearby spiral galaxy IC342 using narrow band [SII] and Hα filters. These observations were carried out in November 2011 with the 2m RCC telescope at Rozhen National Astronomical Observatory in Bulgaria. In this paper we report coordinates, diameters, Hα and [SII] fluxes for 203 HII regions detected in two fields of view in IC342 galaxy. The number of detected HII regions is 5 times higher than previously known in these two parts of the galaxy. [Projekat Ministarstva nauke Republike Srbije, br. 176005: Emission nebulae: structure and evolution

  5. Modeling the distribution of Mg II absorbers around galaxies using background galaxies and quasars

    Energy Technology Data Exchange (ETDEWEB)

    Bordoloi, R.; Lilly, S. J. [Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-Strasse 27, 8093 Zürich (Switzerland); Kacprzak, G. G. [Swinburne University of Technology, Victoria 3122 (Australia); Churchill, C. W., E-mail: rongmonb@phys.ethz.ch [New Mexico State University, Las Cruces, NM 88003 (United States)

    2014-04-01

    We present joint constraints on the distribution of Mg II absorption around high redshift galaxies obtained by combining two orthogonal probes, the integrated Mg II absorption seen in stacked background galaxy spectra and the distribution of parent galaxies of individual strong Mg II systems as seen in the spectra of background quasars. We present a suite of models that can be used to predict, for different two- and three-dimensional distributions, how the projected Mg II absorption will depend on a galaxy's apparent inclination, the impact parameter b and the azimuthal angle between the projected vector to the line of sight and the projected minor axis. In general, we find that variations in the absorption strength with azimuthal angles provide much stronger constraints on the intrinsic geometry of the Mg II absorption than the dependence on the inclination of the galaxies. In addition to the clear azimuthal dependence in the integrated Mg II absorption that we reported earlier in Bordoloi et al., we show that strong equivalent width Mg II absorbers (W{sub r} (2796) ≥ 0.3 Å) are also asymmetrically distributed in azimuth around their host galaxies: 72% of the absorbers in Kacprzak et al., and 100% of the close-in absorbers within 35 kpc of the center of their host galaxies, are located within 50° of the host galaxy's projected semi minor axis. It is shown that either composite models consisting of a simple bipolar component plus a spherical or disk component, or a single highly softened bipolar distribution, can well represent the azimuthal dependencies observed in both the stacked spectrum and quasar absorption-line data sets within 40 kpc. Simultaneously fitting both data sets, we find that in the composite model the bipolar cone has an opening angle of ∼100° (i.e., confined to within 50° of the disk axis) and contains about two-thirds of the total Mg II absorption in the system. The single softened cone model has an exponential fall off with

  6. Starbursts and IRAS galaxies

    International Nuclear Information System (INIS)

    Belfort, P.

    1987-01-01

    Several observational hints suggest that most of the IRAS galaxies are undergoing bursts of star formation. A simple photometric model of starburst galaxy was developed in order to check whether starburst events are really able to account for the far-infrared and optical properties of all the IRAS galaxies with HII region-like spectra. FIR activities up to a few hundred are actually easily reached with rather small bursts in red host-galaxies, and L IR /L B , EW(Hα) and U-B) versus (B-V) diagrams can be used to estimate burst strength and extinction. But more observations are required to conclude about the most extreme cases. Four typical infrared-selected IRAS galaxies are presented and their burst strength and extinction estimated

  7. Addressing Ionization and Depletion in the ISM of Nearby Star-Forming Galaxies

    Science.gov (United States)

    Aloisi, Alessandra

    2017-08-01

    Measuring galaxy metallicity with cosmic time is of paramount importance to understand galaxy formation. ISM abundances are typically determined using emission-line spectroscopy of HII regions. However, HII regions may be self-enriched and not typical of the whole galaxy. This is particularly true for star-forming galaxies (SFGs) where the bulk of metals may be in the neutral gas. Quantifying metals in the ISM is thus important to assess how reliably HII regions trace galaxy abundances at any redshift. We were awarded 34 HST orbits (Cycle 17) to measure abundances in the neutral ISM of 9 nearby SFGs using absorption lines in the COS G130M/1291 spectra of bright UV background sources within the galaxy itself. We found metallicities that differ by up to 2 dex depending on the element. These variations could be real or due to observational effects. Here we request 22 orbits in the new G130M/1222 and in G160M/1623 to access new FUV spectral transitions that will help us characterize ionized-gas contamination and dust depletion, and ultimately nail down the abundances of the different elements. These new data will nicely complement our Cycle 17 COS and Gemini/GMOS IFU programs, the latter aimed at deriving nebular abundances along the same COS sightlines. This first detailed and spatially-accurate comparison between neutral- and ionized-gas abundances in local (z 0) SFGs will provide crucial insights into the metallicity of galaxies at any redshift. If this UV spectroscopic study is not undertaken before HST ceases operation, the (in)homogeneity of the ISM in galaxies of the local Universe will continue to remain uncertain for at least another decade.

  8. The Southern HII Region Discovery Survey: Preliminary Results

    Science.gov (United States)

    Shea, Jeanine; Wenger, Trey; Balser, Dana S.; Anderson, Loren D.; Armentrout, William P.; Bania, Thomas M.; Dawson, Joanne; Miller Dickey, John; Jordan, Christopher; McClure-Griffiths, Naomi M.

    2017-01-01

    HII regions are some of the brightest sources at radio frequencies in the Milky Way and are the sites of massive O and B-type star formation. They have relatively short (Bank Telescope. Candidate HII regions were selected from mid-infrared emission coincident with radio continuum emission, and confirmed as HII regions by the detection of radio recombination lines. Here we discuss the Southern HII Region Discovery Survey (SHRDS), a continuation of the HRDS using the Australia Telescope Compact Array over the Galactic longitude range 230 to 360 degrees. We have reduced and analyzed a small sub-set of the SHRDS sources and discuss preliminary results, including kinematic distances and metallicities.

  9. The Study of Nebular Emission on Nearby Spiral Galaxies in the IFU Era

    Directory of Open Access Journals (Sweden)

    Fernando Fabián Rosales-Ortega

    2013-01-01

    Full Text Available A new generation of wide-field emission-line surveys based on integral field units (IFU is allowing us to obtain spatially resolved information of the gas-phase emission in nearby late-type galaxies, based on large samples of HII regions and full two-dimensional coverage. These observations are allowing us to discover and characterise abundance differentials between galactic substructures and new scaling relations with global physical properties. Here I review some highlights of our current studies employing this technique: (1 the case study of NGC 628, the largest galaxy ever sampled with an IFU; (2 a statistical approach to the abundance gradients of spiral galaxies, which indicates a universal radial gradient for oxygen abundance; and (3 the discovery of a new scaling relation of HII regions in spiral galaxies, the local mass-metallicity relation of star-forming galaxies. The observational properties and constrains found in local galaxies using this new technique will allow us to interpret the gas-phase abundance of analogue high-z systems.

  10. Mg II-Absorbing Galaxies in the UltraVISTA Survey

    Science.gov (United States)

    Stroupe, Darren; Lundgren, Britt

    2018-01-01

    Light that is emitted from distant quasars can become partially absorbed by intervening gaseous structures, including galaxies, in its path toward Earth, revealing information about the chemical content, degree of ionization, organization and evolution of these structures through time. In this project, quasar spectra are used to probe the halos of foreground galaxies at a mean redshift of z=1.1 in the COSMOS Field. Mg II absorption lines in Sloan Digital Sky Survey quasar spectra are paired with galaxies in the UltraVISTA catalog at an impact parameter less than 200 kpc. A sample of 77 strong Mg II absorbers with a rest-frame equivalent width ≥ 0.3 Å and redshift from 0.34 < z < 2.21 are investigated to find equivalent width ratios of Mg II, C IV and Fe II absorption lines, and their relation to the impact parameter and the star formation rates, stellar masses, environments and redshifts of their host galaxies.

  11. H-alpha observations of Sh2-190, Sh2-222, Sh2-229, Sh2-236 HII regions

    Science.gov (United States)

    Sahan, Muhittin

    2018-02-01

    Hα spectral line (6563Å) profiles of four northern HII regions in the our galaxy (Sh2-190, Sh2-222, Sh2-229, Sh2-236) have been obtained using DEFPOS spectrometer, located at coude focus of 150 cm RTT150 telescope at TUBITAK National Observatory (TUG, Antalya, Turkey). Observations were carried out at nights of 2015 December 24-27 with long exposure times ranging from 900s to 3600s. The LSR velocities and the linewidths (Full Width Half Maximum: FWHM) of the Hα emission lines were found to be in the range of -45.46 kms-1 to +3.57 kms-1 and 38.50 kms-1 to 44.10 kms-1, respectively. The Sh2-229 HII region is the faintest one (211.16 R), while the Sh2-236 HII region (IC410) is brightest source (535.75 R). The LSR velocity and the line width (FWHM) results of the DEFPOS/RTT150 system were compared with the data by several authors given in literature and results of DEFPOS data were found to be in good agreement with data given in literature.

  12. Lyman-continuum leakage as dominant source of diffuse ionized gas in the Antennae galaxy

    Science.gov (United States)

    Weilbacher, Peter M.; Monreal-Ibero, Ana; Verhamme, Anne; Sandin, Christer; Steinmetz, Matthias; Kollatschny, Wolfram; Krajnović, Davor; Kamann, Sebastian; Roth, Martin M.; Erroz-Ferrer, Santiago; Marino, Raffaella Anna; Maseda, Michael V.; Wendt, Martin; Bacon, Roland; Dreizler, Stefan; Richard, Johan; Wisotzki, Lutz

    2018-04-01

    The Antennae galaxy (NGC 4038/39) is the closest major interacting galaxy system and is therefore often studied as a merger prototype. We present the first comprehensive integral field spectroscopic dataset of this system, observed with the MUSE instrument at the ESO VLT. We cover the two regions in this system which exhibit recent star formation: the central galaxy interaction and a region near the tip of the southern tidal tail. In these fields, we detect HII regions and diffuse ionized gas to unprecedented depth. About 15% of the ionized gas was undetected by previous observing campaigns. This newly detected faint ionized gas is visible everywhere around the central merger, and shows filamentary structure. We estimate diffuse gas fractions of about 60% in the central field and 10% in the southern region. We are able to show that the southern region contains a significantly different population of HII regions, showing fainter luminosities. By comparing HII region luminosities with the HST catalog of young star clusters in the central field, we estimate that there is enough Lyman-continuum leakage in the merger to explain the amount of diffuse ionized gas that we detect. We compare the Lyman-continuum escape fraction of each HII region against emission line ratios that are sensitive to the ionization parameter. While we find no systematic trend between these properties, the most extreme line ratios seem to be strong indicators of density bounded ionization. Extrapolating the Lyman-continuum escape fractions to the southern region, we conclude that simply from the comparison of the young stellar populations to the ionized gas there is no need to invoke other ionization mechanisms than Lyman-continuum leaking HII regions for the diffuse ionized gas in the Antennae. FITS images and Table of HII regions are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A95 and at http://muse-vlt.eu/science/antennae/

  13. Abundance determinations in HII regions and planetary nebulae

    OpenAIRE

    Stasinska, Grazyna

    2002-01-01

    The methods of abundance determinations in HII regions and planetary nebulae are described, with emphasis on the underlying assumptions and inherent problems. Recent results on abundances in Galactic HII regions and in Galactic and extragalactic Planetary Nebulae are reviewed.

  14. H-II Transfer Vehicle (HTV) and the Operations Concept for Extravehicular Activity (EVA) Hardware

    Science.gov (United States)

    Chullen, Cinda; Blome, Elizabeth; Tetsuya, Sakashita

    2011-01-01

    With the retirement of the Space Shuttle fleet imminent in 2011, a new operations concept will become reality to meet the transportation challenges of the International Space Station (ISS). The planning associated with the retirement of the Space Shuttle has been underway since the announcement in 2004. Since then, several companies and government entities have had to look for innovative low-cost commercial orbital transportation systems to continue to achieve the objectives of ISS delivery requirements. Several options have been assessed and appear ready to meet the large and demanding delivery requirements of the ISS. Options that have been identified that can facilitate the challenge include the Russian Federal Space Agency's Soyuz and Progress spacecraft, European Space Agency's Automated Transfer Vehicle (ATV), and the Japan Aerospace Exploration Agency's (JAXA s) H-II Transfer Vehicle (HTV). The newest of these options is the JAXA's HTV. This paper focuses on the HTV, mission architecture and operations concept for Extra-Vehicular Activities (EVA) hardware, the associated launch system, and details of the launch operations approach.

  15. EXTENDED [C II] EMISSION IN LOCAL LUMINOUS INFRARED GALAXIES

    International Nuclear Information System (INIS)

    Díaz-Santos, T.; Armus, L.; Surace, J. A.; Charmandaris, V.; Stacey, G.; Murphy, E. J.; Haan, S.; Stierwalt, S.; Evans, A. S.; Malhotra, S.; Appleton, P.; Inami, H.; Magdis, G. E.; Elbaz, D.; Mazzarella, J. M.; Xu, C. K.; Lu, N.; Howell, J. H.; Van der Werf, P. P.; Meijerink, R.

    2014-01-01

    We present Herschel/PACS observations of extended [C II] 157.7 μm line emission detected on ∼1-10 kpc scales in 60 local luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey. We find that most of the extra-nuclear emission show [C II]/FIR ratios ≥4 × 10 –3 , larger than the mean ratio seen in the nuclei, and similar to those found in the extended disks of normal star-forming galaxies and the diffuse interstellar medium of our Galaxy. The [C II] ''deficits'' found in the most luminous local LIRGs are therefore restricted to their nuclei. There is a trend for LIRGs with warmer nuclei to show larger differences between their nuclear and extra-nuclear [C II]/FIR ratios. We find an anti-correlation between [C II]/FIR and the luminosity surface density, Σ IR , for the extended emission in the spatially resolved galaxies. However, there is an offset between this trend and that found for the LIRG nuclei. We use this offset to derive a beam filling-factor for the star-forming regions within the LIRG disks of ∼6% relative to their nuclei. We confront the observed trend to photo-dissociation region models and find that the slope of the correlation is much shallower than the model predictions. Finally, we compare the correlation found between [C II]/FIR and Σ IR with measurements of high-redshift starbursting IR-luminous galaxies

  16. Star formation in the outskirts of disk galaxies

    NARCIS (Netherlands)

    Ferguson, AMN

    2002-01-01

    The far outer regions of galactic disks allow an important probe of both star formation and galaxy formation. I discuss how observations of HII regions in these low gas density, low metallicity environments can shed light on the physical processes which drive galactic star formation. The history of

  17. The formation of HII regions. Pt. 1

    International Nuclear Information System (INIS)

    Tenorio-Tagle, G.

    1978-04-01

    Numerical models of the evolution of HII regions accounting for the fact that star formation takes place inside a dense cloud are presented. The gas dynamical effects produced after the ionization of the cloud's edge (from the inside) are here postulated to determine the size, velocity field, and large scale density variation observed in HII regions. The consequences and observational predictions from these models are also given. (orig.) [de

  18. Gravitational instability, evolution of galaxies and star formation

    International Nuclear Information System (INIS)

    Palous, J.

    1979-01-01

    The gravitational collapse is the key to the theories of galaxy and star formation. The observations, showing intrinsic differences between elliptical and spiral galaxies, guide our fundamental conceptions on the formation and evolution of systems in question. Stars in elliptical galaxies and in spherical components of spiral galaxies were formed in a short period of time during early phases of protogalactic collapse, at a time of violent star formation. The disc-like components of spiral galaxies, however, were built gradually in the course of galactic evolution. Star formation in elliptical galaxies is described by the collision model of interstellar clouds, while star formation in discs is characterised by several processes: the expansion of HII regions, the expansion of supernovae remnants and the shock wave related to the presence of the spiral structure. (author)

  19. ISO spectroscopy of compact HII regions in the Galaxy - II. Ionization and elemental abundances

    NARCIS (Netherlands)

    Martin-Hernandez, NL; Peeters, E; Morisset, C; Tielens, AGGM; Cox, P; Roelfsema, PR; Baluteau, JP; Schaerer, D; Mathis, JS; Damour, F; Churchwell, E; Kessler, MF

    Based on the ISO spectral catalogue of compact H II regions by Peeters et al. (2002), we present a first analysis of the hydrogen recombination and atomic fine-structure lines originated in the ionized gas. The sample consists of 34 H II regions located at galactocentric distances between R-Gal = 0

  20. On the Nature of Ultra-faint Dwarf Galaxy Candidates. II. The Case of Cetus II

    Science.gov (United States)

    Conn, Blair C.; Jerjen, Helmut; Kim, Dongwon; Schirmer, Mischa

    2018-04-01

    We obtained deep Gemini GMOS-S g, r photometry of the ultra-faint dwarf galaxy candidate Cetus II with the aim of providing stronger constraints on its size, luminosity, and stellar population. Cetus II is an important object in the size–luminosity plane, as it occupies the transition zone between dwarf galaxies and star clusters. All known objects smaller than Cetus II (r h ∼ 20 pc) are reported to be star clusters, while most larger objects are likely dwarf galaxies. We found a prominent excess of main-sequence stars in the color–magnitude diagram of Cetus II, best described by a single stellar population with an age of 11.2 Gyr, metallicity of [Fe/H] = ‑1.28 dex, an [α/Fe] = 0.0 dex at a heliocentric distance of 26.3 ± 1.2 kpc. As well as being spatially located within the Sagittarius dwarf tidal stream, these properties are well matched to the Sagittarius galaxy’s Population B stars. Interestingly, like our recent findings on the ultra-faint dwarf galaxy candidate Tucana V, the stellar field in the direction of Cetus II shows no evidence of a concentrated overdensity despite tracing the main sequence for over six magnitudes. These results strongly support the picture that Cetus II is not an ultra-faint stellar system in the Milky Way halo, but made up of stars from the Sagittarius tidal stream.

  1. Complete Element Abundances of Nine Stars in the r-process Galaxy Reticulum II

    Science.gov (United States)

    Ji, Alexander P.; Frebel, Anna; Simon, Joshua D.; Chiti, Anirudh

    2016-10-01

    We present chemical abundances derived from high-resolution Magellan/Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (-3.5 contaminated known r-process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r-process sites besides the source of r-process elements in Ret II. Galaxies like Ret II may be the original birth sites of r-process enhanced stars now found in the halo. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  2. Emission line galaxies and active galactic nuclei in WINGS clusters

    Science.gov (United States)

    Marziani, P.; D'Onofrio, M.; Bettoni, D.; Poggianti, B. M.; Moretti, A.; Fasano, G.; Fritz, J.; Cava, A.; Varela, J.; Omizzolo, A.

    2017-03-01

    We present the analysis of the emission line galaxies members of 46 low-redshift (0.04 employing diagnostic diagrams. We examined the emission line properties and frequencies of star-forming galaxies, transition objects, and active galactic nuclei (AGNs: LINERs and Seyferts), unclassified galaxies with emission lines, and quiescent galaxies with no detectable line emission. A deficit of emission line galaxies in the cluster environment is indicated by both a lower frequency, and a systematically lower Balmer emission line equivalent width and luminosity with respect to control samples; this implies a lower amount of ionized gas per unit mass and a lower star formation rate if the source is classified as Hii region. A sizable population of transition objects and of low-luminosity LINERs (≈ 10-20% of all emission line galaxies) are detected among WINGS cluster galaxies. These sources are a factor of ≈1.5 more frequent, or at least as frequent, as in control samples with respect to Hii sources. Transition objects and LINERs in clusters are most affected in terms ofline equivalent width by the environment and appear predominantly consistent with so-called retired galaxies. Shock heating can be a possible gas excitation mechanism that is able to account for observed line ratios. Specific to the cluster environment, we suggest interaction between atomic and molecular gas and the intracluster medium as a possible physical cause of line-emitting shocks. The data whose description is provided in Table B.1, and emission line catalog of the WINGS database are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A83

  3. ALMA Reveals Weak [N II] Emission in "Typical" Galaxies and Intense Starbursts at z = 5-6

    Science.gov (United States)

    Pavesi, Riccardo; Riechers, Dominik A.; Capak, Peter L.; Carilli, Christopher L.; Sharon, Chelsea E.; Stacey, Gordon J.; Karim, Alexander; Scoville, Nicholas Z.; Smolčić, Vernesa

    2016-12-01

    We report interferometric measurements of [N II] 205 μm fine-structure line emission from a representative sample of three galaxies at z = 5-6 using the Atacama Large (sub)Millimeter Array (ALMA). These galaxies were previously detected in [C II] and far-infrared continuum emission and span almost two orders of magnitude in star formation rate (SFR). Our results show at least two different regimes of ionized interstellar medium properties for galaxies in the first billion years of cosmic time, separated by their {L}[{{C}{{II}}]}/{L}[{{N}{{II}}]} ratio. We find extremely low [N II] emission compared to [C II] ({L}[{{C}{{II}}]}/{L}[{{N}{{II}}]}={68}-28+200) from a “typical” ˜ {L}{UV}* star-forming galaxy, likely directly or indirectly (by its effect on the radiation field) related to low dust abundance and low metallicity. The infrared-luminous modestly star-forming Lyman-break galaxy (LBG) in our sample is characterized by an ionized-gas fraction ({L}[{{C}{{II}}]}/{L}[{{N}{{II}}]}≲ 20) typical of local star-forming galaxies and shows evidence for spatial variations in its ionized-gas fraction across an extended gas reservoir. The extreme SFR, warm and compact dusty starburst AzTEC-3 shows an ionized fraction higher than expected given its SFR surface density ({L}[{{C}{{II}}]}/{L}[{{N}{{II}}]}=22+/- 8) suggesting that [N II] dominantly traces a diffuse ionized medium rather than star-forming H II regions in this type of galaxy. This highest redshift sample of [N II] detections provides some of the first constraints on ionized and neutral gas modeling attempts and on the structure of the interstellar medium at z = 5-6 in “normal” galaxies and starbursts.

  4. Chemical Abundances and Physical Parameters of H II Regions in the Magellanic Clouds

    Science.gov (United States)

    Reyes, R. E. C.

    The chemical abundances and physical parameters of H II regions are important pa rameters to determine in order to understand how stars and galaxies evolve. The Magellanic Clouds offer us a unique oportunity to persue such studies in low metallicity galaxies. In this contribution we present the results of the photoionization modeling of 5 H II regions in each of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) sys tems. Optical data were collected from the literature, complemented by our own observa tions (Carlos Reyes et al. 1998), including UV spectra from the new IUE data ban k and infrared fluxes from the IRAS satellite. The chemical abundances of He, C, N, O, Ne, S, Ar and physical parameters like the densities, the ionized masses, the luminosities, the ionization temperatures , the filling factor and optical depth are determined. A comparison of the abundances of these HII regions with those of typical planetary nebulae and supergiants stars is also presented.

  5. Radio continuum interferometry of dark clouds: A search for newly formed HII regions

    International Nuclear Information System (INIS)

    Gilmore, W.S.

    1978-01-01

    A search for compact HII regions embedded in dark clouds has been carried out in an effort to study local massive star formation. Approximately 20% of the total area of opaque dark cloud material in the sky with Av greater than or equal to 6 mag was surveyed with the NRAO three-element interferometer at 2695 MHz, and at least 5% more was surveyed with the NRAO 300-foot telescope at 4750 MHz. The regions surveyed include the dark cloud complexes in Perseus, Taurus, Orion, and Ophiuchus, as well as several smaller cloud complexes and individual clouds. No hidden compact HII regions embedded inside dark clouds were detected with certainty in the radio continuum. However, eleven HII regions with associated visible emission and eighteen other possible HII regions were detected. Five infrared sources thought to have the luminosities of early B stars were not detected in the radio continuum. These five sources showed high correlation with the presence of CO self-absorption, CO emission over a wide range of velocities, and type I OH masers, but an absence of coincident visible nebulosity and detectable radio continuum emission. Therefore, it is suggested that they represent an earlier evolutionary stage than those HII region detected in the radio continuum. This first evolutionary state marks the presence of ''pre-emergent'' (with respect to the molecular cloud) cocoon stars. HII regions in the second evolutionary state are marked by the presence of detectable radio continuum emission, i.e., they are stronger than 10 mJy at 2695 MHz. They have associated visible nebulosity, are relatively large, and appear to be located at the edges of molecular clouds. These are designated as ''emergent edge'' HII regions. The fact that many young HII regions are edge HII regions implies that massive stars are born near the edges of clouds, a phenomenon previously suggested by several other investigators

  6. Version of the galaxy spiral structure model with opposite-directed arms and inter-arm links

    Energy Technology Data Exchange (ETDEWEB)

    Dolidze, M V [AN Gruzinskoj SSR, Abastumani. Abastumanskaya Astrofizicheskaya Observatoriya

    1963-05-01

    An attempt is made to explain some peculiarities of the local spiral structure and large-scale distribution of HII regions in the Galaxy by coexistence of the trailing and leading arm systems of different power and development. The existence of opposite-directed arms and inter-arm links in the circular zone (5-15 kpc) is analysed from the point of view of different Galaxy models.

  7. Star formations rates in the Galaxy

    International Nuclear Information System (INIS)

    Smith, L.F.; Mezger, P.G.; Biermann, P.

    1978-01-01

    Data relevant to giant HII regions in the Galaxy are collected. The production rate for Lyman continuum photons by O stars in giant HII regions is 4.7 10 52 s -1 in the whole Galaxy. The corresponding present rate of star formation is M (sun)/yr, of which 74% occurs in main spiral arms, 13% in the interarm region and 13% in the galactic center. The star formation rates, the observed heavy element and deuterium abundances in the solar neighbourhood are compared to model predictions based on star formation proportional to a power (k) of the gas surface density. The mass function is terminated at Msub(u)=100 M (sun) above and M 1 below. Msub(u)=50 M (sun) is also considered. Comparing with data derived from observations a) the star formation rate, b) metal abundances, c) deuterium abundances, and d) colors of the stellar population, we find that models of k=1/2 to 1, and M 1 1 M (sun) are formed together with O and B stars, but under rather special conditions of the interstellar gas, while lower mass stars form wherever dense molecular clouds exist. The high rate of star formation in the galactic center may represent a burst. (orig.) [de

  8. The Origins of [C ii] Emission in Local Star-forming Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Croxall, K. V. [Department of Astronomy, The Ohio State University, 4051 McPherson Laboratory, 140 W. 18th Avenue, Columbus, OH, 43210 (United States); Smith, J. D. [Max-Planck-Institut fur Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Pellegrini, E. [Department of Physics and Astronomy, University of Toledo, 2801 W. Bancroft Street, Toledo, OH 43606 (United States); Groves, B. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Bolatto, A.; Wolfire, M. G. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Herrera-Camus, R. [Max-Planck-Institut für extraterrestrische Physik, Giessen-bachstr., D-85748 Garching (Germany); Sandstrom, K. M. [Center for Astrophysics and Space Sciences, Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Draine, B. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Armus, L. [Spitzer Science Center, California Institute of Technology, MC 314-6, Pasadena, CA 91125 (United States); Boquien, M. [Unidad de Astronomía, Fac. Cs. Básicas, Universidad de Antofagasta, Avda. U. de Antofagasta 02800, Antofagasta (Chile); Brandl, B. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Dale, D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Galametz, M. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu—CNRS—Université Paris Diderot, CEA-Saclay, 91191, Gif-sur-Yvette (France); Hunt, L., E-mail: jd.smith@utoledo.edu [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Firenze (Italy); and others

    2017-08-20

    The [C ii] 158 μ m fine-structure line is the brightest emission line observed in local star-forming galaxies. As a major coolant of the gas-phase interstellar medium, [C ii] balances the heating, including that due to far-ultraviolet photons, which heat the gas via the photoelectric effect. However, the origin of [C ii] emission remains unclear because C{sup +} can be found in multiple phases of the interstellar medium. Here we measure the fractions of [C ii] emission originating in the ionized and neutral gas phases of a sample of nearby galaxies. We use the [N ii] 205 μ m fine-structure line to trace the ionized medium, thereby eliminating the strong density dependence that exists in the ratio of [C ii]/[N ii] 122 μ m. Using the FIR [C ii] and [N ii] emission detected by the KINGFISH (Key Insights on Nearby Galaxies: a Far- Infrared Survey with Herschel ) and Beyond the Peak Herschel programs, we show that 60%–80% of [C ii] emission originates from neutral gas. We find that the fraction of [C ii] originating in the neutral medium has a weak dependence on dust temperature and the surface density of star formation, and has a stronger dependence on the gas-phase metallicity. In metal-rich environments, the relatively cooler ionized gas makes substantially larger contributions to total [C ii] emission than at low abundance, contrary to prior expectations. Approximate calibrations of this metallicity trend are provided.

  9. Studying the Interstellar Medium of H II/BCD Galaxies Using IFU Spectroscopy

    Directory of Open Access Journals (Sweden)

    Patricio Lagos

    2013-01-01

    Full Text Available We review the results from our studies, and previous published work, on the spatially resolved physical properties of a sample of H ii/BCD galaxies, as obtained mainly from integral-field unit spectroscopy with Gemini/GMOS and VLT/VIMOS. We confirm that, within observational uncertainties, our sample galaxies show nearly spatially constant chemical abundances similar to other low-mass starburst galaxies. They also show He ii  λ4686 emission with the properties being suggestive of a mix of excitation sources and with Wolf-Rayet stars being excluded as the primary ones. Finally, in this contribution, we include a list of all H ii/BCD galaxies studied thus far with integral-field unit spectroscopy.

  10. An evolutionary link between Seyfert I and II galaxies

    International Nuclear Information System (INIS)

    Penston, M.V.; Perez, E.

    1984-01-01

    First spectra from the newly sited Isaac Newton Telescope show NGC 4151 and 3C 390.3 to have taken on a classification very close to Seyfert II. It is proposed that Seyfert II galaxies are Seyfert Is in which the continuum source is temporarily off. (author)

  11. HERSCHEL EXTREME LENSING LINE OBSERVATIONS: [C ii] VARIATIONS IN GALAXIES AT REDSHIFTS z = 1–3

    Energy Technology Data Exchange (ETDEWEB)

    Malhotra, Sangeeta; Rhoads, James E.; Yang, Huan [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Finkelstein, K.; Finkelstein, Steven [University of Texas, Austin, TX 78712 (United States); Carilli, Chris [National Radio Astronomy Observatory, Socorro, NM (United States); Combes, Françoise [Observatoire de Paris, LERMA, CNRS, 61 Avenue de l’Observatoire, F-75014 Paris (France); Dassas, Karine; Guillard, Pierre; Nesvadba, Nicole [Institut d’Astrophysique Spatiale, Centre Universitaire d’Orsay (France); Frye, Brenda [Steward Observatory, University of Arizona, Tucson, AZ (United States); Gerin, Maryvonne [LERMA,24 rue Lhomond, F-75231 Paris Cedex 05 (France); Rigby, Jane [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Shin, Min-Su [Oxford University, Oxford, OX1 3PA (United Kingdom); Spaans, Marco [Kapteyn Astronomical Institute, University of Groningen, Groningen (Netherlands); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States); Papovich, Casey, E-mail: malhotra@asu.edu [George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics, Texas A and M University, College Station, TX 77843 (United States)

    2017-01-20

    We observed the [C ii] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3 σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C ii] with Herschel . The [C ii] luminosity in this sample ranges from 8 × 10{sup 7} L {sub ⊙} to 3.7 × 10{sup 9} L {sub ⊙} (after correcting for magnification), confirming that [C ii] is a strong tracer of the ISM at high redshifts. The ratio of the [C ii] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C ii]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C ii]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C ii]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C ii]/FIR correlates most strongly with dust temperature. The [C ii] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.

  12. HERSCHEL EXTREME LENSING LINE OBSERVATIONS: [C ii] VARIATIONS IN GALAXIES AT REDSHIFTS z = 1–3

    International Nuclear Information System (INIS)

    Malhotra, Sangeeta; Rhoads, James E.; Yang, Huan; Finkelstein, K.; Finkelstein, Steven; Carilli, Chris; Combes, Françoise; Dassas, Karine; Guillard, Pierre; Nesvadba, Nicole; Frye, Brenda; Gerin, Maryvonne; Rigby, Jane; Shin, Min-Su; Spaans, Marco; Strauss, Michael A.; Papovich, Casey

    2017-01-01

    We observed the [C ii] line in 15 lensed galaxies at redshifts 1 < z < 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3 σ or better. High magnifications enable even modestly luminous galaxies to be detected in [C ii] with Herschel . The [C ii] luminosity in this sample ranges from 8 × 10 7 L ⊙ to 3.7 × 10 9 L ⊙ (after correcting for magnification), confirming that [C ii] is a strong tracer of the ISM at high redshifts. The ratio of the [C ii] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C ii]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C ii]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C ii]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C ii]/FIR correlates most strongly with dust temperature. The [C ii] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.

  13. PHYSICAL AND MORPHOLOGICAL PROPERTIES OF [O II] EMITTING GALAXIES IN THE HETDEX PILOT SURVEY

    International Nuclear Information System (INIS)

    Bridge, Joanna S.; Gronwall, Caryl; Ciardullo, Robin; Hagen, Alex; Zeimann, Greg; Malz, A. I.; Schneider, Donald P.

    2015-01-01

    The Hobby-Eberly Dark Energy Experiment pilot survey identified 284 [O II] λ3727 emitting galaxies in a 169 arcmin 2 field of sky in the redshift range 0 < z < 0.57. This line flux limited sample provides a bridge between studies in the local universe and higher-redshift [O II] surveys. We present an analysis of the star formation rates (SFRs) of these galaxies as a function of stellar mass as determined via spectral energy distribution fitting. The [O II] emitters fall on the ''main sequence'' of star-forming galaxies with SFR decreasing at lower masses and redshifts. However, the slope of our relation is flatter than that found for most other samples, a result of the metallicity dependence of the [O II] star formation rate indicator. The mass-specific SFR is higher for lower mass objects, supporting the idea that massive galaxies formed more quickly and efficiently than their lower mass counterparts. This is confirmed by the fact that the equivalent widths of the [O II] emission lines trend smaller with larger stellar mass. Examination of the morphologies of the [O II] emitters reveals that their star formation is not a result of mergers, and the galaxies' half-light radii do not indicate evolution of physical sizes

  14. Characterizing the Interstellar and Circumgalactic Medium in Star-forming Galaxies

    Science.gov (United States)

    Du, Xinnan; Shapley, Alice; Crystal Martin, Alison Coil, Charles Steidel, Tucker Jones, Daniel Stark, Allison Strom

    2018-01-01

    Rest-frame UV and optical spectroscopy provide valuable information on the physical properties of the neutral and ionized interstellar medium (ISM) in star-forming galaxies, including both the systemic interstellar component originating from HII regions, and the multi-phase outflowing component associated with star-formation feedback. My thesis focuses on both the systemic and outflowing ISM in star-forming galaxies at redshift z ~ 1-4. With an unprecedented sample at z~1 with the rest-frame near-UV coverage, we examined how the kinematics of the warm and cool phrases of gas, probed by the interstellar CIV and low-ionization features, respectively, relate to each other. The spectral properties of CIV strongly correlate with the current star-formation rate, indicating a distinct nature of highly-ionized outflowing gas being driven by massive star formation. Additionally, we used the same set of z~1 galaxies to study the properties of the systemic ISM in HII regions by analyzing the nebular CIII] emission. CIII] emission tends to be stronger in lower-mass, bluer, and fainter galaxies with lower metallicity, suggesting that the strong CIII] emitters at lower redshifts can be ideal analogs of young, bursty galaxies at z > 6, which are possibly responsible for reionizing the universe. We are currently investigating the redshift evolution of the neutral, circumgalactic gas in a sample of ~1100 Lyman Break Galaxies at z ~ 2-4. The negative correlation between Lya emission and low-ionization interstellar absorption line strengths appears to be universal across different redshifts, but the fine-structure line emitting regions are found to be more compact for higher-redshift galaxies. With the detailed observational constraints provided by the rest-UV and rest-optical spectroscopy, our study sheds light on how the interstellar and circumgalactic gas components and different phases of gas connect to each other, and therefore provides a comprehensive picture of the overall

  15. Observations of ultraviolet spectra of H II regions and galaxies with IUE

    International Nuclear Information System (INIS)

    Gondhalekar, P.M.

    1982-08-01

    The ultraviolet spectra, obtained with the International Ultraviolet Explorer, of a sample of H II regions and the nuclear regions of spiral and elliptical galaxies are described. The star formation rates in the nuclei of spiral galaxies are similar to the star formation rate in the solar neighbourhood. The data indicate that the current thinking on the synthesis of carbon and nitrogen in galaxies has to be revised and the K-corrections determined from the ultraviolet spectra of galaxies when compared with the photometry of distant galaxies suggests colour evolution of galaxies at z > 0.3. (author)

  16. Unusual broad-line Mg II emitters among luminous galaxies in the baryon oscillation spectroscopic survey

    International Nuclear Information System (INIS)

    Roig, Benjamin; Blanton, Michael R.; Ross, Nicholas P.

    2014-01-01

    Many classes of active galactic nuclei (AGNs) have been observed and recorded since the discovery of Seyfert galaxies. In this paper, we examine the sample of luminous galaxies in the Baryon Oscillation Spectroscopic Survey. We find a potentially new observational class of AGNs, one with strong and broad Mg II λ2799 line emission, but very weak emission in other normal indicators of AGN activity, such as the broad-line Hα, Hβ, and the near-ultraviolet AGN continuum, leading to an extreme ratio of broad Hα/Mg II flux relative to normal quasars. Meanwhile, these objects' narrow-line flux ratios reveal AGN narrow-line regions with levels of activity consistent with the Mg II fluxes and in agreement with that of normal quasars. These AGN may represent an extreme case of the Baldwin effect, with very low continuum and high equivalent width relative to typical quasars, but their ratio of broad Mg II to broad Balmer emission remains very unusual. They may also be representative of a class of AGN where the central engine is observed indirectly with scattered light. These galaxies represent a small fraction of the total population of luminous galaxies (≅ 0.1%), but are more likely (about 3.5 times) to have AGN-like nuclear line emission properties than other luminous galaxies. Because Mg II is usually inaccessible for the population of nearby galaxies, there may exist a related population of broad-line Mg II emitters in the local universe which is currently classified as narrow-line emitters (Seyfert 2 galaxies) or low ionization nuclear emission-line regions.

  17. The evolution of young HII regions. I. Continuum emission and internal dynamics

    Science.gov (United States)

    Klaassen, P. D.; Johnston, K. G.; Urquhart, J. S.; Mottram, J. C.; Peters, T.; Kuiper, R.; Beuther, H.; van der Tak, F. F. S.; Goddi, C.

    2018-04-01

    Context. High-mass stars form in much richer environments than those associated with isolated low-mass stars, and once they reach a certain mass, produce ionised (HII) regions. The formation of these pockets of ionised gas are unique to the formation of high-mass stars (M > 8 M⊙), and present an excellent opportunity to study the final stages of accretion, which could include accretion through the HII region itself. Aim. This study of the dynamics of the gas on both sides of these ionisation boundaries in very young HII regions aims to quantify the relationship between the HII regions and their immediate environments. Methods: We present high-resolution ( 0.5″) ALMA observations of nine HII regions selected from the red MSX source survey with compact radio emission and bolometric luminosities greater than 104 L⊙. We focus on the initial presentation of the data, including initial results from the radio recombination line H29α, some complementary molecules, and the 256 GHz continuum emission. Results: Of the six (out of nine) regions with H29α detections, two appear to have cometary morphologies with velocity gradients across them, and two appear more spherical with velocity gradients suggestive of infalling ionised gas. The remaining two were either observed at low resolution or had signals that were too weak to draw robust conclusions. We also present a description of the interactions between the ionised and molecular gas (as traced by CS (J = 5 - 4)), often (but not always) finding the HII region had cleared its immediate vicinity of molecules. Conclusions: Of our sample of nine, the observations of the two clusters expected to have the youngest HII regions (from previous radio observations) are suggestive of having infalling motions in the H29α emission, which could be indicative of late stage accretion onto the stars despite the presence of an HII region. Table A.2 is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130

  18. OBSERVATIONS OF Mg II ABSORPTION NEAR z ∼ 1 GALAXIES SELECTED FROM THE DEEP2 REDSHIFT SURVEY

    International Nuclear Information System (INIS)

    Lovegrove, Elizabeth; Simcoe, Robert A.

    2011-01-01

    We study the frequency of Mg II absorption in the outer halos of galaxies at z = 0.6-1.4 (with median z = 0.87), using new spectra obtained of 10 background quasars with galaxy impact parameters of b r = 0.15-1.0 A, though not all absorbers correlate with DEEP galaxies. We find five unique absorbers within Δv = 500 km s -1 and b r > 1.0 A, consistent with other samples of galaxy-selected Mg II systems. We speculate that Mg II systems with 0.3 r r are more likely to reflect the more recent star-forming history of their associated galaxies.

  19. Metal-poor dwarf galaxies in the SIGRID galaxy sample. I. H II region observations and chemical abundances

    International Nuclear Information System (INIS)

    Nicholls, David C.; Dopita, Michael A.; Sutherland, Ralph S.; Jerjen, Helmut; Kewley, Lisa J.; Basurah, Hassan

    2014-01-01

    In this paper we present the results of observations of 17 H II regions in thirteen galaxies from the SIGRID sample of isolated gas-rich irregular dwarf galaxies. The spectra of all but one of the galaxies exhibit the auroral [O III] 4363 Å line, from which we calculate the electron temperature, T e , and gas-phase oxygen abundance. Five of the objects are blue compact dwarf galaxies, of which four have not previously been analyzed spectroscopically. We include one unusual galaxy which exhibits no evidence of the [N II] λλ 6548,6584 Å lines, suggesting a particularly low metallicity (< Z ☉ /30). We compare the electron temperature based abundances with those derived using eight of the new strong-line diagnostics presented by Dopita et al. Using a method derived from first principles for calculating total oxygen abundance, we show that the discrepancy between the T e -based and strong-line gas-phase abundances have now been reduced to within ∼0.07 dex. The chemical abundances are consistent with what is expected from the luminosity-metallicity relation. We derive estimates of the electron densities and find them to be between ∼5 and ∼100 cm –3 . We find no evidence for a nitrogen plateau for objects in this sample with metallicities 0.5 > Z ☉ > 0.15.

  20. Metal-poor dwarf galaxies in the SIGRID galaxy sample. I. H II region observations and chemical abundances

    Energy Technology Data Exchange (ETDEWEB)

    Nicholls, David C.; Dopita, Michael A.; Sutherland, Ralph S.; Jerjen, Helmut; Kewley, Lisa J. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston ACT 2611 (Australia); Basurah, Hassan, E-mail: David.Nicholls@anu.edu.au [Astronomy Department, King Abdulaziz University, P.O. Box 80203 Jeddah (Saudi Arabia)

    2014-05-10

    In this paper we present the results of observations of 17 H II regions in thirteen galaxies from the SIGRID sample of isolated gas-rich irregular dwarf galaxies. The spectra of all but one of the galaxies exhibit the auroral [O III] 4363 Å line, from which we calculate the electron temperature, T{sub e} , and gas-phase oxygen abundance. Five of the objects are blue compact dwarf galaxies, of which four have not previously been analyzed spectroscopically. We include one unusual galaxy which exhibits no evidence of the [N II] λλ 6548,6584 Å lines, suggesting a particularly low metallicity (< Z {sub ☉}/30). We compare the electron temperature based abundances with those derived using eight of the new strong-line diagnostics presented by Dopita et al. Using a method derived from first principles for calculating total oxygen abundance, we show that the discrepancy between the T{sub e} -based and strong-line gas-phase abundances have now been reduced to within ∼0.07 dex. The chemical abundances are consistent with what is expected from the luminosity-metallicity relation. We derive estimates of the electron densities and find them to be between ∼5 and ∼100 cm{sup –3}. We find no evidence for a nitrogen plateau for objects in this sample with metallicities 0.5 > Z {sub ☉} > 0.15.

  1. A Young Star Cluster in the Leo a Galaxy

    Directory of Open Access Journals (Sweden)

    Stonkutė R.

    2015-09-01

    Full Text Available We report a serendipitous discovery of a star cluster in the dwarf irregular galaxy Leo A. Young age (~28 Myr and low mass (~510 M⊙ estimates are based on the isochrone fit assuming a metallicity derived for HII regions (Z = 0.0007. The color-magnitude diagrams of the stars, located in and around the cluster area, and the results of aperture photometry of the cluster itself are presented.

  2. Search for [C II] emission in z = 6.5-11 star-forming galaxies

    Energy Technology Data Exchange (ETDEWEB)

    González-López, Jorge; Infante, Leopoldo [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago (Chile); Riechers, Dominik A., E-mail: jgonzal@astro.puc.cl, E-mail: linfante@astro.puc.cl [Astronomy Department, Cornell University 220 Space Sciences Building, Ithaca, NY 14853 (United States); and others

    2014-04-01

    We present the search for the [C II] emission line in three z > 6.5 Lyα emitters (LAEs) and one J-dropout galaxy using the Combined Array for Research in Millimeter-wave Astronomy and the Plateau de Bure Interferometer. We observed three bright z ∼ 6.5-7 LAEs discovered in the Subaru Deep Field (SDF) and the multiple imaged lensed z ∼ 11 galaxy candidate found behind the galaxy cluster MACSJ0647.7+7015. For the LAEs IOK-1 (z = 6.965), SDF J132415.7+273058 (z = 6.541), and SDF J132408.3+271543 (z = 6.554) we find upper limits for the [C II] line luminosity of <2.05, <4.52, and <10.56 × 10{sup 8} L {sub ☉}, respectively. We find upper limits to the far-IR (FIR) luminosity of the galaxies using a spectral energy distribution template of the local galaxy NGC 6946 and taking into account the effects of the cosmic microwave background on the millimeter observations. For IOK-1, SDF J132415.7+273058, and SDF J132408.3+271543 we find upper limits for the FIR luminosity of <2.33, 3.79, and 7.72 × 10{sup 11} L {sub ☉}, respectively. For the lensed galaxy MACS0647-JD, one of the highest-redshift galaxy candidates to date with z{sub ph}=10.7{sub −0.4}{sup +0.6}, we put an upper limit in the [C II] emission of <1.36 × 10{sup 8} × (μ/15){sup –1} L {sub ☉} and an upper limit in the FIR luminosity of <6.1 × 10{sup 10} × (μ/15){sup –1} L {sub ☉} (where μ is the magnification factor). We explore the different conditions relevant for the search for [C II] emission in high-redshift galaxies as well as the difficulties for future observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Cerro Chajnantor Atacama Telescope (CCAT).

  3. STAR CLUSTER COMPLEXES AND THE HOST GALAXY IN THREE H II GALAXIES: Mrk 36, UM 408, AND UM 461

    Energy Technology Data Exchange (ETDEWEB)

    Lagos, P. [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Telles, E. [Observatorio Nacional, Rua Jose Cristino, 77, Rio de Janeiro 20921-400 (Brazil); Nigoche-Netro, A. [Instituto de Astrofisica de Andalucia (IAA), Glorieta de la Astronomia s/n, 18008 Granada (Spain); Carrasco, E. R., E-mail: plagos@astro.up.pt, E-mail: etelles@on.br, E-mail: nigoche@iaa.es, E-mail: rcarrasco@gemini.edu [Gemini Observatory/AURA, Southern Operations Center, Casilla 603, La Serena (Chile)

    2011-11-15

    We present a stellar population study of three H II galaxies (Mrk 36, UM 408, and UM 461) based on the analysis of new ground-based high-resolution near-infrared J, H, and K{sub p} broadband and Br{gamma} narrowband images obtained with Gemini/NIRI. We identify and determine the relative ages and masses of the elementary star clusters and/or star cluster complexes of the starburst regions in each of these galaxies by comparing the colors with evolutionary synthesis models that include the contribution of stellar continuum, nebular continuum, and emission lines. We found that the current star cluster formation efficiency in our sample of low-luminosity H II galaxies is {approx}10%. Therefore, most of the recent star formation is not in massive clusters. Our findings seem to indicate that the star formation mode in our sample of galaxies is clumpy, and that these complexes are formed by a few massive star clusters with masses {approx}>10{sup 4} M{sub Sun }. The age distribution of these star cluster complexes shows that the current burst started recently and likely simultaneously over short timescales in their host galaxies, triggered by some internal mechanism. Finally, the fraction of the total cluster mass with respect to the low surface brightness (or host galaxy) mass, considering our complete range in ages, is less than 1%.

  4. Contamination of the Th II line and the age of the Galaxy

    International Nuclear Information System (INIS)

    Lawler, J.E.; Whaling, W.; Grevesse, N.

    1990-01-01

    The age of the Galaxy may be estimated from observations of the ratio of stellar abundances of thorium, which has only one long-lived isotope with a half-life comparable to the suspected age of the Galaxy, and neodymium, a stable element. The Th/Nd abundance ratio in a sample of G-dwarf stars of different ages was derived from the intensities of one Th II and one Nd II absorption line, and indicated a rather young galactic age of 9.6 Gyr. But the Th II line is blended with a Co I line. Here we determine the transition probability of the Co I line by combining radiative lifetime and branching-ratio measurements. We show that the Co I contribution cannot be neglected in deriving Th/Nd ratios. By comparing our results with predictions based on models of galactic chemical evolution, we suggest a revised age of the Galaxy of 15-20 Gyr. (author)

  5. Tidal disruption of dwarf spheroidal galaxies: the strange case of Crater II

    Science.gov (United States)

    Sanders, Jason L.; Evans, N. W.; Dehnen, W.

    2018-05-01

    Dwarf spheroidal galaxies of the Local Group obey a relationship between the line-of-sight velocity dispersion and half-light radius, although there are a number of dwarfs that lie beneath this relation with suppressed velocity dispersion. The most discrepant of these (in the Milky Way) is the `feeble giant' Crater II. Using analytic arguments supported by controlled numerical simulations of tidally-stripped flattened two-component dwarf galaxies, we investigate interpretations of Crater II within standard galaxy formation theory. Heavy tidal disruption is necessary to explain the velocity-dispersion suppression which is plausible if the proper motion of Crater II is (μα*, μδ) = ( - 0.21 ± 0.09, -0.24 ± 0.09)mas yr-1. Furthermore, we demonstrate that the velocity dispersion of tidally-disrupted systems is solely a function of the total mass loss even for weakly-embedded and flattened systems. The half-light radius evolution depends more sensitively on orbital phase and the properties of the dark matter profile. The half-light radius of weakly-embedded cusped systems rapidly decreases producing some tension with the Crater II observations. This tension is alleviated by cored dark matter profiles, in which the half-light radius can grow after tidal disruption. The evolution of flattened galaxies is characterised by two competing effects: tidal shocking makes the central regions rounder whilst tidal distortion produces a prolate tidally-locked outer envelope. After ˜70% of the central mass is lost, tidal distortion becomes the dominant effect and the shape of the central regions of the galaxy tends to a universal prolate shape irrespective of the initial shape.

  6. Rotation in [C II]-emitting gas in two galaxies at a redshift of 6.8

    Science.gov (United States)

    Smit, Renske; Bouwens, Rychard J.; Carniani, Stefano; Oesch, Pascal A.; Labbé, Ivo; Illingworth, Garth D.; van der Werf, Paul; Bradley, Larry D.; Gonzalez, Valentino; Hodge, Jacqueline A.; Holwerda, Benne W.; Maiolino, Roberto; Zheng, Wei

    2018-01-01

    The earliest galaxies are thought to have emerged during the first billion years of cosmic history, initiating the ionization of the neutral hydrogen that pervaded the Universe at this time. Studying this ‘epoch of reionization’ involves looking for the spectral signatures of ancient galaxies that are, owing to the expansion of the Universe, now very distant from Earth and therefore exhibit large redshifts. However, finding these spectral fingerprints is challenging. One spectral characteristic of ancient and distant galaxies is strong hydrogen-emission lines (known as Lyman-α lines), but the neutral intergalactic medium that was present early in the epoch of reionization scatters such Lyman-α photons. Another potential spectral identifier is the line at wavelength 157.4 micrometres of the singly ionized state of carbon (the [C II] λ = 157.74 μm line), which signifies cooling gas and is expected to have been bright in the early Universe. However, so far Lyman-α-emitting galaxies from the epoch of reionization have demonstrated much fainter [C II] luminosities than would be expected from local scaling relations, and searches for the [C II] line in sources without Lyman-α emission but with photometric redshifts greater than 6 (corresponding to the first billion years of the Universe) have been unsuccessful. Here we identify [C II] λ = 157.74 μm emission from two sources that we selected as high-redshift candidates on the basis of near-infrared photometry; we confirm that these sources are two galaxies at redshifts of z = 6.8540 ± 0.0003 and z = 6.8076 ± 0.0002. Notably, the luminosity of the [C II] line from these galaxies is higher than that found previously in star-forming galaxies with redshifts greater than 6.5. The luminous and extended [C II] lines reveal clear velocity gradients that, if interpreted as rotation, would indicate that these galaxies have similar dynamic properties to the turbulent yet rotation

  7. Chemical evolution of two-component galaxies. II

    International Nuclear Information System (INIS)

    Caimmi, R.

    1978-01-01

    In order to confirm and refine the results obtained in a previous paper the chemical evolution of two-component (spheroid + disk) galaxies is derived rejecting the instantaneous recycling approximation, by means of numerical computations, accounting for (i) the collapse phase of the gas, assumed to be uniform in density and composition, and (ii) a birth-rate stellar function. Computations are performed relatively to the solar neighbourhood and to model galaxies which closely resemble the real morphological sequence: in both cases, numerical results are compared with analytical ones. The numerical models of this paper constitute a first-order approximation, while higher order approximations could be made by rejecting the hypothesis of uniform density and composition, and making use of detailed dynamical models. (Auth.)

  8. Triangulum II: Possibly a Very Dense Ultra-faint Dwarf Galaxy

    Science.gov (United States)

    Kirby, Evan N.; Cohen, Judith G.; Simon, Joshua D.; Guhathakurta, Puragra

    2015-11-01

    Laevens et al. recently discovered Triangulum II (Tri II), a satellite of the Milky Way. Its Galactocentric distance is 36 kpc, and its luminosity is only 450 {L}⊙ . Using Keck/DEIMOS, we measured the radial velocities of six member stars within 1.‧2 of the center of Tri II, and we found a velocity dispersion of {σ }v={5.1}-1.4+4.0 {km} {{{s}}}-1. We also measured the metallicities of three stars and found a range of 0.8 dex in [Fe/H]. The velocity and metallicity dispersions identify Tri II as a dark matter-dominated galaxy. The galaxy is moving very quickly toward the Galactic center ({v}{{GSR}}=-262 {km} {{{s}}}-1). Although it might be in the process of being tidally disrupted as it approaches pericenter, there is no strong evidence for disruption in our data set. The ellipticity is low, and the mean velocity, =-382.1+/- 2.9 {km} {{{s}}}-1, rules out an association with the Triangulum-Andromeda substructure or the Pan-Andromeda Archaeological Survey stellar stream. If Tri II is in dynamical equilibrium, then it would have a mass-to-light ratio of {3600}-2100+3500 {M}⊙ {L}⊙ -1, the highest of any non-disrupting galaxy (those for which dynamical mass estimates are reliable). The density within the 3D half-light radius would be {4.8}-3.5+8.1 {M}⊙ {{{pc}}}-3, even higher than Segue 1. Hence, Tri II is an excellent candidate for the indirect detection of dark matter annihilation. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  9. Further candidates of supermassive stars in other galaxies

    International Nuclear Information System (INIS)

    Schmidt-Kaler, Th.; Feitzinger, J.V.

    1984-01-01

    To look for other supermassive stars in other galaxies means to answer the question: what is the spectroscopic and morphological signature of such objects. The interpretation of WR sources found in other supergiant HII complexes depends basically on our picture of 30 Dor and in particular of R136a. The authors have undertaken a search of possible sites of such supermassive stars on the basis of the morphology of 30 Dor and NGC 604. (Auth.)

  10. X-ray heating and ionization of broad-emission-line regions in QSO's and active galaxies

    International Nuclear Information System (INIS)

    Weisheit, J.C.; Shields, G.A.; Tarter, C.B.

    1980-07-01

    Absorption of x-rays deep within the broad-line emitting clouds in QSO's and the nuclei of active galaxies creates extensive zones of warm (T approx. 10 4 K), partially ionized N/sub e//N approx. 0.1) gas. Because Lyman alpha photons are trapped in these regions, the x-ray energy is efficiently channeled into Balmer lines collisionally excited from the n = 2 level. The HI regions plus the HII regions created by ultraviolet photons illuminating the surfaces of the clouds give rise to integrated Lα/Hα line emission ratios between 1 and 2. Enhanced MgII line emission from the HI regions gives rise to integrated MgII/Hα ratios near 0.5. The OI line lambda 8446 is efficiently pumped by trapped Hα photons and in the x-ray heated zone an intensity ratio I (lambda 8446)/I(Hα) approx. < 0.1 is calculated. All of these computed ratios now are in agreement with observations

  11. Probing the Galactic Structure of the Milky Way with H II Regions

    Science.gov (United States)

    Red, Wesley Alexander; Wenger, Trey V.; Balser, Dana; Anderson, Loren; Bania, Thomas

    2018-01-01

    Mapping the structure of the Milky Way is challenging since we reside within the Galactic disk and distances are difficult to determine. Elemental abundances provide important constraints on theories of the formation and evolution of the Milky Way. HII regions are the brightest objects in the Galaxy at radio wavelengths and are detected across the entire Galactic disk. We use the Jansky Very Large Array (VLA) to observe the radio recombination line (RRL) and continuum emission of 120 Galactic HII regions located across the Galactic disk. In thermal equilibrium, metal abundances are expected to set the nebular electron temperature with high abundances producing low temperatures. We derive the metallicity of HII regions using an empirical relation between an HII region's radio recombination line-to-continuum ratio and nebular metallicity. Here we focus on a subset of 20 HII regions from our sample that have been well studied with the Green Bank Telescope (GBT) to test our data reduction pipeline and analysis methods. Our goal is to expand this study to the Southern skies with the Australia Telescope Compact Array and create a metallicity map of the entire Galactic disk.

  12. Abundance gradients in disc galaxies and chemical evolution models

    International Nuclear Information System (INIS)

    Diaz, A.I.

    1989-01-01

    The present state of abundance gradients and chemical evolution models of spiral galaxies is reviewed. An up to date compilation of abundance data in the literature concerning HII regions over galactic discs is presented. From these data Oxygen and Nitrogen radial gradients are computed. The slope of the Oxygen gradient is shown to have a break at a radius between 1.5 and 1.75 times the value of the effective radius of the disc, i.e. the radius containing half of the light of the disc. The gradient is steeper in the central parts of the disc and becomes flatter in the outer parts. N/O gradients are shown to be rather different from galaxy to galaxy and only a weak trend of N/O with O/H is found. The existing chemical evolution models for spiral galaxies are reviewed with special emphasis in the interpretation of numerical models having a large number of parameters. (author)

  13. Aperture synthesis observations of recombination lines from compact HII regions

    International Nuclear Information System (INIS)

    Gorkom, J.H. van.

    1980-01-01

    This thesis describes a continuation of early attempts to attain a high spectral dynamic range in general and to study recombination lines from compact HII regions in particular. These observations are made with the WSRT, until recently, the only instrument with sufficient angular resolution and sensitivity to provide at 6 cm detailed line maps of compact HII regions. An investigation into the spectral stability of the WSRT is described. Chromatic errors were found and their effects on maps are shown. These errors were found in the 80 channel filter spectrometer which was still in use at that time. The advent of the digital line backend (DLB) improved the dynamic range by an order of magnitude. An experiment is described which was partially aimed at testing the spectral stability of the DLB. It concerns a search for HI emission from the high velocity system of NGC 1275. Recombination line observations of the compact components in five giant HII regions are presented. The author discusses the radiative transfer problem in recombination lines and shows that non-LTE effects and pressure broadening can be of importance in compact HII regions. Observations obtained with the DLB are also presented. Because of the much better instrumental quality and improved insight into calibration procedures, mapping the H110α emission of DR21 and both the H110α and H166α emission of W3 was succeeded. (Auth.)

  14. Optical Observations of M81 Galaxy Group in Narrow Band [SII] and H_alpha Filters: Holmberg IX

    Directory of Open Access Journals (Sweden)

    Arbutina, B.

    2009-12-01

    Full Text Available We present observations of the nearby tidal dwarf galaxy Holmberg IX in M81 galaxy group in narrow band [SII] and H$alpha$ filters, carried out in March and November 2008 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for resident supernova remnants (identified as sources with enhanced [SII] emission relative to their H$alpha$ emission in this galaxy yielded no sources of this kind, besides M&H 10-11 or HoIX X-1. Nevertheless, we found a number of objects with significant H$alpha$ emission that probably represent uncatalogued HII regions.

  15. A two-point diagnostic for the H II galaxy Hubble diagram

    Science.gov (United States)

    Leaf, Kyle; Melia, Fulvio

    2018-03-01

    A previous analysis of starburst-dominated H II galaxies and H II regions has demonstrated a statistically significant preference for the Friedmann-Robertson-Walker cosmology with zero active mass, known as the Rh = ct universe, over Λcold dark matter (ΛCDM) and its related dark-matter parametrizations. In this paper, we employ a two-point diagnostic with these data to present a complementary statistical comparison of Rh = ct with Planck ΛCDM. Our two-point diagnostic compares, in a pairwise fashion, the difference between the distance modulus measured at two redshifts with that predicted by each cosmology. Our results support the conclusion drawn by a previous comparative analysis demonstrating that Rh = ct is statistically preferred over Planck ΛCDM. But we also find that the reported errors in the H II measurements may not be purely Gaussian, perhaps due to a partial contamination by non-Gaussian systematic effects. The use of H II galaxies and H II regions as standard candles may be improved even further with a better handling of the systematics in these sources.

  16. Star bursts and giant HII regions

    International Nuclear Information System (INIS)

    Pagel, B.E.J.

    1990-01-01

    Massive star formation bursts occur in a variety of galactic environments and can temporarily dominate the light output of a galaxy even when a relatively small proportion of its mass is involved. Inferences about their ages, the IMF and its dependence on chemical composition are still somewhat wobbly owing to an excess of unknowns, but certain things can be deduced from emission spectra of associated H II regions when due regard is paid to the effects of chemical composition and ionization parameter: In particular, largest ionization parameters and effective temperatures of exciting stars, at any given oxygen abundance, are anti-correlated with the abundance, and the second effect suggests an increasing proportion of more massive stars at lower abundances, although this is not yet satisfactorily quantified. A new blue compact galaxies could be very young, but it is equally possible that there is an older population of low surface brightness. Some giant H II regions may be self-polluted with nitrogen and helium due to winds from massive stars in the associated burst. (orig.)

  17. CHEMICAL DIVERSITY IN THE ULTRA-FAINT DWARF GALAXY TUCANA II

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Alexander P.; Frebel, Anna; Ezzeddine, Rana [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Casey, Andrew R., E-mail: alexji@mit.edu [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)

    2016-11-20

    We present the first detailed chemical abundance study of the ultra-faint dwarf galaxy Tucana II, based on high-resolution Magellan/MIKE spectra of four red giant stars. The metallicities of these stars range from [Fe/H] = −3.2 to −2.6, and all stars are low in neutron-capture abundances ([Sr/Fe] and [Ba/Fe] < −1). However, a number of anomalous chemical signatures are present. One star is relatively metal-rich ([Fe/H] = −2.6) and shows [Na, α , Sc/Fe] < 0, suggesting an extended star formation history with contributions from AGB stars and SNe Ia. Two stars with [Fe/H] < −3 are mildly carbon-enhanced ([C/Fe] ∼ 0.7) and may be consistent with enrichment by faint supernovae, if such supernovae can produce neutron-capture elements. A fourth star with [Fe/H] = −3 is carbon-normal, and exhibits distinct light element abundance ratios from the carbon-enhanced stars. This carbon-normal star implies that at least two distinct nucleosynthesis sources, both possibly associated with Population III stars, contributed to the early chemical enrichment of this galaxy. Despite its very low luminosity, Tucana II shows a diversity of chemical signatures that preclude it from being a simple “one-shot” first galaxy yet still provide a window into star and galaxy formation in the early universe.

  18. CHEMICAL DIVERSITY IN THE ULTRA-FAINT DWARF GALAXY TUCANA II

    International Nuclear Information System (INIS)

    Ji, Alexander P.; Frebel, Anna; Ezzeddine, Rana; Casey, Andrew R.

    2016-01-01

    We present the first detailed chemical abundance study of the ultra-faint dwarf galaxy Tucana II, based on high-resolution Magellan/MIKE spectra of four red giant stars. The metallicities of these stars range from [Fe/H] = −3.2 to −2.6, and all stars are low in neutron-capture abundances ([Sr/Fe] and [Ba/Fe] < −1). However, a number of anomalous chemical signatures are present. One star is relatively metal-rich ([Fe/H] = −2.6) and shows [Na, α , Sc/Fe] < 0, suggesting an extended star formation history with contributions from AGB stars and SNe Ia. Two stars with [Fe/H] < −3 are mildly carbon-enhanced ([C/Fe] ∼ 0.7) and may be consistent with enrichment by faint supernovae, if such supernovae can produce neutron-capture elements. A fourth star with [Fe/H] = −3 is carbon-normal, and exhibits distinct light element abundance ratios from the carbon-enhanced stars. This carbon-normal star implies that at least two distinct nucleosynthesis sources, both possibly associated with Population III stars, contributed to the early chemical enrichment of this galaxy. Despite its very low luminosity, Tucana II shows a diversity of chemical signatures that preclude it from being a simple “one-shot” first galaxy yet still provide a window into star and galaxy formation in the early universe.

  19. Rotational Modulation and Activity Cycles at Rotational Extremes: 25 yrs of NURO Photometry for HII 1883

    Science.gov (United States)

    Milingo, Jackie; Saar, Steven; Marschall, Laurence

    2018-01-01

    We present a 25 yr compilation of V-band differential photometry for the Pleiades K dwarf HII 1883 (V660 Tau). HII 1883 has a rotational period of ~ 0.24 d and displays significant rotational modulation due to non-uniform surface brightness or "starspots". Preliminary work yields a cycle period of ~ 9 yrs and rotational shear (ΔP_rot/) considerably less than solar. HII 1883 is one of the fastest rotating single stars with a known cycle. With additional data available we compare newly determined P_cyc and ΔP_rot/ values with those of other stars, putting HII 1883 into the broader context of dynamo properties in single cool dwarfs.

  20. Chemical Abundances of New Member Stars in the Tucana II Dwarf Galaxy

    Science.gov (United States)

    Chiti, Anirudh; Frebel, Anna; Ji, Alexander P.; Jerjen, Helmut; Kim, Dongwon; Norris, John E.

    2018-04-01

    We present chemical abundance measurements for seven stars with metallicities ranging from Fe/H] = ‑3.3 to [Fe/H] = ‑2.4 in the Tucana II ultra-faint dwarf galaxy (UFD), based on high-resolution spectra obtained with the MIKE spectrograph on the 6.5 m Magellan-Clay Telescope. For three stars, we present detailed chemical abundances for the first time. Of those, two stars are newly discovered members of Tucana II and were selected as probable members from deep narrowband photometry of the Tucana II UFD taken with the SkyMapper telescope. This result demonstrates the potential for photometrically identifying members of dwarf galaxy systems based on chemical composition. One new star was selected from the membership catalog of Walker et al. The other four stars in our sample have been reanalyzed, following additional observations. Overall, six stars have chemical abundances that are characteristic of the UFD stellar population. The seventh star shows chemical abundances that are discrepant from the other Tucana II members and an atypical, higher strontium abundance than what is expected for typical UFD stars. While unlikely, its strontium abundance raises the possibility that it may be a foreground metal-poor halo star with the same systemic velocity as Tucana II. If we were to exclude this star, Tucana II would satisfy the criteria to be a surviving first galaxy. Otherwise, this star implies that Tucana II has likely experienced somewhat extended chemical evolution. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  1. Condições físicas em galáxias HII

    Science.gov (United States)

    Kehrig, C.; Telles, E.; Cuisinier, F.

    2003-08-01

    Galáxias HII são galáxias anãs de baixa luminosidade que apresentam alta taxa de formação estelar. Seus espectros são dominados por intensas linhas de emissão devido à fotoionização pela presença de um grande número de estrelas do tipo O e B. Nós apresentamos um catálogo espectrofotométrico de 111 galáxias HII observadas no telescópio 1.52m do ESO com o espectrógrafo Boller & Chivens. Determinamos propriedades estatísticas da amostra e derivamos condições físicas (temperatura eletrônica, densidade eletrônica) e abundâncias químicas. Para algumas galáxias, fomos também capazes de resolver espacialmente regiões de formação estelar individuais e determinar propriedades espectroscópicas para estas regiões separadamente, o que nos permitiu avaliar as flutuações das condições físico-químicas dentro das galáxias HII. Em particular, vimos que apesar das galáxias HII apresentarem formação estelar espalhada ao longo do corpo da galáxia, são objetos quimicamente homogêneos. A fim de estudar a evolução temporal dos objetos durante o tempo de vida das estrelas ionizantes construimos também alguns diagramas relacionando razões de linhas de emissão com a largura equivalente de Hb (EW(Hb)). Para interpretar tais diagramas utilizamos modelos de fotoionização para populações estelares integradas. Concluímos que as galáxias HII não correspondem a simples idéia de um burst instantâneo envolvido por um gás opaco aos fótons ionizantes e com densidade constante. As relações observadas entre razões de linhas e EW(Hb) podem ser melhor compreendidas se as galáxias HII apresentarem populações estelares mais velhas, que contribuem para o contínuo óptico observado.

  2. The Taxonomy of Blue Amorphous Galaxies. II. Structure and Evolution

    Science.gov (United States)

    Marlowe, Amanda T.; Meurer, Gerhardt R.; Heckman, Timothy M.

    1999-09-01

    Dwarf galaxies play an important role in our understanding of galaxy formation and evolution, and starbursts are believed to affect the structure and evolution of dwarf galaxies strongly. We have therefore embarked on a systematic study of 12 of the nearest dwarf galaxies thought to be undergoing bursts of star formation. These were selected primarily by their morphological type (blue ``amorphous'' galaxies). We show that these blue amorphous galaxies are not physically distinguishable from dwarfs selected as starbursting by other methods, such as blue compact dwarfs (BCDs) and H II galaxies. All these classes exhibit surface brightness profiles that are exponential in the outer regions (r>~1.5re) but often have a predominantly central blue excess, suggesting a young burst in an older, redder galaxy. Typically, the starbursting ``cores'' are young (~107-108 yr) events compared to the older (~109-1010 yr) underlying galaxy (the ``envelope''). The ratio of the core to envelope in blue light ranges from essentially zero to about 2. These starbursts are therefore modest events involving only a few percent of the stellar mass. The envelopes have surface brightnesses that are much higher than typical dwarf irregular (dI) galaxies, so it is unlikely that there is a straightforward evolutionary relation between typical dIs and dwarf starburst galaxies. Instead we suggest that amorphous galaxies may repeatedly cycle through starburst and quiescent phases, corresponding to the galaxies with strong and weak/absent cores, respectively. Once amorphous galaxies use up the available gas (either through star formation or galactic winds) so that star formation is shut off, the faded remnants would strongly resemble dwarf elliptical galaxies. However, in the current cosmological epoch, this is evidently a slow process that is the aftermath of a series of many weak, recurring bursts. Present-day dE's must have experienced more rapid and intense evolution than this in the distant past.

  3. Large-scale correlations in gas traced by Mg II absorbers around low-mass galaxies

    Science.gov (United States)

    Kauffmann, Guinevere

    2018-03-01

    The physical origin of the large-scale conformity in the colours and specific star formation rates of isolated low-mass central galaxies and their neighbours on scales in excess of 1 Mpc is still under debate. One possible scenario is that gas is heated over large scales by feedback from active galactic nuclei (AGNs), leading to coherent modulation of cooling and star formation between well-separated galaxies. In this Letter, the metal line absorption catalogue of Zhu & Ménard is used to probe gas out to large projected radii around a sample of a million galaxies with stellar masses ˜1010M⊙ and photometric redshifts in the range 0.4 Survey imaging data. This galaxy sample covers an effective volume of 2.2 Gpc3. A statistically significant excess of Mg II absorbers is present around the red-low-mass galaxies compared to their blue counterparts out to projected radii of 10 Mpc. In addition, the equivalent width distribution function of Mg II absorbers around low-mass galaxies is shown to be strongly affected by the presence of a nearby (Rp < 2 Mpc) radio-loud AGNs out to projected radii of 5 Mpc.

  4. A radio catalog of Galactic HII regions for applications from decimeter to millimeter wavelengths

    Science.gov (United States)

    Paladini, R.; Burigana, C.; Davies, R. D.; Maino, D.; Bersanelli, M.; Cappellini, B.; Platania, P.; Smoot, G.

    2003-01-01

    By collecting the information from 24 previously published lists and catalogs, we produce a comprehensive catalog (Master Catalog) of 1442 Galactic HII regions. For each object, we quote the original fluxes and diameters as well as the available information on radio line velocities, line widths and line temperatures and the errors on these quantitities. References to the original works are also reported. By exploiting all these data we produce a Synthetic Catalog of fluxes and diameters (with corresponding errors) at 2.7 GHz. This choice is motivated by the extensive, although not complete, information available at this frequency, widely spread among many different catalogs, and by its relevance for both detailed studies on Galactic HII regions and the extrapolation up to millimetric wavelengths. The catalog can be used for detailed studies of Galactic HII regions and, by extrapolation, for investigations of HII regions up to millimetric wavelengths. In particular, we discuss the study of the effects of microwave emission from HII regions on the new generation of Cosmic Microwave Background (CMB) experiments. We present simulations of the detection of HII regions in the PLANCK high resolution CMB survey, and briefly analize some of the typical applications of our catalog to the evaluation of CMB anisotropy experiments such as calibration, beam reconstruction and straylight effects. The Master Catalog and the Synthetic Catalog are available via ftp at: cdsarc.u-strasbg.fr. This work is related to PLANCK-LFI activities. The Master Catalog and the Synthetic Catalog are only available in electronic form via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/213

  5. Stellar population in star formation regions of galaxies

    Science.gov (United States)

    Gusev, Alexander S.; Shimanovskaya, Elena V.; Shatsky, Nikolai I.; Sakhibov, Firouz; Piskunov, Anatoly E.; Kharchenko, Nina V.

    2018-05-01

    We developed techniques for searching young unresolved star groupings (clusters, associations, and their complexes) and of estimating their physical parameters. Our study is based on spectroscopic, spectrophotometric, and UBVRI photometric observations of 19 spiral galaxies. In the studied galaxies, we found 1510 objects younger than 10 Myr and present their catalogue. Having combined photometric and spectroscopic data, we derived extinctions, chemical abundances, sizes, ages, and masses of these groupings. We discuss separately the specific cases, when the gas extinction does not agree with the interstellar one. We assume that this is due to spatial offset of Hii clouds with respect to the related stellar population.We developed a method to estimate age of stellar population of the studied complexes using their morphology and the relation with associated H emission region. In result we obtained the estimates of chemical abundances for 80, masses for 63, and ages for 57 young objects observed in seven galaxies.

  6. Spectrophotometric observations of very low ionization HII regions in the LMC

    International Nuclear Information System (INIS)

    Pena, M.; Ruiz, M.T.; Rubio, M.

    1987-01-01

    Optical spectrophotometric observations of 17 very low ionization HII regions of the LMC are reported. Physical conditions and chemical composition of these objects are derived from the emission line intensities. The average chemical abundances obtained are: log O/H=8.49+-0.08, log N/H=6.91+-0.07 and log S/H=6.89+-0.10. We do not find evidence of any composition gradient in the LMC. The HII regions in the vicinity of the detected molecular cloud complexes show higher nebular reddening. (Author)

  7. MUSE sneaks a peek at extreme ram-pressure events. III. Tomography of UGC 6697, a massive galaxy falling into Abell 1367

    Science.gov (United States)

    Consolandi, G.; Gavazzi, G.; Fossati, M.; Fumagalli, M.; Boselli, A.; Yagi, M.; Yoshida, M.

    2017-10-01

    We present the MUSE observations of UGC 6697, a giant (M∗ ≈ 1010M⊙) spiral galaxy infalling in the nearby cluster Abell 1367. During its high-velocity transit through the intracluster medium (ICM), the hydrodynamical interactions with the ICM produce a ≈ 100 kpc tail of ionized gas that we map with a mosaic of five MUSE pointings up to 60 kpc from the galaxy. CGCG 97087N, a small companion that lies at few arcminutes in projection from UGC 6697, is also showing signs of the hydrodynamic action of the ICM of the cluster. Along the whole extent of the tail, we detect diffuse Hα emission, and to a lesser extent, Hβ, [OIII]λ5007, and [OI]λ6300. By comparing the kinematics and distribution of gas and stars (as traced by the CaII triplet) for both galaxies, we separate the ionized gas, as traced by the Hα line, into a component that is still bound to the galaxy and a component that is stripped. We find that the bound component shows a low-velocity dispersion and line ratios consistent with photoionization by hot stars. The stripped gas is more turbulent, with velocity dispersions up to ≳100 km s-1, and is excited by shocks, as traced by high values of [OI]/Hα and [NII]/Hα ratio. In the tail of UGC 6697, we identify numerous bright compact knots with line ratios typical of HII regions. These are distributed along the only streams of stripped gas that retain low-velocity dispersions (≲35 km s-1). Despite being in the stripped gas, their physical properties are not different from normal HII regions in galactic disks. We find evidence of a past fast encounter between the two galaxies in the form of a double tail emerging from CGCG 97087N that connects with UGC 6697. This encounter might have increased the efficiency of the stripping process, leaving the stellar distribution and kinematics unaltered. The composite data cube is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http

  8. The Extended Northern ROSAT Galaxy Cluster Survey (NORAS II). I. Survey Construction and First Results

    International Nuclear Information System (INIS)

    Böhringer, Hans; Chon, Gayoung; Trümper, Joachim; Retzlaff, Jörg; Meisenheimer, Klaus; Schartel, Norbert

    2017-01-01

    As the largest, clearly defined building blocks of our universe, galaxy clusters are interesting astrophysical laboratories and important probes for cosmology. X-ray surveys for galaxy clusters provide one of the best ways to characterize the population of galaxy clusters. We provide a description of the construction of the NORAS II galaxy cluster survey based on X-ray data from the northern part of the ROSAT All-Sky Survey. NORAS II extends the NORAS survey down to a flux limit of 1.8 × 10 −12 erg s −1 cm −2 (0.1–2.4 keV), increasing the sample size by about a factor of two. The NORAS II cluster survey now reaches the same quality and depth as its counterpart, the southern REFLEX II survey, allowing us to combine the two complementary surveys. The paper provides information on the determination of the cluster X-ray parameters, the identification process of the X-ray sources, the statistics of the survey, and the construction of the survey selection function, which we provide in numerical format. Currently NORAS II contains 860 clusters with a median redshift of z  = 0.102. We provide a number of statistical functions, including the log N –log S and the X-ray luminosity function and compare these to the results from the complementary REFLEX II survey. Using the NORAS II sample to constrain the cosmological parameters, σ 8 and Ω m , yields results perfectly consistent with those of REFLEX II. Overall, the results show that the two hemisphere samples, NORAS II and REFLEX II, can be combined without problems into an all-sky sample, just excluding the zone of avoidance.

  9. The Extended Northern ROSAT Galaxy Cluster Survey (NORAS II). I. Survey Construction and First Results

    Energy Technology Data Exchange (ETDEWEB)

    Böhringer, Hans; Chon, Gayoung; Trümper, Joachim [Max-Planck-Institut für Extraterrestrische Physik, D-85748 Garching (Germany); Retzlaff, Jörg [ESO, D-85748 Garching (Germany); Meisenheimer, Klaus [Max-Planck-Institut für Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Schartel, Norbert [ESAC, Camino Bajo del Castillo, Villanueva de la Cañada, E-28692 Madrid (Spain)

    2017-05-01

    As the largest, clearly defined building blocks of our universe, galaxy clusters are interesting astrophysical laboratories and important probes for cosmology. X-ray surveys for galaxy clusters provide one of the best ways to characterize the population of galaxy clusters. We provide a description of the construction of the NORAS II galaxy cluster survey based on X-ray data from the northern part of the ROSAT All-Sky Survey. NORAS II extends the NORAS survey down to a flux limit of 1.8 × 10{sup −12} erg s{sup −1} cm{sup −2} (0.1–2.4 keV), increasing the sample size by about a factor of two. The NORAS II cluster survey now reaches the same quality and depth as its counterpart, the southern REFLEX II survey, allowing us to combine the two complementary surveys. The paper provides information on the determination of the cluster X-ray parameters, the identification process of the X-ray sources, the statistics of the survey, and the construction of the survey selection function, which we provide in numerical format. Currently NORAS II contains 860 clusters with a median redshift of z  = 0.102. We provide a number of statistical functions, including the log N –log S and the X-ray luminosity function and compare these to the results from the complementary REFLEX II survey. Using the NORAS II sample to constrain the cosmological parameters, σ {sub 8} and Ω{sub m}, yields results perfectly consistent with those of REFLEX II. Overall, the results show that the two hemisphere samples, NORAS II and REFLEX II, can be combined without problems into an all-sky sample, just excluding the zone of avoidance.

  10. GMRT and VLA Observations at 49 cm and 20 cm of the HII Region ...

    Indian Academy of Sciences (India)

    2007-03-08

    Mar 8, 2007 ... as arising in the diffuse HII region and find that the best fitting model has an electron density ... these observations was to image and determine the physical properties of the diffuse. HII region from which ... At the time of our observations, noise switching to measure the system temperature was not available.

  11. Shape Analysis of HII Regions - I. Statistical Clustering

    Science.gov (United States)

    Campbell-White, Justyn; Froebrich, Dirk; Kume, Alfred

    2018-04-01

    We present here our shape analysis method for a sample of 76 Galactic HII regions from MAGPIS 1.4 GHz data. The main goal is to determine whether physical properties and initial conditions of massive star cluster formation is linked to the shape of the regions. We outline a systematic procedure for extracting region shapes and perform hierarchical clustering on the shape data. We identified six groups that categorise HII regions by common morphologies. We confirmed the validity of these groupings by bootstrap re-sampling and the ordinance technique multidimensional scaling. We then investigated associations between physical parameters and the assigned groups. Location is mostly independent of group, with a small preference for regions of similar longitudes to share common morphologies. The shapes are homogeneously distributed across Galactocentric distance and latitude. One group contains regions that are all younger than 0.5 Myr and ionised by low- to intermediate-mass sources. Those in another group are all driven by intermediate- to high-mass sources. One group was distinctly separated from the other five and contained regions at the surface brightness detection limit for the survey. We find that our hierarchical procedure is most sensitive to the spatial sampling resolution used, which is determined for each region from its distance. We discuss how these errors can be further quantified and reduced in future work by utilising synthetic observations from numerical simulations of HII regions. We also outline how this shape analysis has further applications to other diffuse astronomical objects.

  12. Observations of the Galaxy NGC 3077 in the Narrow-Band [S II] and Hα Filters

    Directory of Open Access Journals (Sweden)

    Andjelić M.

    2011-09-01

    Full Text Available We present observations of the H I tidal arm near a dwarf galaxy NGC 3077 (member of the M81 galaxy group in the narrow-band [S II] and Hα filters. Observations were carried out in 2011 March with the 2 m RCC telescope at the NAO Rozhen, Bulgaria. Our search for possible supernova remnant candidates (identified as sources with enhanced [S II] emission relative to their Hα emission in this region yielded no sources of this kind. Nevertheless, we found a number of objects with significant Hα emission that probably represent uncatalogued, low brightness H II regions.

  13. Mg II ABSORPTION CHARACTERISTICS OF A VOLUME-LIMITED SAMPLE OF GALAXIES AT z ∼ 0.1

    International Nuclear Information System (INIS)

    Barton, Elizabeth J.; Cooke, Jeff

    2009-01-01

    We present an initial survey of Mg II absorption characteristics in the halos of a carefully constructed, volume-limited subsample of galaxies embedded in the spectroscopic part of the Sloan Digital Sky Survey (SDSS). We observed quasars near sightlines to 20 low-redshift (z ∼ 0.1), luminous (M r + 5log h ≤-20.5) galaxies in SDSS DR4 and DR6 with the LRIS-B spectrograph on the Keck I telescope. The primary systematic criteria for the targeted galaxies are a redshift z ∼> 0.1 and the presence of an appropriate bright background quasar within a projected 75 h -1 kpc of its center, although we preferentially sample galaxies with lower impact parameters and slightly more star formation within this range. Of the observed systems, six exhibit strong (W eq (2796) ≥ 0.3 A) Mg II absorption at the galaxy's redshift, six systems have upper limits which preclude strong Mg II absorption, while the remaining observations rule out very strong (W eq (2796) ≥ 1-2 A) absorption. The absorbers fall at higher impact parameters than many non-absorber sightlines, indicating a covering fraction f c ∼ -1 kpc (f c ∼ 0.25). The data are consistent with a possible dependence of covering fraction and/or absorption halo size on the environment or star-forming properties of the central galaxy.

  14. Modelling of Lyman-alpha emitting galaxies and ionized bubbles at the epoch of reionization

    Science.gov (United States)

    Yajima, Hidenobu; Sugimura, Kazuyuki; Hasegawa, Kenji

    2018-04-01

    Understanding {Ly{α }} emitting galaxies (LAEs) can be a key to reveal cosmic reionization and galaxy formation in the early Universe. Based on halo merger trees and {Ly{α }} radiation transfer calculations, we model redshift evolution of LAEs and their observational properties at z ≥ 6. We consider ionized bubbles associated with individual LAEs and IGM transmission of {Ly{α }} photons. We find that {Ly{α }} luminosity tightly correlates with halo mass and stellar mass, while the relation with star formation rate has a large dispersion. Comparing our models with the observed luminosity function by Konno et al., we suggest that LAEs at z ˜ 7 have galactic wind of V_out ≳ 100 km s^{-1} and HI column density of N_HI ≳ 10^{20} cm^{-2}. Number density of bright LAEs rapidly decreases as redshift increases, due to both lower star formation rate and smaller HII bubbles. Our model predicts future wide deep surveys with next generation telescopes, such as JWST, E-ELT and TMT, can detect LAEs at z ˜ 10 with a number density of n_LAE ˜ a few × 10^{-6} Mpc^{-3} for the flux sensitivity of 10^{-18} erg cm^{-2} s^{-1}. When giant HII bubbles are formed by clustering LAEs, the number density of observable LAEs can increase by a factor of few. By combining these surveys with future 21-cm observations, it could be possible to detect both LAEs with L_{Lyα }≳ 10^{42} erg s^{-1} and their associated giant HII bubbles with the size ≳ 250 kpc at z ˜ 10.

  15. THE LIFETIME AND POWERS OF FR IIs IN GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Antognini, Joe; Bird, Jonathan; Martini, Paul

    2012-01-01

    We have identified and studied a sample of 151 FR IIs found in brightest cluster galaxies (BCGs) in the MaxBCG cluster catalog with data from FIRST and NVSS. We have compared the radio luminosities and projected lengths of these FR IIs to the projected length distribution of a range of mock catalogs generated by an FR II model and estimate the FR II lifetime to be 1.9 × 10 8 yr. The uncertainty in the lifetime calculation is a factor of two, primarily due to uncertainties in the intracluster medium (ICM) density and the FR II axial ratio. We furthermore measure the jet power distribution of FR IIs in BCGs and find that it is well described by a log-normal distribution with a median power of 1.1 × 10 37 W and a coefficient of variation of 2.2. These jet powers are nearly linearly related to the observed luminosities, and this relation is steeper than many other estimates, although it is dependent on the jet model. We investigate correlations between FR II and cluster properties and find that galaxy luminosity is correlated with jet power. This implies that jet power is also correlated with black hole mass, as the stellar luminosity of a BCG should be a good proxy for its spheroid mass and therefore the black hole mass. Jet power, however, is not correlated with cluster richness, nor is FR II lifetime strongly correlated with any cluster properties. We calculate the enthalpy of the lobes to examine the impact of the FR IIs on the ICM and find that heating due to adiabatic expansion is too small to offset radiative cooling by a factor of at least six. In contrast, the jet power is approximately an order of magnitude larger than required to counteract cooling. We conclude that if feedback from FR IIs offsets cooling of the ICM, then heating must be primarily due to another mechanism associated with FR II expansion.

  16. THE LIFETIME AND POWERS OF FR IIs IN GALAXY CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Antognini, Joe; Bird, Jonathan; Martini, Paul, E-mail: antognini@astronomy.ohio-state.edu, E-mail: bird@astronomy.ohio-state.edu, E-mail: martini@astronomy.ohio-state.edu [Department of Astronomy, Ohio State University, 140 W 18th Avenue, Columbus, OH 43210 (United States)

    2012-09-10

    We have identified and studied a sample of 151 FR IIs found in brightest cluster galaxies (BCGs) in the MaxBCG cluster catalog with data from FIRST and NVSS. We have compared the radio luminosities and projected lengths of these FR IIs to the projected length distribution of a range of mock catalogs generated by an FR II model and estimate the FR II lifetime to be 1.9 Multiplication-Sign 10{sup 8} yr. The uncertainty in the lifetime calculation is a factor of two, primarily due to uncertainties in the intracluster medium (ICM) density and the FR II axial ratio. We furthermore measure the jet power distribution of FR IIs in BCGs and find that it is well described by a log-normal distribution with a median power of 1.1 Multiplication-Sign 10{sup 37} W and a coefficient of variation of 2.2. These jet powers are nearly linearly related to the observed luminosities, and this relation is steeper than many other estimates, although it is dependent on the jet model. We investigate correlations between FR II and cluster properties and find that galaxy luminosity is correlated with jet power. This implies that jet power is also correlated with black hole mass, as the stellar luminosity of a BCG should be a good proxy for its spheroid mass and therefore the black hole mass. Jet power, however, is not correlated with cluster richness, nor is FR II lifetime strongly correlated with any cluster properties. We calculate the enthalpy of the lobes to examine the impact of the FR IIs on the ICM and find that heating due to adiabatic expansion is too small to offset radiative cooling by a factor of at least six. In contrast, the jet power is approximately an order of magnitude larger than required to counteract cooling. We conclude that if feedback from FR IIs offsets cooling of the ICM, then heating must be primarily due to another mechanism associated with FR II expansion.

  17. Estudo da região HII galática NGC 2579

    Science.gov (United States)

    Riffel, R.; Copetti, M. V. F.

    2003-08-01

    Desde a descoberta dos gradientes de abundância química em galáxias espirais, as regiões HII galáticas têm sido intensamente estudadas com o objetivo de determinar a forma do gradiente de abundância química na Via-Láctea. Entretanto, a forma do gradiente galático continua controversa e existem muitas regiões HII que continuam inexploradas. A região HII galática NGC 2579 é um objeto que aparece em imagens Ha, como uma pequena mancha brilhante de aproximadamente 2 segundos de arco de diâmetro a 20 segundos de arco ao leste de RCW 20, sendo NGC 2579 muitas vezes confundida com esta última. Apesar de seu alto brilho superficial, NGC 2579 é um objeto pouco estudado provavelmente por problemas de identificação deste objeto. Como parte de um projeto de reavaliação dos gradientes de abundância química das regiões HII na Via-Láctea, estamos realizando um estudo extensivo das propriedades físicas básicas como temperatura eletrônica, densidade eletrônica e composição química da região HII galática NGC 2579. Analisamos dados espectrofotométricos de fenda longa na faixa de 3700Å a 7750Å obtidos com o telescópio de 1.52 m do ESO, Chile, em 2002. Determinamos a temperatura eletrônica usando a razão entre as linhas do [OIII] (l4959+l5007/l4363) e a densidade eletrônica pela razão entre as linhas do [SII] (l6716/l6731). As abundâncias químicas do O, N, Cl, S, Ne e He foram determinadas. Realizamos um estudo de imagens fotométricas nas bandas UBVRI obtidas em 2000 no observatório astronômico San Pedro Mártir, México, para identificar e classificar as estrelas ionizantes de NGC 2579 e determinar a distância deste objeto.

  18. Why is observable radio recombination line emission from galactic HII regions always close to LTE

    International Nuclear Information System (INIS)

    Shaver, P.A.

    1980-01-01

    There is no evidence for significant deviations from LTE in single-dish observations of radio recombination line emission from galactic HII regions. This is in agreement with the known properties of HII regions, particularly their density variations and limited range of excitation parameters; the optimum configuration for strong observable non-LTE effects, low electron density and high emission measure, simply does not exist in galactic HII regions, and the observed lines are emitted under near-LTE conditions. Models of the Orion Nebulae and NGC 6604 are presented which fit all available data and show only weak stimulated emission. It is concluded that reliable electron temperatures can indeed be obtained from straightforward analysis of appropriate radio recombination lines. (orig.)

  19. A characteristic oxygen abundance gradient in galaxy disks unveiled with CALIFA

    Czech Academy of Sciences Publication Activity Database

    Sanchez, S.F.; Rosales-Ortega, F.F.; Iglesias-Paramo, J.; Molla, M.; Barrera-Ballesteros, J.; Marino, R.A.; Pérez, E.; Sanchez-Blazquez, P.; Gonzalez Delgado, R.; Jungwiert, Bruno

    2014-01-01

    Roč. 563, March (2014), A49/1-A49/25 ISSN 0004-6361 Grant - others:Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100031241; Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100031201 Program:M Institutional support: RVO:67985815 Keywords : HII regions * galaxies * ISM: abundances Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

  20. THE TYPE II SUPERNOVA RATE IN z {approx} 0.1 GALAXY CLUSTERS FROM THE MULTI-EPOCH NEARBY CLUSTER SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Graham, M. L.; Sand, D. J. [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Santa Barbara, CA 93117 (United States); Bildfell, C. J.; Pritchet, C. J. [Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, STN CSC, Victoria BC V8W 3P6 (Canada); Zaritsky, D.; Just, D. W.; Herbert-Fort, S. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Hoekstra, H. [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden (Netherlands); Sivanandam, S. [Dunlap Institute for Astronomy and Astrophysics, 50 St. George St., Toronto, ON M5S 3H4 (Canada); Foley, R. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-07-01

    We present seven spectroscopically confirmed Type II cluster supernovae (SNe II) discovered in the Multi-Epoch Nearby Cluster Survey, a supernova survey targeting 57 low-redshift 0.05 < z < 0.15 galaxy clusters with the Canada-France-Hawaii Telescope. We find the rate of Type II supernovae within R{sub 200} of z {approx} 0.1 galaxy clusters to be 0.026{sup +0.085}{sub -0.018}(stat){sup +0.003}{sub -0.001}(sys) SNuM. Surprisingly, one SN II is in a red-sequence host galaxy that shows no clear evidence of recent star formation (SF). This is unambiguous evidence in support of ongoing, low-level SF in at least some cluster elliptical galaxies, and illustrates that galaxies that appear to be quiescent cannot be assumed to host only Type Ia SNe. Based on this single SN II we make the first measurement of the SN II rate in red-sequence galaxies, and find it to be 0.007{sup +0.014}{sub -0.007}(stat){sup +0.009}{sub -0.001}(sys) SNuM. We also make the first derivation of cluster specific star formation rates (sSFR) from cluster SN II rates. We find that for all galaxy types the sSFR is 5.1{sup +15.8}{sub -3.1}(stat) {+-} 0.9(sys) M{sub Sun} yr{sup -1} (10{sup 12} M{sub Sun }){sup -1}, and for red-sequence galaxies only it is 2.0{sup +4.2}{sub -0.9}(stat) {+-} 0.4(sys) M{sub Sun} yr{sup -1} (10{sup 12} M{sub Sun }){sup -1}. These values agree with SFRs measured from infrared and ultraviolet photometry, and H{alpha} emission from optical spectroscopy. Additionally, we use the SFR derived from our SNII rate to show that although a small fraction of cluster Type Ia SNe may originate in the young stellar population and experience a short delay time, these results do not preclude the use of cluster SN Ia rates to derive the late-time delay time distribution for SNe Ia.

  1. HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: BOÖTES II

    International Nuclear Information System (INIS)

    Ji, Alexander P.; Frebel, Anna; Simon, Joshua D.; Geha, Marla

    2016-01-01

    We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Boötes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Its variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced α-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs

  2. Optical and near-IR study of LMC HII region N11AB

    International Nuclear Information System (INIS)

    Lee, M.G.

    1990-01-01

    N11 (DEM 34), complex HII region located about 4 degrees from the center of the LMC bar, is a very interesting giant interstellar shell. It has a complicated structure and motion. It is located on the edge of an HI concentration. This is the progress report of the study of its two components, A and B at the optical and near-IR wavelengths to investigate stars, dust and ionized gas associated with them. N11A is a compact high-excitation blob and N11B is a bright HII region in this complex, which embeds OB association Lucke-Hodge 10

  3. Evolutionary behaviour of AGN: Investigations on BL Lac objects and Seyfert II galaxies

    Science.gov (United States)

    Beckmann, V.

    2000-12-01

    The evolution and nature of AGN is still one of the enigmatic questions in astrophysics. While large and complete Quasar samples are available, special classes of AGN, like BL Lac objects and Seyfert II galaxies, are still rare objects. In this work I present two new AGN samples. The first one is the HRX-BL Lac survey, resulting in a sample of X-ray selected BL Lac objects. This sample results from 223 BL Lac candidates based on a correlation of X-ray sources with radio sources. The identification of this sample is 98% complete. 77 objects have been identified as BL Lac objects and form the HRX-BL Lac complete sample, the largest homogeneous sample of BL Lac objects existing today. For this sample, redshifts are now known for 62 objects (81 %). In total I present 101 BL Lac objects in the enlarged HRX-BL Lac survey, for which redshift information is available for 84 objects. During the HRX-BL Lac survey I found several objects of special interest. 1ES 1517+656 turned out to be the brightest known BL Lac object in the universe. 1ES 0927+500 could be the first BL Lac object with a line detected in the X-ray region. RX J1211+2242 is probably the the counterpart of the up to now unidentified gamma-ray source 3EG J1212+2304. Additionally I present seven candidates for ultra high frequency peaked BL Lac objects. RX J1054+3855 and RX J1153+3517 are rare high redshift X-ray bright QSO or accreting binary systems with huge magnetic fields. For the BL Lac objects I suggest an unified scenario in which giant elliptical galaxies, formed by merging events of spiral galaxies at z > 2, start as powerful, radio dominated BL Lacs. As the jet gets less powerful, the BL Lacs start to get more X-ray dominated, showing less total luminosities (for z definition to objects with a calcium break up to 40%, but do not support for the HBL the idea of allowing emission lines in the spectra of BL Lac galaxies. A way to find high redshift BL Lac objects might be the identification of faint X

  4. Direct Measurement of Dust Attenuation in z approx. 1.5 Star-Forming Galaxies from 3D-HST: Implications for Dust Geometry and Star Formation Rates

    Science.gov (United States)

    Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B; Conroy, Charlie; Schreiber, Natascha M. Foerster; Franx, Marijn; Fumagalli, Mattia; Lundren, Britt; Momcheva, Ivelina; Nelson, Erica J.; hide

    2013-01-01

    The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust towards star-forming regions (measured using Balmer decrements) and the integrated dust properties (derived by comparing spectral energy distributions [SEDs] with stellar population and dust models) for a statistically significant sample of distant galaxies. We select a sample of 163 galaxies between 1.36 or = 5 and measure Balmer decrements from stacked spectra. First, we stack spectra in bins of integrated stellar dust attenuation, and find that there is extra dust extinction towards star-forming regions (AV,HII is 1.81 times the integrated AV, star), though slightly lower than found for low-redshift starburst galaxies. Next, we stack spectra in bins of specific star formation rate (log sSFR), star formation rate (log SFR), and stellar mass (logM*). We find that on average AV,HII increases with SFR and mass, but decreases with increasing sSFR. The amount of extra extinction also decreases with increasing sSFR and decreasing stellar mass. Our results are consistent with the two-phase dust model - in which galaxies contain both a diffuse and a stellar birth cloud dust component - as the extra extinction will increase once older stars outside the star-forming regions become more dominant. Finally, using our Balmer decrements we derive dust-corrected H(alpha) SFRs, and find evidence that SED fitting produces incorrect SFRs if very rapidly declining SFHs are included in the explored parameter space. Subject headings: dust, extinction- galaxies: evolution- galaxies: high-redshift

  5. A Foreground Masking Strategy for [C II] Intensity Mapping Experiments Using Galaxies Selected by Stellar Mass and Redshift

    Science.gov (United States)

    Sun, G.; Moncelsi, L.; Viero, M. P.; Silva, M. B.; Bock, J.; Bradford, C. M.; Chang, T.-C.; Cheng, Y.-T.; Cooray, A. R.; Crites, A.; Hailey-Dunsheath, S.; Uzgil, B.; Hunacek, J. R.; Zemcov, M.

    2018-04-01

    Intensity mapping provides a unique means to probe the epoch of reionization (EoR), when the neutral intergalactic medium was ionized by energetic photons emitted from the first galaxies. The [C II] 158 μm fine-structure line is typically one of the brightest emission lines of star-forming galaxies and thus a promising tracer of the global EoR star formation activity. However, [C II] intensity maps at 6 ≲ z ≲ 8 are contaminated by interloping CO rotational line emission (3 ≤ J upp ≤ 6) from lower-redshift galaxies. Here we present a strategy to remove the foreground contamination in upcoming [C II] intensity mapping experiments, guided by a model of CO emission from foreground galaxies. The model is based on empirical measurements of the mean and scatter of the total infrared luminosities of galaxies at z {10}8 {M}ȯ selected in the K-band from the COSMOS/UltraVISTA survey, which can be converted to CO line strengths. For a mock field of the Tomographic Ionized-carbon Mapping Experiment, we find that masking out the “voxels” (spectral–spatial elements) containing foreground galaxies identified using an optimized CO flux threshold results in a z-dependent criterion {m}{{K}}AB}≲ 22 (or {M}* ≳ {10}9 {M}ȯ ) at z cost of a moderate ≲8% loss of total survey volume.

  6. Young stellar population and star formation history ofW4 HII region/Cluster Complex

    Science.gov (United States)

    Panwar, Neelam

    2018-04-01

    The HII region/cluster complex has been a subject of numerous investigations to study the feedback effect of massive stars on their surroundings. Massive stars not only alter the morphology of the parental molecular clouds, but also influence star formation, circumstellar disks and the mass function of low-mass stars in their vicinity. However, most of the studies of low-mass stellar content of the HII regions are limited only to the nearby regions. We study the star formation in the W4 HII region using deep optical observations obtained with the archival data from Canada - France - Hawaii Telescope, Two-Micron All Sky Survey, Spitzer, Herschel and Chandra. We investigate the spatial distribution of young stellar objects in the region, their association with the remnant molecular clouds, and search for the clustering to establish the sites of recent star formation. Our analysis suggests that the influence of massive stars on circumstellar disks is significant only to thei! r immediate neighborhood. The spatial correlation of the young stars with the distribution of gas and dust of the complex indicate that the clusters would have formed in a large filamentary cloud. The observing facilities at the 3.6-m Devasthal Optical Telescope (DOT), providing high-resolution spectral and imaging capabilities, will fulfill the major objectives in the study of HII regions.

  7. Herschel observations in the ultracompact HII region Mon R2 : Water in dense photon-dominated regions (PDRs)

    NARCIS (Netherlands)

    Fuente, A.; Berne, O.; Cernicharo, J.; Rizzo, J. R.; Gonzalez-Garcia, M.; Goicoechea, J. R.; Pilleri, P.; Ossenkopf, V.; Gerin, M.; Guesten, R.; Akyilmaz, M.; Benz, A. O.; Boulanger, F.; Bruderer, S.; Dedes, C.; France, K.; Garcia-Burillo, S.; Harris, A.; Joblin, C.; Klein, T.; Kramer, C.; Le Petit, F.; Lord, S. D.; Martin, P. G.; Martin-Pintado, J.; Mookerjea, B.; Neufeld, D. A.; Okada, Y.; Pety, J.; Phillips, T. G.; Roellig, M.; Simon, R.; Stutzki, J.; van der Tak, F.; Teyssier, D.; Usero, A.; Yorke, H.; Schuster, K.; Melchior, M.; Lorenzani, A.; Szczerba, R.; Fich, M.; McCoey, C.; Pearson, J.; Dieleman, P.

    2010-01-01

    Context. Monoceros R2, at a distance of 830 pc, is the only ultracompact Hii region (UC Hii) where the photon-dominated region (PDR) between the ionized gas and the molecular cloud can be resolved with Herschel. Therefore, it is an excellent laboratory to study the chemistry in extreme PDRs (G0 >

  8. ALMA imaging of gas and dust in a galaxy protocluster at redshift 5.3: [C II] emission in 'typical' galaxies and dusty starbursts ≈1 billion years after the big bang

    Energy Technology Data Exchange (ETDEWEB)

    Riechers, Dominik A. [Department of Astronomy, Cornell University, 220 Space Sciences Building, Ithaca, NY 14853 (United States); Carilli, Christopher L. [National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801 (United States); Capak, Peter L.; Yan, Lin [Spitzer Science Center, California Institute of Technology, MC 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Scoville, Nicholas Z. [Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Smolčić, Vernesa [University of Zagreb, Physics Department, Bijenička cesta 32, 10002 Zagreb (Croatia); Schinnerer, Eva [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Yun, Min [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Cox, Pierre [ALMA Santiago Central Office, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Bertoldi, Frank; Karim, Alexander, E-mail: dr@astro.cornell.edu [Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, Bonn, D-53121 (Germany)

    2014-12-01

    We report interferometric imaging of [C II]({sup 2} P {sub 3/2}→{sup 2} P {sub 1/2}) and OH({sup 2}Π{sub 1/2} J = 3/2→1/2) emission toward the center of the galaxy protocluster associated with the z = 5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [C II], OH, and rest-frame 157.7 μm continuum emission toward the SMG. The [C II]({sup 2} P {sub 3/2}→{sup 2} P {sub 1/2}) emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 × 10{sup 10} M {sub ☉}, and a star formation rate (SFR) surface density of Σ{sub SFR} = 530 M {sub ☉} yr{sup –1} kpc{sup –2}. This suggests that AzTEC-3 forms stars at Σ{sub SFR} approaching the Eddington limit for radiation pressure supported disks. We find that the OH emission is slightly blueshifted relative to the [C II] line, which may indicate a molecular outflow associated with the peak phase of the starburst. We also detect and dynamically resolve [C II]({sup 2} P {sub 3/2}→{sup 2} P {sub 1/2}) emission over a scale of 7.5 kpc toward a triplet of Lyman-break galaxies with moderate UV-based SFRs in the protocluster at ∼95 kpc projected distance from the SMG. These galaxies are not detected in the continuum, suggesting far-infrared SFRs of <18-54 M {sub ☉} yr{sup –1}, consistent with a UV-based estimate of 22 M {sub ☉} yr{sup –1}. The spectral energy distribution of these galaxies is inconsistent with nearby spiral and starburst galaxies, but resembles those of dwarf galaxies. This is consistent with expectations for young starbursts without significant older stellar populations. This suggests that these galaxies are significantly metal-enriched, but not heavily dust-obscured, 'normal' star-forming galaxies at z > 5, showing that ALMA can detect the interstellar medium in 'typical' galaxies in the very early universe.

  9. The group environment of Seyfert galaxies. II. Spectrophotometry of galaxies in groups

    International Nuclear Information System (INIS)

    Fricke, K.J.; Kollatschny, W.

    1989-01-01

    Medium-resolution spectrophotometric data of 104 galaxies have been obtained. These galaxies are members of 22 loose groups of < 1 Mpc size. Thirteen of these groups contain Seyfert galaxies. In this paper we present calibrated emission-line data and absolute optical spectra of the individual galaxies as well as plates of each group

  10. Detecting metal-poor gas accretion in the star-forming dwarf galaxies UM 461 and Mrk 600

    Science.gov (United States)

    Lagos, P.; Scott, T. C.; Nigoche-Netro, A.; Demarco, R.; Humphrey, A.; Papaderos, P.

    2018-03-01

    Using VIMOS-IFU observations, we study the interstellar medium (ISM) of two star-forming dwarf galaxies, UM 461 and Mrk 600. Our aim was to search for the existence of metallicity inhomogeneities that might arise from infall of nearly pristine gas feeding ongoing localized star-formation. The IFU data allowed us to study the impact of external gas accretion on the chemical evolution as well as the ionised gas kinematics and morphologies of these galaxies. Both systems show signs of morphological distortions, including cometary-like morphologies. We analysed the spatial variation of 12 + log(O/H) abundances within both galaxies using the direct method (Te), the widely applied HII-CHI-mistry code, as well as by employing different standard calibrations. For UM 461 our results show that the ISM is fairly well mixed, at large scales, however we find an off-centre and low-metallicity region with 12 + log(O/H) ISM in our analysed galaxies are consistent with these systems being at different evolutionary stages.

  11. On the lack of correlation between Mg II 2796, 2803 Å and Lyα emission in lensed star-forming galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Rigby, J. R. [Astrophysics Science Division, Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Bayliss, M. B. [Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138 (United States); Gladders, M. D. [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637 (United States); Sharon, K. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Wuyts, E. [Max Plank Institute for Extraterrestrial Physics, Giessenbachstrasse 1, D-85748 Garching (Germany); Dahle, H. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway)

    2014-07-20

    We examine the Mg II 2796, 2803 Å, Lyα, and nebular line emission in five bright star-forming galaxies at 1.66 < z < 1.91 that have been gravitationally lensed by foreground galaxy clusters. All five galaxies show prominent Mg II emission and absorption in a P Cygni profile. We find no correlation between the equivalent widths of Mg II and Lyα emission. The Mg II emission has a broader range of velocities than do the nebular emission line profiles; the Mg II emission is redshifted with respect to systemic by 100-200 km s{sup –1}. When present, Lyα is even more redshifted. The reddest components of Mg II and Lyα emission have tails to 500-600 km s{sup –1}, implying a strong outflow. The lack of correlation in the Mg II and Lyα equivalent widths, the differing velocity profiles, and the high ratios of Mg II to nebular line fluxes together suggest that the bulk of Mg II emission does not ultimately arise as nebular line emission, but may instead be reprocessed stellar continuum emission.

  12. A WIDE AREA SURVEY FOR HIGH-REDSHIFT MASSIVE GALAXIES. II. NEAR-INFRARED SPECTROSCOPY OF BzK-SELECTED MASSIVE STAR-FORMING GALAXIES

    International Nuclear Information System (INIS)

    Onodera, Masato; Daddi, Emanuele; Arimoto, Nobuo; Renzini, Alvio; Kong Xu; Cimatti, Andrea; Broadhurst, Tom; Alexander, Dave M.

    2010-01-01

    Results are presented from near-infrared spectroscopic observations of a sample of BzK-selected, massive star-forming galaxies (sBzKs) at 1.5 < z < 2.3 that were obtained with OHS/CISCO at the Subaru telescope and with SINFONI at the Very Large Telescope. Among the 28 sBzKs observed, Hα emission was detected in 14 objects, and for 11 of them the [N II] λ6583 flux was also measured. Multiwavelength photometry was also used to derive stellar masses and extinction parameters, whereas Hα and [N II] emissions have allowed us to estimate star formation rates (SFRs), metallicities, ionization mechanisms, and dynamical masses. In order to enforce agreement between SFRs from Hα with those derived from rest-frame UV and mid-infrared, additional obscuration for the emission lines (that originate in H II regions) was required compared to the extinction derived from the slope of the UV continuum. We have also derived the stellar mass-metallicity relation, as well as the relation between stellar mass and specific SFR (SSFR), and compared them to the results in other studies. At a given stellar mass, the sBzKs appear to have been already enriched to metallicities close to those of local star-forming galaxies of similar mass. The sBzKs presented here tend to have higher metallicities compared to those of UV-selected galaxies, indicating that near-infrared selected galaxies tend to be a chemically more evolved population. The sBzKs show SSFRs that are systematically higher, by up to ∼2 orders of magnitude, compared to those of local galaxies of the same mass. The empirical correlations between stellar mass and metallicity, and stellar mass and SSFR are then compared with those of evolutionary population synthesis models constructed either with the simple closed-box assumption, or within an infall scenario. Within the assumptions that are built-in such models, it appears that a short timescale for the star formation (≅100 Myr) and large initial gas mass appear to be required

  13. Composition gradients across spiral galaxies II. The stellar mass limit

    International Nuclear Information System (INIS)

    Shields, G.A.; Tinsley, B.M.

    1976-01-01

    The equivalent width of the Hβ emission from H ii regions in spiral galaxies increases with distance from the nucleus. This W (Hβ) gradient is interpreted in terms of a radial gradient in the temperature of the hottest exciting stars. (T/subu/). From Searle's observations of M101, an increase Δ log T/subu/=0.02--0.13 from the intermediate to outermost spiral arms of M101 is inferred. There is also a radial decrease in the metal abundance (Z) across M101, and the T/subu/ gradient is consistent with the prediction of Kahn's recent theory that the upper mass limit for star formation should be smaller in regions of high Z. It is noted also that, even in the absence of changes in the upper mass limit, a T/subu/ gradient is expected because metal-rich stars of given mass have smaller effective temperatures. Several observational and theoretical improvements are needed before firm conclusions can be drawn, but it is clear that the presence of a T/subu/ gradient may lead to several important systematic changes in the interpretation of gradients in the properties of H ii regions across galaxies. A T/subu/ gradient reduces the Z gradient that is inferred from emission-line ratios, and it may help to explain why O ii is strong in the innermost regions where O iii is weak. A T/subu/ gradient may also partly camouflage a helium abundance gradient

  14. Fractal dimension and turbulence in Giant HII Regions

    International Nuclear Information System (INIS)

    Caicedo-Ortiz, H E; Santiago-Cortes, E; López-Bonilla, J; er piso, CP 07738, México D.F (Mexico))" data-affiliation=" (ESFM, Instituto Politécnico Nacional, Edif. 9, 1er piso, CP 07738, México D.F (Mexico))" >Castañeda, H O

    2015-01-01

    We have measured the fractal dimensions of the Giant HII Regions Hubble X and Hubble V in NGC6822 using images obtained with the Hubble's Wide Field Planetary Camera 2 (WFPC2). These measures are associated with the turbulence observed in these regions, which is quantified through the velocity dispersion of emission lines in the visible. Our results suggest low turbulence behaviour

  15. ON THE COMPACT H II GALAXY UM 408 AS SEEN BY GMOS-IFU: PHYSICAL CONDITIONS

    International Nuclear Information System (INIS)

    Lagos, Patricio; Telles, Eduardo; Munoz-Tunon, Casiana; Carrasco, Eleazar R.; Cuisinier, Francois; Tenorio-Tagle, Guillermo

    2009-01-01

    We present Integral Field Unit GMOS-IFU data of the compact H II galaxy UM 408, obtained at the Gemini South telescope, in order to derive the spatial distribution of emission lines and line ratios, kinematics, plasma parameters, and oxygen abundances as well the integrated properties over an area of 3''x4.''4 equivalent with ∼750 pc x 1100 pc located in the central part of the galaxy. The starburst in this area is resolved into two giant regions of about 1.''5 and 1'' (∼375 and ∼250 pc) diameter, respectively and separated 1.5-2'' (∼500 pc). The extinction distribution concentrate its highest values close but not coincident with the maxima of Hα emission around each one of the detected regions. This indicates that the dust has been displaced from the exciting clusters by the action of their stellar winds. The ages of these two regions, estimated using Hβ equivalent widths, suggest that they are coeval events of ∼5 Myr with stellar masses of ∼10 4 M sun . We have also used [O III]/Hβ and [S II]/Hα ratio maps to explore the excitation mechanisms in this galaxy. Comparing the data points with theoretical diagnostic models, we found that all of them are consistent with excitation by photoionization by massive stars. The Hα emission line was used to measure the radial velocity and velocity dispersion. The heliocentric radial velocity shows an apparent systemic motion where the east part of the galaxy is blueshifted, while the west part is redshifted, with a relative motion of ∼10 km s -1 . The velocity dispersion map shows supersonic values typical for extragalactic H II regions. We derived an integrated oxygen abundance of 12+log(O/H) = 7.87 summing over all spaxels in our field of view. An average value of 12+log(O/H) = 7.77 and a difference of Δ(O/H) = 0.47 between the minimum and maximum values (7.58 ± 0.06-8.05 ± 0.04) were found, considering all data points where the oxygen abundance was measured. The spatial distribution of oxygen abundance

  16. Lactobacillus paracasei HII01, xylooligosaccharides, and synbiotics reduce gut disturbance in obese rats.

    Science.gov (United States)

    Thiennimitr, Parameth; Yasom, Sakawdaurn; Tunapong, Wannipa; Chunchai, Titikorn; Wanchai, Keerati; Pongchaidecha, Anchalee; Lungkaphin, Anusorn; Sirilun, Sasithorn; Chaiyasut, Chaiyavat; Chattipakorn, Nipon; Chattipakorn, Siriporn C

    2018-03-20

    The beneficial effects of pro-, pre-, and synbiotics on obesity with insulin resistance have been reported previously. However, the strain-specific effect of probiotics and the combination with various types of prebiotic fiber yield controversial outcomes and limit clinical applications. Our previous study demonstrated that the probiotic Lactobacillus paracasei (L. paracasei) HII01, prebiotic xylooligosaccharide (XOS), and synbiotics share similar efficacy in attenuating cardiac mitochondrial dysfunction in obese-insulin resistant rats. Nonetheless, the roles of HII01 and XOS on gut dysbiosis and gut inflammation under obese-insulin resistant conditions have not yet, to our knowledge, been investigated. Our hypothesis was that pro-, pre-, and synbiotics improve the metabolic parameters in obese-insulin resistant rats by reducing gut dysbiosis and gut inflammation. Male Wistar rats were fed with either a normal or high-fat diet that contained 19.77% and 59.28% energy from fat, respectively, for 12 wk. Then, the high-fat diet rats were fed daily with a 10 8 colony forming unit of the probiotic HII01, 10% prebiotic XOS, and synbiotics for 12 wk. The metabolic parameters, serum lipopolysaccharide levels, fecal Firmicutes/Bacteroidetes ratios, levels of Enterobacteriaceae, Bifidobacteria, and gut proinflammatory cytokine gene expression were quantified. The consumption of probiotic L. paracasei HII01, prebiotic XOS, and synbiotics for 12 wk led to a decrease in metabolic endotoxemia, gut dysbiosis (a reduction in the Firmicutes/Bacteroidetes ratio and Enterobacteriaceae), and gut inflammation in obese-insulin resistant rats. Pro-, pre-, and synbiotics reduced gut dysbiosis and gut inflammation, which lead to improvements in metabolic dysfunction in obese-insulin resistant rats. Copyright © 2018 Elsevier Inc. All rights reserved.

  17. SURFACE BRIGHTNESS PROFILES OF DWARF GALAXIES. II. COLOR TRENDS AND MASS PROFILES

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, Kimberly A. [Penn State Mont Alto, 1 Campus Drive, Mont Alto, PA 17237 (United States); Hunter, Deidre A. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Elmegreen, Bruce G., E-mail: kah259@psu.edu, E-mail: dah@lowell.edu, E-mail: bge@us.ibm.com [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States)

    2016-06-01

    In this second paper of a series, we explore the B  −  V , U  −  B , and FUV−NUV radial color trends from a multi-wavelength sample of 141 dwarf disk galaxies. Like spirals, dwarf galaxies have three types of radial surface brightness profiles: (I) single exponential throughout the observed extent (the minority), (II) down-bending (the majority), and (III) up-bending. We find that the colors of (1) Type I dwarfs generally become redder with increasing radius, unlike spirals which have a blueing trend that flattens beyond ∼1.5 disk scale lengths, (2) Type II dwarfs come in six different “flavors,” one of which mimics the “U” shape of spirals, and (3) Type III dwarfs have a stretched “S” shape where the central colors are flattish, become steeply redder toward the surface brightness break, then remain roughly constant beyond, which is similar to spiral Type III color profiles, but without the central outward bluing. Faint (−9 >  M{sub B}  > −14) Type II dwarfs tend to have continuously red or “U” shaped colors and steeper color slopes than bright (−14 >  M{sub B}  > −19) Type II dwarfs, which additionally have colors that become bluer or remain constant with increasing radius. Sm dwarfs and BCDs tend to have at least some blue and red radial color trend, respectively. Additionally, we determine stellar surface mass density (Σ) profiles and use them to show that the break in Σ generally remains in Type II dwarfs (unlike Type II spirals) but generally disappears in Type III dwarfs (unlike Type III spirals). Moreover, the break in Σ is strong, intermediate, and weak in faint dwarfs, bright dwarfs, and spirals, respectively, indicating that Σ may straighten with increasing galaxy mass. Finally, the average stellar surface mass density at the surface brightness break is roughly 1−2  M {sub ⊙} pc{sup −2} for Type II dwarfs but higher at 5.9  M {sub ⊙} pc{sup −2} or 27  M {sub ⊙} pc{sup −2} for

  18. On The gamma-ray emission from Reticulum II and other dwarf galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, Dan; Linden, Tim

    2015-09-01

    The recent discovery of ten new dwarf galaxy candidates by the Dark Energy Survey (DES) and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) could increase the Fermi Gamma-Ray Space Telescope's sensitivity to annihilating dark matter particles, potentially enabling a definitive test of the dark matter interpretation of the long-standing Galactic Center gamma-ray excess. In this paper, we compare the previous analyses of Fermi data from the directions of the new dwarf candidates (including the relatively nearby Reticulum II) and perform our own analysis, with the goal of establishing the statistical significance of any gamma-ray signal from these sources. We confirm the presence of an excess from Reticulum II, with a spectral shape that is compatible with the Galactic Center signal. The significance of this emission is greater than that observed from 99.84% of randomly chosen high-latitude blank-sky locations, corresponding to a local detection significance of 3.2σ. We caution that any dark matter interpretation of this excess must be validated through observations of additional dwarf spheroidal galaxies, and improved calculations of the relative J-factor of dwarf spheroidal galaxies. We improve upon the standard blank-sky calibration approach through the use of multi-wavelength catalogs, which allow us to avoid regions that are likely to contain unresolved gamma-ray sources.

  19. SDSS-II SUPERNOVA SURVEY: AN ANALYSIS OF THE LARGEST SAMPLE OF TYPE IA SUPERNOVAE AND CORRELATIONS WITH HOST-GALAXY SPECTRAL PROPERTIES

    International Nuclear Information System (INIS)

    Wolf, Rachel C.; Gupta, Ravi R.; Sako, Masao; Fischer, John A.; March, Marisa C.; Fischer, Johanna-Laina; D’Andrea, Chris B.; Smith, Mathew; Kessler, Rick; Scolnic, Daniel M.; Jha, Saurabh W.; Campbell, Heather; Nichol, Robert C.; Olmstead, Matthew D.; Richmond, Michael; Schneider, Donald P.

    2016-01-01

    Using the largest single-survey sample of Type Ia supernovae (SNe Ia) to date, we study the relationship between properties of SNe Ia and those of their host galaxies, focusing primarily on correlations with Hubble residuals (HRs). Our sample consists of 345 photometrically classified or spectroscopically confirmed SNe Ia discovered as part of the SDSS-II Supernova Survey (SDSS-SNS). This analysis utilizes host-galaxy spectroscopy obtained during the SDSS-I/II spectroscopic survey and from an ancillary program on the SDSS-III Baryon Oscillation Spectroscopic Survey that obtained spectra for nearly all host galaxies of SDSS-II SN candidates. In addition, we use photometric host-galaxy properties from the SDSS-SNS data release such as host stellar mass and star formation rate. We confirm the well-known relation between HR and host-galaxy mass and find a 3.6 σ significance of a nonzero linear slope. We also recover correlations between HR and host-galaxy gas-phase metallicity and specific star formation rate as they are reported in the literature. With our large data set, we examine correlations between HR and multiple host-galaxy properties simultaneously and find no evidence of a significant correlation. We also independently analyze our spectroscopically confirmed and photometrically classified SNe Ia and comment on the significance of similar combined data sets for future surveys.

  20. The GAN Exonuclease or the Flap Endonuclease Fen1 and RNase HII Are Necessary for Viability of Thermococcus kodakarensis.

    Science.gov (United States)

    Burkhart, Brett W; Cubonova, Lubomira; Heider, Margaret R; Kelman, Zvi; Reeve, John N; Santangelo, Thomas J

    2017-07-01

    Many aspects of and factors required for DNA replication are conserved across all three domains of life, but there are some significant differences surrounding lagging-strand synthesis. In Archaea , a 5'-to-3' exonuclease, related to both bacterial RecJ and eukaryotic Cdc45, that associates with the replisome specifically through interactions with GINS was identified and designated GAN (for G INS- a ssociated n uclease). Despite the presence of a well-characterized flap endonuclease (Fen1), it was hypothesized that GAN might participate in primer removal during Okazaki fragment maturation, and as a Cdc45 homologue, GAN might also be a structural component of an archaeal CMG (Cdc45, MCM, and GINS) replication complex. We demonstrate here that, individually, either Fen1 or GAN can be deleted, with no discernible effects on viability and growth. However, deletion of both Fen1 and GAN was not possible, consistent with both enzymes catalyzing the same step in primer removal from Okazaki fragments in vivo RNase HII has also been proposed to participate in primer processing during Okazaki fragment maturation. Strains with both Fen1 and RNase HII deleted grew well. GAN activity is therefore sufficient for viability in the absence of both RNase HII and Fen1, but it was not possible to construct a strain with both RNase HII and GAN deleted. Fen1 alone is therefore insufficient for viability in the absence of both RNase HII and GAN. The ability to delete GAN demonstrates that GAN is not required for the activation or stability of the archaeal MCM replicative helicase. IMPORTANCE The mechanisms used to remove primer sequences from Okazaki fragments during lagging-strand DNA replication differ in the biological domains. Bacteria use the exonuclease activity of DNA polymerase I, whereas eukaryotes and archaea encode a flap endonuclease (Fen1) that cleaves displaced primer sequences. RNase HII and the GINS-associated exonuclease GAN have also been hypothesized to assist in primer

  1. Ultrahigh-energy Cosmic Rays from Fanaroff Riley class II radio galaxies

    Science.gov (United States)

    Rachen, Joerg; Biermann, Peter L.

    1992-08-01

    The hot spots of very powerful radio galaxies (Fanaroff Riley class II) are argued to be the sources of the ultrahigh energy component in Cosmic Rays. We present calculations of Cosmic Ray transport in an evolving universe, taking the losses against the microwave background properly into account. As input we use the models for the cosmological radio source evolution derived by radioastronomers (mainly Peacock 1985). The model we adopt for the acceleration in the radio hot spots has been introduced by Biermann and Strittmatter (1987), and Meisenheimer et al. (1989) and is based on first order Fermi theory of particle acceleration at shocks (see, e.g., Drury 1983). As an unknown the actual proportion of energy density in protons enters, which together with structural uncertainties in the hot spots should introduce no more than one order of magnitude in uncertainty: We easily reproduce the observed spectra of high energy cosmic rays. It follows that scattering of charged energetic particles in intergalactic space must be sufficiently small in order to obtain contributions from sources as far away as even the nearest Fanaroff Riley class II radio galaxies. This implies a strong constraint on the turbulent magnetic field in intergalactic space.

  2. Enhanced lipid accumulation and biodiesel production by oleaginous Chlorella protothecoides under a structured heterotrophic-iron (II) induction strategy.

    Science.gov (United States)

    Li, Yuqin; Mu, Jinxiu; Chen, Di; Xu, Hua; Han, Fangxin

    2015-05-01

    A structured heterotrophic-iron (II) induction (HII) strategy was proposed to enhance lipid accumulation in oleaginous Chlorella protothecoides. C. protothecoides subjected to heterotrophic-iron (II) induction achieved a favorable lipid accumulation up to 62 % and a maximum lipid productivity of 820.17 mg/day, representing 2.78-fold and 3.64-fold increase respectively over heterotrophic cultivation alone. HII-induced cells produced significantly elevated levels of 16:0, 18:1(Δ9), and 18:2(Δ9,12) fatty acids (over 90 %). The lipid contents and plant lipid-like fatty acid compositions exhibit the potential of HII-induced C. protothecoides as biodiesel feedstock. Furthermore, 31 altered proteins in HII-induced algal cells were successfully identified. These differentially expressed proteins were assigned into nine molecular function categories, including carbohydrate metabolism, lipid biosynthesis, Calvin cycle, cellular respiration, photosynthesis, energy and transport, protein biosynthesis, regulate and defense, and unclassified. Analysis using the Kyoto encyclopedia of genes and genomes and gene ontology annotation showed that malic enzyme, acyltransferase, and ACP were key metabolic checkpoints found to modulate lipid accumulation in C. protothecoides. The results provided possible applications of HII cultivation strategy in other microalgal species and new possibilities in developing genetic and metabolic engineering microalgae for desirable lipid productivity.

  3. The relation between radio flux density and ionizing ultra-violet flux for HII regions and supernova remnants in the Large Magellanic cloud

    Directory of Open Access Journals (Sweden)

    Filipović M.D.

    2003-01-01

    Full Text Available We present a comparison between the Parkes radio surveys (Filipović et al 1995 and Vacuum Ultra-Violet (VUV surveys (Smith et al. 1987 of the Large Magellanic Clouds (LMC. We have found 72 sources in common in the LMC which are known HII regions (52 and supernova remnants (SNRs (19. Some of these radio sources are associated with two or more UV stellar associations. A comparison of the radio flux densities and ionizing UV flux for HII regions shows a very good correlation, as expected from theory. Many of the Magellanic Clouds (MCs SNRs are embedded in HII regions, so there is also a relation between radio and UV which we attribute to the surrounding HII regions.

  4. ALFALFA DISCOVERY OF THE NEARBY GAS-RICH DWARF GALAXY LEO P. II. OPTICAL IMAGING OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Rhode, Katherine L.; Salzer, John J.; Haurberg, Nathalie C.; Van Sistine, Angela; Young, Michael D. [Department of Astronomy, Indiana University, 727 East Third Street, Bloomington, IN 47405 (United States); Haynes, Martha P.; Giovanelli, Riccardo; Adams, Elizabeth A. K. [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Cannon, John M. [Department of Physics and Astronomy, Macalester College, Saint Paul, MN 55105 (United States); Skillman, Evan D.; McQuinn, Kristen B. W., E-mail: rhode@astro.indiana.edu, E-mail: slaz@astro.indiana.edu, E-mail: riccardo@astro.cornell.edu, E-mail: haynes@astro.cornell.edu, E-mail: betsey@astro.cornell.edu, E-mail: jcannon@macalester.edu, E-mail: skillman@astro.umn.edu, E-mail: kmcquinn@astro.umn.edu [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States)

    2013-06-15

    We present results from ground-based optical imaging of a low-mass dwarf galaxy discovered by the ALFALFA 21 cm H I survey. Broadband (BVR) data obtained with the WIYN 3.5 m telescope at Kitt Peak National Observatory (KPNO) are used to construct color-magnitude diagrams of the galaxy's stellar population down to V{sub o} {approx} 25. We also use narrowband H{alpha} imaging from the KPNO 2.1 m telescope to identify a H II region in the galaxy. We use these data to constrain the distance to the galaxy to be between 1.5 and 2.0 Mpc. This places Leo P within the Local Volume but beyond the Local Group. Its properties are extreme: it is the lowest-mass system known that contains significant amounts of gas and is currently forming stars.

  5. Polar ring galaxies in the Galaxy Zoo

    Science.gov (United States)

    Finkelman, Ido; Funes, José G.; Brosch, Noah

    2012-05-01

    We report observations of 16 candidate polar-ring galaxies (PRGs) identified by the Galaxy Zoo project in the Sloan Digital Sky Survey (SDSS) data base. Deep images of five galaxies are available in the SDSS Stripe82 data base, while to reach similar depth we observed the remaining galaxies with the 1.8-m Vatican Advanced Technology Telescope. We derive integrated magnitudes and u-r colours for the host and ring components and show continuum-subtracted Hα+[N II] images for seven objects. We present a basic morphological and environmental analysis of the galaxies and discuss their properties in comparison with other types of early-type galaxies. Follow-up photometric and spectroscopic observations will allow a kinematic confirmation of the nature of these systems and a more detailed analysis of their stellar populations.

  6. Examining Sites of Recent Star Formation in the Galactic Center: A Closer Look at the Arched Filaments and H HII Regions

    Science.gov (United States)

    Hankins, Matthew; Herter, Terry; Lau, Ryan; Morris, Mark; Mills, Elisabeth

    2018-01-01

    In this dissertation presentation, we analyze mid-infrared imaging of the Arched Filaments and H HII regions in the Galactic center taken with the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST). Examining these regions are of great interest because they provide insights on star formation in the Galactic center and the interactions massive stars have with the ISM. The Arched Filaments are a collection of molecular cloud ridges which are ionized by the nearby Arches star cluster, and give the appearance of large (~25 pc) arch-like structures. The H HII regions are a collection of HII regions just to the west of the Arches cluster (~5-15 pc). The origin of the stars powering the H HII regions is uncertain, as they may have formed in a nearby molecular cloud or could be ejected members of the Arches cluster. FORCAST observations of these regions were used to study the morphology and heating structure of the HII regions, as well as constrain their luminosities.Color-temperature maps of the Arched Filaments created with the FORCAST data reveals fairly uniform dust temperatures (~70-100 K) across the length filaments. The temperature uniformity of the clouds can be explained if they are heated by the Arches cluster but are located at a larger distance from the cluster than they appear. The density of the Arched Filaments clouds was estimated from the FORCAST data and was found to be below the threshold for tidal shearing, indicating that that the clouds will be destroyed by the strong tidal field near the Galactic center. To the west of the Arched Filaments, there is an interesting collection of HII regions, referred to as the H HII regions. These regions are likely heated by massive O/B type stars, and the morphology of the dust emission associated with these objects indicate a mixture of potential in situ formation mechanisms and interlopers. Interestingly, FORCAST imaging of the H HII regions also reveal several compact sources, which may be young

  7. Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Peterson, B. M.

    2005-01-01

    We study the low-contrast Fe II emission blends in the ultraviolet (1250--2200A) and optical (4000--6000A) spectra of the Seyfert 1 galaxy NGC 5548 and show that these features vary in flux and that these variations are correlated with those of the optical continuum. The amplitude of variability ...... are correlated indicates that line fluorescence in a photoionized plasma, rather than collisional excitation, is responsible for the Fe II emission. The iron emission templates are available upon request....

  8. The binary fraction of stars in dwarf galaxies: the case of Leo II

    OpenAIRE

    Spencer, Meghin; Mateo, Mario; Walker, Matthew; Olszewski, Edward; McConnachie, Alan; Kirby, Evan; Koch, Andreas

    2017-01-01

    We combine precision radial velocity data from four different published works of the stars in the Leo II dwarf spheroidal galaxy. This yields a data set that spans 19 years, has 14 different epochs of observation, and contains 372 unique red giant branch stars, 196 of which have repeat observations. Using this multi-epoch data set, we constrain the binary fraction for Leo II. We generate a suite of Monte Carlo simulations that test different binary fractions using Bayesian analysis and determ...

  9. ALMA [N ii] 205 μ m Imaging Spectroscopy of the Interacting Galaxy System BRI 1202-0725 at Redshift 4.7

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Nanyao; Xu, C. Kevin; Zhu, Lei [National Astronomical Observatories, Chinese Academy of Sciences (CAS), Beijing 100012 (China); Zhao, Yinghe [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Díaz-Santos, Tanio [Nucleo de Astronomia de la Facultad de Ingenieria, Universidad Diego Portales, Av. Ejercito Libertador 441, Santiago (Chile); Charmandaris, Vassilis [Department of Physics, University of Crete, GR-71003 Heraklion (Greece); Gao, Yu [Purple Mountain Observatory, CAS, Nanjing 210008 (China); Van der Werf, Paul P. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Privon, George C. [Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Inami, Hanae [Centre de Recherche Astrophysique de Lyon (CRAL), Observatoire de Lyon, CNRS, UMR5574, F-69230, Saint-Genis-Laval (France); Rigopoulou, Dimitra [Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Sanders, David B., E-mail: nanyao.lu@gmail.com [University of Hawaii, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2017-06-20

    We present the results from Atacama Large Millimeter/submillimeter Array imaging in the [N ii] 205 μ m fine-structure line (hereafter [N ii]) and the underlying continuum of BRI 1202-0725, an interacting galaxy system at z = 4.7, consisting of a quasi-stellar object (QSO), a submillimeter galaxy (SMG), and two Ly α emitters, all within ∼25 kpc of the QSO. We detect the QSO and SMG in both [N ii] and continuum. At the ∼1″ (or 6.6 kpc) resolution, both the QSO and SMG are resolved in [N ii], with the de-convolved major axes of ∼9 and ∼14 kpc, respectively. In contrast, their continuum emissions are much more compact and unresolved even at an enhanced resolution of ∼0.″7. The ratio of the [N ii] flux to the existing CO(7−6) flux is used to constrain the dust temperature ( T {sub dust}) for a more accurate determination of the FIR luminosity L {sub FIR}. Our best estimated T {sub dust} equals 43 (±2) K for both galaxies (assuming an emissivity index β = 1.8). The resulting L {sub CO(7−6)}/ L {sub FIR} ratios are statistically consistent with that of local luminous infrared galaxies, confirming that L {sub CO(7−6)} traces the star formation (SF) rate (SFR) in these galaxies. We estimate that the ongoing SF of the QSO (SMG) has an SFR of 5.1 (6.9) × 10{sup 3} M {sub ⊙} yr{sup −1} (±30%) assuming Chabrier initial mass function, takes place within a diameter (at half maximum) of 1.3 (1.5) kpc, and will consume the existing 5 (5) × 10{sup 11} M {sub ⊙} of molecular gas in 10 (7) × 10{sup 7} years.

  10. The H IX galaxy survey - II. H I kinematics of H I eXtreme galaxies

    Science.gov (United States)

    Lutz, K. A.; Kilborn, V. A.; Koribalski, B. S.; Catinella, B.; Józsa, G. I. G.; Wong, O. I.; Stevens, A. R. H.; Obreschkow, D.; Dénes, H.

    2018-05-01

    By analysing a sample of galaxies selected from the H I Parkes All Sky Survey (HIPASS) to contain more than 2.5 times their expected H I content based on their optical properties, we investigate what drives these H I eXtreme (H IX) galaxies to be so H I-rich. We model the H I kinematics with the Tilted Ring Fitting Code TiRiFiC and compare the observed H IX galaxies to a control sample of galaxies from HIPASS as well as simulated galaxies built with the semi-analytic model DARK SAGE. We find that (1) H I discs in H IX galaxies are more likely to be warped and more likely to host H I arms and tails than in the control galaxies, (2) the average H I and average stellar column density of H IX galaxies is comparable to the control sample, (3) H IX galaxies have higher H I and baryonic specific angular momenta than control galaxies, (4) most H IX galaxies live in higher spin haloes than most control galaxies. These results suggest that H IX galaxies are H I-rich because they can support more H I against gravitational instability due to their high specific angular momentum. The majority of the H IX galaxies inherits their high specific angular momentum from their halo. The H I content of H IX galaxies might be further increased by gas-rich minor mergers. This paper is based on data obtained with the Australia Telescope Compact Array through the large program C 2705.

  11. New 20-cm radio-continuum study of the small Magellanic cloud - part III: Compact Hii regions

    Directory of Open Access Journals (Sweden)

    Wong G.F.

    2012-01-01

    Full Text Available We present and discuss a new catalogue of 48 compact Hii regions in the Small Magellanic Cloud (SMC and a newly created deep 1420 MHz (λ=20 cm radio-continuum image of the N19 region located in the southwestern part of the SMC. The new images were created by merging 1420 MHz radiocontinuum archival data from the Australian Telescope Compact Array. The majority of these detected radio compact Hii regions have rather flat spectral indices which indicates, as expected, that the dominant emission mechanism is of thermal nature.

  12. Hydra II: A Faint and Compact Milky Way Dwarf Galaxy Found in the Survey of the Magellanic Stellar History

    OpenAIRE

    Martin, NF; Nidever, DL; Besla, G; Olsen, K; Walker, AR; Vivas, AK; Gruendl, RA; Kaleida, CC; Muñoz, RR; Blum, RD; Saha, A; Conn, BC; Bell, EF; Chu, YH; Cioni, MRL

    2015-01-01

    © 2015. The American Astronomical Society. All rights reserved.We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within the data from the ongoing Survey of the Magellanic Stellar History conducted with the Dark Energy Camera on the Blanco 4 m Telescope. The new satellite is compact (rh = 68 ± 11 pc) and faint (MV = -4.8 ± 0.3), but well within the realm of dwarf galaxies. The stellar distribution of Hydra II in the color-magnitude diagram is well-described by a m...

  13. Gemini NIFS survey of feeding and feedback processes in nearby active galaxies - II. The sample and surface mass density profiles

    Science.gov (United States)

    Riffel, R. A.; Storchi-Bergmann, T.; Riffel, R.; Davies, R.; Bianchin, M.; Diniz, M. R.; Schönell, A. J.; Burtscher, L.; Crenshaw, M.; Fischer, T. C.; Dahmer-Hahn, L. G.; Dametto, N. Z.; Rosario, D.

    2018-02-01

    We present and characterize a sample of 20 nearby Seyfert galaxies selected for having BAT 14-195 keV luminosities LX ≥ 1041.5 erg s-1, redshift z ≤ 0.015, being accessible for observations with the Gemini Near-Infrared Field Spectrograph (NIFS) and showing extended [O III]λ5007 emission. Our goal is to study Active Galactic Nucleus (AGN) feeding and feedback processes from near-infrared integral-field spectra, which include both ionized (H II) and hot molecular (H2) emission. This sample is complemented by other nine Seyfert galaxies previously observed with NIFS. We show that the host galaxy properties (absolute magnitudes MB, MH, central stellar velocity dispersion and axial ratio) show a similar distribution to those of the 69 BAT AGN. For the 20 galaxies already observed, we present surface mass density (Σ) profiles for H II and H2 in their inner ˜500 pc, showing that H II emission presents a steeper radial gradient than H2. This can be attributed to the different excitation mechanisms: ionization by AGN radiation for H II and heating by X-rays for H2. The mean surface mass densities are in the range (0.2 ≤ ΣH II ≤ 35.9) M⊙ pc-2, and (0.2 ≤ ΣH2 ≤ 13.9)× 10-3 M⊙ pc-2, while the ratios between the H II and H2 masses range between ˜200 and 8000. The sample presented here will be used in future papers to map AGN gas excitation and kinematics, providing a census of the mass inflow and outflow rates and power as well as their relation with the AGN luminosity.

  14. Optical emission line spectra of Seyfert galaxies and radio galaxies

    International Nuclear Information System (INIS)

    Osterbrock, D.E.

    1978-01-01

    Many radio galaxies have strong emission lines in their optical spectra, similar to the emission lines in the spectra of Seyfert galaxies. The range of ionization extends from [O I] and [N I] through [Ne V] and [Fe VII] to [Fe X]. The emission-line spectra of radio galaxies divide into two types, narrow-line radio galaxies whose spectra are indistinguishable from Seyfert 2 galaxies, and broad-line radio galaxies whose spectra are similar to Seyfert 1 galaxies. However on the average the broad-line radio galaxies have steeper Balmer decrements, stronger [O III] and weaker Fe II emission than the Seyfert 1 galaxies, though at least one Seyfert 1 galaxy not known to be a radio source has a spectrum very similar to typical broad-line radio galaxies. Intermediate-type Seyfert galaxies exist that show various mixtures of the Seyfert 1 and Seyfert 2 properties, and the narrow-line or Seyfert 2 property seems to be strongly correlated with radio emission. (Auth.)

  15. CO J=2-1 observations toward southern HII regions

    International Nuclear Information System (INIS)

    Martin, R.N.; Ruf, K.; Wilson, T.L.; Zimmermann, P.; Emerson, D.T.

    1983-01-01

    A spectral line receiver system developed at the Max-Planck-Institut fuer Radioastronomie in Bonn was installed on the ESO 3.6-m and 1-m telescopes in July 1981. The cooled mixer front end gave DSB receiver temperatures of 260-600 K at 230 GHz. The spectrometer was a 256 x 1 MHz filterbank. The authors have observed the CO 2-1 transition towards 42 positions corresponding to the brightest southern HII regions. (Auth.)

  16. The Merger History, AGN and Dwarf Galaxies of Hickson Compact Group 59

    Science.gov (United States)

    Konstantopoulos, I. S.; Gallagher, S. C.; Fedotov, K.; Durrell, P. R.; Tzanavaris, P.; Hill, A. R.; Zabludoff, A. I.; Maier, M. L.; Elmegreen, D. M.; Charlton, J. C.; hide

    2011-01-01

    Compact group galaxies often appear unaffected by their unusually dense environment. Closer examination can, however, reveal the subtle, cumulative effects of multiple galaxy interactions. Hickson Compact Group (HCG) 59 is an excellent example of this situation. We present a photometric study of this group in the optical (HST), infrared (Spitzer) and X-ray (Chandra) regimes aimed at characterizing the star formation and nuclear activity in its constituent galaxies and intra-group medium. We associate five dwarf galaxies with the group and update the velocity dispersion, leading to an increase in the dynamical mass of the group of up to a factor of 10 (to 2.8 x 10(exp 13) Stellar Mass), and a subsequent revision of its evolutionary stage. Star formation is proceeding at a level consistent with the morphological types of the four main galaxies, of which two are star-forming and the other two quiescent. Unlike in some other compact groups, star-forming complexes across HCG 59 closely follow mass-radius scaling relations typical of nearby galaxies. In contrast, the ancient globular cluster populations in galaxies HCG 59A and B show intriguing irregularities, and two extragalactic HII regions are found just west of B. We age-date a faint stellar stream in the intra-group medium at approx. 1 Gyr to examine recent interactions. We detect a likely low-luminosity AGN in HCG 59A by its approx. 10(exp 40) erg/s X-ray emission; the active nucleus rather than star formation can account for the UV+IR SED. We discuss the implications of our findings in the context of galaxy evolution in dense environments.

  17. Confusion-limited galaxy fields. II. Classical analyses

    International Nuclear Information System (INIS)

    Chokshi, A.; Wright, E.L.

    1989-01-01

    Chokshi and Wright presented a detailed model for simulating angular distribution of galaxy images in fields that extended to very high redshifts. Standard tools are used to analyze these simulated galaxy fields for the Omega(O) = 0 and the Omega(O) = 1 cases in order to test the discriminatory power of these tools. Classical number-magnitude diagrams and surface brightness-color-color diagrams are employed to study crowded galaxy fields. An attempt is made to separate the effects due to stellar evolution in galaxies from those due to the space time geometry. The results show that this discrimination is maximized at near-infrared wavelengths where the stellar photospheres are still visible but stellar evolution effects are less severe than those observed at optical wavelenghts. Rapid evolution of the stars on the asymptotic giant branch is easily recognized in the simulated data for both cosmologies and serves to discriminate between the two extreme values of Omega(O). Measurements of total magnitudes of individual galaxies are not essential for studying light distribution in galaxies as a function of redshift. Calculations for the extragalactic background radiation are carried out using the simulated data, and compared to integrals over the evolutionary models used. 29 refs

  18. Escape of ionizing radiation from star-forming regions in Young galaxies

    DEFF Research Database (Denmark)

    Razoumov, A; Sommer-Larsen, Jesper

    2006-01-01

    Galaxies: Formation, Galaxies: Intergalactic Medium, ISM: H II Regions, Radiative Transfer Udgivelsesdato: Nov. 10......Galaxies: Formation, Galaxies: Intergalactic Medium, ISM: H II Regions, Radiative Transfer Udgivelsesdato: Nov. 10...

  19. IRAS low-resolution spectra of galaxies

    International Nuclear Information System (INIS)

    Cohen, M.; Volk, K.

    1989-01-01

    The spectra of external galaxies are selected and extracted from the IRAS LRS database. Twenty-one objects present viable spectra. One is a peculiar star-forming E-S0 galaxy. The remainder are all starburst or H II region galaxies. Their average spectrum demonstrates the importance of the PAH emission bands in the 8-23-micron region and reinforces the conclusion reached from ground-based spectra, that there is a strong correlation between the PAH bands and the starburst or H II region character of a galaxy. 32 refs

  20. Galaxy mergers and active nuclei. II. Cosmological evolution

    International Nuclear Information System (INIS)

    Roos, N.

    1985-01-01

    Galaxy mergers may produce active galactic nuclei (AGNs) by repopulating stellar loss-cone orbits around a central black hole. In the companion paper we derived a local bolometric luminosity function of AGNs based on this process. In this paper we interpret the observed cosmological evolution of the luminosity function of AGNs as due to evolution of the merging rate among galaxies after their formation at a redshift of approx.3. An important difference between our model and previous (empirical) models is that the evolution depends on galactic (stellar) luminosity instead of central nonthermal luminosity. The radio counts at 1.4 GHz and optical counts are reproduced by the model if the merging rate of the galaxies at the bright end of the galaxy luminosity function evolves considerably faster than the merging rate of the smaller galaxies. The theoretical and observed luminosity functions at high redshift have similar characteristics: (i) at high luminosity the evolution is best described by luminosity evolution, and (2) the luminosity function has a maximum at approx.10 3 Gpc -3 , which is the space density of the most massive galaxies. A large fraction of these galaxies are presumably formed in the precursors of rich clusters. Their merger rate is high initially and declines rapidly on a time scale of a few billion years. If the initial density fluctuation spectrum for protoclusters of mass M/sub cl/ has the form deltarho/rhoproportionalM/sup( -1+n//3)/2/sub cl/, then the steep evolution of the most luminous galaxies suggests nroughly-equal-1.3 at a redshift of approx.3, which is consistent with the observed clustering of galaxies

  1. THE EFFECT OF HOST GALAXIES ON TYPE Ia SUPERNOVAE IN THE SDSS-II SUPERNOVA SURVEY

    International Nuclear Information System (INIS)

    Lampeitl, Hubert; Smith, Mathew; Nichol, Robert C.; Bassett, Bruce; Cinabro, David; Dilday, Benjamin; Jha, Saurabh W.; Foley, Ryan J.; Frieman, Joshua A.; Garnavich, Peter M.; Goobar, Ariel; Nordin, Jakob; Im, Myungshin; Marriner, John; Miquel, Ramon; Oestman, Linda; Riess, Adam G.; Sako, Masao; Schneider, Donald P.; Sollerman, Jesper

    2010-01-01

    We present an analysis of the host galaxy dependences of Type Ia Supernovae (SNe Ia) from the full three year sample of the SDSS-II Supernova Survey. We re-discover, to high significance, the strong correlation between host galaxy type and the width of the observed SN light curve, i.e., fainter, quickly declining SNe Ia favor passive host galaxies, while brighter, slowly declining Ia's favor star-forming galaxies. We also find evidence (at between 2σ and 3σ) that SNe Ia are ≅0.1 ± 0.04 mag brighter in passive host galaxies than in star-forming hosts, after the SN Ia light curves have been standardized using the light-curve shape and color variations. This difference in brightness is present in both the SALT2 and MCLS2k2 light-curve fitting methodologies. We see evidence for differences in the SN Ia color relationship between passive and star-forming host galaxies, e.g., for the MLCS2k2 technique, we see that SNe Ia in passive hosts favor a dust law of R V = 1.0 ± 0.2, while SNe Ia in star-forming hosts require R V = 1.8 +0.2 -0.4 . The significance of these trends depends on the range of SN colors considered. We demonstrate that these effects can be parameterized using the stellar mass of the host galaxy (with a confidence of >4σ) and including this extra parameter provides a better statistical fit to our data. Our results suggest that future cosmological analyses of SN Ia samples should include host galaxy information.

  2. Toward the comprehension of the infrared to submillimeter view of the interstellar medium of nearby galaxies

    International Nuclear Information System (INIS)

    Galametz, Maud

    2010-01-01

    was the logical following step. We obtain LABOCA observations of a resolved star forming region of the Large Magellanic Cloud (LMC), the N158/N159/N160 complex, situated in the south of the 30 Doradus complex. The proximity of the LMC enables us to resolve structures of a few parsecs at the LABOCA resolution to model the SEDs of individual and isolated regions across the complex and get a handle on the temperature distribution of the dust (hot, warm, cold). I am also comparing the dust distribution with the HI, CO and Hα observations to spatially quantify the variations of the D/G. I finally present the first Herschel observations of the galaxies NGC 6822 and NGC 1705, two low- metallicity galaxies observed as part of the Science Demonstration phase of the telescope launched in May 2009. In NGC 6822, we model the SEDs of some Hii regions and less active regions across the galaxy and find that the SEDs of HII regions show warmer ranges of dust temperatures. We derive very high dust masses when graphite is used in our model to describe carbon dust. Using amorphous carbon, instead, requires less dust mass to account for the same sub-mm emission due to its lower emissivity properties. This indicates that SED models including Herschel constraints may require different dust properties than commonly used. (author) [fr

  3. Indirect dark matter searches in the dwarf satellite galaxy Ursa Major II with the MAGIC telescopes

    Science.gov (United States)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Arcaro, C.; Baack, D.; Babić, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berse, R. Ch.; Berti, A.; Bhattacharyya, W.; Biland, A.; Blanch, O.; Bonnoli, G.; Carosi, R.; Carosi, A.; Ceribella, G.; Chatterjee, A.; Colak, S. M.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Cumani, P.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Delfino, M.; Delgado, J.; Di Pierro, F.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Elsaesser, D.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Maggio, C.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Masuda, S.; Mazin, D.; Mielke, K.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Nagayoshi, T.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pedaletti, G.; Peresano, M.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saito, T.; Satalecka, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takahashi, M.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Torres-Albà, N.; Treves, A.; Tsujimoto, S.; Vanzo, G.; Vazquez Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Zarić, D.

    2018-03-01

    The dwarf spheroidal galaxy Ursa Major II (UMaII) is believed to be one of the most dark-matter dominated systems among the Milky Way satellites and represents a suitable target for indirect dark matter (DM) searches. The MAGIC telescopes carried out a deep observation campaign on UMaII between 2014 and 2016, collecting almost one hundred hours of good-quality data. This campaign enlarges the pool of DM targets observed at very high energy (E gtrsim 50 GeV) in search for signatures of DM annihilation in the wide mass range between ~100 GeV and ~100 TeV. To this end, the data are analyzed with the full likelihood analysis, a method based on the exploitation of the spectral information of the recorded events for an optimal sensitivity to the explored DM models. We obtain constraints on the annihilation cross-section for different channels that are among the most robust and stringent achieved so far at the TeV mass scale from observations of dwarf satellite galaxies.

  4. Smoothed particle hydrodynamic simulations of expanding HII regions

    Science.gov (United States)

    Bisbas, Thomas G.

    2009-09-01

    This thesis deals with numerical simulations of expanding ionized regions, known as HII regions. We implement a new three dimensional algorithm in Smoothed Particle Hydrodynamics for including the dynamical effects of the interaction between ionizing radiation and the interstellar medium. This interaction plays a crucial role in star formation at all epochs. We study the influence of ionizing radiation in spherically symmetric clouds. In particular, we study the spherically symmetric expansion of an HII region inside a uniform-density, non-self-gravitating cloud. We examine the ability of our algorithm to reproduce the known theoretical solution and we find that the agreement is very good. We also study the spherically symmetric expansion inside a uniform-density, self-gravitating cloud. We propose a new differential equation of motion for the expanding shell that includes the effects of gravity. Comparing its numerical solution with the simulations, we find that the equation predicts the position of the shell accurately. We also study the expansion of an off-centre HII region inside a uniform-density, non- self-gravitating cloud. This results in an evolution known as the rocket effect, where the ionizing radiation pushes and accelerates the cloud away from the exciting star leading to its dispersal. During this evolution, cometary knots appear as a result of Rayleigh-Taylor and Vishniac instabilities. The knots are composed of a dense head with a conic tail behind them, a structure that points towards the ionizing source. Our simulations show that these knots are very reminiscent of the observed structures in planetary nebula, such as in the Helix nebula. The last part of this thesis is dedicated to the study of cores ionized by an exciting source which is placed outside and far away from them. The evolution of these cores is known as radiation driven compression (or implosion). We perform simulations and compare our findings with results of other workers and we

  5. Herschel Spectroscopy of Early-type Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Lapham, Ryen Carl; Young, Lisa M. [Physics Department, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 (United States); Crocker, Alison, E-mail: ryen.lapham@student.nmt.edu, E-mail: lyoung@physics.nmt.edu, E-mail: crockera@reed.edu [Physics Department, Reed College, Portland, OR 97202 (United States)

    2017-05-01

    We present Herschel spectroscopy of atomic lines arising in photodissociation regions as well as ionization regions of nearby early-type galaxies (ETGs), focusing on the volume-limited Atlas3D sample. Our data include the [C ii], [O i], and [N ii] 122 and 205 μ m lines, along with ancillary data including CO and H i maps. We find that ETGs have [C ii]/FIR ratios slightly lower than spiral galaxies in the KINGFISH sample, and several ETGs have unusually large [N ii] 122/[C ii] ratios. The [N ii] 122/[C ii] ratio is correlated with UV colors and there is a strong anti-correlation of [C ii]/FIR with NUV-K seen in both spirals and ETGs, likely due to a softer radiation field with fewer photons available to ionize carbon and heat the gas. The correlation thus makes a [C ii] deficit in galaxies with redder stellar populations. The high [N ii] 122/[C ii] (and low [C ii]/FIR) line ratios could also be affected by the removal of much of the diffuse, low-density gas, which is consistent with the low H i/H{sub 2} ratios. [C ii] is now being used as a star-formation indicator, and we find that it is just as good for ETGs as in spirals. The [C ii]/CO ratios found are also similar to those found in spiral galaxies. Through the use of the [N ii] 205 μ m line, estimates of the percentage of [C ii] emission arising from ionized gas indicate that a significant portion could arise in ionized regions.

  6. Exploring the 13CO/C18O abundance ratio towards Galactic young stellar objects and HII regions

    Science.gov (United States)

    Areal, M. B.; Paron, S.; Celis Peña, M.; Ortega, M. E.

    2018-05-01

    Aims: Determining molecular abundance ratios is important not only for the study of Galactic chemistry, but also because they are useful to estimate physical parameters in a large variety of interstellar medium environments. One of the most important molecules for tracing the molecular gas in the interstellar medium is CO, and the 13CO/C18O abundance ratio is usually used to estimate molecular masses and densities of regions with moderate to high densities. Nowadays isotope ratios are in general indirectly derived from elemental abundances ratios. We present the first 13CO/C18O abundance ratio study performed from CO isotope observations towards a large sample of Galactic sources of different natures at different locations. Methods: To study the 13CO/C18O abundance ratio, we used 12CO J = 3 - 2 data obtained from the CO High-Resolution Survey, 13CO and C18O J = 3 - 2 data from the 13CO/C18O (J = 3 - 2) Heterodyne Inner Milky Way Plane Survey, and some complementary data extracted from the James Clerk Maxwell Telescope database. We analyzed a sample of 198 sources composed of young stellar objects (YSOs), and HII and diffuse HII regions as catalogued in the Red MSX Source Survey in 27.°5 ≤ l ≤ 46.°5 and |b|0.°5. Results: Most of the analyzed sources are located in the galactocentric distance range 4.0-6.5 kpc. We found that YSOs have, on average, lower 13CO/C18O abundance ratios than HII and diffuse HII regions. Taking into account that the gas associated with YSOs should be less affected by the radiation than in the case of the others sources, selective far-UV photodissociation of C18O is confirmed. The 13CO/C18O abundance ratios obtained in this work are systematically lower than those predicted from the known elemental abundance relations. These results will be useful in future studies of molecular gas related to YSOs and HII regions based on the observation of these isotopes.

  7. HII regions in collapsing massive molecular clouds

    International Nuclear Information System (INIS)

    Yorke, H.W.; Bodenheimer, P.; Tenorio-Tagle, G.

    1982-01-01

    Results of two-dimensional numerical calculations of the evolution of HII regions associated with self-gravitating, massive molecular clouds are presented. Depending on the location of the exciting star, a champagne flow can occur concurrently with the central collapse of a nonrotating cloud. Partial evaporation of the cloud at a rate of about 0.005 solar masses/yr results. When 100 O-stars are placed at the center of a freely falling cloud of 3x10 5 solar masses no evaporation takes place. Rotating clouds collapse to disks and the champagne flow can evaporate the cloud at a higher rate (0.01 solar masses/yr). It is concluded that massive clouds containing OB-stars have lifetimes of no more than 10 7 yr. (Auth.)

  8. Physical Conditions of the Interstellar Medium in Star-forming Galaxies at z1.5

    Science.gov (United States)

    Hayashi, Masao; Ly, Chun; Shimasaku, Kazuhiro; Motohara, Kentaro; Malkan, Matthew A.; Nagao, Tohru; Kashikawa, Nobunari; Goto, Ryosuke; Naito, Yoshiaki

    2015-01-01

    We present results from Subaru/FMOS near-infrared (NIR) spectroscopy of 118 star-forming galaxies at z approximately equal to 1.5 in the Subaru Deep Field. These galaxies are selected as [O II] lambda 3727 emitters at z approximately equal to 1.47 and 1.62 from narrow-band imaging. We detect H alpha emission line in 115 galaxies, [O III] lambda 5007 emission line in 45 galaxies, and H Beta, [N II] lambda 6584, and [S II]lambda lambda 6716, 6731 in 13, 16, and 6 galaxies, respectively. Including the [O II] emission line, we use the six strong nebular emission lines in the individual and composite rest-frame optical spectra to investigate physical conditions of the interstellar medium in star-forming galaxies at z approximately equal to 1.5. We find a tight correlation between H alpha and [O II], which suggests that [O II] can be a good star formation rate (SFR) indicator for galaxies at z approximately equal to 1.5. The line ratios of H alpha / [O II] are consistent with those of local galaxies. We also find that [O II] emitters have strong [O III] emission lines. The [O III]/[O II] ratios are larger than normal star-forming galaxies in the local Universe, suggesting a higher ionization parameter. Less massive galaxies have larger [O III]/[O II] ratios. With evidence that the electron density is consistent with local galaxies, the high ionization of galaxies at high redshifts may be attributed to a harder radiation field by a young stellar population and/or an increase in the number of ionizing photons from each massive star.

  9. The Taxonomy of Blue Amorphous Galaxies. I. Hα and UBVI Data

    Science.gov (United States)

    Marlowe, Amanda T.; Meurer, Gerhardt R.; Heckman, Timothy M.; Schommer, Robert

    1997-10-01

    Dwarf galaxies play an important role in our understanding of galaxy formation and evolution. We have embarked on a systematic study of 12 nearby dwarf galaxies (most of which have been classified as amorphous) selected preferentially by their blue colors. The properties of the galaxies in the sample suggest that they are in a burst or postburst state. It seems likely that these amorphous galaxies are closely related to other ``starburst'' dwarfs such as blue compact dwarfs (BCDs) and H II galaxies but are considerably closer and therefore easier to study. If so, these galaxies may offer important insights into dwarf galaxy evolution. In an effort to clarify the role of starbursts in evolutionary scenarios for dwarf galaxies, we present Hα and UBVI data for our sample. Blue amorphous galaxies, like BCDs and H II galaxies, have surface brightness profiles that are exponential in the outer regions (r >~ 1.5re) but have a predominantly blue central excess, which suggests a young burst in an older, redder galaxy. Seven of the galaxies have the bubble or filamentary Hα morphology and double-peaked emission lines that are the signature of superbubbles or superwind activity. These galaxies are typically the ones with the strongest central excesses. The underlying exponential galaxies are very similar to those found in BCDs and H II galaxies. How amorphous galaxies fit into the dwarf irregular-``starburst dwarf''-dwarf elliptical evolutionary debate is less clear. In this paper, we present our data and make some preliminary comparisons between amorphous galaxies and other classes of dwarf galaxies. In a future companion paper, we will compare this sample more quantitatively with other dwarf galaxy samples in an effort to determine if amorphous galaxies are a physically different class of object from other starburst dwarfs such as BCDs and H II galaxies and also investigate their place in dwarf galaxy evolution scenarios.

  10. Star formation in the inner galaxy: a far-infrared and radio study of two H2 regions

    International Nuclear Information System (INIS)

    Lester, D.F.; Dinerstein, H.L.; Werner, M.W.; Harvey, P.M.; Evans, N.J.; Brown, R.L.

    1985-09-01

    Far-infrared and radio continuum maps have been made of the central 6' of the inner-galaxy HII regions G30.8-0.0 (in the W43 complex) and G25.4-0.2, along with radio and molecular line measurements at selected positions. The purpose of this study is an effort to understand star formation in the molecular ring at 5 kpc in galactic radius. Measurements at several far infrared wavelengths allow the dust temperature structures and total far infrared fluxes to be determined. Comparison of the radio and infrared maps shows a close relationship between the ionized gas and the infrared-emitting material. There is evidence that parts of G30.8 are substantially affected by extinction, even at far-infrared wavelengths. Using radio recombination line and CO line data for G25.4-0.2, the distance ambiguity for this source is resolved. The large distance previously ascribed to the entire complex is found to apply to only one of the two main components. The confusion in distance determination is found to result from an extraordinary near-superposition of two bright HII regions. Using the revised distances of 4.3 kpc for G25.4SE and 12 kpc for G25.4NW, it is found that the latter, which is apparently the fainter of the two sources, is actually the more luminous. The ratio of total luminosity to ionizing luminosity is very similar to that of HII regions in the solar circle. Assuming a coeval population of ionizing stars, a normal initial mass function is indicated

  11. Low-redshift Lyman continuum leaking galaxies with high [O III]/[O II] ratios

    Science.gov (United States)

    Izotov, Y. I.; Worseck, G.; Schaerer, D.; Guseva, N. G.; Thuan, T. X.; Fricke, K. J.; Verhamme, A.; Orlitová, I.

    2018-05-01

    We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of five star-forming galaxies at redshifts z in the range 0.2993 - 0.4317 and with high emission-line flux ratios O32 = [O III]λ5007/[O II]λ3727 ˜ 8 - 27 aiming to detect the Lyman continuum (LyC) emission. We detect LyC emission in all galaxies with the escape fractions fesc(LyC) in a range of 2 - 72 per cent. A narrow Lyα emission line with two peaks in four galaxies and with three peaks in one object is seen in medium-resolution COS spectra with a velocity separation between the peaks Vsep varying from ˜153 km s-1 to ˜ 345 km s-1. We find a general increase of the LyC escape fraction with increasing O32 and decreasing stellar mass M⋆, but with a large scatter of fesc(LyC). A tight anti-correlation is found between fesc(LyC) and Vsep making Vsep a good parameter for the indirect determination of the LyC escape fraction. We argue that one possible source driving the escape of ionizing radiation is stellar winds and radiation from hot massive stars.

  12. A MULTI-WAVELENGTH STUDY OF LOW-REDSHIFT CLUSTERS OF GALAXIES. II. ENVIRONMENTAL IMPACT ON GALAXY GROWTH

    International Nuclear Information System (INIS)

    Atlee, David W.; Martini, Paul

    2012-01-01

    Galaxy clusters provide powerful laboratories for the study of galaxy evolution, particularly the origin of correlations of morphology and star formation rate (SFR) with density. We construct visible to MIR spectral energy distributions of galaxies in eight low-redshift (z * (>99% confidence) with no dependence on R/R 200 or projected local density at fixed mass. A merged sample of galaxies from the five best measured clusters shows (SFR)∝(R/R 200 ) 1.1±0.3 for galaxies with R/R 200 ≤ 0.4. A decline in the fraction of SFGs toward the cluster center contributes most of this effect, but it is accompanied by a reduction in (SFR) for SFGs with R ≤ 0.1 R 200 . The increase in the fraction of SFGs toward larger R/R 200 and the isolation of SFGs with reduced SFRs near the cluster center are consistent with the truncation of star formation by ram-pressure stripping, as is the tendency for more massive SFGs to have higher SFRs. We conclude that stripping is more likely than slower processes to drive the properties of SFGs with R 200 in clusters. We also find that galaxies near the cluster center are more massive than galaxies farther out in the cluster at ∼3.5σ, which suggests that dynamical relaxation significantly impacts the distribution of cluster galaxies as the clusters evolve.

  13. A MULTI-WAVELENGTH STUDY OF LOW-REDSHIFT CLUSTERS OF GALAXIES. II. ENVIRONMENTAL IMPACT ON GALAXY GROWTH

    Energy Technology Data Exchange (ETDEWEB)

    Atlee, David W.; Martini, Paul, E-mail: atlee@noao.edu [Department of Astronomy, Ohio State University, 4055 McPherson Laboratory, 140 W. 18th Ave., Columbus, OH 43210 (United States)

    2012-12-20

    Galaxy clusters provide powerful laboratories for the study of galaxy evolution, particularly the origin of correlations of morphology and star formation rate (SFR) with density. We construct visible to MIR spectral energy distributions of galaxies in eight low-redshift (z < 0.3) clusters and use them to measure stellar masses and SFRs as a function of environment. A partial correlation analysis indicates that the SFRs of star-forming galaxies (SFGs) depend strongly on M{sub *} (>99% confidence) with no dependence on R/R{sub 200} or projected local density at fixed mass. A merged sample of galaxies from the five best measured clusters shows (SFR){proportional_to}(R/R{sub 200}){sup 1.1{+-}0.3} for galaxies with R/R{sub 200} {<=} 0.4. A decline in the fraction of SFGs toward the cluster center contributes most of this effect, but it is accompanied by a reduction in (SFR) for SFGs with R {<=} 0.1 R{sub 200}. The increase in the fraction of SFGs toward larger R/R{sub 200} and the isolation of SFGs with reduced SFRs near the cluster center are consistent with the truncation of star formation by ram-pressure stripping, as is the tendency for more massive SFGs to have higher SFRs. We conclude that stripping is more likely than slower processes to drive the properties of SFGs with R < 0.4 R{sub 200} in clusters. We also find that galaxies near the cluster center are more massive than galaxies farther out in the cluster at {approx}3.5{sigma}, which suggests that dynamical relaxation significantly impacts the distribution of cluster galaxies as the clusters evolve.

  14. The globular cluster system of NGC 1316. II. The extraordinary object SH2

    Science.gov (United States)

    Richtler, T.; Kumar, B.; Bassino, L. P.; Dirsch, B.; Romanowsky, A. J.

    2012-07-01

    Context. SH2 has been described as an isolated HII-region, located about 6.5' south of the nucleus of NGC 1316 (Fornax A), a merger remnant in the the outskirts of the Fornax cluster of galaxies. Aims: We give a first, preliminary description of the stellar content and environment of this remarkable object. Methods: We used photometric data in the Washington system and HST photometry from the Hubble Legacy Archive for a morphological description and preliminary aperture photometry. Low-resolution spectroscopy provides radial velocities of the brightest star cluster in SH2 and a nearby intermediate-age cluster. Results: SH2 is not a normal HII-region, ionized by very young stars. It contains a multitude of star clusters with ages of approximately 108 yr. A ring-like morphology is striking. SH2 seems to be connected to an intermediate-age massive globular cluster with a similar radial velocity, which itself is the main object of a group of fainter clusters. Metallicity estimates from emission lines remain ambiguous. Conclusions: The present data do not yet allow firm conclusions about the nature or origin of SH2. It might be a dwarf galaxy that has experienced a burst of extremely clustered star formation. We may witness how globular clusters are donated to a parent galaxy. Based on observations taken at the European Southern Observatory, Cerro Paranal, Chile, under the programmes 082.B-0680, on observations taken at the Interamerican Observatory, Cerro Tololo, Chile. Furthermore based on observations made with the NASA/ESA Hubble Space Telescope (HST, PI: A. Sandage, Prop.ID: 7504), and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).

  15. STELLAR POPULATIONS AND RADIAL MIGRATIONS IN VIRGO DISK GALAXIES

    International Nuclear Information System (INIS)

    Roediger, Joel C.; Courteau, Stéphane; Sánchez-Blázquez, Patricia; McDonald, Michael

    2012-01-01

    We present new stellar age profiles, derived from well-resolved optical and near-infrared images of 64 Virgo cluster disk galaxies, whose analysis poses a challenge for current disk galaxy formation models. Our ability to break the age-metallicity degeneracy and the significant size of our sample represent key improvements over complementary studies of field disk galaxies. Our results can be summarized as follows: first, and contrary to observations of disk galaxies in the field, these cluster galaxies are distributed almost equally amongst the three main types of disk galaxy luminosity profiles (I/II/III), indicating that the formation and/or survival of Type II breaks is suppressed within the cluster environment. Second, we find examples of statistically significant inversions ( U -shapes ) in the age profiles of all three disk galaxy types, reminiscent of predictions from high-resolution simulations of classically truncated Type II disks in the field. These features characterize the age profiles for only about a third (≤36%) of each disk galaxy type in our sample. An even smaller fraction of cluster disks (∼11% of the total sample) exhibit age profiles that decrease outward (i.e., negative age gradients). Instead, flat and/or positive age gradients prevail (≥50%) within our Type I, II, and III subsamples. These observations thus suggest that while stellar migrations and inside-out growth can play a significant role in the evolution of all disk galaxy types, other factors contributing to the evolution of galaxies can overwhelm the predicted signatures of these processes. We interpret our observations through a scenario whereby Virgo cluster disk galaxies formed initially like their brethren in the field but which, upon falling into the cluster, were transformed into their present state through external processes linked to the environment (e.g., ram-pressure stripping and harassment). Current disk galaxy formation models, which have largely focused on field

  16. Stellar feedback in galaxies and the origin of galaxy-scale winds

    Science.gov (United States)

    Hopkins, Philip F.; Quataert, Eliot; Murray, Norman

    2012-04-01

    Feedback from massive stars is believed to play a critical role in driving galactic super-winds that enrich the intergalactic medium and shape the galaxy mass function, mass-metallicity relation and other global galaxy properties. In previous papers, we have introduced new numerical methods for implementing stellar feedback on sub-giant molecular cloud (sub-GMC) through galactic scales in numerical simulations of galaxies; the key physical processes include radiation pressure in the ultraviolet through infrared, supernovae (Type I and Type II), stellar winds ('fast' O star through 'slow' asymptotic giant branch winds), and H II photoionization. Here, we show that these feedback mechanisms drive galactic winds with outflow rates as high as ˜10-20 times the galaxy star formation rate. The mass-loading efficiency (wind mass-loss rate divided by the star formation rate) scales roughly as ? (where Vc is the galaxy circular velocity), consistent with simple momentum-conservation expectations. We use our suite of simulations to study the relative contribution of each feedback mechanism to the generation of galactic winds in a range of galaxy models, from Small Magellanic Cloud like dwarfs and Milky Way (MW) analogues to z˜ 2 clumpy discs. In massive, gas-rich systems (local starbursts and high-z galaxies), radiation pressure dominates the wind generation. By contrast, for MW-like spirals and dwarf galaxies the gas densities are much lower and sources of shock-heated gas such as supernovae and stellar winds dominate the production of large-scale outflows. In all of our models, however, the winds have a complex multiphase structure that depends on the interaction between multiple feedback mechanisms operating on different spatial scales and time-scales: any single feedback mechanism fails to reproduce the winds observed. We use our simulations to provide fitting functions to the wind mass loading and velocities as a function of galaxy properties, for use in cosmological

  17. Study of starburst galaxies and active galactic nuclei in the mid-infrared with the ISOCAM instrument

    International Nuclear Information System (INIS)

    Laurent, Olivier

    1999-01-01

    This thesis is dedicated to the study of starburst galaxies and active galactic nuclei (AGNs) in the mid-infrared between 3 and 16 μm with the ISOCAM instrument. The study of nearby prototypical galaxies such as NGC 1068 and M 82 lead me to decompose the emission into three components. The star forming regions are characterized by (1) the infrared bands at 6.2, 7.7, 8.6, 11.3 and 12.7 μm originating from the photo-dissociation regions and also by (2) a continuum at 15 μm produced by the very small grains in HII regions. I show that AGNs have (3) strong continuum with an important contribution between 3 and 10 μm arising from hot dust heated to high temperatures of the order of 1000 K. I present two diagnostic diagrams based on the spectral properties of the three components allowing me to distinguish AGNs from starburst regions. In interacting galaxies, I show that some extra-nuclear regions harboring starburst activity can dominate the emission at 15 μm as in the Cartwheel and the Antennae galaxies. Using mid-infrared spectral features, I also define two prototypes of ultra-luminous galaxies dominated either by starburst activity in the case of Arp 220 or by the AGN in the Super-Antennae galaxy (IRAS 19254-7245). I explain how this diagram and the selection criteria evolve according to redshift. Finally, I show how we can develop new diagnostics using filters of the IRAC instrument on board the next infrared space observatory SIRTF. (author) [fr

  18. THE ESCAPE FRACTION OF IONIZING RADIATION FROM GALAXIES

    International Nuclear Information System (INIS)

    Benson, Andrew; Venkatesan, Aparna; Shull, J. Michael

    2013-01-01

    The escape of ionizing radiation from galaxies plays a critical role in the evolution of gas in galaxies, and the heating and ionization history of the intergalactic medium. We present semi-analytic calculations of the escape fraction of ionizing radiation for both hydrogen and helium from galaxies ranging from primordial systems to disk-type galaxies that are not heavily dust-obscured. We consider variations in the galaxy density profile, source type, location, and spectrum, and gas overdensity/distribution factors. For sufficiently hard first-light sources, the helium ionization fronts closely track or advance beyond that of hydrogen. Key new results in this work include calculations of the escape fractions for He I and He II ionizing radiation, and the impact of partial ionization from X-rays from early active galactic nuclei or stellar clusters on the escape fractions from galaxy halos. When factoring in frequency-dependent effects, we find that X-rays play an important role in boosting the escape fractions for both hydrogen and helium, but especially for He II. We briefly discuss the implications of these results for recent observations of the He II reionization epoch at low redshifts, as well as the UV data and emission-line signatures from early galaxies anticipated from future satellite missions.

  19. THE ESCAPE FRACTION OF IONIZING RADIATION FROM GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Benson, Andrew [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Venkatesan, Aparna [Department of Physics and Astronomy, University of San Francisco, San Francisco, CA 94117 (United States); Shull, J. Michael, E-mail: abenson@obs.carnegiescience.edu, E-mail: avenkatesan@usfca.edu, E-mail: michael.shull@colorado.edu [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

    2013-06-10

    The escape of ionizing radiation from galaxies plays a critical role in the evolution of gas in galaxies, and the heating and ionization history of the intergalactic medium. We present semi-analytic calculations of the escape fraction of ionizing radiation for both hydrogen and helium from galaxies ranging from primordial systems to disk-type galaxies that are not heavily dust-obscured. We consider variations in the galaxy density profile, source type, location, and spectrum, and gas overdensity/distribution factors. For sufficiently hard first-light sources, the helium ionization fronts closely track or advance beyond that of hydrogen. Key new results in this work include calculations of the escape fractions for He I and He II ionizing radiation, and the impact of partial ionization from X-rays from early active galactic nuclei or stellar clusters on the escape fractions from galaxy halos. When factoring in frequency-dependent effects, we find that X-rays play an important role in boosting the escape fractions for both hydrogen and helium, but especially for He II. We briefly discuss the implications of these results for recent observations of the He II reionization epoch at low redshifts, as well as the UV data and emission-line signatures from early galaxies anticipated from future satellite missions.

  20. Effects of Pop III to PopII transition on the lowest metallicity stars in dwarf galaxies

    Science.gov (United States)

    Zhang, Yimiao; Keres, Dusan; FIRE Team

    2018-01-01

    We examine the effects of the enrichments from Population III (Pop III) stars on the formation and properties of the first generation of the Population II (Pop II) stars. Pop III stars begin to transition towards Pop II stars when the metals dispersed in Pop III supernovae pollute the nearby gas. However, details of this transition are still largely unknown. We use dwarf galaxy simulations from the Feedback In Realistic Environments (FIRE) project to identify the star-forming gas that is likely to be pre-enriched by Pop III supernovae and follow the stars that form in such gas. This pre-enrichment will leave the signature in the lowest metallicity stars that can be used to better constrain the details of the Pop III-to-Pop II transition.

  1. Baryonic distributions in galaxy dark matter haloes - II. Final results

    Science.gov (United States)

    Richards, Emily E.; van Zee, L.; Barnes, K. L.; Staudaher, S.; Dale, D. A.; Braun, T. T.; Wavle, D. C.; Dalcanton, J. J.; Bullock, J. S.; Chandar, R.

    2018-06-01

    Re-creating the observed diversity in the organization of baryonic mass within dark matter haloes represents a key challenge for galaxy formation models. To address the growth of galaxy discs in dark matter haloes, we have constrained the distribution of baryonic and non-baryonic matter in a statistically representative sample of 44 nearby galaxies defined from the Extended Disk Galaxy Exploration Science (EDGES) Survey. The gravitational potentials of each galaxy are traced using rotation curves derived from new and archival radio synthesis observations of neutral hydrogen (H I). The measured rotation curves are decomposed into baryonic and dark matter halo components using 3.6 μm images for the stellar content, the H I observations for the atomic gas component, and, when available, CO data from the literature for the molecular gas component. The H I kinematics are supplemented with optical integral field spectroscopic (IFS) observations to measure the central ionized gas kinematics in 26 galaxies, including 13 galaxies that are presented for the first time in this paper. Distributions of baryonic-to-total mass ratios are determined from the rotation curve decompositions under different assumptions about the contribution of the stellar component and are compared to global and radial properties of the dominant stellar populations extracted from optical and near-infrared photometry. Galaxies are grouped into clusters of similar baryonic-to-total mass distributions to examine whether they also exhibit similar star and gas properties. The radial distribution of baryonic-to-total mass in a galaxy does not appear to correlate with any characteristics of its star formation history.

  2. HERSCHEL SPECTROSCOPIC OBSERVATIONS OF LITTLE THINGS DWARF GALAXIES

    International Nuclear Information System (INIS)

    Cigan, Phil; Young, Lisa; Cormier, Diane; Lebouteiller, Vianney; Madden, Suzanne; Hunter, Deidre; Brinks, Elias; Elmegreen, Bruce; Schruba, Andreas; Heesen, Volker

    2016-01-01

    We present far-infrared (FIR) spectral line observations of five galaxies from the Little Things sample: DDO 69, DDO 70, DDO 75, DDO 155, and WLM. While most studies of dwarfs focus on bright systems or starbursts due to observational constraints, our data extend the observed parameter space into the regime of low surface brightness dwarf galaxies with low metallicities and moderate star formation rates. Our targets were observed with Herschel at the [C ii] 158 μm, [O i] 63 μm, [O iii] 88 μm, and [N ii] 122 μm emission lines using the PACS Spectrometer. These high-resolution maps allow us for the first time to study the FIR properties of these systems on the scales of larger star-forming complexes. The spatial resolution in our maps, in combination with star formation tracers, allows us to identify separate photodissociation regions (PDRs) in some of the regions we observed. Our systems have widespread [C ii] emission that is bright relative to continuum, averaging near 0.5% of the total infrared (TIR) budget—higher than in solar-metallicity galaxies of other types. [N ii] is weak, suggesting that the [C ii] emission in our galaxies comes mostly from PDRs instead of the diffuse ionized interstellar medium (ISM). These systems exhibit efficient cooling at low dust temperatures, as shown by ([O i]+[C ii])/TIR in relation to 60 μm/100 μm, and low [O i]/[C ii] ratios which indicate that [C ii] is the dominant coolant of the ISM. We observe [O iii]/[C ii] ratios in our galaxies that are lower than those published for other dwarfs, but similar to levels noted in spirals

  3. HERSCHEL SPECTROSCOPIC OBSERVATIONS OF LITTLE THINGS DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Cigan, Phil; Young, Lisa [Physics Department, New Mexico Institute of Mining and Technology, Socorro, NM 87801 (United States); Cormier, Diane [Institut für Theoretische Astrophysik, Zentrum für Astronomie der Universität Heidelberg, Albert-Ueberle Str. 2, D-69120 Heidelberg (Germany); Lebouteiller, Vianney; Madden, Suzanne [Laboratoire AIM, CEA/DSM—CNRS—Université Paris Diderot, Irfu/Service d’Astrophysique, CEA Saclay, F-91191 Gif-sur-Yvette (France); Hunter, Deidre [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Brinks, Elias [Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, AL10 9AB (United Kingdom); Elmegreen, Bruce [IBM T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Hts., NY 10598 (United States); Schruba, Andreas [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Heesen, Volker, E-mail: pcigan@alumni.nmt.edu [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Collaboration: LITTLE THINGS Team

    2016-01-15

    We present far-infrared (FIR) spectral line observations of five galaxies from the Little Things sample: DDO 69, DDO 70, DDO 75, DDO 155, and WLM. While most studies of dwarfs focus on bright systems or starbursts due to observational constraints, our data extend the observed parameter space into the regime of low surface brightness dwarf galaxies with low metallicities and moderate star formation rates. Our targets were observed with Herschel at the [C ii] 158 μm, [O i] 63 μm, [O iii] 88 μm, and [N ii] 122 μm emission lines using the PACS Spectrometer. These high-resolution maps allow us for the first time to study the FIR properties of these systems on the scales of larger star-forming complexes. The spatial resolution in our maps, in combination with star formation tracers, allows us to identify separate photodissociation regions (PDRs) in some of the regions we observed. Our systems have widespread [C ii] emission that is bright relative to continuum, averaging near 0.5% of the total infrared (TIR) budget—higher than in solar-metallicity galaxies of other types. [N ii] is weak, suggesting that the [C ii] emission in our galaxies comes mostly from PDRs instead of the diffuse ionized interstellar medium (ISM). These systems exhibit efficient cooling at low dust temperatures, as shown by ([O i]+[C ii])/TIR in relation to 60 μm/100 μm, and low [O i]/[C ii] ratios which indicate that [C ii] is the dominant coolant of the ISM. We observe [O iii]/[C ii] ratios in our galaxies that are lower than those published for other dwarfs, but similar to levels noted in spirals.

  4. Nebular metallicities in two isolated local void dwarf galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Nicholls, David C.; Jerjen, Helmut; Dopita, Michael A. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd., Weston ACT 2611 (Australia); Basurah, Hassan, E-mail: David.Nicholls@anu.edu.au [Astronomy Department, King Abdulaziz University, P.O. Box 80203, Jeddah (Saudi Arabia)

    2014-01-01

    Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H II regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609-04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity H II region, while the second is in a more vigorous star forming phase with several bright H II regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral hydrogen.

  5. Nebular Metallicities in Two Isolated Local Void Dwarf Galaxies

    Science.gov (United States)

    Nicholls, David C.; Jerjen, Helmut; Dopita, Michael A.; Basurah, Hassan

    2014-01-01

    Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H II regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609-04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity H II region, while the second is in a more vigorous star forming phase with several bright H II regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral hydrogen.

  6. THE CARNEGIE-IRVINE GALAXY SURVEY. II. ISOPHOTAL ANALYSIS

    International Nuclear Information System (INIS)

    Li Zhaoyu; Ho, Luis C.; Barth, Aaron J.; Peng, Chien Y.

    2011-01-01

    The Carnegie-Irvine Galaxy Survey (CGS) is a comprehensive investigation of the physical properties of a complete, representative sample of 605 bright (B T ≤ 12.9 mag) galaxies in the southern hemisphere. This contribution describes the isophotal analysis of the broadband (BVRI) optical imaging component of the project. We pay close attention to sky subtraction, which is particularly challenging for some of the large galaxies in our sample. Extensive crosschecks with internal and external data confirm that our calibration and sky subtraction techniques are robust with respect to the quoted measurement uncertainties. We present a uniform catalog of one-dimensional radial profiles of surface brightness and geometric parameters, as well as integrated colors and color gradients. Composite profiles highlight the tremendous diversity of brightness distributions found in disk galaxies and their dependence on Hubble type. A significant fraction of S0 and spiral galaxies exhibit non-exponential profiles in their outer regions. We perform Fourier decomposition of the isophotes to quantify non-axisymmetric deviations in the light distribution. We use the geometric parameters, in conjunction with the amplitude and phase of the m = 2 Fourier mode, to identify bars and quantify their size and strength. Spiral arm strengths are characterized using the m = 2 Fourier profiles and structure maps. Finally, we utilize the information encoded in the m = 1 Fourier profiles to measure disk lopsidedness. The databases assembled here and in Paper I lay the foundation for forthcoming scientific applications of CGS.

  7. Searching gravitational microlensing events in the galaxy spiral arms by EROS II

    International Nuclear Information System (INIS)

    Derue, Frederic

    1999-01-01

    The EROS II experiment is searching for microlensing events due to compact massive objects passing through the line-of-sight of luminous stars. These objects are candidates to explain the baryonic component of Dark Matter in our Galaxy. EROS II was dedicated to different lines-of-sight: Small and Large Magellanic Clouds, Galactic Centre and 4 directions towards the Spiral Arms of the Galaxy. This thesis presents the first search for microlensing towards these last lines-of-sight (about 9 million stars). Simple criteria based on the search for significant fluctuations allowed one to discover a low noise sample of 7 candidates to the microlensing effect, with an average timescale of 50 days. A detailed analysis of the light curve of one candidate allows us to give a confidence interval on its mass 2.7 x 10 -3 0 0 = 50 ± 3 days. To improve the knowledge of the distance of the target stars, we have combined observations of EROS II with bibliographic sources on associations of stars linked with the spiral arm features, and we have developed a program to find variable stars. Ten cepheids have thus been found. Distances obtained with different methods are in rough agreement with each other. The average optical depth measured towards the four directions is τ-bar = 0.45 0.11 +0.23 x 10 -6 . It is compatible with expectations from simple galactic models. The long duration of most events favours interpretation of lensing by objects belonging to the disk instead of the halo. It also seems that some events due to bulge lenses have influenced measurements towards the line-of-sight which is closest to the Galactic Centre. Observation continue towards spiral arms. More accurate measurements should be obtained with increase of statistics, allowing one to estimate the disk contribution to the optical depth towards the bulge and the Magellanic Clouds. (author)

  8. A MEASUREMENT OF THE RATE OF TYPE Ia SUPERNOVAE IN GALAXY CLUSTERS FROM THE SDSS-II SUPERNOVA SURVEY

    International Nuclear Information System (INIS)

    Dilday, Benjamin; Jha, Saurabh W.; Bassett, Bruce; Becker, Andrew; Bender, Ralf; Hopp, Ulrich; Castander, Francisco; Cinabro, David; Frieman, Joshua A.; Galbany, LluIs; Miquel, Ramon; Garnavich, Peter; Goobar, Ariel; Ihara, Yutaka; Kessler, Richard; Lampeitl, Hubert; Nichol, Robert C.; Marriner, John; Molla, Mercedes

    2010-01-01

    We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z ≤ 0.17 and 27 SN events in 492 maxBCG clusters at 0.1 ≤ z ≤ 0.3. We find values for the cluster SN Ia rate of (0.37 +0.17+0.01 -0.12-0.01 ) SNur h 2 and (0.55 +0.13+0.02 -0.11-0.01 ) SNur h 2 (SNux = 10 -12 L -1 xsun yr -1 ) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be (0.31 +0.18+0.01 -0.12-0.01 ) SNur h 2 and (0.49 +0.15+0.02 -0.11-0.01 ) SNur h 2 in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be (2.04 +1.99+0.07 -1.11-0.04 ) SNur h 2 and (0.36 +0.84+0.01 -0.30-0.01 ) SNur h 2 in C4 and maxBCG clusters, respectively. The ratio of the SN Ia rate in cluster early-type galaxies to that of the SN Ia rate in field early-type galaxies is 1.94 +1.31+0.043 -0.91-0.015 and 3.02 +1.31+0.062 -1.03-0.048 , for C4 and maxBCG clusters, respectively. The SN rate in galaxy clusters as a function of redshift, which probes the late time SN Ia delay distribution, shows only weak dependence on redshift. Combining our current measurements with previous measurements, we fit the cluster SN Ia rate data to a linear function of redshift, and find r L = [(0.49 +0.15 -0.14 )+(0.91 +0.85 -0.81 ) x z] SNuB h 2 . A comparison of the radial distribution of SNe in cluster to field early-type galaxies shows possible evidence for an enhancement of the SN rate in the cores of cluster early-type galaxies. With an observation of at most three hostless, intra-cluster SNe Ia, we estimate the fraction of cluster SNe that are hostless to be (9.4 +8.3 -5.1 )%.

  9. MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. II. CATALOG OF STARS IN MILKY WAY DWARF SATELLITE GALAXIES

    International Nuclear Information System (INIS)

    Kirby, Evan N.; Cohen, Judith G.; Guhathakurta, Puragra; Rockosi, Constance M.; Simon, Joshua D.; Geha, Marla C.; Sneden, Christopher; Sohn, Sangmo Tony; Majewski, Steven R.; Siegel, Michael

    2010-01-01

    We present a catalog of Fe, Mg, Si, Ca, and Ti abundances for 2961 stars in eight dwarf satellite galaxies of the Milky Way (MW): Sculptor, Fornax, Leo I, Sextans, Leo II, Canes Venatici I, Ursa Minor, and Draco. For the purposes of validating our measurements, we also observed 445 red giants in MW globular clusters and 21 field red giants in the MW halo. The measurements are based on Keck/DEIMOS medium-resolution spectroscopy (MRS) combined with spectral synthesis. We estimate uncertainties in [Fe/H] by quantifying the dispersion of [Fe/H] measurements in a sample of stars in monometallic globular clusters (GCs). We estimate uncertainties in Mg, Si, Ca, and Ti abundances by comparing to high-resolution spectroscopic abundances of the same stars. For this purpose, a sample of 132 stars with published high-resolution spectroscopy in GCs, the MW halo field, and dwarf galaxies has been observed with MRS. The standard deviations of the differences in [Fe/H] and ([α/Fe]) (the average of [Mg/Fe], [Si/Fe], [Ca/Fe], and [Ti/Fe]) between the two samples is 0.15 and 0.16, respectively. This catalog represents the largest sample of multi-element abundances in dwarf galaxies to date. The next papers in this series draw conclusions on the chemical evolution, gas dynamics, and star formation histories from the catalog presented here. The wide range of dwarf galaxy luminosity reveals the dependence of dwarf galaxy chemical evolution on galaxy stellar mass.

  10. Peering Into an Early Galaxy

    Science.gov (United States)

    Kohler, Susanna

    2018-04-01

    reports on what weve learned peering into CR7s interior with ALMA.ALMA observations of [C II] (white contours) are overlaid on an ultraviolet image of the galaxy CR7 taken with Hubble (background image). The presence of [C II] throughout the galaxy indicate that CR7 does not primarily consist of metal-free gas, as had been previously proposed. [Matthee et al. 2017]Metals yet No Dust?Matthee and collaborators deep spectroscopic observations of CR7 targeted the far-infrared dust continuum emission and a gas emission line, [C II]. The authors detected [C II] emission in a large region in and around the galaxy, including near the ultraviolet clumps. This clearly indicates the presence of metals in these star-forming regions, and it rules out the possibility that CR7s gas is mostly primordial and forming metal-free Pop III stars.The authors do not detect far infrared continuum emission from dust, which sets an unusually low upper limit on the amount of dust that may be present in this galaxy. This limit allows them to better interpret their measurements of star formation rates in CR7, providing more information about the galaxys properties.Lastly, Matthee and collaborators note that the [C II] emission is detected in multiple different components that have different velocities. The authors propose that these components are accreting satellite galaxies. If this is correct, then CR7 is not only a target to learn about early sources of light in the universe its also a rare opportunity to directly witness the build-up of a central galaxy in the early universe.CitationJ. Matthee et al 2017 ApJ 851 145. doi:10.3847/1538-4357/aa9931

  11. Properties of Narrow line Seyfert 1 galaxies

    Science.gov (United States)

    Rakshit, Suvendu; Stalin, Chelliah Subramonian; Chand, Hum; Zhang, Xue-Guang

    2018-04-01

    Narrow line Seyfert 1 (NLSy1) galaxies constitute a class of active galactic nuclei characterized by the full width at half maximum (FWHM) of the Hα broad emission line 10 pixel-1. A strong correlation between the Hα and Hα emission lines is found both in the FWHM and flux. The nuclear continuum luminosity is found to be strongly correlated with the luminosity of Hα, Hα and [O III] emission lines. The black hole mass in NLSy1 galaxies is lower compared to their broad line counterparts. Compared to BLSy1 galaxies, NLSy1 galaxies have a stronger FeII emission and a higher Eddington ratio that place them in the extreme upper right corner of the R4570 - λEdd diagram. The distribution of the radio-loudness parameter (R) in NLSy1 galaxies drops rapidly at R>10 compared to the BLSy1 galaxies that have powerful radio jets. The soft X-ray photon index in NLSy1 galaxies is on average higher (2.9 ± 0.9) than BLSy1 galaxies (2.4 ± 0.8). It is anti-correlated with the Hα width but correlated with the FeII strength. NLSy1 galaxies on average have a lower amplitude of optical variability compared to their broad lines counterparts. These results suggest Eddington ratio as the main parameter that drives optical variability in these sources.

  12. Galaxies clustering around QSOs with z = 0.9-1.5 and the origin of blue field galaxies

    Science.gov (United States)

    Hintzen, Paul; Romanishin, W.; Valdes, Francisco

    1991-01-01

    Deep CCD images were obtained in Mould-Cousins R and I passbands of 16 radio quasars with z values between 0.9 and 1.5 and absolute values of b above 35 deg, chosen from the Veron-Cetty and Veron (1984) catalog. Results indicate that, in this population of radio quasars, there is a statistically significant excess of galaxies within 15 arcsec of the quasars and brighter than R = 23 and I = 22. However, contrary to the report of Tyson (1986), no excess was found of galaxies with R less than 21 lying within 30 arcsec of quasars in this redshift range. Data were also obtained for very blue galaxies seen among objects in the general field, all of which are bluer in R-I than Magellanic irregulars at any redshift less than 3. It is suggested that this population might be comprised of low-redshift low-luminosity (H II region) galaxies of the type studied by French (1980) and/or higher redshift galaxies with strong cooling flows and forbidden O II lines.

  13. Modeling Fe II Emission and Revised Fe II (UV) Empirical Templates for the Seyfert 1 Galaxy I Zw 1

    Science.gov (United States)

    Bruhweiler, F.; Verner, E.

    2008-03-01

    We use the narrow-lined broad-line region (BLR) of the Seyfert 1 galaxy, I Zw 1, as a laboratory for modeling the ultraviolet (UV) Fe II 2100-3050 Å emission complex. We calculate a grid of Fe II emission spectra representative of BLR clouds and compare them with the observed I Zw 1 spectrum. Our predicted spectrum for log [nH/(cm -3) ] = 11.0, log [ΦH/(cm -2 s-1) ] = 20.5, and ξ/(1 km s-1) = 20, using Cloudy and an 830 level model atom for Fe II with energies up to 14.06 eV, gives a better fit to the UV Fe II emission than models with fewer levels. Our analysis indicates (1) the observed UV Fe II emission must be corrected for an underlying Fe II pseudocontinuum; (2) Fe II emission peaks can be misidentified as that of other ions in active galactic nuclei (AGNs) with narrow-lined BLRs possibly affecting deduced physical parameters; (3) the shape of 4200-4700 Å Fe II emission in I Zw 1 and other AGNs is a relative indicator of narrow-line region (NLR) and BLR Fe II emission; (4) predicted ratios of Lyα, C III], and Fe II emission relative to Mg II λ2800 agree with extinction corrected observed I Zw 1 fluxes, except for C IV λ1549 (5) the sensitivity of Fe II emission strength to microturbulence ξ casts doubt on existing relative Fe/Mg abundances derived from Fe II (UV)/Mg II flux ratios. Our calculated Fe II emission spectra, suitable for BLRs in AGNs, are available at http://iacs.cua.edu/people/verner/FeII. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 05-26555.

  14. MAGIICAT II. GENERAL CHARACTERISTICS OF THE Mg II ABSORBING CIRCUMGALACTIC MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, Nikole M.; Churchill, Christopher W. [New Mexico State University, Las Cruces, NM 88003 (United States); Kacprzak, Glenn G., E-mail: nnielsen@nmsu.edu, E-mail: cwc@nmsu.edu, E-mail: gkacprzak@astro.swin.edu.au [Swinburne University of Technology, Victoria 3122 (Australia)

    2013-10-20

    We examine the Mg II absorbing circumgalactic medium (CGM) for the 182 intermediate redshift (0.072 ≤ z ≤ 1.120) galaxies in the 'Mg II Absorber-Galaxy Catalog' (MAGIICAT). We parameterize the anti-correlation between equivalent width, W{sub r} (2796), and impact parameter, D, with a log-linear fit, and show that a power law poorly describes the data. We find that higher luminosity galaxies have larger W{sub r} (2796) at larger D (4.3σ). The covering fractions, f{sub c} , decrease with increasing D and W{sub r} (2796) detection threshold. Higher luminosity galaxies have larger f{sub c} ; no absorption is detected in lower luminosity galaxies beyond 100 kpc. Bluer and redder galaxies have similar f{sub c} for D < 100 kpc, but for D > 100 kpc, bluer galaxies have larger f{sub c} , as do higher redshift galaxies. The 'absorption radius', R(L) = R{sub *}(L/L*){sup β}, which we examine for four different W{sub r} (2796) detection thresholds, is more luminosity sensitive to the B-band than the K-band, more sensitive for redder galaxies than for bluer galaxies, and does not evolve with redshift for the K-band, but becomes more luminosity sensitive toward lower redshift for the B-band. These trends clearly indicate a more extended Mg II absorbing CGM around higher luminosity, bluer, and higher redshift galaxies. Several of our findings are in conflict with other works. We address these conflicts and discuss the implications of our results for the low-ionization, intermediate redshift CGM.

  15. Colliding and merging galaxies. II. S0 galaxies with polar rings

    International Nuclear Information System (INIS)

    Schweizer, F.; Whitmore, B.D.; Rubin, V.C.

    1983-01-01

    We first present a detailed optical study of A0136-0801, a 16 1/2 -mag ''spindle'' galaxy girdled by a ring of gas, dust, and young stars. The spindle is a normal S0 disk seen nearly edge-on, as shown by its photometric profile and fast rotation (v/sub rot//sigma/sub v/ = 2.2); a prolate structure seems to be ruled out. The surrounding ring runs over the poles of this S0 disk and serves as a probe of the vertical potential. The ring motions suggest that a massive halo extends far beyond the S0 disk (out to 3R 25 ) and that this halo is more nearly spherical than flat. We then list 22 related galaxies and derive that a few percent of all field S0's possess near-polar rings or disks. We suggest that these structures are due to a second event, most likely the transfer of mass from a companion galaxy during a close encounter and occasionally also the merger of a companion. Although accretion occurs presumably at random angles, polar rings are favored statistically because of their slow differential precession and consequent longevity. Alternate evolutionary schemes are also discussed. Finally, we suggest that M82 may be forming a polar ring from former M81 material, and predict that the ''tilted bulge'' of UGC 7576 is an S0 disk seen nearly edge-on

  16. THE SINS/zC-SINF SURVEY OF z ∼ 2GALAXY KINEMATICS: THE NATURE OF DISPERSION-DOMINATED GALAXIES

    International Nuclear Information System (INIS)

    Newman, Sarah F.; Genzel, Reinhard; Förster Schreiber, Natascha M.; Buschkamp, Peter; Davies, Ric; Eisenhauer, Frank; Kurk, Jaron; Lutz, Dieter; Shapiro Griffin, Kristen; Mancini, Chiara; Renzini, Alvio; Lilly, Simon J.; Carollo, C. Marcella; Peng, Yingjie; Bouché, Nicolas; Burkert, Andreas; Cresci, Giovanni; Genel, Shy; Hicks, Erin K. S.; Naab, Thorsten

    2013-01-01

    We analyze the spectra, spatial distributions, and kinematics of Hα, [N II], and [S II] emission in a sample of 38, z ∼ 2.2 UV/optically selected star-forming galaxies (SFGs) from the SINS and zC-SINF surveys, 34 of which were observed in the adaptive optics mode of SINFONI and 30 of those contain data presented for the first time here. This is supplemented by kinematic data from 43 z ∼ 1-2.5 galaxies from the literature. None of these 81 galaxies is an obvious major merger. We find that the kinematic classification of high-z SFGs as ''dispersion dominated'' or ''rotation dominated'' correlates most strongly with their intrinsic sizes. Smaller galaxies are more likely ''dispersion-dominated'' for two main reasons: (1) the rotation velocity scales linearly with galaxy size but intrinsic velocity dispersion does not depend on size or may even increase in smaller galaxies, and as such, their ratio is systematically lower for smaller galaxies, and (2) beam smearing strongly decreases large-scale velocity gradients and increases observed dispersion much more for galaxies with sizes at or below the resolution. Dispersion-dominated SFGs may thus have intrinsic properties similar to ''rotation-dominated'' SFGs, but are primarily more compact, lower mass, less metal enriched, and may have higher gas fractions, plausibly because they represent an earlier evolutionary state.

  17. IRAS bright galaxy sample. II. The sample and luminosity function

    International Nuclear Information System (INIS)

    Soifer, B.T.; Sanders, D.B.; Neugebauer, G.; Madore, B.F.; Danielson, G.E.; David Dunlap Observatory, Richmond Hill, Canada; Palomar Observatory; California Institute of Technology, Pasadena)

    1987-01-01

    A statistically complete sample of 324 of the brightest infrared galaxies discovered at 60 microns in the IRAS all-sky survey is described. The results show that far-infrared emission is a significant luminosity component in the local universe, representing 25 percent of the luminosity emitted by stars in the same volume. Above 10 to the 11th solar luminosities, the infrared luminous galaxies are the dominant population of objects in the universe, being as numerous as the Seyfert galaxies and more numerous than quasars at higher luminosities. The infrared luminosity appears to be independent of the optical luminosity of galaxies. Most infrared bright galaxies appear to require much of the interstellar matter to be contributing to the observed infrared luminosity. Approximately 60-80 percent of the far-infrared luminosity of the local universe can be attributed, directly or indirectly, to recent or ongoing star formation. 67 references

  18. H I-SELECTED GALAXIES IN THE SLOAN DIGITAL SKY SURVEY. II. THE COLORS OF GAS-RICH GALAXIES

    International Nuclear Information System (INIS)

    West, Andrew A.; Garcia-Appadoo, Diego A.; Dalcanton, Julianne J.; Ivezic, Zeljko; Disney, Mike J.; Rockosi, Constance M.

    2009-01-01

    We utilize color information for an H I-selected sample of 195 galaxies to explore the star formation histories and physical conditions that produce the observed colors. We show that the H I selection creates a significant offset toward bluer colors that can be explained by enhanced recent bursts of star formation. There is also no obvious color bimodality, because the H I selection restricts the sample to bluer, actively star-forming systems, diminishing the importance of the red sequence. Rising star formation rates are still required to explain the colors of galaxies bluer than g - r< 0.3. We also demonstrate that the colors of the bluest galaxies in our sample are dominated by emission lines and that stellar population synthesis models alone (without emission lines) are not adequate for reproducing many of the galaxy colors. These emission lines produce large changes in the r - i colors but leave the g - r color largely unchanged. In addition, we find an increase in the dispersion of galaxy colors at low masses that may be the result of a change in the star formation process in low-mass galaxies.

  19. The Oxygen and Nitrogen Abundance of Leo A and GR 8

    Science.gov (United States)

    van Zee, L.; Skillman, E. D.; Haynes, M. P.

    1999-05-01

    Gas phase abundances are one of the best measures of the intrinsic metallicity of low mass galaxies. We recently obtained low resolution long slit optical spectra of several HII regions in Leo A and GR 8 with the Palomar 5m telescope. Previous studies of the resolved stellar population of Leo A indicated that the stars have metallicities approximately 2% of solar (Tolstoy et al. 1998). Preliminary analysis of the HII region spectra, and that of a planetary nebula, indicates that the gas phase oxygen abundance of Leo A is approximately 3% of solar. This confirms the result of Skillman et al. (1989), who also derived an oxygen abundance for Leo A from a planetary nebula. Similarly, for GR 8 we find a mean oxygen abundance of 5% of solar. For all the HII regions, the derived log(N/O) is -1.5 +/- 0.1, as has been found for other low metallicity systems. These new observations of multiple HII regions in Leo A and GR 8 confirm that metals in low mass galaxies are well mixed.

  20. A Substellar Companion to Pleiades HII 3441

    Science.gov (United States)

    Konishi, Mihoko; Matsuo, Taro; Yamamoto, Kodai; Samland, Matthias; Sudo, Jun; Shibai, Hiroshi; Itoh, Yoichi; Fukagawa, Misato; Sumi, Takhiro; Kudo, Tomoyuki; hide

    2016-01-01

    We find a new substellar companion to the Pleiades member star, Pleiades HII 3441, using the Subaru telescope with adaptive optics. The discovery is made as part of the high-contrast imaging survey to search for planetary-mass and substellar companions in the Pleiades and young moving groups. The companion has a projected separation of 0". 49+/-0". 02 (66+/-2 au) and a mass of 68+/-5M(sub J) based on three observations in the J-, H-, and K(sub s)-bands. The spectral type is estimated to be M7 (approx. 2700 K), and thus no methane absorption is detected in the H band. Our Pleiades observations result in the detection of two substellar companions including one previously reported among 20 observed Pleiades stars, and indicate that the fraction of substellar companions in the Pleiades is about 10.0+26.1 -8.8 %. This is consistent with multiplicity studies of both the Pleiades stars and other open clusters.

  1. A GMOS-N IFU study of the central H II region in the blue compact dwarf galaxy NGC 4449: kinematics, nebular metallicity and star formation

    Science.gov (United States)

    Kumari, Nimisha; James, Bethan L.; Irwin, Mike J.

    2017-10-01

    We use integral field spectroscopic (IFS) observations from the Gemini Multi-Object Spectrograph North (GMOS-N) to study the central H II region in a nearby blue compact dwarf (BCD) galaxy NGC 4449. The IFS data enable us to explore the variation of physical and chemical conditions of the star-forming region and the surrounding gas on spatial scales as small as 5.5 pc. Our kinematical analysis shows possible signatures of shock ionization and shell structures in the surroundings of the star-forming region. The metallicity maps of the region, created using direct Te and indirect strong line methods (R23, O3N2 and N2), do not show any chemical variation. From the integrated spectrum of the central H II region, we find a metallicity of 12 + log(O/H) = 7.88 ± 0.14 ({˜ }0.15^{+0.06}_{-0.04} Z⊙) using the direct method. Comparing the central H II region metallicity derived here with those of H II regions throughout this galaxy from previous studies, we find evidence of increasing metallicity with distance from the central nucleus. Such chemical inhomogeneities can be due to several mechanisms, including gas loss via supernova blowout, galactic winds or metal-poor gas accretion. However, we find that the localized area of decreased metallicity aligns spatially with the peak of star-forming activity in the galaxy, suggesting that gas accretion may be at play here. Spatially resolved IFS data for the entire galaxy are required to confirm the metallicity inhomogeneity found in this study and determine its possible cause.

  2. PLANETARY NEBULAE IN FACE-ON SPIRAL GALAXIES. II. PLANETARY NEBULA SPECTROSCOPY

    International Nuclear Information System (INIS)

    Herrmann, Kimberly A.; Ciardullo, Robin

    2009-01-01

    As the second step in our investigation of the mass-to-light ratio of spiral disks, we present the results of a spectroscopic survey of planetary nebulae (PNe) in five nearby, low-inclination galaxies: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). Using 50 setups of the WIYN/Hydra and Blanco/Hydra spectrographs, and 25 observations with the Hobby-Eberly Telescope's Medium Resolution Spectrograph, we determine the radial velocities of 99, 102, 162, 127, and 48 PNe, respectively, to a precision better than 15 km s -1 . Although the main purpose of this data set is to facilitate dynamical mass measurements throughout the inner and outer disks of large spiral galaxies, our spectroscopy has other uses as well. Here, we co-add these spectra to show that, to first order, the [O III] and Balmer line ratios of PNe vary little over the top ∼1.5 mag of the PN luminosity function. The only obvious spectral change occurs with [N II], which increases in strength as one proceeds down the luminosity function. We also show that typical [O III]-bright planetaries have E(B - V) ∼ 0.2 of circumstellar extinction, and that this value is virtually independent of [O III] luminosity. We discuss the implications this has for understanding the population of PN progenitors.

  3. A NEW SCALING RELATION FOR H II REGIONS IN SPIRAL GALAXIES: UNVEILING THE TRUE NATURE OF THE MASS-METALLICITY RELATION

    Energy Technology Data Exchange (ETDEWEB)

    Rosales-Ortega, F. F.; Diaz, A. I. [Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Sanchez, S. F.; Iglesias-Paramo, J.; Vilchez, J. M.; Mast, D. [Instituto de Astrofisica de Andalucia (CSIC), Camino Bajo de Huetor s/n, Aptdo. 3004, E-18080 Granada (Spain); Bland-Hawthorn, J. [Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006 (Australia); Husemann, B., E-mail: frosales@cantab.net [Leibniz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

    2012-09-10

    We demonstrate the existence of a local mass, metallicity, star formation relation using spatially resolved optical spectroscopy of H II regions in the local universe. One of the projections of this distribution-the local mass-metallicity relation-extends over a wide range in this parameter space: three orders of magnitude in mass and a factor of eight in metallicity. We explain the new relation as the combined effect of the differential distributions of mass and metallicity in the disks of galaxies, and a selective star formation efficiency. We use this local relation to reproduce-with a noticeable agreement-the mass-metallicity relation seen in galaxies, and conclude that the latter is a scale-up integrated effect of a local relation, supporting the inside-out growth and downsizing scenarios of galaxy evolution.

  4. A NEW SCALING RELATION FOR H II REGIONS IN SPIRAL GALAXIES: UNVEILING THE TRUE NATURE OF THE MASS-METALLICITY RELATION

    International Nuclear Information System (INIS)

    Rosales-Ortega, F. F.; Díaz, A. I.; Sánchez, S. F.; Iglesias-Páramo, J.; Vílchez, J. M.; Mast, D.; Bland-Hawthorn, J.; Husemann, B.

    2012-01-01

    We demonstrate the existence of a local mass, metallicity, star formation relation using spatially resolved optical spectroscopy of H II regions in the local universe. One of the projections of this distribution—the local mass-metallicity relation—extends over a wide range in this parameter space: three orders of magnitude in mass and a factor of eight in metallicity. We explain the new relation as the combined effect of the differential distributions of mass and metallicity in the disks of galaxies, and a selective star formation efficiency. We use this local relation to reproduce—with a noticeable agreement—the mass-metallicity relation seen in galaxies, and conclude that the latter is a scale-up integrated effect of a local relation, supporting the inside-out growth and downsizing scenarios of galaxy evolution.

  5. The Infrared-Radio Correlation of Dusty Star Forming Galaxies at High Redshift

    Science.gov (United States)

    Lower, Sidney; Vieira, Joaquin Daniel; Jarugula, Sreevani

    2018-01-01

    Far-infrared (FIR) and radio continuum emission in galaxies are related by a common origin: massive stars and the processes triggered during their birth, lifetime, and death. FIR emission is produced by cool dust, heated by the absorption of UV emission from massive stars, which is then re-emitted in the FIR. Thermal free-free radiation emitted from HII regions dominates the spectral energy density (SED) of galaxies at roughly 30 GHz, while non-thermal synchrotron radiation dominates at lower frequencies. At low redshift, the infrared radio correlation (IRC, or qIR) holds as a tight empirical relation for many star forming galaxy types, but until recently, there has not been sensitive enough radio observations to extend this relation to higher redshifts. Many selection biases cloud the results of these analyses, leaving the evolution of the IRC with redshift ambiguous. In this poster, I present CIGALE fitted spectral energy distributions (SEDs) for 24 gravitationally-lensed sources selected in the mm-wave from the South Pole Telescope (SPT) survey. I fit the IRC from infrared and submillimeter fluxes obtained with Herschel, Atacama Pathfinder Experiment (APEX), and SPT and radio fluxes obtained with ATCA at 2.1, 5.5, 9, and 30 GHz. This sample of SPT sources has a spectroscopic redshift range of 2.1poster, I will present the results of this study and compare our results to various results in the literature.

  6. DYNAMIC S0 GALAXIES. II. THE ROLE OF DIFFUSE HOT GAS

    International Nuclear Information System (INIS)

    Li Jiangtao; Chen Yang; Daniel Wang, Q.; Li Zhiyuan

    2011-01-01

    Cold gas loss is thought to be important in star formation quenching and morphological transition during the evolution of S0 galaxies. In high-density environments, this gas loss can be achieved via many external mechanisms. However, in relatively isolated environments, where these external mechanisms cannot be efficient, the gas loss must then be dominated by some internal processes. We have performed Chandra analysis of hot gas in five nearby isolated S0 galaxies, based on the quantitative subtraction of various stellar contributions. We find that all the galaxies studied in the present work are X-ray faint, with the luminosity of the hot gas (L X ) typically accounting for ∼ X at the low-mass end (typically with K-band luminosity L K ∼ 11 L sun,K ). However, at the high-mass end, S0 galaxies tend to have significantly lower L X than elliptical galaxies of the same stellar masses, as already shown in previous observational and theoretical works. We further discuss the potential relationship of the diffuse X-ray emission with the cold (atomic and molecular) gas content in the S0 and elliptical galaxies included in our study. We find that L X /L 2 K tends to correlate positively with the total cold gas mass (M H 2 +H i ) for cold-gas-poor galaxies with M H 2 +H i ∼ 8 M sun , while they anti-correlate with each other for cold-gas-rich galaxies. This cold-hot gas relationship can be explained in a scenario of early-type galaxy evolution, with the leftover cold gas from the precursor star-forming galaxy mainly removed by the long-lasting Type Ia supernova (SN) feedback. The two different trends for cold-gas-rich and cold-gas-poor galaxies may be the results of the initial fast decreasing SN rate and the later fast decreasing mass loading to hot gas, respectively.

  7. A Measurement of the Rate of Type Ia Supernovae in Galaxy Clusters from the SDSS-II Supernova Survey

    Energy Technology Data Exchange (ETDEWEB)

    Dilday, Benjamin; /Rutgers U., Piscataway /Chicago U. /KICP, Chicago; Bassett, Bruce; /Cape Town U., Dept. Math. /South African Astron. Observ.; Becker, Andrew; /Washington U., Seattle, Astron. Dept.; Bender, Ralf; /Munich, Tech. U. /Munich U. Observ.; Castander, Francisco; /Barcelona, IEEC; Cinabro, David; /Wayne State U.; Frieman, Joshua A.; /Chicago U. /Fermilab; Galbany, Lluis; /Barcelona, IFAE; Garnavich, Peter; /Notre Dame U.; Goobar, Ariel; /Stockholm U., OKC /Stockholm U.; Hopp, Ulrich; /Munich, Tech. U. /Munich U. Observ. /Tokyo U.

    2010-03-01

    We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z {le} 0.17 and 27 SN events in 492 maxBCG clusters at 0.1 {le} z {le} 0.3. We find values for the cluster SN Ia rate of (0.37{sub -0.12-0.01}{sup +0.17+0.01}) SNur h{sup 2} and (0.55{sub -0.11-0.01}{sup +0.13+0.02}) SNur h{sup 2} (SNux = 10{sup -12}L{sub x{circle_dot}}{sup -1} yr{sup -1}) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be (0.31{sub -0.12-0.01}{sup +0.18+0.01}) SNur h{sup 2} and (0.49{sub -0.11-0.01}{sup +0.15+0.02}) SNur h{sup 2} in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be (2.04{sub -1.11-0.04}{sup +1.99+0.07}) SNur h{sup 2} and (0.36{sub -0.30-0.01}{sup +0.84+0.01}) SNur h{sup 2} in C4 and maxBCG clusters, respectively. The ratio of the SN Ia rate in cluster early-type galaxies to that of the SN Ia rate in field early-type galaxies is 1.94{sub -0.91-0.015}{sup +1.31+0.043} and 3.02{sub -1.03-0.048}{sup +1.31+0.062}, for C4 and maxBCG clusters, respectively. The SN rate in galaxy clusters as a function of redshift, which probes the late time SN Ia delay distribution, shows only weak dependence on redshift. Combining our current measurements with previous measurements, we fit the cluster SN Ia rate data to a linear function of redshift, and find r{sub L} = [(0.49{sub -0.14}{sup +0.15}) + (0.91{sub -0.81}{sup +0.85}) x z] SNuB h{sup 2}. A comparison of the radial distribution of SNe in cluster to field early-type galaxies shows possible evidence for an enhancement of the SN rate in the cores of cluster early-type galaxies. With an observation of at most 3 hostless, intra-cluster SNe Ia, we estimate the fraction of cluster SNe that are

  8. VizieR Online Data Catalog: Multiwavelength study of HII region S311 (Yadav+, 2016)

    Science.gov (United States)

    Yadav, R. K.; Pandey, A. K.; Sharma, S.; Ojha, D. K.; Samal, M. R.; Mallick, K. K.; Jose, J.; Ogura, K.; Richichi, A.; Irawati, P.; Kobayashi, N.; Eswaraiah, C.

    2017-11-01

    We observed the HII region S311 (centred on RA(2000)=07:52:24, DE(2000)=-26:24:58.40) in NIR broad-bands J (1.25um), H (1.63um) and Ks (2.14um) on 2010 March 3 using the Infrared Side Port Imager (ISPI) camera mounted on the CTIO Blanco 4-m telescope. We consider only those sources having error data files).

  9. nIFTy galaxy cluster simulations II: radiative models

    CSIR Research Space (South Africa)

    Sembolini, F

    2016-04-01

    Full Text Available Valerio 2, I-34127 Trieste, Italy 12Physics Department, University of the Western Cape, Cape Town 7535, Sotuh Africa 13Physics Department, University of Western Cape, Bellville, Cape Town 7535, South Africa 14South African Astronomical Observatory, PO Box...IFTy cluster comparison project (Sembolini et al., 2015): a study of the latest state-of- the-art hydrodynamical codes using simulated galaxy clusters as a testbed for theories of galaxy formation. Simulations are indis- pensable tools in the interpretation...

  10. THE SINS/zC-SINF SURVEY OF z {approx} 2GALAXY KINEMATICS: THE NATURE OF DISPERSION-DOMINATED GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Foerster Schreiber, Natascha M.; Buschkamp, Peter; Davies, Ric; Eisenhauer, Frank; Kurk, Jaron; Lutz, Dieter [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching (Germany); Shapiro Griffin, Kristen [Space Sciences Research Group, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Mancini, Chiara; Renzini, Alvio [Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, Padova I-35122 (Italy); Lilly, Simon J.; Carollo, C. Marcella; Peng, Yingjie [Institute of Astronomy, Department of Physics, Eidgenoessische Technische Hochschule, ETH Zuerich CH-8093 (Switzerland); Bouche, Nicolas [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France); Burkert, Andreas [Universitaets-Sternwarte Ludwig-Maximilians-Universitaet (USM), Scheinerstr. 1, Muenchen D-81679 (Germany); Cresci, Giovanni [Istituto Nazionale di Astrofisica Osservatorio Astronomico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hicks, Erin K. S. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Naab, Thorsten, E-mail: sfnewman@berkeley.edu [Max-Planck Institute for Astrophysics, Karl Schwarzschildstrasse 1, D-85748 Garching (Germany); and others

    2013-04-20

    We analyze the spectra, spatial distributions, and kinematics of H{alpha}, [N II], and [S II] emission in a sample of 38, z {approx} 2.2 UV/optically selected star-forming galaxies (SFGs) from the SINS and zC-SINF surveys, 34 of which were observed in the adaptive optics mode of SINFONI and 30 of those contain data presented for the first time here. This is supplemented by kinematic data from 43 z {approx} 1-2.5 galaxies from the literature. None of these 81 galaxies is an obvious major merger. We find that the kinematic classification of high-z SFGs as ''dispersion dominated'' or ''rotation dominated'' correlates most strongly with their intrinsic sizes. Smaller galaxies are more likely ''dispersion-dominated'' for two main reasons: (1) the rotation velocity scales linearly with galaxy size but intrinsic velocity dispersion does not depend on size or may even increase in smaller galaxies, and as such, their ratio is systematically lower for smaller galaxies, and (2) beam smearing strongly decreases large-scale velocity gradients and increases observed dispersion much more for galaxies with sizes at or below the resolution. Dispersion-dominated SFGs may thus have intrinsic properties similar to ''rotation-dominated'' SFGs, but are primarily more compact, lower mass, less metal enriched, and may have higher gas fractions, plausibly because they represent an earlier evolutionary state.

  11. ZOMG - II. Does the halo assembly history influence central galaxies and gas accretion?

    Science.gov (United States)

    Romano-Díaz, Emilio; Garaldi, Enrico; Borzyszkowski, Mikolaj; Porciani, Cristiano

    2017-08-01

    The growth rate and the internal dynamics of galaxy-sized dark-matter haloes depend on their location within the cosmic web. Haloes that sit at the nodes grow in mass till the present time and are dominated by radial orbits. Conversely, haloes embedded in prominent filaments do not change much in size and are dominated by tangential orbits. Using zoom hydrodynamical simulations including star formation and feedback, we study how gas accretes on to these different classes of objects, which, for simplicity, we dub 'accreting' and 'stalled' haloes. We find that all haloes get a fresh supply of newly accreted gas in their inner regions, although this slowly decreases with time, in particular for the stalled haloes. The inflow of new gas is always higher than (but comparable with) that of recycled material. Overall, the cold-gas fraction increases (decreases) with time for the accreting (stalled) haloes. In all cases, a stellar disc and a bulge form at the centre of the simulated haloes. The total stellar mass is in excellent agreement with expectations based on the abundance-matching technique. Many properties of the central galaxies do not seem to correlate with the large-scale environment in which the haloes reside. However, there are two notable exceptions that characterize stalled haloes with respect to their accreting counterparts: (I) The galaxy disc contains much older stellar populations. (II) Its vertical scaleheight is larger by a factor of 2 or more. This thickening is likely due to the heating of the long-lived discs by mergers and close flybys.

  12. Studying the highly bent spectra of FR II-type radio galaxies with the KDA EXT model

    Science.gov (United States)

    Kuligowska, Elżbieta

    2018-04-01

    Context. The Kaiser, Dennett-Thorpe & Alexander (KDA, 1997, MNRAS, 292, 723) EXT model, that is, the extension of the KDA model of Fanaroff & Riley (FR) II-type source evolution, is applied and confronted with the observational data for selected FR II-type radio sources with significantly aged radio spectra. Aim. A sample of FR II-type radio galaxies with radio spectra strongly bent at their highest frequencies is used for testing the usefulness of the KDA EXT model. Methods: The dynamical evolution of FR II-type sources predicted with the KDA EXT model is briefly presented and discussed. The results are then compared to the ones obtained with the classical KDA approach, assuming the source's continuous injection and self-similarity. Results: The results and corresponding diagrams obtained for the eight sample sources indicate that the KDA EXT model predicts the observed radio spectra significantly better than the best spectral fit provided by the original KDA model.

  13. Viscosity of HI-I2-H2O solution at atmospheric pressure

    International Nuclear Information System (INIS)

    Chen, Songzhe; Zhang, Ping; Wang, Laijun; Xu, Jingming; Gao, Mengxue

    2014-01-01

    Iodine-Sulfur thermochemical cycle (IS-cycle) is one of the most promising massive hydrogen production methods. Basic properties data of the HI-I 2 -H 2 O solution involved in the HI decomposition section of IS-cycle are found to be very important. HI, I 2 , and H 2 O make up a highly non-ideal solution system. Viscosity and its variation with the composition/temperature are very essential for the flowsheet work and HI-H 2 O-I 2 solution’s fluid simulation, especially in the distillation and electro-electrodialysis processes. In this paper, viscosity values of HI-H 2 O-I 2 solutions were measured at atmospheric pressure and varying temperatures (from 20 to 125 ºC). As for the composition, the HI/H2O molar ratio of the samples ranged from 1:5.36 to 1:12.00, while the HI/I 2 molar ratio from 1.0 to 1.4.0. Both temperature and composition have dramatic influence on the viscosity. Increasing temperature or H 2 O/HI molar ratio will lead to the reduction of viscosity; while increasing of I 2 /HI molar ratio results in the increase of viscosity. It was also found that I 2 content has a larger and more complex influence on the viscosity of the HI-H 2 O-I 2 solution than H 2 O content does, especially at low temperature (<50 °C). (author)

  14. Searching gravitational microlensing events in the galaxy spiral arms by EROS II; Recherche d'evenements de microlentille gravitationnelle dans les bras spiraux de la galaxie avec EROS II

    Energy Technology Data Exchange (ETDEWEB)

    Derue, Frederic [Paris-11 Univ., 91 Orsay (France)

    1999-04-15

    The EROS II experiment is searching for microlensing events due to compact massive objects passing through the line-of-sight of luminous stars. These objects are candidates to explain the baryonic component of Dark Matter in our Galaxy. EROS II was dedicated to different lines-of-sight: Small and Large Magellanic Clouds, Galactic Centre and 4 directions towards the Spiral Arms of the Galaxy. This thesis presents the first search for microlensing towards these last lines-of-sight (about 9 million stars). Simple criteria based on the search for significant fluctuations allowed one to discover a low noise sample of 7 candidates to the microlensing effect, with an average timescale of 50 days. A detailed analysis of the light curve of one candidate allows us to give a confidence interval on its mass 2.7 x 10{sup -3} < M/M{sub 0} < 0.84 at 95% CL. The amplification curve of another candidate shows a modulation which can be interpreted as a microlensing effect acting on a binary source, with an orbital period of P{sub 0} = 50 {+-} 3 days. To improve the knowledge of the distance of the target stars, we have combined observations of EROS II with bibliographic sources on associations of stars linked with the spiral arm features, and we have developed a program to find variable stars. Ten cepheids have thus been found. Distances obtained with different methods are in rough agreement with each other. The average optical depth measured towards the four directions is {tau}-bar = 0.45{sub 0.11}{sup +0.23} x 10{sup -6}. It is compatible with expectations from simple galactic models. The long duration of most events favours interpretation of lensing by objects belonging to the disk instead of the halo. It also seems that some events due to bulge lenses have influenced measurements towards the line-of-sight which is closest to the Galactic Centre. Observation continue towards spiral arms. More accurate measurements should be obtained with increase of statistics, allowing one to

  15. Supernova rates, galaxy emission, and Hubble type

    International Nuclear Information System (INIS)

    Van Den Bergh, S.

    1991-01-01

    Supernova discovery frequency is found to correlate with emission-line (H-alpha + forbidden N II line) equivalent width, except for the most active galaxies in which some supernovae might be hidden by dust. SNII occur preferentially in active galaxies with emission-line EW not less than 20 A, whereas SNIa favor less active galaxies with EW less than 20 A. The intrinsic frequency of supernovae is found to be an order of magnitude higher in Sc galaxies than it is in early type spirals. The relatively high frequency of SNIa in late-type galaxies suggests that not all such objects have old progenitors. 13 refs

  16. METALLICITY DISTRIBUTION FUNCTIONS OF FOUR LOCAL GROUP DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Teresa L.; Holtzman, Jon [Department of Astronomy, New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003-8001 (United States); Saha, Abhijit [NOAO, 950 Cherry Avenue, Tucson, AZ 85726-6732 (United States); Anthony-Twarog, Barbara J., E-mail: rosst@nmsu.edu, E-mail: holtz@nmsu.edu, E-mail: bjat@ku.edu [Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045-7582 (United States)

    2015-06-15

    We present stellar metallicities in Leo I, Leo II, IC 1613, and Phoenix dwarf galaxies derived from medium (F390M) and broad (F555W, F814W) band photometry using the Wide Field Camera 3 instrument on board the Hubble Space Telescope. We measured metallicity distribution functions (MDFs) in two ways, (1) matching stars to isochrones in color–color diagrams and (2) solving for the best linear combination of synthetic populations to match the observed color–color diagram. The synthetic technique reduces the effect of photometric scatter and produces MDFs 30%–50% narrower than the MDFs produced from individually matched stars. We fit the synthetic and individual MDFs to analytical chemical evolution models (CEMs) to quantify the enrichment and the effect of gas flows within the galaxies. Additionally, we measure stellar metallicity gradients in Leo I and II. For IC 1613 and Phoenix our data do not have the radial extent to confirm a metallicity gradient for either galaxy. We find the MDF of Leo I (dwarf spheroidal) to be very peaked with a steep metal-rich cutoff and an extended metal-poor tail, while Leo II (dwarf spheroidal), Phoenix (dwarf transition), and IC 1613 (dwarf irregular) have wider, less peaked MDFs than Leo I. A simple CEM is not the best fit for any of our galaxies; therefore we also fit the “Best Accretion Model” of Lynden-Bell. For Leo II, IC 1613, and Phoenix we find similar accretion parameters for the CEM even though they all have different effective yields, masses, star formation histories, and morphologies. We suggest that the dynamical history of a galaxy is reflected in the MDF, where broad MDFs are seen in galaxies that have chemically evolved in relative isolation and narrowly peaked MDFs are seen in galaxies that have experienced more complicated dynamical interactions concurrent with their chemical evolution.

  17. Rapidly star-forming galaxies adjacent to quasars at redshifts exceeding 6.

    Science.gov (United States)

    Decarli, R; Walter, F; Venemans, B P; Bañados, E; Bertoldi, F; Carilli, C; Fan, X; Farina, E P; Mazzucchelli, C; Riechers, D; Rix, H-W; Strauss, M A; Wang, R; Yang, Y

    2017-05-24

    The existence of massive (10 11 solar masses) elliptical galaxies by redshift z ≈ 4 (refs 1, 2, 3; when the Universe was 1.5 billion years old) necessitates the presence of galaxies with star-formation rates exceeding 100 solar masses per year at z > 6 (corresponding to an age of the Universe of less than 1 billion years). Surveys have discovered hundreds of galaxies at these early cosmic epochs, but their star-formation rates are more than an order of magnitude lower. The only known galaxies with very high star-formation rates at z > 6 are, with one exception, the host galaxies of quasars, but these galaxies also host accreting supermassive (more than 10 9 solar masses) black holes, which probably affect the properties of the galaxies. Here we report observations of an emission line of singly ionized carbon ([C ii] at a wavelength of 158 micrometres) in four galaxies at z > 6 that are companions of quasars, with velocity offsets of less than 600 kilometres per second and linear offsets of less than 100 kiloparsecs. The discovery of these four galaxies was serendipitous; they are close to their companion quasars and appear bright in the far-infrared. On the basis of the [C ii] measurements, we estimate star-formation rates in the companions of more than 100 solar masses per year. These sources are similar to the host galaxies of the quasars in [C ii] brightness, linewidth and implied dynamical mass, but do not show evidence for accreting supermassive black holes. Similar systems have previously been found at lower redshift. We find such close companions in four out of the twenty-five z > 6 quasars surveyed, a fraction that needs to be accounted for in simulations. If they are representative of the bright end of the [C ii] luminosity function, then they can account for the population of massive elliptical galaxies at z ≈ 4 in terms of the density of cosmic space.

  18. Gathering dust: A galaxy-wide study of dust emission from cloud complexes in NGC 300

    Science.gov (United States)

    Riener, M.; Faesi, C. M.; Forbrich, J.; Lada, C. J.

    2018-05-01

    Aims: We use multi-band observations by the Herschel Space Observatory to study the dust emission properties of the nearby spiral galaxy NGC 300. We compile a first catalogue of the population of giant dust clouds (GDCs) in NGC 300, including temperature and mass estimates, and give an estimate of the total dust mass of the galaxy. Methods: We carried out source detection with the multiwavelength source extraction algorithm getsources. We calculated physical properties, including mass and temperature, of the GDCs from five-band Herschel PACS and SPIRE observations from 100 to 500 μm; the final size and mass estimates are based on the observations at 250 μm that have an effective spatial resolution of 170 pc. We correlated our final catalogue of GDCs to pre-existing catalogues of HII regions to infer the number of GDCs associated with high-mass star formation and determined the Hα emission of the GDCs. Results: Our final catalogue of GDCs includes 146 sources, 90 of which are associated with known HII regions. We find that the dust masses of the GDCs are completely dominated by the cold dust component and range from 1.1 × 103 to 1.4 × 104 M⊙. The GDCs have effective temperatures of 13-23 K and show a distinct cold dust effective temperature gradient from the centre towards the outer parts of the stellar disk. We find that the population of GDCs in our catalogue constitutes 16% of the total dust mass of NGC 300, which we estimate to be about 5.4 × 106 M⊙. At least about 87% of our GDCs have a high enough average dust mass surface density to provide sufficient shielding to harbour molecular clouds. We compare our results to previous pointed molecular gas observations in NGC 300 and results from other nearby galaxies and also conclude that it is very likely that most of our GDCs are associated with complexes of giant molecular clouds. The catalogue is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http

  19. Revisiting The First Galaxies: The epoch of Population III stars

    Energy Technology Data Exchange (ETDEWEB)

    Muratov, Alexander L. [U. Michigan, Dept. Astron.; Gnedin, Oleg Y. [U. Michigan, Dept. Astron.; Gnedin, Nickolay Y. [Chicago U., Astron. Astrophys. Ctr.; Zemp, Marcel [Beijing, KITPC

    2013-07-19

    We investigate the transition from primordial Population III (Pop III) star formation to normal Pop II star formation in the first galaxies using new cosmological hydrodynamic simulations. We find that while the first stars seed their host galaxies with metals, they cannot sustain significant outflows to enrich the intergalactic medium, even assuming a top-heavy initial mass function. This means that Pop III star formation could potentially continue until z 6 in different unenriched regions of the universe, before being ultimately shut off by cosmic reionization. Within an individual galaxy, the metal production and stellar feedback from Pop II stars overtake Pop III stars in 20-200 Myr, depending on galaxy mass.

  20. Star-formation complexes in the `galaxy-sized' supergiant shell of the galaxy Holmberg I

    Science.gov (United States)

    Egorov, Oleg V.; Lozinskaya, Tatiana A.; Moiseev, Alexei V.; Smirnov-Pinchukov, Grigory V.

    2018-05-01

    We present the results of observations of the galaxy Holmberg I carried out at the Russian 6-m telescope in the narrow-band imaging, long-slit spectroscopy, and scanning Fabry-Perot interferometer modes. A detailed analysis of gas kinematics, ionization conditions, and metallicity of star-forming regions in the galaxy is presented. The aim of the paper is to analyse the propagation of star formation in the galaxy and to understand the role of the ongoing star formation in the evolution of the central `galaxy-sized' supergiant H I shell (SGS), where all regions of star formation are observed. We show that star formation in the galaxy occurs in large unified complexes rather than in individual giant H II regions. Evidence of the triggered star formation is observed both on scales of individual complexes and of the whole galaxy. We identified two supernova-remnant candidates and one late-type WN star and analysed their spectrum and surrounding-gas kinematics. We provide arguments indicating that the SGS in Holmberg I is destructing by the influence of star formation occurring on its rims.

  1. Hydra II: A Faint and Compact Milky Way Dwarf Galaxy Found in the Survey of the Magellanic Stellar History

    NARCIS (Netherlands)

    Martin, Nicolas F.; Nidever, David L.; Besla, Gurtina; Olsen, Knut; Walker, Alistair R.; Vivas, A. Katherina; Gruendl, Robert A.; Kaleida, Catherine C.; Muñoz, Ricardo R.; Blum, Robert D.; Saha, Abhijit; Conn, Blair C.; Bell, Eric F.; Chu, You-Hua; Cioni, Maria-Rosa L.; de Boer, Thomas J. L.; Gallart, Carme; Jin, Shoko; Kunder, Andrea; Majewski, Steven R.; Martinez-Delgado, David; Monachesi, Antonela; Monelli, Matteo; Monteagudo, Lara; Noël, Noelia E. D.; Olszewski, Edward W.; Stringfellow, Guy S.; van der Marel, Roeland P.; Zaritsky, Dennis

    We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within the data from the ongoing Survey of the Magellanic Stellar History conducted with the Dark Energy Camera on the Blanco 4 m Telescope. The new satellite is compact ({{r}h}=68 ± 11 pc) and faint ({{M}V}=-4.8 ± 0.3),

  2. Star Formation Histories of Dwarf Irregular Galaxies

    Science.gov (United States)

    Skillman, Evan

    1995-07-01

    We propose to obtain deep WFPC2 `BVI' color-magnitude diagrams {CMDs} for the dwarf irregular {dI} Local Group galaxies GR 8, Leo A, Pegasus, and Sextans A. In addition to resolved stars, we will use star clusters, and especially any globulars, to probe the history of intense star formation. These data will allow us to map the Pop I and Pop II stellar components, and thereby construct the first detailed star formation histories for non-interacting dI galaxies. Our results will bear on a variety of astrophysical problems, including the evolution of small galaxies, distances in the Local Group, age-metallicity distributions in small galaxies, ages of dIs, and the physics of star formation. The four target galaxies are typical dI systems in terms of luminosity, gas content, and H II region abundance, and represent a range in current star forming activity. They are sufficiently near to allow us to reach to stars at M_V = 0, have 0.1 of the luminosity of the SMC and 0.25 of its oxygen abundance. Unlike the SMC, these dIs are not near giant galaxies. This project will allow the extension of our knowledge of stellar populations in star forming galaxies from the spirals in the Local Group down to its smallest members. We plan to take maximum advantage of the unique data which this project will provide. Our investigator team brings extensive and varied experience in studies of dwarf galaxies, stellar populations, imaging photometry, and stellar evolution to this project.

  3. Clustering of galaxies around gamma-ray burst sight-lines

    DEFF Research Database (Denmark)

    Sudilovsky, V.; Greiner, J.; Rau, A.

    2013-01-01

    -lines, as strong MgII tends to trace these sources. In this work, we test this expectation by calculating the two point angular correlation function of galaxies within 120'' (~470 h Kpc470h71-1Kpc at z ~ 0.4) of GRB afterglows. We compare the gamma-ray burst optical and near-infrared detector (GROND) GRB afterglow.......3. This result is contrary to the expectations from the MgII excess derived from GRB afterglow spectroscopy, although many confirmed galaxy counterparts to MgII absorbers may be too faint to detect in our sample-especially those at z > 1. We note that the addition of higher sensitivity Spitzer/IRAC or HST/WFC3......There is evidence of an overdensity of strong intervening MgII absorption line systems distributed along the lines of sight toward gamma-ray burst (GRB) afterglows relative to quasar sight-lines. If this excess is real, one should also expect an overdensity of field galaxies around GRB sight...

  4. Smooth-arm spiral galaxies: their properties and significance to cluster-galaxy evolution

    International Nuclear Information System (INIS)

    Wilkerson, M.S.

    1979-01-01

    In this dissertation a number of galaxies with optical appearances between those of normal, actively-star-forming spirals and SO galaxies have been examined. These so-called smooth-arm spiral galaxies exhibit spiral arms without any of the spiral tracers - H II regions, O-B star associations, dust - indicative of current star formation. Tests were made to find if, perhaps, these smooth-arm spirals could have, at one time, been normal, actively-star-forming spirals whose gas had been somehow removed; and that are currently transforming into SO galaxies. This scenario proceeds as (1) removal of gas, (2) gradual dying of disk density wave, (3) emergence of SO galaxy. If the dominant method of gas removal is ram-pressure stripping by a hot, intracluster medium, then smooth-arm spirals should occur primarily in x-ray clusters. Some major findings of this dissertation are as follows: (1) Smooth-arm spirals are redder than normal spirals of the same morphological type. Most smooth-arm spirals cannot be distinguished by color from SO galaxies. (2) A weak trend exists for smooth-arm spirals with stronger arms to be bluer than those with weaker arms; thus implying that the interval since gas removal has been shorter for the galaxies with stronger arms. (3) Smooth-arm spirals are deficient in neutral hydrogen - sometimes by an order of magnitude or, possibly, more

  5. Infrared emission from galactic H II regions

    International Nuclear Information System (INIS)

    Zeilik, M. II.

    1975-01-01

    Near-infrared observations are presented of selected galactic HII regions (especially G45.5 + 0.1, G45.1 + 0.1, S88, and W3A) to infer the physical conditions of the dust responsible for the 2 to 25 micron emission. Two-component dust models are developed to match the observed characteristics of the infrared emission from HII regions. The dust, assumed to be bare and well-mixed with the gas in the ionized volume, consists of large (0.1 micron) ''silicate'' grains and small (0.2 micron) graphite grains. The ''silicates'' have their cosmic maximum abundance with respect to hydrogen, but the graphite grains are depleted by factors of 25 to 100 in mass. The Lyman-alpha radiation field predominately heats the ''silicate'' grains, which produce almost all the emission at 20 microns and most of it from 8 to 13 microns. The stellar radiation field predominately heats the graphite grains, which generate most of the emission at 3.5 and 5 microns. Roughly half of the observed 2 to 25 micron luminosity (when corrected for extinction) arises from Lyman-alpha photons and the other half from the Lyman and Balmer continua. The grains are too hot to provide significant emission in the far-infrared; this probably arises from a dust shell around the HII region. This two-component model predicts that HII regions should have smaller sizes at 3.5 and 5 microns than at 10 and 20 microns. The emissivities of fine-structure infrared lines for the regions are calculated. In the one instance where observations of such lines have been published (G29.9 - 0.0), predicted emissivities fall below those observed, especially for the 12.86-micron line of NeII. The discrepancy probably arises from an incorrect modeling of the region's ionization structure, but it might also reflect variations in elemental abundances or deficiencies in model stellar atmospheres for hot stars

  6. ISM Parameters in the Normal Galaxy NGC 5713

    Science.gov (United States)

    Lord, S. D.; Malhotra, S.; Lim, T.; Helou, G.; Beichman, C. A.; Dinerstein, H.; Hollenbach, D. J.; Hunter, D. A.; Lo, K. Y.; Lu, N. Y.; hide

    1996-01-01

    We report ISO Long Wavelength Spectrometer (LWS) observations fo the Sbc(s) pec galaxy NGC 5713. We have obtained strong detections of the fine-structure forbidden transitions [C(sub ii)] 158(micro)m, [O(sub i)]63(micro)m, and [O(sub iii)] 88(micro)m, and significant upper limits for[N(sub ii)]122(micro)m, [O(sub iii)] 52(micro)m, and [N(sub iii)] 57(micro)m. We also detect the galaxy's dust continuum emission between 43 and 197 microns.

  7. The H II regions of IC 1613

    International Nuclear Information System (INIS)

    Hodge, P.; Lee, M.G.; Gurwell, M.

    1990-01-01

    Narrow-band CCD H-alpha imaging of the Local Group irregular galaxy IC 1613 has revealed a total of 77 H II regions, five of which are complexes of several smaller emission regions. Positions, H-alpha luminosities, and sizes of these objects are tabulated. The H-alpha luminosity function has the same shape as that for more luminous galaxies, following a power law with an exponent of -1.6. The faintest H II regions are at the low-luminosity end of the generally observed luminosity function for H II regions in galaxies, with fluxes of only 10 to the 35th erg/sec. The size distribution has an exponential shape, as for other galaxies, with a size scale of 56 pc. The morphologies of different H II regions are discussed and compared to those in other galaxies. Published radio continuum maps compare well with the H-alpha emission distribution. The distribution of H I is also similar in the central areas to the H II with, however, a tendency for the H II regions to lie to one side of H I peaks. 31 refs

  8. GREEN GALAXIES IN THE COSMOS FIELD

    International Nuclear Information System (INIS)

    Pan, Zhizheng; Kong, Xu; Fan, Lulu

    2013-01-01

    We present research on the morphologies, spectra, and environments of ≈2350 'green valley' galaxies at 0.2 + color is used to define 'green valley'; it removes dusty star-forming galaxies from galaxies that are truly transitioning between the blue cloud and the red sequence. Morphological parameters of green galaxies are intermediate between those of blue and red galaxy populations, both on the Gini-asymmetry and the Gini-M 20 planes. Approximately 60%-70% of green disk galaxies have intermediate or big bulges, and only 5%-10% are pure disk systems, based on morphological classification using the Zurich Estimator of Structural Types. The obtained average spectra of green galaxies are intermediate between blue and red ones in terms of [O II], Hα, and Hβ emission lines. Stellar population synthesis on the average spectra shows that green galaxies are on average older than blue galaxies but younger than red galaxies. Green galaxies and blue galaxies have similar projected galaxy density (Σ 10 ) distributions at z > 0.7. At z * 10.0 M ☉ green galaxies located in a dense environment are found to be significantly larger than those of blue galaxies. The morphological and spectral properties of green galaxies are consistent with the transitioning population between the blue cloud and the red sequence. The possible mechanisms for quenching star formation activities in green galaxies are discussed. The importance of active galactic nucleus feedback cannot be well constrained in our study. Finally, our findings suggest that environmental conditions, most likely starvation and harassment, significantly affect the transformation of M * 10.0 M ☉ blue galaxies into red galaxies, especially at z < 0.5

  9. Type Ia Supernova Properties as a Function of the Distance to the Host Galaxy in the SDSS-II SN Survey

    Energy Technology Data Exchange (ETDEWEB)

    Galbany, Lluis [Institut de Fisica d' Altes Energies (IFAE), Barcelona (Spain); et al.

    2012-08-20

    We use type-Ia supernovae (SNe Ia) discovered by the SDSS-II SN Survey to search for dependencies between SN Ia properties and the projected distance to the host galaxy center, using the distance as a proxy for local galaxy properties (local star-formation rate, local metallicity, etc.). The sample consists of almost 200 spectroscopically or photometrically confirmed SNe Ia at redshifts below 0.25. The sample is split into two groups depending on the morphology of the host galaxy. We fit light-curves using both MLCS2k2 and SALT2, and determine color (AV, c) and light-curve shape (delta, x1) parameters for each SN Ia, as well as its residual in the Hubble diagram. We then correlate these parameters with both the physical and the normalized distances to the center of the host galaxy and look for trends in the mean values and scatters of these parameters with increasing distance. The most significant (at the 4-sigma level) finding is that the average fitted AV from MLCS2k2 and c from SALT2 decrease with the projected distance for SNe Ia in spiral galaxies. We also find indications that SNe in elliptical galaxies tend to have narrower light-curves if they explode at larger distances, although this may be due to selection effects in our sample. We do not find strong correlations between the residuals of the distance moduli with respect to the Hubble flow and the galactocentric distances, which indicates a limited correlation between SN magnitudes after standardization and local host metallicity.

  10. THE HETDEX PILOT SURVEY. IV. THE EVOLUTION OF [O II] EMITTING GALAXIES FROM z ∼ 0.5 TO z ∼ 0

    International Nuclear Information System (INIS)

    Ciardullo, Robin; Gronwall, Caryl; Schneider, Donald P.; Zeimann, Gregory R.

    2013-01-01

    We present an analysis of the luminosities and equivalent widths of the 284 z 2 pilot survey for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). By combining emission-line fluxes obtained from the Mitchell spectrograph on the McDonald 2.7 m telescope with deep broadband photometry from archival data, we derive each galaxy's dereddened [O II] λ3727 luminosity and calculate its total star formation rate. We show that over the last ∼5 Gyr of cosmic time, there has been substantial evolution in the [O II] emission-line luminosity function, with L* decreasing by ∼0.6 ± 0.2 dex in the observed function, and by ∼0.9 ± 0.2 dex in the dereddened relation. Accompanying this decline is a significant shift in the distribution of [O II] equivalent widths, with the fraction of high equivalent-width emitters declining dramatically with time. Overall, the data imply that the relative intensity of star formation within galaxies has decreased over the past ∼5 Gyr, and that the star formation rate density of the universe has declined by a factor of ∼2.5 between z ∼ 0.5 and z ∼ 0. These observations represent the first [O II]-based star formation rate density measurements in this redshift range, and foreshadow the advancements which will be generated by the main HETDEX survey.

  11. Blueberry Galaxies: The Lowest Mass Young Starbursts

    Science.gov (United States)

    Yang, Huan; Malhotra, Sangeeta; Rhoads, James E.; Wang, Junxian

    2017-09-01

    Searching for extreme emission line galaxies allows us to find low-mass metal-poor galaxies that are good analogs of high redshift Lyα emitting galaxies. These low-mass extreme emission line galaxies are also potential Lyman-continuum leakers. Finding them at very low redshifts (z≲ 0.05) allows us to be sensitive to even lower stellar masses and metallicities. We report on a sample of extreme emission line galaxies at z≲ 0.05 (blueberry galaxies). We selected them from SDSS broadband images on the basis of their broadband colors and studied their properties with MMT spectroscopy. From the entire SDSS DR12 photometric catalog, we found 51 photometric candidates. We spectroscopically confirm 40 as blueberry galaxies. (An additional seven candidates are contaminants, and four remain without spectra.) These blueberries are dwarf starburst galaxies with very small sizes (<1 kpc) and very high ionization ([O III]/[O II] ˜ 10-60). They also have some of the lowest stellar masses ({log}(M/{M}⊙ )˜ 6.5{--}7.5) and lowest metallicities (7.1< 12+{log}({{O}}/{{H}})< 7.8) of starburst galaxies. Thus, they are small counterparts to green pea galaxies and high redshift Lyα emitting galaxies.

  12. PROBING THE PHYSICS OF NARROW LINE REGIONS IN ACTIVE GALAXIES. II. THE SIDING SPRING SOUTHERN SEYFERT SPECTROSCOPIC SNAPSHOT SURVEY (S7)

    Energy Technology Data Exchange (ETDEWEB)

    Dopita, Michael A.; Davies, Rebecca; Kewley, Lisa; Hampton, Elise; Sutherland, Ralph [RSAA, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Shastri, Prajval; Kharb, Preeti; Jose, Jessy; Bhatt, Harish; Ramya, S. [Indian Institute of Astrophysics, Koramangala 2 B Block, Bangalore 560034 (India); Scharwächter, Julia [LERMA, Observatoire de Paris, CNRS, UMR 8112, 61 Avenue de l’Observatoire, F-75014 Paris (France); Jin, Chichuan [Qian Xuesen Laboratory for Space Technology, Beijing (China); Banfield, Julie [CSIRO Astronomy and Space Science, P.O. Box 76, Epping NSW, 1710 Australia (Australia); Zaw, Ingyin [New York University (Abu Dhabi), 70 Washington Square South, New York, NY 10012 (United States); Juneau, Stéphanie [CEA-Saclay, DSM/IRFU/SAp, F-91191 Gif-sur-Yvette (France); James, Bethan [Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0HA (United Kingdom); Srivastava, Shweta, E-mail: Michael.Dopita@anu.edu.au [Astronomy and Astrophysics Division, Physical Research Laboratory, Ahmedabad 380009 (India)

    2015-03-15

    Here we describe the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7) and present results on 64 galaxies drawn from the first data release. The S7 uses the Wide Field Spectrograph mounted on the ANU 2.3 m telescope located at the Siding Spring Observatory to deliver an integral field of 38 × 25 arcsec at a spectral resolution of R = 7000 in the red (530–710 nm), and R = 3000 in the blue (340–560 nm). From these data cubes we have extracted the narrow-line region spectra from a 4 arcsec aperture centered on the nucleus. We also determine the Hβ and [O iii] λ5007 fluxes in the narrow lines, the nuclear reddening, the reddening-corrected relative intensities of the observed emission lines, and the Hβ and [O iii] λ5007 luminosities determined from spectra for which the stellar continuum has been removed. We present a set of images of the galaxies in [O iii] λ5007, [N ii] λ6584, and Hα, which serve to delineate the spatial extent of the extended narrow-line region and also to reveal the structure and morphology of the surrounding H ii regions. Finally, we provide a preliminary discussion of those Seyfert 1 and Seyfert 2 galaxies that display coronal emission lines in order to explore the origin of these lines.

  13. The Centaurus cluster of galaxies. II. The bimodal-velocity structure

    International Nuclear Information System (INIS)

    Lucey, J.R.; Currie, M.J.; Dickens, R.J.

    1985-09-01

    This is the second paper in a series that describes an extensive study of the Centaurus cluster of galaxies. The paper concerns the bimodal velocity distribution of the galaxies in the cluster. The likely location of the two main cluster components is discussed. The data strongly favours the hypothesis that the two components lie within the same cluster. (UK)

  14. A Variation of the Present Star Formation Activity of Spiral Galaxies

    OpenAIRE

    Tomita, Akihiko; Tomita, Yoshio; Saito, Mamoru

    1996-01-01

    The star formation rate in spiral galaxies is considered to be decreasing continuously with time in a time scale of $10^{9}$ yr. The present star formation activity, on the other hand, shows various degrees among galaxies. We make a new data set of 1681 nearby spiral galaxies from available databases and study the statistics of the present star formation activity. We analyze far-infrared and optical B-band surface brightnesses of the H II regions and the non-H II regions in M~31 and show that...

  15. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Pagel, B.E.J.

    1979-01-01

    The chemical evolution of disk galaxies is discussed with special reference to results obtained from studies of the oxygen abundance in H II regions. Normal spirals (including our own) display the by now well known radial abundance gradient, which is discussed on the basis of the simple enrichment model and other models. The Magellanic Clouds, on the other hand, and the barred spiral NGC 1365, have been found to have little or no abundance gradient, implying a very different sort of evolution that may involve large-scale mixing. Finally, the simple model is tested against a number of results in H II regions where the ratio of total mass to mass of residual gas can be estimated. It turns out to fit adequately the Magellanic Clouds and a number of H II regions in the outer parts of spiral galaxies, but in more inner parts it fails, as do more sophisticated models involving infall during the formation of galactic disks that have proved very successful in other respects. (Auth.)

  16. GREEN GALAXIES IN THE COSMOS FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Zhizheng; Kong, Xu; Fan, Lulu, E-mail: panzz@mail.ustc.edu.cn, E-mail: xkong@ustc.edu.cn [Center of Astrophysics, University of Science and Technology of China, Hefei 230026 (China)

    2013-10-10

    We present research on the morphologies, spectra, and environments of ≈2350 'green valley' galaxies at 0.2 < z < 1.0 in the COSMOS field. The bimodality of dust-corrected NUV–r {sup +} color is used to define 'green valley'; it removes dusty star-forming galaxies from galaxies that are truly transitioning between the blue cloud and the red sequence. Morphological parameters of green galaxies are intermediate between those of blue and red galaxy populations, both on the Gini-asymmetry and the Gini-M{sub 20} planes. Approximately 60%-70% of green disk galaxies have intermediate or big bulges, and only 5%-10% are pure disk systems, based on morphological classification using the Zurich Estimator of Structural Types. The obtained average spectra of green galaxies are intermediate between blue and red ones in terms of [O II], Hα, and Hβ emission lines. Stellar population synthesis on the average spectra shows that green galaxies are on average older than blue galaxies but younger than red galaxies. Green galaxies and blue galaxies have similar projected galaxy density (Σ{sub 10}) distributions at z > 0.7. At z < 0.7, the fractions of M{sub *} < 10{sup 10.0} M{sub ☉} green galaxies located in a dense environment are found to be significantly larger than those of blue galaxies. The morphological and spectral properties of green galaxies are consistent with the transitioning population between the blue cloud and the red sequence. The possible mechanisms for quenching star formation activities in green galaxies are discussed. The importance of active galactic nucleus feedback cannot be well constrained in our study. Finally, our findings suggest that environmental conditions, most likely starvation and harassment, significantly affect the transformation of M{sub *} < 10{sup 10.0} M{sub ☉} blue galaxies into red galaxies, especially at z < 0.5.

  17. Bright emission lines in new Seyfert galaxies

    International Nuclear Information System (INIS)

    Afanasev, V.L.; Denisiuk, E.K.; Lipovetskii, V.A.; Shapovalova, A.I.

    1983-01-01

    Observational data are given on bright emission lines (H-alpha, H-beta, and forbidden N II, S II, and O III) for 14 recently discovered Seyfert galaxies. The investigated objects can be divided into three groups, which correspond approximately to the first (5 objects), the intermediate (4 objects), and the second (4 objects) Seyfert types. Attention is drawn to the properties of the galaxy Markaryan 1018, which has features of both the first and the second type and is distinguished by the weakness of its emission lines, which is probably due to a gas deficit. 7 references

  18. Metal-poor dwarf galaxies in the SIGRID galaxy sample. II. The electron temperature-abundance calibration and the parameters that affect it

    Energy Technology Data Exchange (ETDEWEB)

    Nicholls, David C.; Dopita, Michael A.; Sutherland, Ralph S.; Jerjen, Helmut; Kewley, Lisa J., E-mail: David.Nicholls@anu.edu.au [Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd., Weston ACT 2611 (Australia)

    2014-07-20

    In this paper, we use the Mappings photoionization code to explore the physical parameters that impact on the measurement of electron temperature and abundance in H II regions. In our previous paper, we presented observations and measurements of physical properties from the spectra of 17 H II regions in 14 isolated dwarf irregular galaxies from the SIGRID sample. Here, we analyze these observations further, together with three additional published data sets. We explore the effects of optical thickness, electron density, ionization parameter, ionization source, and non-equilibrium effects on the relation between electron temperature and metallicity. We present a standard model that fits the observed data remarkably well at metallicities between one-tenth and 1 solar. We investigate the effects of optically thin H II regions, and show that they can have a considerable effect on the measured electron temperature, and that there is evidence that some of the observed objects are optically thin. We look at the role of the ionization parameter and find that lower ionization parameter values give better fits at higher oxygen abundance. We show that higher pressures combined with low optical depth, and also κ electron energy distributions at low κ values, can generate the apparent high electron temperatures in low-metallicity H II regions, and that the former provides the better fit to observations. We examine the effects of these parameters on the strong line diagnostic methods. We extend this to three-dimensional diagnostic grids to confirm how well the observations are described by the grids.

  19. Optical photometry of galaxies

    International Nuclear Information System (INIS)

    Comte, G.

    1981-01-01

    The present status of the optical and near-infrared photometry of galaxies is reviewed. Part I introduces to the goals and general methods of both photographic surface photometry and integrated multicolor aperture photoelectric photometry for extended stellar systems, with a summary of the necessary corrections to the observed magnitudes and colors. Part II (surface photometry) summarizes recent results on the empirical luminosity laws for spheroidal systems and the separation of components in disk-plus-bulge systems. Part III (color problems) discusses integrated color effects (color and gas content, color-absolute magnitude relation for early-type systems, colors of interacting galaxies) and color gradient across spheroidal and disk galaxies. In part IV are summarized some constraints on the luminosity function of the stellar population in spheroidal systems given by narrow-band photometry [fr

  20. Demographics of Starbursts in Nearby Seyfert Galaxies

    Science.gov (United States)

    Schinnerer, E.; Colbert, E.; Armus, L.; Scoville, N. Z.; Heckman, T.

    2002-12-01

    We investigate the frequency of circumnuclear starbursts in Seyfert galaxies using medium-resolution H and K band spectroscopy. An unbiased sample of ~20 nearby Seyfert galaxies was observed at the KeckII telescope with an average seeing of ~0.7''. Preliminary analysis shows strong stellar absorption lines for most galaxies in our sample. Comparison of stellar equivalent widths in the H and K band will allow us to determine the average age of the dominating stellar population. Evidence for an age trend with Seyfert type would provide a strong hint toward a starburst/AGN connection.

  1. Host galaxy spectra and consequences for supernova typing from the SDSS SN survey

    Energy Technology Data Exchange (ETDEWEB)

    Olmstead, Matthew D.; Brown, Peter J.; Brownstein, Joel R.; Dawson, Kyle S. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Sako, Masao; Gupta, Ravi R. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Bassett, Bruce; Kunz, Martin [African Institute for Mathematical Sciences, 6 Melrose Road, Muizenberg, 7945 (South Africa); Bizyaev, Dmitry; Brinkmann, J.; Brewington, Howard; Ebelke, Garrett L. [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States); Campbell, Heather [Institute of Astronomy, Madingley Road, Cambridge CB4 0HA (United Kingdom); D' Andrea, Chris B.; Lampeitl, Hubert [Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Frieman, Joshua A. [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Galbany, Lluís [Institut de Física d' Altes Energies, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Barcelona) (Spain); Garnavich, Peter [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Hlozek, Renee [Department of Astrophysics, Peyton Hall, 4 Ivy Lane, Princeton, NJ 08544 (United States); Jha, Saurabh W., E-mail: olmstead@physics.utah.edu [Department of Physics and Astronomy, Rutgers, the State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); and others

    2014-04-01

    We present the spectroscopy from 5254 galaxies that hosted supernovae (SNe) or other transient events in the Sloan Digital Sky Survey II (SDSS-II). Obtained during SDSS-I, SDSS-II, and the Baryon Oscillation Spectroscopic Survey, this sample represents the largest systematic, unbiased, magnitude limited spectroscopic survey of SN host galaxies. Using the host galaxy redshifts, we test the impact of photometric SN classification based on SDSS imaging data with and without using spectroscopic redshifts of the host galaxies. Following our suggested scheme, there are a total of 1166 photometrically classified SNe Ia when using a flat redshift prior and 1126 SNe Ia when the host spectroscopic redshift is assumed. For 1024 (87.8%) candidates classified as likely SNe Ia without redshift information, we find that the classification is unchanged when adding the host galaxy redshift. Using photometry from SDSS imaging data and the host galaxy spectra, we also report host galaxy properties for use in future analysis of SN astrophysics. Finally, we investigate the differences in the interpretation of the light curve properties with and without knowledge of the redshift. Without host galaxy redshifts, we find that SALT2 light curve fits are systematically biased toward lower photometric redshift estimates and redder colors in the limit of low signal-to-noise data. The general improvements in performance of the light curve fitter and the increased diversity of the host galaxy sample highlights the importance of host galaxy spectroscopy for current photometric SN surveys such as the Dark Energy Survey and future surveys such as the Large Synoptic Survey Telescope.

  2. Are star formation rates of galaxies bimodal?

    Science.gov (United States)

    Feldmann, Robert

    2017-09-01

    Star formation rate (SFR) distributions of galaxies are often assumed to be bimodal with modes corresponding to star-forming and quiescent galaxies, respectively. Both classes of galaxies are typically studied separately, and SFR distributions of star-forming galaxies are commonly modelled as lognormals. Using both observational data and results from numerical simulations, I argue that this division into star-forming and quiescent galaxies is unnecessary from a theoretical point of view and that the SFR distributions of the whole population can be well fitted by zero-inflated negative binomial distributions. This family of distributions has three parameters that determine the average SFR of the galaxies in the sample, the scatter relative to the star-forming sequence and the fraction of galaxies with zero SFRs, respectively. The proposed distributions naturally account for (I) the discrete nature of star formation, (II) the presence of 'dead' galaxies with zero SFRs and (III) asymmetric scatter. Excluding 'dead' galaxies, the distribution of log SFR is unimodal with a peak at the star-forming sequence and an extended tail towards low SFRs. However, uncertainties and biases in the SFR measurements can create the appearance of a bimodal distribution.

  3. GLACE: freezing the environment of line--emitting cluster galaxies

    Science.gov (United States)

    Pintos--Castro, I.; Sánchez--Portal, M.; Cepa, J.; Povi, M.; Santos, J.; Altieri, B.; Bongiovanni, A.; Ederoclite, A.; Oteo, I.; Pérez García, A.; Pérez--Martínez, R.; Polednikova, J.; Ramón--Pérez, M.

    2015-05-01

    GLACE is performing a survey of emission-line galaxies in clusters with the main aim of studying the effect of the environment in the star formation activity. The innovation of this work is the use of tunable filters in scan mode to obtain low resolution spectra of the desired emission lines. Although the survey is in its initial stage, we have analysed two line datasets in two different clusters: Hα in Cl0024 at z=0.4 and [O II] in RXJ1257 at z = 0.9. The first is a well known intermediate redshift cluster that has been used to test the observational strategy. We reached the planned SFRs and we could deblend the [N II] component, thus being able to discriminate the AGN population from the star-forming galaxies. Also the spectral resolution is allowing us to exploit the data for dynamical analysis. The second target is a recently discovered cluster, that we have studied regarding its FIR and [O II] emission. The [O II] observations are revealing a fainter and less massive sample, when compared with the FIR emitters, showing two different populations of star-forming galaxies. The cluster emitters have shown that no evident correlation exist between the SFR (or sSFR) and the environment. Nevertheless, we have found that both samples, FIR- and [O II]-emitters, are concentrated in the areas of intermediate to even high local density. Additionally, we explored the morphological properties of the cluster galaxies using the non-parametric galSVM code.

  4. EVOLUTION OF GASEOUS DISK VISCOSITY DRIVEN BY SUPERNOVA EXPLOSION. II. STRUCTURE AND EMISSIONS FROM STAR-FORMING GALAXIES AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    Yan Changshuo; Wang Jianmin

    2010-01-01

    High spatial resolution observations show that high-redshift galaxies are undergoing intensive evolution of dynamical structure and morphologies displayed by the Hα, Hβ, [O III], and [N II] images. It has been shown that supernova explosion (SNexp) of young massive stars during the star formation epoch, as kinetic feedback to host galaxies, can efficiently excite the turbulent viscosity. We incorporate the feedback into the dynamical equations through mass dropout and angular momentum transportation driven by the SNexp-excited turbulent viscosity. The empirical Kennicutt-Schmidt law is used for star formation rates (SFRs). We numerically solve the equations and show that there can be intensive evolution of structure of the gaseous disk. Secular evolution of the disk shows interesting characteristics: (1) high viscosity excited by SNexp can efficiently transport the gas from 10 kpc to ∼1 kpc forming a stellar disk whereas a stellar ring forms for the case with low viscosity; (2) starbursts trigger SMBH activity with a lag of ∼10 8 yr depending on SFRs, prompting the joint evolution of SMBHs and bulges; and (3) the velocity dispersion is as high as ∼100 km s -1 in the gaseous disk. These results are likely to vary with the initial mass function (IMF) that the SNexp rates rely on. Given the IMF, we use the GALAXEV code to compute the spectral evolution of stellar populations based on the dynamical structure. In order to compare the present models with the observed dynamical structure and images, we use the incident continuum from the simple stellar synthesis and CLOUDY to calculate emission line ratios of Hα, Hβ, [O III], and [N II], and Hα brightness of gas photoionized by young massive stars formed on the disks. The models can produce the main features of emission from star-forming galaxies. We apply the present model to two galaxies, BX 389 and BX 482 observed in the SINS high-z sample, which are bulge and disk-dominated, respectively. Two successive

  5. Halo histories versus galaxy properties at z = 0 II: large-scale galactic conformity

    Science.gov (United States)

    Tinker, Jeremy L.; Hahn, ChangHoon; Mao, Yao-Yuan; Wetzel, Andrew R.; Conroy, Charlie

    2018-06-01

    Using group catalogues from the Sloan Digital Sky Survey (SDSS) Data Release 7, we measure galactic conformity in the local universe. We measure the quenched fraction of neighbour galaxies around isolated primary galaxies, dividing the isolated sample into star-forming and quiescent objects. We restrict our measurements to scales >1 Mpc to probe the correlations between halo formation histories. Over the stellar mass range 109.7 ≤ M*/M⊙ ≤ 1010.9, we find minimal evidence for conformity. We further compare these data to predictions of the halo age-matching model, in which the oldest galaxies are associated with the oldest haloes. For models with strong correlations between halo and stellar age, the conformity is too large to be consistent with the data. Weaker implementations of the age-matching model would not produce a detectable signal in SDSS data. We reproduce the results of Kauffmann et al., in which the star formation rates of neighbour galaxies are reduced around primary galaxies when the primaries are low star formers. However, we find this result is mainly driven by contamination in the isolation criterion; when removing the small fraction of satellite galaxies in the sample, the conformity signal largely goes away. Lastly, we show that small conformity signals, i.e. 2-5 per cent differences in the quenched fractions of neighbour galaxies, can be produced by mechanisms other than halo assembly bias. For example, if passive galaxies occupy more massive haloes than star-forming galaxies of the same stellar mass, a conformity signal that is consistent with recent measurements from PRIMUS (Berti et al.) can be produced.

  6. Optical observations of the nearby galaxy IC342 with narrow band [SII] and hα filters. II - detection of 16 optically-identified supernova remnant candidates

    Directory of Open Access Journals (Sweden)

    Vučetić M.M.

    2015-01-01

    Full Text Available We present the detection of 16 optical supernova remnant (SNR candidates in the nearby spiral galaxy IC342. The candidates were detected by applying the [Sii]/Hα ratio criterion on observations made with the 2 m RCC telescope at Rozhen National Astronomical Observatory in Bulgaria. In this paper, we report the coordinates, diameters, Hα and [S ii] fluxes for 16 SNRs detected in two fields of view in the IC342 galaxy. Also, we estimate the contamination of total Hα flux from SNRs in the observed portion of IC342 to be 1.4%. This would represent the fractional error when the star formation rate (SFR for this galaxy is derived from the total galaxy’s Hα emission.

  7. Spectrophotometry of the Seyfert galaxy NGC 4593

    International Nuclear Information System (INIS)

    MacAlpine, G.M.; Williams, G.A.; Lewis, D.W.

    1979-01-01

    Spectrophotometry of the bright class 1 Seyfert galaxy NGC 4593 is presented. The emission-line characteristics are briefly discussed and compared with those of other Seyfert galaxies. The measured hydrogen Balmer-line ratios are reasonably consistent with expected recombination values, and the emission intensities of Fe II, He I 5876, and forbidden O III 4363 relative to other lines are stronger than average in NGC 4593

  8. The Westerbork HI survey of spiral and irregular galaxies - II. R-band surface photometry of late-type dwarf galaxies

    NARCIS (Netherlands)

    Swaters, RA; Balcells, M

    R-band surface photometry is presented for 171 late-type dwarf and irregular galaxies. For a subsample of 46 galaxies B-band photometry is presented as well. We present surface brightness profiles as well as isophotal and photometric parameters including magnitudes, diameters and central surface

  9. CHARACTERISTICS OF SPIRAL ARMS IN LATE-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Honig, Z. N.; Reid, M. J.

    2015-01-01

    We have measured the positions of large numbers of H II regions in four nearly face-on, late-type, spiral galaxies: NGC 628 (M74), NGC 1232, NGC 3184, and NGC 5194 (M51). Fitting log-periodic spiral models to segments of each arm yields local estimates of spiral pitch angle and arm width. While pitch angles vary considerably along individual arms, among arms within a galaxy, and among galaxies, we find no systematic trend with galactocentric distance. We estimate the widths of the arm segments from the scatter in the distances of the H II regions from the spiral model. All major arms in these galaxies show spiral arm width increasing with distance from the galactic center, similar to the trend seen in the Milky Way. However, in the outermost parts of the galaxies, where massive star formation declines, some arms reverse this trend and narrow. We find that spiral arms often appear to be composed of segments of ∼5 kpc length, which join to form kinks and abrupt changes in pitch angle and arm width; these characteristics are consistent with properties seen in the large N-body simulations of D'Onghia et al. and others

  10. The Canada-France deep fields survey-II: Lyman-break galaxies and galaxy clustering at z ~ 3

    Science.gov (United States)

    Foucaud, S.; McCracken, H. J.; Le Fèvre, O.; Arnouts, S.; Brodwin, M.; Lilly, S. J.; Crampton, D.; Mellier, Y.

    2003-10-01

    We present a large sample of z ~ 3 U-band dropout galaxies extracted from the Canada-France deep fields survey (CFDF). Our catalogue covers an effective area of ~ 1700 arcmin2 divided between three large, contiguous fields separated widely on the sky. To IAB=24.5, the survey contains 1294 Lyman-break candidates, in agreement with previous measurements by other authors, after appropriate incompleteness corrections have been applied to our data. Based on comparisons with spectroscopic observations and simulations, we estimate that our sample of Lyman-break galaxies is contaminated by stars and interlopers (lower-redshift galaxies) at no more than { ~ } 30%. We find that omega (theta ) is well fitted by a power-law of fixed slope, gamma =1.8, even at small (theta University of Hawaii, and at the Cerro Tololo Inter-American Observatory and Mayall 4-meter Telescopes, divisions of the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation.

  11. CHEMICAL ABUNDANCES OF SEVEN IRREGULAR AND THREE TIDAL DWARF GALAXIES IN THE M81 GROUP

    International Nuclear Information System (INIS)

    Croxall, Kevin V.; Van Zee, Liese; Lee, Henry; Miller, Bryan W.; Skillman, Evan D.; Lee, Janice C.; Cote, Stephanie; Kennicutt, Robert C.

    2009-01-01

    We have derived nebular abundances for 10 dwarf galaxies belonging to the M81 Group, including several galaxies which do not have abundances previously reported in the literature. For each galaxy, multiple H II regions were observed with GMOS-N at the Gemini Observatory in order to determine abundances of several elements (oxygen, nitrogen, sulfur, neon, and argon). For seven galaxies, at least one H II region had a detection of the temperature sensitive [O III] λ4363 line, allowing a 'direct' determination of the oxygen abundance. No abundance gradients were detected in the targeted galaxies, and the observed oxygen abundances are typically in agreement with the well-known metallicity-luminosity relation. However, three candidate 'tidal dwarf' galaxies lie well off this relation: UGC 5336, Garland, and KDG 61. The nature of these systems suggests that UGC 5336 and Garland are indeed recently formed systems, whereas KDG 61 is most likely a dwarf spheroidal galaxy which lies along the same line of sight as the M81 tidal debris field. We propose that these H II regions formed from previously enriched gas which was stripped from nearby massive galaxies (e.g., NGC 3077 and M81) during a recent tidal interaction.

  12. QUALITATIVE INTERPRETATION OF GALAXY SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Almeida, J.; Morales-Luis, A. B. [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain); Terlevich, R.; Terlevich, E. [Instituto Nacional de Astrofisica, Optica y Electronica, Tonantzintla, Puebla (Mexico); Cid Fernandes, R., E-mail: jos@iac.es, E-mail: abml@iac.es, E-mail: rjt@ast.cam.ac.uk, E-mail: eterlevi@inaoep.mx, E-mail: cid@astro.ufsc.br [Departamento de Fisica-CFM, Universidade Federal de Santa Catarina, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil)

    2012-09-10

    We describe a simple step-by-step guide to qualitative interpretation of galaxy spectra. Rather than an alternative to existing automated tools, it is put forward as an instrument for quick-look analysis and for gaining physical insight when interpreting the outputs provided by automated tools. Though the recipe is for general application, it was developed for understanding the nature of the Automatic Spectroscopic K-means-based (ASK) template spectra. They resulted from the classification of all the galaxy spectra in the Sloan Digital Sky Survey data release 7, thus being a comprehensive representation of the galaxy spectra in the local universe. Using the recipe, we give a description of the properties of the gas and the stars that characterize the ASK classes, from those corresponding to passively evolving galaxies, to H II galaxies undergoing a galaxy-wide starburst. The qualitative analysis is found to be in excellent agreement with quantitative analyses of the same spectra. We compare the mean ages of the stellar populations with those inferred using the code STARLIGHT. We also examine the estimated gas-phase metallicity with the metallicities obtained using electron-temperature-based methods. A number of byproducts follow from the analysis. There is a tight correlation between the age of the stellar population and the metallicity of the gas, which is stronger than the correlations between galaxy mass and stellar age, and galaxy mass and gas metallicity. The galaxy spectra are known to follow a one-dimensional sequence, and we identify the luminosity-weighted mean stellar age as the affine parameter that describes the sequence. All ASK classes happen to have a significant fraction of old stars, although spectrum-wise they are outshined by the youngest populations. Old stars are metal-rich or metal-poor depending on whether they reside in passive galaxies or in star-forming galaxies.

  13. LBT/LUCIFER OBSERVATIONS OF THE z ∼ 2 LENSED GALAXY J0900+2234

    International Nuclear Information System (INIS)

    Bian Fuyan; Fan Xiaohui; Bechtold, Jill; McGreer, Ian D.; Just, Dennis W.; Sand, David J.; Green, Richard F.; Thompson, David; Peng, Chien Y.; Seifert, Walter; Ageorges, Nancy; Buschkamp, Peter; Juette, Marcus; Knierim, Volker

    2010-01-01

    We present rest-frame optical images and spectra of the gravitationally lensed, star-forming galaxy J0900+2234 (z = 2.03). The observations were performed with the newly commissioned LUCIFER1 near-infrared (NIR) instrument mounted on the Large Binocular Telescope. We fitted lens models to the rest-frame optical images and found that the galaxy has an intrinsic effective radius of 7.4 ± 0.8 kpc with a lens magnification factor of about 5 for the A and B components. We also discovered a new arc belonging to another lensed high-z source galaxy, which makes this lens system a potential double Einstein ring system. Using the high signal-to-noise ratio rest-frame spectra covered by the H + K band, we detected Hβ, [O III], Hα, [N II], and [S II] emission lines. Detailed physical properties of this high-z galaxy were derived. The extinction toward the ionized H II regions (E g (B - V)) was computed from the flux ratio of Hα and Hβ and appears to be much higher than that toward the stellar continuum (E s (B - V)), derived from the optical and NIR broadband photometry fitting. The metallicity was estimated using N2 and O3N2 indices. It is in the range of 1/5 - 1/3 solar abundance, which is much lower than for typical z ∼ 2 star-forming galaxies. From the flux ratio of [S II]λ6717 and [S II]λ6732, we found that the electron number density of the H II regions in the high-z galaxy was ≅1000 cm -3 , consistent with other z ∼ 2 galaxies but much higher than that in local H II regions. The star formation rate was estimated via the Hα luminosity, after correction for the lens magnification, to be about 365 ± 69 M sun yr -1 . Combining the FWHM of Hα emission lines and the half-light radius, we found that the dynamical mass of the lensed galaxy is (5.8 ± 0.9) x 10 10 M sun . The gas mass is (5.1 ± 1.1) x 10 10 M sun from the Hα flux surface density using global Kennicutt-Schmidt law, indicating a very high gas fraction of 0.79 ± 0.19 in J0900+2234.

  14. OSO 8 X-ray spectra of clusters of galaxies. II - Discussion

    Science.gov (United States)

    Smith, B. W.; Mushotzky, R. F.; Serlemitsos, P. J.

    1979-01-01

    An observational description of X-ray clusters of galaxies is given based on OSO 8 X-ray results for spatially integrated spectra of 20 such clusters and various correlations obtained from these results. It is found from a correlation between temperature and velocity dispersion that the X-ray core radius should be less than the galaxy core radius or, alternatively, that the polytropic index is about 1.1 for most of the 20 clusters. Analysis of a correlation between temperature and emission integral yields evidence that more massive clusters accumulate a larger fraction of their mass as intracluster gas. Galaxy densities and optical morphology, as they correlate with X-ray properties, are reexamined for indications as to how mass injection by galaxies affects the density structure of the gas. The physical arguments used to derive iron abundances from observed equivalent widths of iron line features in X-ray spectra are critically evaluated, and the associated uncertainties in abundances derived in this manner are estimated to be quite large.

  15. Optical spectrophotometry of Wolf-Rayet galaxies

    Science.gov (United States)

    Vacca, William D.; Conti, Peter S.

    1992-01-01

    We have obtained long-slit optical spectra of 10 Wolf-Rayet galaxies and four other starburst galaxies. Using the nebular emission lines we have determined the electron temperatures, electron densities, extinctions, oxygen abundances, mass of ionized hydrogen, and numbers of ionizing photons due to hot stars in these galaxies. The various forbidden line ratios clearly indicate a stellar origin for the emission-line spectrum. From the flux of the broad He II 4686 A emission feature we have estimated the number of Wolf-Rayet stars present. We have accounted for the contribution of these stars to the total ionizing flux and have calculated the ratio of the number of these stars to the number of O stars. Wolf-Rayet galaxies are among the youngest examples of the starburst phenomenon, which we observed at a propitious moment.

  16. ALFALFA DISCOVERY OF THE NEARBY GAS-RICH DWARF GALAXY LEO P. III. AN EXTREMELY METAL DEFICIENT GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Skillman, Evan D.; Berg, Danielle A.; Olive, Keith A.; McQuinn, Kristen B. W., E-mail: skillman@astro.umn.edu, E-mail: berg@astro.umn.edu, E-mail: olive@physics.umn.edu, E-mail: kmcquinn@astro.umn.edu [Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); and others

    2013-07-01

    We present KPNO 4 m and LBT/MODS spectroscopic observations of an H II region in the nearby dwarf irregular galaxy Leo P discovered recently in the Arecibo ALFALFA survey. In both observations, we are able to accurately measure the temperature sensitive [O III] {lambda}4363 line and determine a ''direct'' oxygen abundance of 12 + log(O/H) = 7.17 {+-} 0.04. Thus, Leo P is an extremely metal deficient (XMD) galaxy, and, indeed, one of the most metal deficient star-forming galaxies ever observed. For its estimated luminosity, Leo P is consistent with the relationship between luminosity and oxygen abundance seen in nearby dwarf galaxies. Leo P shows normal {alpha} element abundance ratios (Ne/O, S/O, and Ar/O) when compared to other XMD galaxies, but elevated N/O, consistent with the ''delayed release'' hypothesis for N/O abundances. We derive a helium mass fraction of 0.2509{sup +0.0184}{sub -0.0123}, which compares well with the WMAP + BBN prediction of 0.2483 {+-} 0.0002 for the primordial helium abundance. We suggest that surveys of very low mass galaxies compete well with emission line galaxy surveys for finding XMD galaxies. It is possible that XMD galaxies may be divided into two classes: the relatively rare XMD emission line galaxies which are associated with starbursts triggered by infall of low-metallicity gas and the more common, relatively quiescent XMD galaxies like Leo P, with very low chemical abundances due to their intrinsically small masses.

  17. The SINS/zC-SINF survey of z ∼ 2 galaxy kinematics: Evidence for powerful active galactic nucleus-driven nuclear outflows in massive star-forming galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Förster Schreiber, N. M.; Genzel, R.; Kurk, J. D.; Lutz, D.; Tacconi, L. J.; Wuyts, S.; Bandara, K.; Buschkamp, P.; Davies, R.; Eisenhauer, F.; Lang, P. [Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Newman, S. F. [Department of Astronomy, Hearst Field Annex, University of California, Berkeley, CA 94720 (United States); Burkert, A. [Universitäts-Sternwarte, Ludwig-Maximilians-Universität, Scheinerstrasse 1, D-81679 München (Germany); Carollo, C. M.; Lilly, S. J. [Institute for Astronomy, Department of Physics, Eidgenössische Technische Hochschule, 8093-CH Zürich (Switzerland); Cresci, G. [Istituto Nazionale di Astrofisica—Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Daddi, E. [CEA Saclay, DSM/IRFU/SAp, F-91191 Gif-sur-Yvette (France); Hicks, E. K. S. [Department of Astronomy, University of Washington, P.O. Box 351580, Seattle, WA 98195-1580 (United States); Mainieri, V. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Mancini, C. [Istituto Nazionale di Astrofisica—Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); and others

    2014-05-20

    We report the detection of ubiquitous powerful nuclear outflows in massive (≥10{sup 11} M {sub ☉}) z ∼ 2 star-forming galaxies (SFGs), which are plausibly driven by an active galactic nucleus (AGN). The sample consists of the eight most massive SFGs from our SINS/zC-SINF survey of galaxy kinematics with the imaging spectrometer SINFONI, six of which have sensitive high-resolution adaptive optics-assisted observations. All of the objects are disks hosting a significant stellar bulge. The spectra in their central regions exhibit a broad component in Hα and forbidden [N II] and [S II] line emission, with typical velocity FWHM ∼ 1500 km s{sup –1}, [N II]/Hα ratio ≈ 0.6, and intrinsic extent of 2-3 kpc. These properties are consistent with warm ionized gas outflows associated with Type 2 AGN, the presence of which is confirmed via independent diagnostics in half the galaxies. The data imply a median ionized gas mass outflow rate of ∼60 M {sub ☉} yr{sup –1} and mass loading of ∼3. At larger radii, a weaker broad component is detected but with lower FWHM ∼485 km s{sup –1} and [N II]/Hα ≈ 0.35, characteristic for star formation-driven outflows as found in the lower-mass SINS/zC-SINF galaxies. The high inferred mass outflow rates and frequent occurrence suggest that the nuclear outflows efficiently expel gas out of the centers of the galaxies with high duty cycles and may thus contribute to the process of star formation quenching in massive galaxies. Larger samples at high masses will be crucial in confirming the importance and energetics of the nuclear outflow phenomenon and its connection to AGN activity and bulge growth.

  18. The Milky Way galaxy

    International Nuclear Information System (INIS)

    Woerden, H. van; Allen, R.J.; Burton, W.B.

    1985-01-01

    IAU Symposium 106, held at the Kapteyn Institute in Groningen, presents an overview of all major aspects of galactic astronomy. The vast subject is covered in 20 authoritative review papers and 22 invited papers, each with discussion, plus 81 shorter contributions. The book opens with 4 reviews by historians of science, outlining the history of galactic research. Part 2 deals with (i) galactic rotation, (ii) the large-scale distributions of matter, of both old and young stellar populations, and of the atomic, molecular and high-energy components of the interstellar medium, (iii) small-scale structure in the gas, (iv) the galactic nucleus, (v) the high-velocity clouds. Part 3 discusses the dynamics of the local group of Galaxies and of the Milky Way-Magellanic clouds system, the dynamical and chemical evolution of the Galaxy and of its disk and halo components and the formation of the Galaxy. The controversial subject of spiral structure and star formation is analyzed in several extensive reviews and lively discussions, featuring both observational and theoretical developments. Results of extragalactic research are blended with studies of our Galaxy throughout the book, and there is a separate comparison between Andromeda and Milky Way Galaxies. The Symposium featured the first maps produced by IRAS, and results from most major telescopes in a variety of wavebands. Many review papers present material not published elsewhere. The book closes with a lecture on life in the Galaxy and with an imaginative symposium summary. (orig.)

  19. Biases in Metallicity Measurements from Global Galaxy Spectra: The Effects of Flux Weighting and Diffuse Ionized Gas Contamination

    Science.gov (United States)

    Sanders, Ryan L.; Shapley, Alice E.; Zhang, Kai; Yan, Renbin

    2017-12-01

    Galaxy metallicity scaling relations provide a powerful tool for understanding galaxy evolution, but obtaining unbiased global galaxy gas-phase oxygen abundances requires proper treatment of the various line-emitting sources within spectroscopic apertures. We present a model framework that treats galaxies as ensembles of H II and diffuse ionized gas (DIG) regions of varying metallicities. These models are based upon empirical relations between line ratios and electron temperature for H II regions, and DIG strong-line ratio relations from SDSS-IV MaNGA IFU data. Flux-weighting effects and DIG contamination can significantly affect properties inferred from global galaxy spectra, biasing metallicity estimates by more than 0.3 dex in some cases. We use observationally motivated inputs to construct a model matched to typical local star-forming galaxies, and quantify the biases in strong-line ratios, electron temperatures, and direct-method metallicities as inferred from global galaxy spectra relative to the median values of the H II region distributions in each galaxy. We also provide a generalized set of models that can be applied to individual galaxies or galaxy samples in atypical regions of parameter space. We use these models to correct for the effects of flux-weighting and DIG contamination in the local direct-method mass-metallicity and fundamental metallicity relations, and in the mass-metallicity relation based on strong-line metallicities. Future photoionization models of galaxy line emission need to include DIG emission and represent galaxies as ensembles of emitting regions with varying metallicity, instead of as single H II regions with effective properties, in order to obtain unbiased estimates of key underlying physical properties.

  20. GALAXIES IN X-RAY GROUPS. II. A WEAK LENSING STUDY OF HALO CENTERING

    Energy Technology Data Exchange (ETDEWEB)

    George, Matthew R.; Ma, Chung-Pei [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Leauthaud, Alexie; Bundy, Kevin [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, University of Tokyo, Kashiwa 277-8583 (Japan); Finoguenov, Alexis [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Rykoff, Eli S. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Tinker, Jeremy L. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Massey, Richard [Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Mei, Simona, E-mail: mgeorge@astro.berkeley.edu [Bureau des Galaxies, Etoiles, Physique, Instrumentation (GEPI), University of Paris Denis Diderot, F-75205 Paris Cedex 13 (France)

    2012-09-20

    Locating the centers of dark matter halos is critical for understanding the mass profiles of halos, as well as the formation and evolution of the massive galaxies that they host. The task is observationally challenging because we cannot observe halos directly, and tracers such as bright galaxies or X-ray emission from hot plasma are imperfect. In this paper, we quantify the consequences of miscentering on the weak lensing signal from a sample of 129 X-ray-selected galaxy groups in the COSMOS field with redshifts 0 < z < 1 and halo masses in the range 10{sup 13}-10{sup 14} M{sub Sun }. By measuring the stacked lensing signal around eight different candidate centers (such as the brightest member galaxy, the mean position of all member galaxies, or the X-ray centroid), we determine which candidates best trace the center of mass in halos. In this sample of groups, we find that massive galaxies near the X-ray centroids trace the center of mass to {approx}< 75 kpc, while the X-ray position and centroids based on the mean position of member galaxies have larger offsets primarily due to the statistical uncertainties in their positions (typically {approx}50-150 kpc). Approximately 30% of groups in our sample have ambiguous centers with multiple bright or massive galaxies, and some of these groups show disturbed mass profiles that are not well fit by standard models, suggesting that they are merging systems. We find that halo mass estimates from stacked weak lensing can be biased low by 5%-30% if inaccurate centers are used and the issue of miscentering is not addressed.

  1. Host Galaxy Spectra and Consequences for SN Typing from the SDSS SN Survey

    Energy Technology Data Exchange (ETDEWEB)

    Olmstead, Matthew D.; Brown, Peter J.; Sako, Masao; Bassett, Bruce; Bizyaev, Dmitry; Brinkmann, J.; Brownstein, Joel R.; Brewington, Howard; Campbell, Heather; D’Andrea, Chris B.; Dawson, Kyle S.; Ebelke, Garrett L.; Frieman, Joshua A.; Galbany, Lluís; Garnavich, Peter; Gupta, Ravi R.; Hlozek, Renee; Jha, Saurabh W.; Kunz, Martin; Lampeitl, Hubert; Malanushenko, Elena; Malanushenko, Viktor; Marriner, John; Miquel, Ramon; Montero-Dorta, Antonio D.; Nichol, Robert C.; Oravetz, Daniel J.; Pan, Kaike; Schneider, Donald P.; Simmons, Audrey E.; Smith, Mathew; Snedden, Stephanie A.

    2014-03-06

    We present the spectroscopy from 5254 galaxies that hosted supernovae (SNe) or other transient events in the Sloan Digital Sky Survey II (SDSS-II). Obtained during SDSS-I, SDSS-II, and the Baryon Oscillation Spectroscopic Survey (BOSS), this sample represents the largest systematic, unbiased, magnitude limited spectroscopic survey of supernova (SN) host galaxies. Using the host galaxy redshifts, we test the impact of photometric SN classification based on SDSS imaging data with and without using spectroscopic redshifts of the host galaxies. Following our suggested scheme, there are a total of 1166 photometrically classified SNe Ia when using a flat redshift prior and 1126 SNe Ia when the host spectroscopic redshift is assumed. For 1024 (87.8%) candidates classified as likely SNe Ia without redshift information, we find that the classification is unchanged when adding the host galaxy redshift. Using photometry from SDSS imaging data and the host galaxy spectra, we also report host galaxy properties for use in future nalysis of SN astrophysics. Finally, we investigate the differences in the interpretation of the light curve properties with and without knowledge of the redshift. When using the SALT2 light curve fitter, we find a 21% increase in the number of fits that converge when using the spectroscopic redshift. Without host galaxy redshifts, we find that SALT2 light curve fits are systematically biased towards lower photometric redshift estimates and redder colors in the limit of low signal-to-noise data. The general improvements in performance of the light curve fitter and the increased diversity of the host galaxy sample highlights the importance of host galaxy spectroscopy for current photometric SN surveys such as the Dark Energy Survey and future surveys such as the Large Synoptic Survey Telescope.

  2. MASS AND ENVIRONMENT AS DRIVERS OF GALAXY EVOLUTION. II. THE QUENCHING OF SATELLITE GALAXIES AS THE ORIGIN OF ENVIRONMENTAL EFFECTS

    Energy Technology Data Exchange (ETDEWEB)

    Peng Yingjie; Lilly, Simon J.; Carollo, Marcella [Institute of Astronomy, ETH Zurich, 8093 Zurich (Switzerland); Renzini, Alvio [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

    2012-09-20

    We extend the phenomenological study of the evolving galaxy population of Peng et al. (2010) to the central/satellite dichotomy in Yang et al. Sloan Digital Sky Survey (SDSS) groups. We find that satellite galaxies are responsible for all the environmental effects in our earlier work. The fraction of centrals that are red does not depend on their environment but only on their stellar masses, whereas that of the satellites depends on both. We define a relative satellite quenching efficiency {epsilon}{sub sat}, which is the fraction of blue centrals that are quenched upon becoming the satellite of another galaxy. This is shown to be independent of stellar mass, but to depend strongly on local overdensity, {delta}, ranging between 0.2 and at least 0.8. The red fraction of satellites correlate much better with the local overdensity {delta}, a measure of location within the group, than with the richness of the group, i.e., dark matter halo mass. This, and the fact that satellite quenching depends on local density and not on either the stellar mass of the galaxy or the dark matter halo mass, gives clues as to the nature of the satellite-quenching process. We furthermore show that the action of mass quenching on satellite galaxies is also independent of the dark matter mass of the parent halo. We then apply the Peng et al. approach to predict the mass functions of central and satellite galaxies, split into passive and active galaxies, and show that these match very well the observed mass functions from SDSS, further strengthening the validity of this phenomenological approach. We highlight the fact that the observed M* is exactly the same for the star-forming centrals and satellites and the observed M* for the star-forming satellites is independent of halo mass above 10{sup 12} M{sub Sun }, which emphasizes the universality of the mass-quenching process that we identified in Peng et al. Post-quenching merging modifies the mass function of the central galaxies but can

  3. NEAR-INFRARED SPECTROSCOPY OF NEARBY SEYFERT GALAXIES: IS THERE EVIDENCE FOR SHOCK EXCITATION IN NARROW-LINE REGIONS?

    Energy Technology Data Exchange (ETDEWEB)

    Terao, K. [Graduate School of Science and Engineering, Ehime University, Bunkyo-cho 2-5, Matsuyama, Ehime 790-8577 (Japan); Nagao, T.; Toba, Y. [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, Matsuyama, Ehime 790-8577 (Japan); Hashimoto, T. [National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan (China); Yanagisawa, K. [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Honjo 3037-5, Kamogata-cho, Asaguchi, Okayama 719-0232 (Japan); Matsuoka, K. [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Ikeda, H. [National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo, 181-8588 (Japan); Taniguchi, Y., E-mail: terao@cosmos.phys.sci.ehime-u.ac.jp [The Open University of Japan, Wakaba 2-11, Mihama-ku, Chiba 261-8586 (Japan)

    2016-12-20

    One of the important unsettled problems regarding active galactic nuclei (AGNs) is the major ionization mechanism of gas clouds in AGN narrow-line regions (NLRs). In order to investigate this issue, we present our J -band spectroscopic observations of a sample of 26 nearby Seyfert galaxies. In our study, we use the flux ratio of the following two forbidden emission lines, [Fe ii]1.257  μ m and [P ii]1.188  μ m, because it is known that this ratio is sensitive to the ionization mechanism. We obtain the [Fe ii]/[P ii] flux ratio or its lower limit for 19 objects. In addition to our data, we compile this flux ratio (or its lower limit) for 23 nearby Seyfert galaxies from the literature. Based on the collected data, we find that three Seyfert galaxies show very large lower limits of the [Fe ii]/[P ii] flux ratios (≳10): NGC 2782, NGC 5005, and Mrk 463. It is thus suggested that the contribution of the fast shock in the gas excitation is significantly large for them. However, more than half of the Seyfert galaxies in our sample show moderate [Fe ii]/[P ii] flux ratios (∼2), which is consistent with pure photoionization by power-law ionizing continuum emission. We also find that the [Fe ii]/[P ii] flux ratio shows no clear correlation with the radio loudness, suggesting that the radio jet is not the primary origin of shocks in NLRs of Seyfert galaxies.

  4. H2 region detection

    International Nuclear Information System (INIS)

    Comte, G.

    1978-01-01

    The now classical technique of detection of HII regions is by means of photography and/or interferometry through narrow-band interference filters, with a large aperture ratio of the imaging optics. It enables the detailed study of the spiral structure and the repartition of ionized gas in our Galaxy as well as in the external galaxies [fr

  5. H α IMAGING OF NEARBY SEYFERT HOST GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Theios, Rachel L.; Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095 (United States); Ross, Nathaniel R., E-mail: rtheios@astro.caltech.edu [Raytheon Space and Airborne Systems, 2000 E El Segundo Boulevard, El Segundo, CA 90245 (United States)

    2016-05-01

    We used narrowband (Δ λ = 70 Å) interference filters with the CCD imaging camera on the Nickel 1.0 m telescope at Lick Observatory to observe 31 nearby ( z < 0.03) Seyfert galaxies in the 12 μ m active galaxy sample. We obtained pure emission-line images of each galaxy, which reach down to a flux limit of 7.3 × 10{sup −15} erg cm{sup −2} s{sup −1} arcsec{sup −2}, and corrected these images for [N ii] emission and extinction. We separated the H α emission line of the “nucleus” (central 100–1000 pc) from that of the host galaxy. The extended H α emission is expected to be powered by newly formed hot stars, and indeed correlates well with other indicators of current star formation rates (SFRs) in these galaxies: extended 7.7 μ m polycyclic aromatic hydrocarbon, total far-infrared, and radio luminosity. Relative to what would be expected from recent star formation, there is a 0.8 dex excess of radio emission in our Seyfert galaxies. The H α luminosity we measured in the centers of our galaxies is dominated by the active galactic nucleus (AGN), and is linearly correlated with the hard X-ray luminosity. There is, however, an upward offset of 1 dex in this correlation for the Seyfert 1s, because their nuclear H α emission includes a strong additional contribution from the broad-line region. We found a correlation between SFR and AGN luminosity. In spite of selection effects, we concluded that the absence of bright Seyfert nuclei in galaxies with low SFRs is real, albeit only weakly significant. Finally, we used our measured spatial distributions of H α emission to determine what these Seyfert galaxies would look like when observed through fixed apertures (e.g., a spectroscopic fiber) at high redshifts. We found that although all of these Seyfert galaxies would be detectable emission-line galaxies at any redshift, most of them would appear to be dominated by (>67%) their H ii region emission. Only the most luminous AGNs (log( L {sub Hα}/erg s

  6. Galaxy modelling. II. Multi-wavelength faint counts from a semi-analytic model of galaxy formation

    Science.gov (United States)

    Devriendt, J. E. G.; Guiderdoni, B.

    2000-11-01

    This paper predicts self-consistent faint galaxy counts from the UV to the submm wavelength range. The stardust spectral energy distributions described in Devriendt et al. \\citeparyear{DGS99} (Paper I) are embedded within the explicit cosmological framework of a simple semi-analytic model of galaxy formation and evolution. We begin with a description of the non-dissipative and dissipative collapses of primordial perturbations, and plug in standard recipes for star formation, stellar evolution and feedback. We also model the absorption of starlight by dust and its re-processing in the IR and submm. We then build a class of models which capture the luminosity budget of the universe through faint galaxy counts and redshift distributions in the whole wavelength range spanned by our spectra. In contrast with a rather stable behaviour in the optical and even in the far-IR, the submm counts are dramatically sensitive to variations in the cosmological parameters and changes in the star formation history. Faint submm counts are more easily accommodated within an open universe with a low value of Omega_0 , or a flat universe with a non-zero cosmological constant. We confirm the suggestion of Guiderdoni et al. \\citeparyear{GHBM98} that matching the current multi-wavelength data requires a population of heavily-extinguished, massive galaxies with large star formation rates ( ~ 500 M_sun yr-1) at intermediate and high redshift (z >= 1.5). Such a population of objects probably is the consequence of an increase of interaction and merging activity at high redshift, but a realistic quantitative description can only be obtained through more detailed modelling of such processes. This study illustrates the implementation of multi-wavelength spectra into a semi-analytic model. In spite of its simplicity, it already provides fair fits of the current data of faint counts, and a physically motivated way of interpolating and extrapolating these data to other wavelengths and fainter flux

  7. Dynamical evolution of galaxies in clusters

    International Nuclear Information System (INIS)

    Ostriker, J.P.

    1977-01-01

    In addition to the processes involved in the evolution of star clusters, there are three kinds of processes that are peculiar to, or far more important in, galaxy clusters than in star clusters: galaxy interactions with gas, high-velocity tidal interactions, and accretion and cannibalism. The latter is discussed at some length; analytical calculations for the apparent luminosity evolution of the first brightest galaxy and the apparent luminosity evolution of M 12 are described, along with the numerical simulation of cluster evolution. It appears that many of the notable features of centrally condensed clusters of galaxies, particularly the presence of very luminous but low-surface-brightness central cD systems, can be understood in terms of a straightforward dynamical theory of galactic cannibalism. It is possible to maintain the hypothesis that dynamical evolution gradually transforms Bautz--Morgan III clusters to type II systems or type I systems. 36 references, 5 figures

  8. Synthetic nebular emission from massive galaxies - I: origin of the cosmic evolution of optical emission-line ratios

    Science.gov (United States)

    Hirschmann, Michaela; Charlot, Stephane; Feltre, Anna; Naab, Thorsten; Choi, Ena; Ostriker, Jeremiah P.; Somerville, Rachel S.

    2017-12-01

    Galaxies occupy different regions of the [O III]λ5007/H β-versus-[N II]λ6584/H α emission-line ratio diagram in the distant and local Universe. We investigate the origin of this intriguing result by modelling self-consistently, for the first time, nebular emission from young stars, accreting black holes (BHs) and older, post-asymptotic giant branch (post-AGB) stellar populations in galaxy formation simulations in a full cosmological context. In post-processing, we couple new-generation nebular-emission models with high-resolution, cosmological zoom-in simulations of massive galaxies to explore which galaxy physical properties drive the redshift evolution of the optical-line ratios [O III]λ5007/H β, [N II]λ6584/H α, [S II]λλ6717, 6731/H α and [O I]λ6300/H α. The line ratios of simulated galaxies agree well with observations of both star-forming and active local Sloan Digital Sky Survey galaxies. Towards higher redshifts, at fixed galaxy stellar mass, the average [O III]/H β is predicted to increase and [N II]/H α, [S II]/H α and [O I]/H α to decrease - widely consistent with observations. At fixed stellar mass, we identify star formation history, which controls nebular emission from young stars via the ionization parameter, as the primary driver of the cosmic evolution of [O III]/H β and [N II]/H α. For [S II]/H α and [O I]/H α, this applies only to redshifts greater than z = 1.5, the evolution at lower redshift being driven in roughly equal parts by nebular emission from active galactic nuclei and post-AGB stellar populations. Instead, changes in the hardness of ionizing radiation, ionized-gas density, the prevalence of BH accretion relative to star formation and the dust-to-metal mass ratio (whose impact on the gas-phase N/O ratio we model at fixed O/H) play at most a minor role in the cosmic evolution of simulated galaxy line ratios.

  9. Velocity dispersions in the bulges of spiral and SO galaxies. II. Further observations and a simple three-component model for spiral galaxies

    International Nuclear Information System (INIS)

    Whitmore, B.C.; Kirshner, R.P.

    1981-01-01

    We have obtained velocity dispersions for 24 galaxies in the Virgo cluster to supplement our earlier results. A 2000 channel intensified Reticon scanner has again been used on the 1.3 m telescope of McGraw-Hill Observatory, and a Fourier quotient technique has been employed to yield dispersions. We have confirmed our earlier result that spiral bulges exhibit a relation between total luminosity and velocity dispersion with the form L proportional sigma 4 , but with velocity dispersions that are 17 +- 8% smaller than elliptical galaxies at the same absolute magnitude. However, possible systematic errors may still affect the reality of this gap. The scatter in the L proportional sigma 4 relationship is substantially larger for the spiral bulges than for the elliptical galaxies. This larger scatter probably indicates that spiral bulges comprise a more heterogeneous sample than do elliptical galaxies. we also find that the bulge components of SO galaxies follow a L proportional sigma 4 relation with no gap with the ellipticals. The similarity in this relation for the spheroidal components of spiral, SO, and elliptical galaxies indicates that the systems are dynamically similar

  10. A More Extreme View of Molecular Gas in the Center of the Milky Way galaxy

    Science.gov (United States)

    Mills, Elisabeth Anne Crossfield

    This thesis examines the molecular gas properties in the central 600 parsecs of the Galaxy (the CMZ). I first present a study of a group of HII regions in the central 10 parsecs embedded within the M-0.02-0.07 cloud, adjacent to the Sgr A East supernova remnant. To better depict the physical relationship between these sources, I use archival VLA observations and Paschen-alpha images from the Hubble Space telescope to determine the extinction toward the HII regions. From the measured extinctions and source morphologies, I determine that three of the HII regions lie on the front side of the cloud and formed in the eastern part of the cloud which is unaffected by the supernova remnant's expansion. The higher extinction of the fourth HII region indicates it is embedded in the supernova-compressed ridge, and though younger than the other HII regions, is still older than the supernova. This work is an important determination of the their line-of-sight placement of these sources which helps to define their interaction and strengthens the case that the supernova did not trigger the formation of the HII regions. I next present results from a project I led to survey a sample of CMZ clouds for hot gas using the Green Bank Telescope. I observe multiple highly-excited lines of ammonia, and detect emission from the (9,9) line of ammonia, (excitation energy = 840 K) in 13 of 17 clouds, many of which have no associated star formation. For the three strongest sources, I derive rotation temperatures of 400-500 K, substantially higher than previous temperatures of 200-300 K measured for these clouds. The widespread detections of gas hotter than 400 K indicates for the first time that his hot gas must be heated by global processes in the CMZ. These extremely high temperatures also suggest that cosmic rays are not responsible for the heating of this gas. I also present a determination of the density of the Circumnuclear disk (CND) in the central two parsecs using multiple transitions

  11. Interactions of galaxies outside clusters and massive groups

    Science.gov (United States)

    Yadav, Jaswant K.; Chen, Xuelei

    2018-06-01

    We investigate the dependence of physical properties of galaxies on small- and large-scale density environment. The galaxy population consists of mainly passively evolving galaxies in comparatively low-density regions of Sloan Digital Sky Survey (SDSS). We adopt (i) local density, ρ _{20}, derived using adaptive smoothing kernel, (ii) projected distance, r_p, to the nearest neighbor galaxy and (iii) the morphology of the nearest neighbor galaxy as various definitions of environment parameters of every galaxy in our sample. In order to detect long-range interaction effects, we group galaxy interactions into four cases depending on morphology of the target and neighbor galaxies. This study builds upon an earlier study by Park and Choi (2009) by including improved definitions of target and neighbor galaxies, thus enabling us to better understand the effect of "the nearest neighbor" interaction on the galaxy. We report that the impact of interaction on galaxy properties is detectable at least up to the pair separation corresponding to the virial radius of (the neighbor) galaxies. This turns out to be mostly between 210 and 360 h^{-1}kpc for galaxies included in our study. We report that early type fraction for isolated galaxies with r_p > r_{vir,nei} is almost ignorant of the background density and has a very weak density dependence for closed pairs. Star formation activity of a galaxy is found to be crucially dependent on neighbor galaxy morphology. We find star formation activity parameters and structure parameters of galaxies to be independent of the large-scale background density. We also exhibit that changing the absolute magnitude of the neighbor galaxies does not affect significantly the star formation activity of those target galaxies whose morphology and luminosities are fixed.

  12. Supernova rates from the SUDARE VST-Omegacam search II. Rates in a galaxy sample

    Science.gov (United States)

    Botticella, M. T.; Cappellaro, E.; Greggio, L.; Pignata, G.; Della Valle, M.; Grado, A.; Limatola, L.; Baruffolo, A.; Benetti, S.; Bufano, F.; Capaccioli, M.; Cascone, E.; Covone, G.; De Cicco, D.; Falocco, S.; Haeussler, B.; Harutyunyan, V.; Jarvis, M.; Marchetti, L.; Napolitano, N. R.; Paolillo, M.; Pastorello, A.; Radovich, M.; Schipani, P.; Tomasella, L.; Turatto, M.; Vaccari, M.

    2017-02-01

    Aims: This is the second paper of a series in which we present measurements of the supernova (SN) rates from the SUDARE survey. The aim of this survey is to constrain the core collapse (CC) and Type Ia SN progenitors by analysing the dependence of their explosion rate on the properties of the parent stellar population averaging over a population of galaxies with different ages in a cosmic volume and in a galaxy sample. In this paper, we study the trend of the SN rates with the intrinsic colours, the star formation activity and the masses of the parent galaxies. To constrain the SN progenitors we compare the observed rates with model predictions assuming four progenitor models for SNe Ia with different distribution functions of the time intervals between the formation of the progenitor and the explosion, and a mass range of 8-40 M⊙ for CC SN progenitors. Methods: We considered a galaxy sample of approximately 130 000 galaxies and a SN sample of approximately 50 events. The wealth of photometric information for our galaxy sample allows us to apply the spectral energy distribution (SED) fitting technique to estimate the intrinsic rest frame colours, the stellar mass and star formation rate (SFR) for each galaxy in the sample. The galaxies have been separated into star-forming and quiescent galaxies, exploiting both the rest frame U-V vs. V-J colour-colour diagram and the best fit values of the specific star formation rate (sSFR) from the SED fitting. Results: We found that the SN Ia rate per unit mass is higher by a factor of six in the star-forming galaxies with respect to the passive galaxies, identified as such both on the U-V vs. V-J colour-colour diagram and for their sSFR. The SN Ia rate per unit mass is also higher in the less massive galaxies that are also younger. These results suggest a distribution of the delay times (DTD) less populated at long delay times than at short delays. The CC SN rate per unit mass is proportional to both the sSFR and the galaxy

  13. Spatially Offset Active Galactic Nuclei. II. Triggering in Galaxy Mergers

    Energy Technology Data Exchange (ETDEWEB)

    Barrows, R. Scott; Comerford, Julia M. [Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, Boulder, CO 80309 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Pooley, David, E-mail: Robert.Barrows@Colorado.edu [Department of Physics and Astronomy, Trinity University, San Antonio, TX 78212 (United States)

    2017-04-01

    Galaxy mergers are likely to play a role in triggering active galactic nuclei (AGNs), but the conditions under which this process occurs are poorly understood. In Paper I, we constructed a sample of spatially offset X-ray AGNs that represent galaxy mergers hosting a single AGN. In this paper, we use our offset AGN sample to constrain the parameters that affect AGN observability in galaxy mergers. We also construct dual-AGN samples with similar selection properties for comparison. We find that the offset AGN fraction shows no evidence for a dependence on AGN luminosity, while the dual-AGN fractions show stronger evidence for a positive dependence, suggesting that the merger events forming dual AGNs are more efficient at instigating accretion onto supermassive black holes than those forming offset AGNs. We also find that the offset and dual-AGN fractions both have a negative dependence on nuclear separation and are similar in value at small physical scales. This dependence may become stronger when restricted to high AGN luminosities, although a larger sample is needed for confirmation. These results indicate that the probability of AGN triggering increases at later merger stages. This study is the first to systematically probe down to nuclear separations of <1 kpc (∼0.8 kpc) and is consistent with predictions from simulations that AGN observability peaks in this regime. We also find that the offset AGNs are not preferentially obscured compared to the parent AGN sample, suggesting that our selection may be targeting galaxy mergers with relatively dust-free nuclear regions.

  14. Spatially Offset Active Galactic Nuclei. II. Triggering in Galaxy Mergers

    Science.gov (United States)

    Barrows, R. Scott; Comerford, Julia M.; Greene, Jenny E.; Pooley, David

    2017-04-01

    Galaxy mergers are likely to play a role in triggering active galactic nuclei (AGNs), but the conditions under which this process occurs are poorly understood. In Paper I, we constructed a sample of spatially offset X-ray AGNs that represent galaxy mergers hosting a single AGN. In this paper, we use our offset AGN sample to constrain the parameters that affect AGN observability in galaxy mergers. We also construct dual-AGN samples with similar selection properties for comparison. We find that the offset AGN fraction shows no evidence for a dependence on AGN luminosity, while the dual-AGN fractions show stronger evidence for a positive dependence, suggesting that the merger events forming dual AGNs are more efficient at instigating accretion onto supermassive black holes than those forming offset AGNs. We also find that the offset and dual-AGN fractions both have a negative dependence on nuclear separation and are similar in value at small physical scales. This dependence may become stronger when restricted to high AGN luminosities, although a larger sample is needed for confirmation. These results indicate that the probability of AGN triggering increases at later merger stages. This study is the first to systematically probe down to nuclear separations of <1 kpc (˜0.8 kpc) and is consistent with predictions from simulations that AGN observability peaks in this regime. We also find that the offset AGNs are not preferentially obscured compared to the parent AGN sample, suggesting that our selection may be targeting galaxy mergers with relatively dust-free nuclear regions.

  15. Triaxiality in elliptical galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Benacchio, L; Galletta, G [Padua Univ. (Italy). Ist. di Astronomia

    1980-12-01

    The existence of a triaxial shape for elliptical galaxies has been considered in recent years to explain the new kinematical and geometrical findings, i.e. (a) the low rotation/velocity dispersion ratio found also in some flat systems, (b) the presence of twisting in the isophotes, (c) the recently found correlation between maximum twisting and maximum flattening, (d) the presence of rotation along the minor axis. A simple geometrical model of elliptical galaxies having shells with different axial ratios c/a, b/a has been produced to interpret three fundamental key-features of elliptical galaxies: (i) the distribution of the maximum flattening observed; (ii) the percentage of ellipticals showing twisting; and (iii) the correlation between maximum twisting and maximum flattening. The model has been compared with observational data for 348 elliptical systems as given by Strom and Strom. It is found that a triaxial ellipsoid with coaxial shells having axial ratios c/a and b/a mutually dependent in a linear way can satisfy the observations.

  16. DETERMINING THE LARGE-SCALE ENVIRONMENTAL DEPENDENCE OF GAS-PHASE METALLICITY IN DWARF GALAXIES

    International Nuclear Information System (INIS)

    Douglass, Kelly A.; Vogeley, Michael S.

    2017-01-01

    We study how the cosmic environment affects galaxy evolution in the universe by comparing the metallicities of dwarf galaxies in voids with dwarf galaxies in more dense regions. Ratios of the fluxes of emission lines, particularly those of the forbidden [O iii] and [S ii] transitions, provide estimates of a region’s electron temperature and number density. From these two quantities and the emission line fluxes [O ii] λ 3727, [O iii] λ 4363, and [O iii] λλ 4959, 5007, we estimate the abundance of oxygen with the direct T e  method. We estimate the metallicity of 42 blue, star-forming void dwarf galaxies and 89 blue, star-forming dwarf galaxies in more dense regions using spectroscopic observations from the Sloan Digital Sky Survey Data Release 7, as reprocessed in the MPA-JHU value-added catalog. We find very little difference between the two sets of galaxies, indicating little influence from the large-scale environment on their chemical evolution. Of particular interest are a number of extremely metal-poor dwarf galaxies that are less prevalent in voids than in the denser regions.

  17. Chemical enrichment in isolated barred spiral galaxies.

    Science.gov (United States)

    Martel, Hugo; Carles, Christian; Robichaud, Fidéle; Ellison, Sara L.; Williamson, David J.

    2018-04-01

    To investigate the role of bars in the chemical evolution of isolated disc galaxies, we performed a series of 39 gas dynamical simulations of isolated barred and unbarred galaxies with various masses, initial gas fractions, and AGN feedback models. The presence of a bar drives a substantial amount of gas toward the central region of the galaxy. In the most massive galaxies, this results in a violent starburst, followed by a drop in star formation resulting from gas exhaustion. The time delay between Type Ia and Type II supernovae explosions means that barred galaxies experience a rapid increase in [O/H] in the central region, and a much more gradual increase in [Fe/H]. In unbarred galaxies, star formation proceeds at a slow and steady rate, and oxygen and iron are produced at steady rates which are similar except for a time offset. Comparing the abundance ratios in barred and unbarred galaxies with the same central stellar mass M*, we find in barred galaxies an enhancement of 0.07 dex in [O/H], 0.05 dex in [Fe/H], and 0.05 dex in [O/Fe]. The [O/H] enhancement is in excellent agreement with observations from the SDSS. The initial gas fraction has very little effect on the abundance ratios in barred and unbarred galaxies, unless the galaxies experience a starburst. We considered AGN-host galaxies located near the bottom of the AGN regime, M* ≳ 3 × 1010M⊙, where AGN feedback dominates over supernovae feedback. We found that the impact of AGN feedback on the central abundances is marginal.

  18. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    Energy Technology Data Exchange (ETDEWEB)

    Park, Youngsoo [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Krause, Elisabeth [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Dodelson, Scott [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Jain, Bhuvnesh [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Amara, Adam [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Becker, Matt [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Bridle, Sarah [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Clampitt, Joseph [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Crocce, Martin [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Honscheid, Klaus [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Gaztanaga, Enrique [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Sanchez, Carles [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Wechsler, Risa [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2015-01-01

    Combining galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth rate of large scale structure, a quantity that will shed light on the mechanism driving the acceleration of the Universe. The Dark Energy Survey (DES) is a prime candidate for such an analysis, with its measurements of both the distribution of galaxies on the sky and the tangential shears of background galaxies induced by these foreground lenses. By constructing an end-to-end analysis that combines large-scale galaxy clustering and small-scale galaxy-galaxy lensing, we also forecast the potential of a combined probes analysis on DES datasets. In particular, we develop a practical approach to a DES combined probes analysis by jointly modeling the assumptions and systematics affecting the different components of the data vector, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. Furthermore, we study the effect of external priors on different subsets of these parameters. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the universe, conservatively/ optimistically constraining the growth function to 8%/4.9% with its first-year data covering 1000 square degrees, and to 4%/2.3% with its full five-year data covering 5000 square degrees.

  19. Revisiting The First Galaxies: The effects of Population III stars on their host galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Muratov, Alexander L. [U. Michigan, Dept. Astron.; Gnedin, Oleg Y. [U. Michigan, Dept. Astron.; Gnedin, Nickolay Y. [Chicago U., Astron. Astrophys. Ctr.; Zemp, Marcel [Beijing, KITPC

    2013-07-12

    We revisit the formation and evolution of the first galaxies using new hydrodynamic cosmological simulations with the adaptive refinement tree code. Our simulations feature a recently developed model for H2 formation and dissociation, and a star formation recipe that is based on molecular rather than atomic gas. Here, we develop and implement a recipe for the formation of metal-free Population III (Pop III) stars in galaxy-scale simulations that resolve primordial clouds with sufficiently high density. We base our recipe on the results of prior zoom-in simulations that resolved the protostellar collapse in pre-galactic objects. We find the epoch during which Pop III stars dominated the energy and metal budget of the first galaxies to be short-lived. Galaxies that host Pop III stars do not retain dynamical signatures of their thermal and radiative feedback for more than 108 years after the lives of the stars end in pair-instability supernovae, even when we consider the maximum reasonable efficiency of the feedback. Though metals ejected by the supernovae can travel well beyond the virial radius of the host galaxy, they typically begin to fall back quickly, and do not enrich a large fraction of the intergalactic medium. Galaxies with a total mass in excess of 3 × 106 M re-accrete most of their baryons and transition to metal-enriched Pop II star formation.

  20. Evolution of N/O ratios in galaxies from cosmological hydrodynamical simulations

    Science.gov (United States)

    Vincenzo, Fiorenzo; Kobayashi, Chiaki

    2018-04-01

    We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual ISM regions within single spatially-resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved galaxies. We make use of a cosmological hydrodynamical simulation including detailed chemical enrichment, which properly takes into account the variety of different stellar nucleosynthetic sources of O and N in galaxies. We identify 33 galaxies in the simulation, lying within dark matter halos with virial mass in the range 1011 ≤ MDM ≤ 1013 M⊙ and reconstruct how they evolved with redshift. For the local and global measurements, the observed increasing trend of N/O at high O/H can be explained, respectively, (i) as the consequence of metallicity gradients which have settled in the galaxy interstellar medium, where the innermost galactic regions have the highest O/H abundances and the highest N/O ratios, and (ii) as the consequence of an underlying average mass-metallicity relation that galaxies obey as they evolve across cosmic epochs, where - at any redshift - less massive galaxies have lower average O/H and N/O ratios than the more massive ones. We do not find a strong dependence on the environment. For both local and global relations, the predicted N/O-O/H relation is due to the mostly secondary origin of N in stars. We also predict that the O/H and N/O gradients in the galaxy interstellar medium gradually flatten as functions of redshift, with the average N/O ratios being strictly coupled with the galaxy star formation history. Because N production strongly depends on O abundances, we obtain a universal relation for the N/O-O/H abundance diagram whether we consider average abundances of many unresolved galaxies put together or many abundance measurements within a single spatially-resolved galaxy.

  1. The Galaxy Evolution Probe

    Science.gov (United States)

    Glenn, Jason; Galaxy Evolution Probe Team

    2018-01-01

    The Galaxy Evolution Probe (GEP) is a concept for a far-infrared observatory to survey large regions of sky for star-forming galaxies from z = 0 to beyond z = 3. Our knowledge of galaxy formation is incomplete and requires uniform surveys over a large range of redshifts and environments to accurately describe mass assembly, star formation, supermassive black hole growth, interactions between these processes, and what led to their decline from z ~ 2 to the present day. Infrared observations are sensitive to dusty, star-forming galaxies, which have bright polycyclic aromatic hydrocarbon (PAH) emission features and warm dust continuum in the rest-frame mid infrared and cooler thermal dust emission in the far infrared. Unlike previous far-infrared continuum surveys, the GEP will measure photometric redshifts commensurate with galaxy detections from PAH emission and Si absorption features, without the need for obtaining spectroscopic redshifts of faint counterparts at other wavelengths.The GEP design includes a 2 m diameter telescope actively cooled to 4 K and two instruments: (1) An imager covering 10 to 300 um with 25 spectral resolution R ~ 8 bands (with lower R at the longest wavelengths) to detect star-forming galaxies and measure their redshifts photometrically. (2) A 23 – 190 um, R ~ 250 dispersive spectrometer for redshift confirmation and identification of obscured AGN using atomic fine-structure lines. Lines including [Ne V], [O IV], [O III], [O I], and [C II] will probe gas physical conditions, radiation field hardness, and metallicity. Notionally, the GEP will have a two-year mission: galaxy surveys with photometric redshifts in the first year and a second year devoted to follow-up spectroscopy. A comprehensive picture of star formation in galaxies over the last 10 billion years will be assembled from cosmologically relevant volumes, spanning environments from field galaxies and groups, to protoclusters, to dense galaxy clusters.Commissioned by NASA, the

  2. SLOWLY ROTATING GAS-RICH GALAXIES IN MODIFIED NEWTONIAN DYNAMICS (MOND)

    International Nuclear Information System (INIS)

    Sánchez-Salcedo, F. J.; Martínez-García, E. E.; Hidalgo-Gámez, A. M.

    2013-01-01

    We have carried out a search for gas-rich dwarf galaxies that have lower rotation velocities in their outskirts than MOdified Newtonian Dynamics (MOND) predicts, so that the amplitude of their rotation curves cannot be fitted by arbitrarily increasing the mass-to-light ratio of the stellar component or by assuming additional undetected matter. With presently available data, the gas-rich galaxies UGC 4173, Holmberg II, ESO 245-G05, NGC 4861, and ESO 364-G029 deviate most from MOND predictions and, thereby, provide a sample of promising targets in testing the MOND framework. In the case of Holmberg II and NGC 4861, we find that their rotation curves are probably inconsistent with MOND, unless their inclinations and distances differ significantly from the nominal ones. The galaxy ESO 364-G029 is a promising target because its baryonic mass and rotation curve are similar to Holmberg II but presents a higher inclination. Deeper photometric and H I observations of ESO 364-G029, together with further decreasing systematic uncertainties, may provide a strong test to MOND.

  3. First Detections of the [NII] 122 Micrometer Line at High Redshift: Demonstrating the Utility of the Line for Studying Galaxies in the Early Universe

    Science.gov (United States)

    Ferkinhoff, Carl; Brisbin, Drew; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Phillips, Thomas G.; Falgarone, Edith; Benford, Dominic J.; Staguhn, Johannes G.; Tucker, Carol E.

    2011-01-01

    We report the first detections of the [NIl] 122 {\\mu} m line from a high redshift galaxy. The line was strongly (> 6{\\sigma}) detected from SMMJ02399-0136, and HI413+ 117 (the Cloverleaf QSO) using the Redshift(z) and Early Universe Spectrometer (ZEUS) on the CSO. The lines from both sources are quite bright with line-to-FIR continuum luminosity ratios that are approx.7.0x10(exp -4) (Cloverleaf) and 2.1x10(exp -3) (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line-to-continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, approx.8 to 17% of the molecular gas mass. The [OIII]/[NII] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an AGN. Using our previous detection of the [01II] 88 {\\mu}m line, the [OIII]/ [NIl] line ratio for SMMJ02399-0136 indicates the dominant source of the line emission is either stellar HII regions ionized by 09.5 stars, or the NLR of the AGN with ionization parameter 10g(U) = -3.3 to -4.0. A composite system, where 30 to 50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of approx.200 M82like starbursts accounting for all of the FIR emission and 43% of the [NIl] line. The remainder may come from the NLR. This work demonstrates the utility of the [NIl] and [OIII] lines in constraining properties of the ionized medium.

  4. Constraints on stellar populations in elliptical galaxies

    International Nuclear Information System (INIS)

    Rose, J.A.

    1985-01-01

    Photographic image-tube spectra in the wavelength interval 3400--4500 A have been obtained for 12 elliptical galaxy nuclei and for a number of Galactic globular and open clusters in integrated light. The spectra have a wavelength resolution of 2.5 A and a high signal-to-noise ratio. A new quantitative three-dimensional spectral-classification system that has been calibrated on a sample of approx.200 individual stars (Rose 1984) is used to analyze the integrated spectra of the ellipical galaxy nuclei and to compare them with those of the globular clusters. This system is based on spectral indices that are formed by comparing neighborhood spectral features and is unaffected by reddening. The following results have been found: (1) Hot stars (i.e., spectral types A and B) contribute only 2% to the integrated spectra of elliptical galaxies at approx.4000 A, except in the nucleus of NGC 205, where the hot component dominates. This finding is based on a spectral index formed from the relative central intensities in the Ca II H+Hepsilon and Ca II K lines, which is shown to be constant for late-type (i.e., F, G, and K) stars, but changes drastically at earlier types. The observed Ca II H+Hepsilon/Ca II K indices in ellipticals can be reproduced by the inclusion of a small metal-poor population (as in the globular cluster M5) that contributes approx.8% of the light at 4000 A. Such a contribution is qualitatively consistent with the amount of

  5. Weighing galaxy clusters with gas. II. On the origin of hydrostatic mass bias in ΛCDM galaxy clusters

    International Nuclear Information System (INIS)

    Nelson, Kaylea; Nagai, Daisuke; Yu, Liang; Lau, Erwin T.; Rudd, Douglas H.

    2014-01-01

    The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to the bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (≲ 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.

  6. SDSS IV MaNGA: Deep observations of extra-planar, diffuse ionized gas around late-type galaxies from stacked IFU spectra

    Science.gov (United States)

    Jones, A.; Kauffmann, G.; D'Souza, R.; Bizyaev, D.; Law, D.; Haffner, L.; Bahé, Y.; Andrews, B.; Bershady, M.; Brownstein, J.; Bundy, K.; Cherinka, B.; Diamond-Stanic, A.; Drory, N.; Riffel, R. A.; Sánchez, S. F.; Thomas, D.; Wake, D.; Yan, R.; Zhang, K.

    2017-03-01

    We have conducted a study of extra-planar diffuse ionized gas using the first year data from the MaNGA IFU survey. We have stacked spectra from 49 edge-on, late-type galaxies as a function of distance from the midplane of the galaxy. With this technique we can detect the bright emission lines Hα, Hβ, [O II]λλ3726, 3729, [O III]λ5007, [N II]λλ6549, 6584, and [S II]λλ6717, 6731 out to about 4 kpc above the midplane. With 16 galaxies we can extend this analysis out to about 9 kpc, I.e. a distance of 2Re, vertically from the midplane. In the halo, the surface brightnesses of the [O II] and Hα emission lines are comparable, unlike in the disk where Hα dominates. When we split the sample by specific star-formation rate, concentration index, and stellar mass, each subsample's emission line surface brightness profiles and ratios differ, indicating that extra-planar gas properties can vary. The emission line surface brightnesses of the gas around high specific star-formation rate galaxies are higher at all distances, and the line ratios are closer to ratios characteristic of H II regions compared with low specific star-formation rate galaxies. The less concentrated and lower stellar mass samples exhibit line ratios that are more like H II regions at larger distances than their more concentrated and higher stellar mass counterparts. The largest difference between different subsamples occurs when the galaxies are split by stellar mass. We additionally infer that gas far from the midplane in more massive galaxies has the highest temperatures and steepest radial temperature gradients based on their [N II]/Hα and [O II]/Hα ratios between the disk and the halo. SDSS IV.

  7. LeMMINGs - I. The eMERLIN legacy survey of nearby galaxies. 1.5-GHz parsec-scale radio structures and cores

    Science.gov (United States)

    Baldi, R. D.; Williams, D. R. A.; McHardy, I. M.; Beswick, R. J.; Argo, M. K.; Dullo, B. T.; Knapen, J. H.; Brinks, E.; Muxlow, T. W. B.; Aalto, S.; Alberdi, A.; Bendo, G. J.; Corbel, S.; Evans, R.; Fenech, D. M.; Green, D. A.; Klöckner, H.-R.; Körding, E.; Kharb, P.; Maccarone, T. J.; Martí-Vidal, I.; Mundell, C. G.; Panessa, F.; Peck, A. B.; Pérez-Torres, M. A.; Saikia, D. J.; Saikia, P.; Shankar, F.; Spencer, R. E.; Stevens, I. R.; Uttley, P.; Westcott, J.

    2018-05-01

    We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H II galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H II galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s-1: LINERs and H II galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ˜107 M⊙, but a break emerges at lower masses. Using [O III] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H II galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H II galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

  8. NEW PERSPECTIVE ON GALAXY OUTFLOWS FROM THE FIRST DETECTION OF BOTH INTRINSIC AND TRAVERSE METAL-LINE ABSORPTION

    Energy Technology Data Exchange (ETDEWEB)

    Kacprzak, Glenn G.; Cooke, Jeff [Swinburne University of Technology, Victoria 3122 (Australia); Martin, Crystal L.; Ho, Stephanie H. [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Bouché, Nicolas; LeReun, Audrey; Schroetter, Ilane [CNRS, Institut de Recherche en Astrophysique et Planétologie (IRAP) de Toulouse, 14 Avenue E. Belin, F-31400 Toulouse (France); Churchill, Christopher W.; Klimek, Elizabeth, E-mail: gkacprzak@astro.swin.edu.au [New Mexico State University, Las Cruces, NM 88003 (United States)

    2014-09-01

    We present the first observation of a galaxy (z = 0.2) that exhibits metal-line absorption back-illuminated by the galaxy (down-the-barrel) and transversely by a background quasar at a projected distance of 58 kpc. Both absorption systems, traced by Mg II, are blueshifted relative to the galaxy systemic velocity. The quasar sight line, which resides almost directly along the projected minor axis of the galaxy, probes Mg I and Mg II absorption obtained from the Keck/Low Resolution Imaging Spectrometer as well as Lyα, Si II, and Si III absorption obtained from the Hubble Space Telescope/Cosmic Origins Spectrograph. For the first time, we combine two independent models used to quantify the outflow properties for down-the-barrel and transverse absorption. We find that the modeled down-the-barrel deprojected outflow velocities range between V {sub dtb} = 45-255 km s{sup –1}. The transverse bi-conical outflow model, assuming constant-velocity flows perpendicular to the disk, requires wind velocities V {sub outflow} = 40-80 km s{sup –1} to reproduce the transverse Mg II absorption kinematics, which is consistent with the range of V {sub dtb}. The galaxy has a metallicity, derived from Hα and N II, of [O/H] = –0.21 ± 0.08, whereas the transverse absorption has [X/H] = –1.12 ± 0.02. The galaxy star formation rate is constrained between 4.6-15 M {sub ☉} yr{sup –1} while the estimated outflow rate ranges between 1.6-4.2 M {sub ☉} yr{sup –1} and yields a wind loading factor ranging between 0.1-0.9. The galaxy and gas metallicities, the galaxy-quasar sight-line geometry, and the down-the-barrel and transverse modeled outflow velocities collectively suggest that the transverse gas originates from ongoing outflowing material from the galaxy. The ∼1 dex decrease in metallicity from the base of the outflow to the outer halo suggests metal dilution of the gas by the time it reached 58 kpc.

  9. Deep spectroscopy of nearby galaxy clusters - IV. The quench of the star formation in galaxies in the infall region of Abell 85

    Science.gov (United States)

    Aguerri, J. A. L.; Agulli, I.; Méndez-Abreu, J.

    2018-06-01

    Our aim is to understand the role of the environment in the quenching of star formation of galaxies located in the infall cluster region of Abell 85 (A85). This is achieved by studying the post-starburst galaxy population as tracer of recent quenching. By measuring the equivalent width (EW) of the [O II] and Hδ spectral lines, we classify the galaxies into three groups: passive (PAS), emission line (EL), and post-starburst (PSB) galaxies. The PSB galaxy population represents ˜ 4.5 per cent of the full sample. Dwarf galaxies (Mr > -18.0) account for ˜ 70 - 80 per cent of PSBs, which indicates that most of the galaxies undergoing recent quenching are low-mass objects. Independently of the environment, PSB galaxies are disc-like objects with g - r colour between the blue ELs and the red PAS ones. The PSB and EL galaxies in low-density environments show similar luminosities and local galaxy densities. The dynamics and local galaxy density of the PSB population in high-density environments are shared with PAS galaxies. However, PSB galaxies inside A85 are at shorter clustercentric radius than PAS and EL ones. The value of the EW(Hδ) is larger for those PSBs closer to the cluster centre. We propose two different physical mechanisms producing PSB galaxies depending on the environment. In low-density environments, gas-rich minor mergers or accretions could produce the PSB galaxies. For high-density environments like A85, PSBs would be produced by the removal of the gas reservoirs of EL galaxies by ram-pressure stripping when they pass near the cluster centre.

  10. The outer disks of early-type galaxies. I. Surface-brightness profiles of barred galaxies

    NARCIS (Netherlands)

    Erwin, Peter; Pohlen, Michael; Beckman, John E.

    We present a study of 66 barred, early-type (S0-Sb) disk galaxies, focused on the disk surface brightness profile outside the bar region, with the aim of throwing light on the nature of Freeman type I and II profiles, their origins, and their possible relation to disk truncations. This paper

  11. CONSTRAINING VERY HIGH MASS POPULATION III STARS THROUGH He II EMISSION IN GALAXY BDF-521 AT z = 7.01

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Zheng; Fan, Xiaohui; Davé, Romeel; Zabludoff, Ann [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Jiang, Linhua [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Oh, S. Peng [Department of Physics, University of California, Broida Hall, Santa Barbara, CA 93106-9530 (United States); Yang, Yujin, E-mail: caiz@email.arizona.edu [Argelander-Institut fuer Astronomie, Auf dem Huegel 71, D-53121 Bonn (Germany)

    2015-01-30

    Numerous theoretical models have long proposed that a strong He II λ1640 emission line is the most prominent and unique feature of massive Population III (Pop III) stars in high-redshift galaxies. The He II λ1640 line strength can constrain the mass and initial mass function (IMF) of Pop III stars. We use F132N narrowband filter on the Hubble Space Telescope's (HST) Wide Field Camera 3 to look for strong He II λ1640 emission in the galaxy BDF-521 at z = 7.01, one of the most distant spectroscopically confirmed galaxies to date. Using deep F132N narrowband imaging, together with our broadband imaging with F125W and F160W filters, we do not detect He II emission from this galaxy, but place a 2σ upper limit on the flux of 5.3×10{sup −19} erg s{sup −1} cm{sup −2}. This measurement corresponds to a 2σ upper limit on the Pop III star formation rate (SFR{sub PopIII}) of ∼0.2 M {sub ☉} yr{sup –1}, assuming a Salpeter IMF with 50 ≲ M/M {sub ☉} ≲ 1000. From the high signal-to-noise broadband measurements in F125W and F160W, we fit the UV continuum for BDF-521. The spectral flux density is ∼3.6×10{sup −11}×λ{sup −2.32} erg s{sup −1} cm{sup −2} Å{sup –1}, which corresponds to an overall unobscured SFR of ∼5 M {sub ☉} yr{sup –1}. Our upper limit on SFR{sub PopIII} suggests that massive Pop III stars represent ≲ 4% of the total star formation. Further, the HST high-resolution imaging suggests that BDF-521 is an extremely compact galaxy, with a half-light radius of 0.6 kpc.

  12. The pre-launch Planck Sky Model: a model of sky emission at submillimetre to centimetre wavelengths

    CERN Document Server

    Delabrouille, J.; Melin, J.-B.; Miville-Deschenes, M.-A.; Gonzalez-Nuevo, J.; Jeune, M.Le; Castex, G.; de Zotti, G.; Basak, S.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A.; Bernard, J.-P.; Bouchet, F.R.; Clements, D.L.; da Silva, A.; Dickinson, C.; Dodu, F.; Dolag, K.; Elsner, F.; Fauvet, L.; Fay, G.; Giardino, G.; Leach, S.; Lesgourgues, J.; Liguori, M.; Macias-Perez, J.F.; Massardi, M.; Matarrese, S.; Mazzotta, P.; Montier, L.; Mottet, S.; Paladini, R.; Partridge, B.; Piffaretti, R.; Prezeau, G.; Prunet, S.; Ricciardi, S.; Roman, M.; Schaefer, B.; Toffolatti, L.

    2012-01-01

    We present the Planck Sky Model (PSM), a parametric model for the generation of all-sky, few arcminute resolution maps of sky emission at submillimetre to centimetre wavelengths, in both intensity and polarisation. Several options are implemented to model the cosmic microwave background, Galactic diffuse emission (synchrotron, free-free, thermal and spinning dust, CO lines), Galactic H-II regions, extragalactic radio sources, dusty galaxies, and thermal and kinetic Sunyaev-Zeldovich signals from clusters of galaxies. Each component is simulated by means of educated interpolations/extrapolations of data sets available at the time of the launch of the Planck mission, complemented by state-of-the-art models of the emission. Distinctive features of the simulations are: spatially varying spectral properties of synchrotron and dust; different spectral parameters for each point source; modeling of the clustering properties of extragalactic sources and of the power spectrum of fluctuations in the cosmic infrared back...

  13. The SAMI Galaxy Survey: spatially resolving the main sequence of star formation

    Science.gov (United States)

    Medling, Anne M.; Cortese, Luca; Croom, Scott M.; Green, Andrew W.; Groves, Brent; Hampton, Elise; Ho, I.-Ting; Davies, Luke J. M.; Kewley, Lisa J.; Moffett, Amanda J.; Schaefer, Adam L.; Taylor, Edward; Zafar, Tayyaba; Bekki, Kenji; Bland-Hawthorn, Joss; Bloom, Jessica V.; Brough, Sarah; Bryant, Julia J.; Catinella, Barbara; Cecil, Gerald; Colless, Matthew; Couch, Warrick J.; Drinkwater, Michael J.; Driver, Simon P.; Federrath, Christoph; Foster, Caroline; Goldstein, Gregory; Goodwin, Michael; Hopkins, Andrew; Lawrence, J. S.; Leslie, Sarah K.; Lewis, Geraint F.; Lorente, Nuria P. F.; Owers, Matt S.; McDermid, Richard; Richards, Samuel N.; Sharp, Robert; Scott, Nicholas; Sweet, Sarah M.; Taranu, Dan S.; Tescari, Edoardo; Tonini, Chiara; van de Sande, Jesse; Walcher, C. Jakob; Wright, Angus

    2018-04-01

    We present the ˜800 star formation rate maps for the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey based on H α emission maps, corrected for dust attenuation via the Balmer decrement, that are included in the SAMI Public Data Release 1. We mask out spaxels contaminated by non-stellar emission using the [O III]/H β, [N II]/H α, [S II]/H α, and [O I]/H α line ratios. Using these maps, we examine the global and resolved star-forming main sequences of SAMI galaxies as a function of morphology, environmental density, and stellar mass. Galaxies further below the star-forming main sequence are more likely to have flatter star formation profiles. Early-type galaxies split into two populations with similar stellar masses and central stellar mass surface densities. The main-sequence population has centrally concentrated star formation similar to late-type galaxies, while galaxies >3σ below the main sequence show significantly reduced star formation most strikingly in the nuclear regions. The split populations support a two-step quenching mechanism, wherein halo mass first cuts off the gas supply and remaining gas continues to form stars until the local stellar mass surface density can stabilize the reduced remaining fuel against further star formation. Across all morphologies, galaxies in denser environments show a decreased specific star formation rate from the outside in, supporting an environmental cause for quenching, such as ram-pressure stripping or galaxy interactions.

  14. The Cosmic Abundance of 3He: Green Bank Telescope Observations

    Science.gov (United States)

    Balser, Dana; Bania, Thomas

    2018-01-01

    The Big Bang theory for the origin of the Universe predicts that during the first ~1,000 seconds significant amounts of the light elements (2H, 3He, 4He, and 7Li) were produced. Many generations of stellar evolution in the Galaxy modifies these primordial abundances. Observations of the 3He+ hyperfine transition in Galactic HII regions reveals a 3He/H abundance ratio that is constant with Galactocentric radius to within the uncertainties, and is consistent with the primordial value as determined from cosmic microwave background experiments (e.g., WMAP). This "3He Plateau" indicates that the net production and destruction of 3He in stars is approximately zero. Recent stellar evolution models that include thermohaline mixing, however, predict that 3He/H abundance ratios should slightly decrease with Galactocentric radius, or in places in the Galaxy with lower star formation rates. Here we discuss sensitive Green Bank Telescope (GBT) observations of 3He+ at 3.46 cm in a subset of our HII region sample. We develop HII region models and derive accurate 3He/H abundance ratios to better constrain these new stellar evolution models.

  15. Deficiency of normal galaxies among Markaryan galaxies

    International Nuclear Information System (INIS)

    Iyeveer, M.M.

    1986-01-01

    Comparison of the morphological types of Markaryan galaxies and other galaxies in the Uppsala catalog indicates a strong deficiency of normal ellipticals among the Markaryan galaxies, for which the fraction of type E galaxies is ≤ 1% against 10% among the remaining galaxies. Among the Markaryan galaxies, an excess of barred galaxies is observed - among the Markaryan galaxies with types Sa-Scd, approximately half or more have bars, whereas among the remaining galaxies of the same types bars are found in about 1/3

  16. Exploring the Dust Content of Galactic Winds with Herschel. II. Nearby Dwarf Galaxies*

    Science.gov (United States)

    McCormick, Alexander; Veilleux, Sylvain; Meléndez, Marcio; Martin, Crystal L.; Bland-Hawthorn, Joss; Cecil, Gerald; Heitsch, Fabian; Müller, Thomas; Rupke, David S. N.; Engelbracht, Chad

    2018-03-01

    We present results from analysis of deep Herschel Space Observatory observations of six nearby dwarf galaxies known to host galactic-scale winds. The superior far-infrared sensitivity and angular resolution of Herschel have allowed detection of cold circumgalactic dust features beyond the stellar components of the host galaxies traced by Spitzer 4.5 μm images. Comparisons of these cold dust features with ancillary data reveal an imperfect spatial correlation with the ionized gas and warm dust wind components. We find that typically ˜10-20% of the total dust mass in these galaxies resides outside of their stellar disks, but this fraction reaches ˜60% in the case of NGC 1569. This galaxy also has the largest metallicity (O/H) deficit in our sample for its stellar mass. Overall, the small number of objects in our sample precludes drawing strong conclusions on the origin of the circumgalactic dust. We detect no statistically significant trends with star formation properties of the host galaxies, as might be expected if the dust were lifted above the disk by energy inputs from on-going star formation activity. Although a case for dust entrained in a galactic wind is seen in NGC 1569, in all cases, we cannot rule out the possibility that some of the circumgalactic dust might be associated instead with gas accreted or removed from the disk by recent galaxy interaction events, or that it is part of the outer gas-rich portion of the disk that lies below the sensitivity limit of the Spitzer 4.5 μm data.

  17. The Reliability of [C II] as a Star Formation Rate Indicator

    Directory of Open Access Journals (Sweden)

    De Looze Ilse

    2011-09-01

    Full Text Available We present a calibration of the star formation rate (SFR as a function of the [C II] 157.74 μm luminosity for a sample of 24 star-forming galaxies in the nearby universe. In order to calibrate the SFR against the line luminosity, we rely on both GALEX FUV data, which is an ideal tracer of the unobscured star formation, and Spitzer MIPS 24 μm, to probe the dust-enshrouded fraction of star formation. For this sample of normal star-forming galaxies, the [C II] luminosity correlates well with the star formation rate. However, the extension of this relation to more quiescent (Hα EW≤10 Å or ultra luminous galaxies (LTIR ≥1012 L⊙ should be handled with caution, since these objects show a non-linearity in the L[C II]-to-LFIR ratio as a function of LFIR (and thus, their star formation activity. Two possible scenarios can be invoked to explain the tight correlation between the [C II] emission and the star formation activity on a global galaxy-scale. The first interpretation could be that the [C II] emission from photo dissociation regions arises from the immediate surroundings of actively star-forming regions and contributes a more or less constant fraction on a global galaxy-scale. Alternatively, we consider the possibility that the [C II] emission is associated to the cold interstellar medium, which advocates an indirect link with the star formation activity in a galaxy through the Schmidt law.

  18. Understanding r-process nucleosynthesis with dwarf galaxies

    Science.gov (United States)

    Ji, Alexander P.

    2018-06-01

    The Milky Way's faintest dwarf galaxy satellites each sample short, independent bursts of star formation from the first 1-2 Gyr of the universe. Their simple formation history makes them ideal systems to understand how rare events like neutron star mergers contribute to early enrichment of r-process elements. I will focus on the ultra-faint galaxy Reticulum II, which experienced a single prolific r-process event that left ~80% of its stars extremely enriched in r-process elements. I will present abundances of ~40 elements derived from the highest signal-to-noise high-resolution spectrum ever taken for an ultra-faint dwarf galaxy star. Precise measurements of elements from all three r-process peaks reaffirm the universal nature of the r-process abundance pattern from Ba to Ir. The first r-process peak is significantly lower than solar but matches other r-process enhanced stars. This constrains the neutron-richness of r-process ejecta in neutron star mergers. The radioactive element thorium is detected with a somewhat low abundance. Naive application of currently predicted initial production ratios could imply an age >20 Gyr, but more likely indicates that the initial production ratios require revision. The abundance of lighter elements up to Zn are consistent with extremely metal-poor Milky Way halo stars. These elements may eventually provide a way to test for other hypothesized r-process sites, but only after a more detailed understanding of the chemical evolution in this galaxy. Reticulum II provides a clean view of early r-process enrichment that can be used to understand the increasing number of r-process measurements in other dwarf galaxies.

  19. A far-infrared spectroscopic survey of intermediate redshift (ultra) luminous infrared galaxies

    International Nuclear Information System (INIS)

    Magdis, Georgios E.; Rigopoulou, D.; Hopwood, R.; Clements, D.; Huang, J.-S.; Farrah, D.; Pearson, C.; Alonso-Herrero, Almudena; Bock, J. J.; Cooray, A.; Griffin, M. J.; Oliver, S.; Perez Fournon, I.; Riechers, D.; Swinyard, B. M.; Thatte, N.; Scott, D.; Valtchanov, I.; Vaccari, M.

    2014-01-01

    We present Herschel far-IR photometry and spectroscopy as well as ground-based CO observations of an intermediate redshift (0.21 ≤ z ≤ 0.88) sample of Herschel-selected (ultra)-luminous infrared galaxies (L IR > 10 11.5 L ☉ ). With these measurements, we trace the dust continuum, far-IR atomic line emission, in particular [C II] 157.7 μm, as well as the molecular gas of z ∼ 0.3 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and perform a detailed investigation of the interstellar medium of the population. We find that the majority of Herschel-selected intermediate redshift (U)LIRGs have L C II /L FIR ratios that are a factor of about 10 higher than that of local ULIRGs and comparable to that of local normal and high-z star-forming galaxies. Using our sample to bridge local and high-z [C II] observations, we find that the majority of galaxies at all redshifts and all luminosities follow an L C II –L FIR relation with a slope of unity, from which local ULIRGs and high- z active-galactic-nucleus-dominated sources are clear outliers. We also confirm that the strong anti-correlation between the L C II /L FIR ratio and the far-IR color L 60 /L 100 observed in the local universe holds over a broad range of redshifts and luminosities, in the sense that warmer sources exhibit lower L C II /L FIR at any epoch. Intermediate redshift ULIRGs are also characterized by large molecular gas reservoirs and by lower star formation efficiencies compared to that of local ULIRGs. The high L C II /L FIR ratios, the moderate star formation efficiencies (L IR /L CO ′ or L IR /M H 2 ), and the relatively low dust temperatures of our sample (which are also common characteristics of high-z star-forming galaxies with ULIRG-like luminosities) indicate that the evolution of the physical properties of (U)LIRGs between the present day and z > 1 is already significant by z ∼ 0.3.

  20. Initial mass function for early-type stars in starburst galaxies

    International Nuclear Information System (INIS)

    Sekiguchi, K.; Anderson, K.S.

    1987-01-01

    The IMF slope of early-type stars in starburst galaxies is investigated using IUE observations and a technique that utilizes mass-linewidth relations for early-type stars. Fourteen low-resolution IUE spectra of eight starburst galaxies and three H II region galaxies are used to obtain line-strength ratios Si IV(1400 A)/C IV(1550 A). These are compared to model line ratios, and indicate that the average IMF slope for OB stars in these intense star-formation regions is appreciably flatter than that of the solar neighborhood. 46 references

  1. An Empirical Ultraviolet Iron Spectrum Template Applicable to Active Galaxies

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Wilkes, B. J.

    2001-01-01

    Iron emission is often a severe contaminant in optical-ultraviolet spectra of active galaxies. Its presence complicates emission line studies. A viable solution, already successfully applied at optical wavelengths, is to use an empirical iron emission template. We have generated FeII and Fe......III templates for ultraviolet active galaxy spectra based on HST archival 1100 - 3100 A spectra of IZw1. Their application allows fitting and subtraction of the iron emission in active galaxy spectra. This work has shown that in particular CIII] lambda 1909 can be heavily contaminated by other line emission...

  2. Spectral classification of emission-line galaxies

    International Nuclear Information System (INIS)

    Veilleux, S.; Osterbrock, D.E.

    1987-01-01

    A revised method of classification of narrow-line active galaxies and H II region-like galaxies is proposed. It involves the line ratios which take full advantage of the physical distinction between the two types of objects and minimize the effects of reddening correction and errors in the flux calibration. Large sets of internally consistent data are used, including new, previously unpublished measurements. Predictions of recent photoionization models by power-law spectra and by hot stars are compared with the observations. The classification is based on the observational data interpreted on the basis of these models. 63 references

  3. Carbon-enhanced metal-poor stars in dwarf galaxies

    OpenAIRE

    Salvadori, Stefania; Skuladottir, Asa; Tolstoy, Eline

    2015-01-01

    We investigate the frequency and origin of carbon-enhanced metal-poor (CEMP) stars in Local Group dwarf galaxies by means of a statistical, data-calibrated cosmological model for the hierarchical build-up of the Milky Way and its dwarf satellites. The model self-consistently explains the variation with dwarf galaxy luminosity of the observed: i) frequency and [Fe/H] range of CEMP stars; ii) metallicity distribution functions; iii) star formation histories. We show that if primordial faint sup...

  4. GALAXY CLUSTERS IN THE IRAC DARK FIELD. II. MID-INFRARED SOURCES

    International Nuclear Information System (INIS)

    Krick, J. E.; Surace, J. A.; Yan, L.; Thompson, D.; Ashby, M. L. N.; Hora, J. L.; Gorjian, V.

    2009-01-01

    We present infrared (IR) luminosities, star formation rates (SFR), colors, morphologies, locations, and active galactic nuclei (AGNs) properties of 24 μm detected sources in photometrically detected high-redshift clusters in order to understand the impact of environment on star formation (SF) and AGN evolution in cluster galaxies. We use three newly identified z = 1 clusters selected from the IRAC dark field; the deepest ever mid-IR survey with accompanying, 14 band multiwavelength data including deep Hubble Space Telescope imaging and deep wide-area Spitzer MIPS 24 μm imaging. We find 90 cluster members with MIPS detections within two virial radii of the cluster centers, of which 17 appear to have spectral energy distributions dominated by AGNs and the rest dominated by SF. We find that 43% of the star-forming sample have IR luminosities L IR > 10 11 L sun (luminous IR galaxies). The majority of sources (81%) are spirals or irregulars. A large fraction (at least 25%) show obvious signs of interactions. The MIPS-detected member galaxies have varied spatial distributions as compared to the MIPS-undetected members with one of the three clusters showing SF galaxies being preferentially located on the cluster outskirts, while the other two clusters show no such trend. Both the AGN fraction and the summed SFR of cluster galaxies increase from redshift zero to one, at a rate that is a few times faster in clusters than over the same redshift range in the field. Cluster environment does have an effect on the evolution of both AGN fraction and SFR from redshift one to the present, but does not affect the IR luminosities or morphologies of the MIPS sample. SF happens in the same way regardless of environment making MIPS sources look the same in the cluster and field, however the cluster environment does encourage a more rapid evolution with time as compared to the field.

  5. VLT/UVES abundances in four nearby dwarf spheroidal galaxies. II. Implications for understanding galaxy evolution

    NARCIS (Netherlands)

    Tolstoy, E; Venn, KA; Shetrone, M; Primas, F; Hill, [No Value; Kaufer, A; Szeifert, T

    We have used the Ultraviolet Visual-Echelle Spectrograph (UVES) on Kueyen (UT2) of the Very Large Telescope to take spectra of 15 individual red giant stars in the centers of four nearby dwarf spheroidal galaxies (dSph's) : Sculptor, Fornax, Carina, and Leo I. We measure the abundance variations of

  6. Exploring the dust content of galactic winds with Herschel - II. Nearby dwarf galaxies

    Science.gov (United States)

    McCormick, Alexander; Veilleux, Sylvain; Meléndez, Marcio; Martin, Crystal L.; Bland-Hawthorn, Joss; Cecil, Gerald; Heitsch, Fabian; Müller, Thomas; Rupke, David S. N.; Engelbracht, Chad

    2018-06-01

    We present the results from an analysis of deep Herschel Space Observatory observations of six nearby dwarf galaxies known to host galactic-scale winds. The superior far-infrared sensitivity and angular resolution of Herschel have allowed detection of cold circumgalactic dust features beyond the stellar components of the host galaxies traced by Spitzer 4.5 μm images. Comparisons of these cold dust features with ancillary data reveal an imperfect spatial correlation with the ionized gas and warm dust wind components. We find that typically ˜10-20 per cent of the total dust mass in these galaxies resides outside of their stellar discs, but this fraction reaches ˜60 per cent in the case of NGC 1569. This galaxy also has the largest metallicity (O/H) deficit in our sample for its stellar mass. Overall, the small number of objects in our sample precludes drawing strong conclusions on the origin of the circumgalactic dust. We detect no statistically significant trends with star formation properties of the host galaxies, as might be expected if the dust were lifted above the disc by energy inputs from ongoing star formation activity. Although a case for dust entrained in a galactic wind is seen in NGC 1569, in all cases, we cannot rule out the possibility that some of the circumgalactic dust might be associated instead with gas accreted or removed from the disc by recent galaxy interaction events, or that it is part of the outer gas-rich portion of the disc that lies below the sensitivity limit of the Spitzer 4.5 μm data.

  7. Hα3: an Hα imaging survey of HI selected galaxies from ALFALFA. II. Star formation properties of galaxies in the Virgo cluster and surroundings

    Science.gov (United States)

    Gavazzi, G.; Fumagalli, M.; Fossati, M.; Galardo, V.; Grossetti, F.; Boselli, A.; Giovanelli, R.; Haynes, M. P.

    2013-05-01

    Context. We present the analysis of Hα3, an Hα narrow-band imaging follow-up survey of 409 galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Local Supercluster, including the Virgo cluster, in the region 11h advantage of Hα3, which provides the complete census of the recent massive star formation rate (SFR) in HI-rich galaxies in the local Universe and of ancillary optical data from SDSS we explore the relations between the stellar mass, the HI mass, and the current, massive SFR of nearby galaxies in the Virgo cluster. We compare these with those of isolated galaxies in the Local Supercluster, and we investigate the role of the environment in shaping the star formation properties of galaxies at the present cosmological epoch. Methods: By using the Hα hydrogen recombination line as a tracer of recent star formation, we investigated the relationships between atomic neutral gas and newly formed stars in different environments (cluster and field), for many morphological types (spirals and dwarfs), and over a wide range of stellar masses (107.5 to 1011.5 M⊙). To quantify the degree of environmental perturbation, we adopted an updated calibration of the HI deficiency parameter which we used to divide the sample into three classes: unperturbed galaxies (DefHI ≤ 0.3), perturbed galaxies (0.3 model. Once considered as a whole, the Virgo cluster is effective in removing neutral hydrogen from galaxies, and this perturbation is strong enough to appreciably reduce the SFR of its entire galaxy population. Conclusions: An estimate of the present infall rate of 300-400 galaxies per Gyr in the Virgo cluster is obtained from the number of existing HI-rich late-type systems, assuming 200-300 Myr as the time scale for HI ablation. If the infall process has been acting at a constant rate, this would imply that the Virgo cluster has formed approximately 2 Gyr ago, consistently with the idea that Virgo is in a young state of dynamical evolution. Based

  8. SURFACE BRIGHTNESS PROFILES OF DWARF GALAXIES. I. PROFILES AND STATISTICS

    International Nuclear Information System (INIS)

    Herrmann, Kimberly A.; Hunter, Deidre A.; Elmegreen, Bruce G.

    2013-01-01

    Radial surface brightness profiles of spiral galaxies are classified into three types: (I) single exponential, or the light falls off with one exponential to a break before falling off (II) more steeply, or (III) less steeply. Profile breaks are also found in dwarf disks, but some dwarf Type IIs are flat or increasing out to a break before falling off. Here we re-examine the stellar disk profiles of 141 dwarfs: 96 dwarf irregulars (dIms), 26 Blue Compact Dwarfs (BCDs), and 19 Magellanic-type spirals (Sms). We fit single, double, or even triple exponential profiles in up to 11 passbands: GALEX FUV and NUV, ground-based UBVJHK and Hα, and Spitzer 3.6 and 4.5 μm. We find that more luminous galaxies have brighter centers, larger inner and outer scale lengths, and breaks at larger radii; dwarf trends with M B extend to spirals. However, the V-band break surface brightness is independent of break type, M B , and Hubble type. Dwarf Type II and III profiles fall off similarly beyond the breaks but have different interiors and IIs break ∼twice as far as IIIs. Outer Type II and III scale lengths may have weak trends with wavelength, but pure Type II inner scale lengths clearly decrease from the FUV to visible bands whereas Type III inner scale lengths increase with redder bands. This suggests the influence of different star formation histories on profile type, but nonetheless the break location is approximately the same in all passbands. Dwarfs continue trends between profile and Hubble types such that later-type galaxies have more Type II but fewer Type I and III profiles than early-type spirals. BCDs and Sms are over-represented as Types III and II, respectively, compared to dIms

  9. Severe Extracellular Matrix Abnormalities and Chondrodysplasia in Mice Lacking Collagen Prolyl 4-Hydroxylase Isoenzyme II in Combination with a Reduced Amount of Isoenzyme I.

    Science.gov (United States)

    Aro, Ellinoora; Salo, Antti M; Khatri, Richa; Finnilä, Mikko; Miinalainen, Ilkka; Sormunen, Raija; Pakkanen, Outi; Holster, Tiina; Soininen, Raija; Prein, Carina; Clausen-Schaumann, Hauke; Aszódi, Attila; Tuukkanen, Juha; Kivirikko, Kari I; Schipani, Ernestina; Myllyharju, Johanna

    2015-07-03

    Collagen prolyl 4-hydroxylases (C-P4H-I, C-P4H-II, and C-P4H-III) catalyze formation of 4-hydroxyproline residues required to form triple-helical collagen molecules. Vertebrate C-P4Hs are α2β2 tetramers differing in their catalytic α subunits. C-P4H-I is the major isoenzyme in most cells, and inactivation of its catalytic subunit (P4ha1(-/-)) leads to embryonic lethality in mouse, whereas P4ha1(+/-) mice have no abnormalities. To study the role of C-P4H-II, which predominates in chondrocytes, we generated P4ha2(-/-) mice. Surprisingly, they had no apparent phenotypic abnormalities. To assess possible functional complementarity, we established P4ha1(+/-);P4ha2(-/-) mice. They were smaller than their littermates, had moderate chondrodysplasia, and developed kyphosis. A transient inner cell death phenotype was detected in their developing growth plates. The columnar arrangement of proliferative chondrocytes was impaired, the amount of 4-hydroxyproline and the Tm of collagen II were reduced, and the extracellular matrix was softer in the growth plates of newborn P4ha1(+/-);P4ha2(-/-) mice. No signs of uncompensated ER stress were detected in the mutant growth plate chondrocytes. Some of these defects were also found in P4ha2(-/-) mice, although in a much milder form. Our data show that C-P4H-I can to a large extent compensate for the lack of C-P4H-II in proper endochondral bone development, but their combined partial and complete inactivation, respectively, leads to biomechanically impaired extracellular matrix, moderate chondrodysplasia, and kyphosis. Our mouse data suggest that inactivating mutations in human P4HA2 are not likely to lead to skeletal disorders, and a simultaneous decrease in P4HA1 function would most probably be required to generate such a disease phenotype. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  10. The Evolution of Neutral Hydrogen in Galaxy Groups

    Science.gov (United States)

    Sanderson, Kelly Nicole; Wilcots, Eric; Hess, Kelley M.

    2018-01-01

    The Illustris suite of simulations is held as the standard of large scale gravitational and hydro-dynamical simulations and allows us to make a better comparisons with physical processes at the gaseous level by providing a higher mass resolution than previously available through the Millenium-II simulation. We present a comparison of an analysis on the HI content and distribution of galaxies in groups as a function of their group dark matter halo to the results of a large scale cosmological simulation. From the simulation we select optical group members above a Mr=-18 r-band magnitude and HI group members with HI above 109.5M⊙. We find that 74% of the HI detected galaxies are in groups or clusters and 84% of the optically detected galaxies are in groups or clusters. In the Hess & Wilcots (2013) paper it was found that as group membership, or group dark matter halo mass, increased, the fraction of galaxies detected in HI decreased and the spatial distribution of galaxies in these groups increased. We show the spatial distributions of galaxies, HI and optically detected, in order to reproduce these results. We find that Illustris qualitatively reproduces these trends, however, the simulation seems to be overestimating the mass of HI gas in all of its galaxies as well as the number of galaxies above the 109.5M⊙ limit.

  11. TRACING OUTFLOWS AND ACCRETION: A BIMODAL AZIMUTHAL DEPENDENCE OF Mg II ABSORPTION

    International Nuclear Information System (INIS)

    Kacprzak, Glenn G.; Churchill, Christopher W.; Nielsen, Nikole M.

    2012-01-01

    We report a bimodality in the azimuthal angle distribution of gas around galaxies as traced by Mg II absorption: halo gas prefers to exist near the projected galaxy major and minor axes. The bimodality is demonstrated by computing the mean azimuthal angle probability distribution function using 88 spectroscopically confirmed Mg II-absorption-selected galaxies [W r (2796) ≥ 0.1 Å] and 35 spectroscopically confirmed non-absorbing galaxies [W r (2796) r (2796) r (2796) distribution for gas along the major axis is likely skewed toward weaker Mg II absorption than for gas along the projected minor axis. These combined results are highly suggestive that the bimodality is driven by gas accreted along the galaxy major axis and outflowing along the galaxy minor axis. Adopting these assumptions, we find that the opening angle of outflows and inflows to be 100° and 40°, respectively. We find that the probability of detecting outflows is ∼60%, implying that winds are more commonly observed.

  12. RING STAR FORMATION RATES IN BARRED AND NONBARRED GALAXIES

    International Nuclear Information System (INIS)

    Grouchy, R. D.; Buta, R. J.; Salo, H.; Laurikainen, E.

    2010-01-01

    Nonbarred ringed galaxies are relatively normal galaxies showing bright rings of star formation in spite of lacking a strong bar. This morphology is interesting because it is generally accepted that a typical galactic disk ring forms when material collects near a resonance, set up by the pattern speed of a bar or bar-like perturbation. Our goal in this paper is to examine whether the star formation properties of rings are related to the strength of a bar or, in the absence of a bar, to the non-axisymmetric gravity potential in general. For this purpose, we obtained Hα emission line images and calculated the line fluxes and star formation rates (SFRs) for 16 nonbarred SA galaxies and four weakly barred SAB galaxies with rings. For comparison, we combine our new observations with a re-analysis of previously published data on five SA, seven SAB, and 15 SB galaxies with rings, three of which are duplicates from our sample. With these data, we examine what role a bar may play in the star formation process in rings. Compared to barred ringed galaxies, we find that the inner ring SFRs and Hα+[N II] equivalent widths in nonbarred ringed galaxies show a similar range and trend with absolute blue magnitude, revised Hubble type, and other parameters. On the whole, the star formation properties of inner rings, excluding the distribution of H II regions, are independent of the ring shapes and the bar strength in our small samples. We confirm that the deprojected axis ratios of inner rings correlate with maximum relative gravitational force Q g ; however, if we consider all rings, a better correlation is found when a local bar forcing at the radius of the ring, Q r , is used. Individual cases are described and other correlations are discussed. By studying the physical properties of these galaxies, we hope to gain a better understanding of their placement in the scheme of the Hubble sequence and how they formed rings without the driving force of a bar.

  13. [C II] 158 μm EMISSION AS A STAR FORMATION TRACER

    Energy Technology Data Exchange (ETDEWEB)

    Herrera-Camus, R.; Bolatto, A. D.; Wolfire, M. G. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Smith, J. D. [Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States); Croxall, K. V. [Department of Astronomy, The Ohio State University, 4051 McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210 (United States); Kennicutt, R. C.; Boquien, M. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Calzetti, D. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Helou, G. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Walter, F.; Meidt, S. E. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Leroy, A. K. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Draine, B. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Brandl, B. R. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden (Netherlands); Armus, L. [Spitzer Science Center, California Institute of Technology, MC 314-6, Pasadena, CA 91125 (United States); Sandstrom, K. M. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Dale, D. A. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Aniano, G. [Institut d' Astrophysique Spatiale, CNRS (UMR8617) Université Paris-Sud 11, Batiment 121, Orsay (France); Hunt, L. K. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy); Galametz, M. [European Southern Observatory, Karl Schwarzschild Strasse 2, D-85748 Garching (Germany); and others

    2015-02-10

    The [C II] 157.74 μm transition is the dominant coolant of the neutral interstellar gas, and has great potential as a star formation rate (SFR) tracer. Using the Herschel KINGFISH sample of 46 nearby galaxies, we investigate the relation of [C II] surface brightness and luminosity with SFR. We conclude that [C II] can be used for measurements of SFR on both global and kiloparsec scales in normal star-forming galaxies in the absence of strong active galactic nuclei (AGNs). The uncertainty of the Σ{sub [C} {sub II]} – Σ{sub SFR} calibration is ±0.21 dex. The main source of scatter in the correlation is associated with regions that exhibit warm IR colors, and we provide an adjustment based on IR color that reduces the scatter. We show that the color-adjusted Σ{sub [C} {sub II]} – Σ{sub SFR} correlation is valid over almost five orders of magnitude in Σ{sub SFR}, holding for both normal star-forming galaxies and non-AGN luminous infrared galaxies. Using [C II] luminosity instead of surface brightness to estimate SFR suffers from worse systematics, frequently underpredicting SFR in luminous infrared galaxies even after IR color adjustment (although this depends on the SFR measure employed). We suspect that surface brightness relations are better behaved than the luminosity relations because the former are more closely related to the local far-UV field strength, most likely the main parameter controlling the efficiency of the conversion of far-UV radiation into gas heating. A simple model based on Starburst99 population-synthesis code to connect SFR to [C II] finds that heating efficiencies are 1%-3% in normal galaxies.

  14. SDSS IV MaNGA: Dependence of Global and Spatially Resolved SFR–M ∗ Relations on Galaxy Properties

    Science.gov (United States)

    Pan, Hsi-An; Lin, Lihwai; Hsieh, Bau-Ching; Sánchez, Sebastián F.; Ibarra-Medel, Héctor; Boquien, Médéric; Lacerna, Ivan; Argudo-Fernández, Maria; Bizyaev, Dmitry; Cano-Díaz, Mariana; Drory, Niv; Gao, Yang; Masters, Karen; Pan, Kaike; Tabor, Martha; Tissera, Patricia; Xiao, Ting

    2018-02-01

    The galaxy integrated Hα star formation rate–stellar mass relation, or SFR(global)–M *(global) relation, is crucial for understanding star formation history and evolution of galaxies. However, many studies have dealt with SFR using unresolved measurements, which makes it difficult to separate out the contamination from other ionizing sources, such as active galactic nuclei and evolved stars. Using the integral field spectroscopic observations from SDSS-IV MaNGA, we spatially disentangle the contribution from different Hα powering sources for ∼1000 galaxies. We find that, when including regions dominated by all ionizing sources in galaxies, the spatially resolved relation between Hα surface density (ΣHα (all)) and stellar mass surface density (Σ*(all)) progressively turns over at the high Σ*(all) end for increasing M *(global) and/or bulge dominance (bulge-to-total light ratio, B/T). This in turn leads to the flattening of the integrated Hα(global)–M *(global) relation in the literature. By contrast, there is no noticeable flattening in both integrated Hα(H II)–M *(H II) and spatially resolved ΣHα (H II)–Σ*(H II) relations when only regions where star formation dominates the ionization are considered. In other words, the flattening can be attributed to the increasing regions powered by non-star-formation sources, which generally have lower ionizing ability than star formation. An analysis of the fractional contribution of non-star-formation sources to total Hα luminosity of a galaxy suggests a decreasing role of star formation as an ionizing source toward high-mass, high-B/T galaxies and bulge regions. This result indicates that the appearance of the galaxy integrated SFR–M * relation critically depends on their global properties (M *(global) and B/T) and relative abundances of various ionizing sources within the galaxies.

  15. Galaxies

    International Nuclear Information System (INIS)

    1981-01-01

    Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented

  16. Galaxies

    International Nuclear Information System (INIS)

    1987-01-01

    The size and nature of any large-scale anisotropy in the three-dimensional distribution of galaxies is still little understood. Recent studies have indicated that large fluctuations in the matter distribution on a scale from tens up to several hundreds of megaparsecs may exist. Work at the South African Astronomical Observatory (SAAO) in recent years has made major contributions to studies of the large scale distribution of galaxies, as well as to solving the problems of the galactic and extragalactic distance scale. Other studies of galaxies undertaken at SAAO include: quasars in the fields of nearby galaxies; dwarf irregular galaxies; IRAS galaxies; Seyfert galaxies; 'hot spot' galaxies; supernovae in NGC 5128 and NGC 1559 and superclusters. 4 figs

  17. First Detections of the [N II] 122 micron Line at High Redshift: Demonstrating the Utility of the Line for Studying Galaxies in the Early Universe

    Science.gov (United States)

    Ferkinhoff, Carl; Brisbin, Drew; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Phillips, Thomas G.; Falgarone, Edith; Benford, Dominic J.; Staguhn, Johannes G.; Tucker, Carol E.

    2011-01-01

    We report the first detections of the [N II] 122 micron line from a high-redshift galaxy. The line was strongly (>6(sigma)) detected from SMMJ02399-0136, and H1413 + 117 (the Cloverleaf QSO) using the Redshift (zeta) and Early Universe Spectrometer on the Caltech Submillimeter Observatory. The lines from both sources are quite bright with line to far-infrared (FIR) continuum luminosity ratios that are approx.7.0 x 10(exp -4) (Cloverleaf) and 2.1 x 10(exo -3) (SMMJ02399). With ratios 2-10 times larger than the average value for nearby galaxies, neither source exhibits the line to continuum deficits seen in nearby sources. The line strengths also indicate large ionized gas fractions, approx.8%-17% of the molecUlar gas mass. The [O III]/[N II] line ratio is very sensitive to the effective temperature of ionizing stars and the ionization parameter for emission arising in the narrow-line region (NLR) of an active galactic nucleus (AGN). Using Our previous detection of the [O III] 88 micron line, the [O III]/[N II]line ratio for SMMJ02399-0136 indicates that the dominant source of the line emission is either stellar H II regions ionized by O9.5 stars, or the NLR of the AGN with ionization parameter log(U) = -3.3 to -4.0. A composite system, where 30%-50% of the FIR lines arise in the NLR also matches the data. The Cloverleaf is best modeled by a superposition of approx.200 M82-like starbursts accounting for all of the FIR emission and 43% of the [N II]line. The remainder may come from the NLR. This war!< demonstrates the utility of the [N II] and [O III] lines in constraining properties of the ionized medium.

  18. TRACING OUTFLOWS AND ACCRETION: A BIMODAL AZIMUTHAL DEPENDENCE OF Mg II ABSORPTION

    Energy Technology Data Exchange (ETDEWEB)

    Kacprzak, Glenn G. [Swinburne University of Technology, Victoria 3122 (Australia); Churchill, Christopher W.; Nielsen, Nikole M., E-mail: gkacprzak@astro.swin.edu.au [New Mexico State University, Las Cruces, NM 88003 (United States)

    2012-11-20

    We report a bimodality in the azimuthal angle distribution of gas around galaxies as traced by Mg II absorption: halo gas prefers to exist near the projected galaxy major and minor axes. The bimodality is demonstrated by computing the mean azimuthal angle probability distribution function using 88 spectroscopically confirmed Mg II-absorption-selected galaxies [W{sub r} (2796) {>=} 0.1 A] and 35 spectroscopically confirmed non-absorbing galaxies [W{sub r} (2796) < 0.1 A] imaged with Hubble Space Telescope and Sloan Digital Sky Survey. The azimuthal angle distribution for non-absorbers is flat, indicating no azimuthal preference for gas characterized by W{sub r} (2796) < 0.1 A. We find that blue star-forming galaxies clearly drive the bimodality while red passive galaxies may exhibit an excess along their major axis. These results are consistent with galaxy evolution scenarios where star-forming galaxies accrete new gas, forming new stars and producing winds, while red galaxies exist passively due to reduced gas reservoirs. We further compute an azimuthal angle dependent Mg II absorption covering fraction, which is enhanced by as much as 20%-30% along the major and minor axes. The W{sub r} (2796) distribution for gas along the major axis is likely skewed toward weaker Mg II absorption than for gas along the projected minor axis. These combined results are highly suggestive that the bimodality is driven by gas accreted along the galaxy major axis and outflowing along the galaxy minor axis. Adopting these assumptions, we find that the opening angle of outflows and inflows to be 100 Degree-Sign and 40 Degree-Sign , respectively. We find that the probability of detecting outflows is {approx}60%, implying that winds are more commonly observed.

  19. OPTICAL SPECTROSCOPY AND NEBULAR OXYGEN ABUNDANCES OF THE SPITZER/SINGS GALAXIES

    International Nuclear Information System (INIS)

    Moustakas, John; Kennicutt, Robert C. Jr.; Tremonti, Christy A.; Dale, Daniel A.; Smith, John-David T.; Calzetti, Daniela

    2010-01-01

    We present intermediate-resolution optical spectrophotometry of 65 galaxies obtained in support of the Spitzer Infrared Nearby Galaxies Survey (SINGS). For each galaxy we obtain a nuclear, circumnuclear, and semi-integrated optical spectrum designed to coincide spatially with mid- and far-infrared spectroscopy from the Spitzer Space Telescope. We make the reduced, spectrophotometrically calibrated one-dimensional spectra, as well as measurements of the fluxes and equivalent widths of the strong nebular emission lines, publicly available. We use optical emission-line ratios measured on all three spatial scales to classify the sample into star-forming, active galactic nuclei (AGNs), and galaxies with a mixture of star formation and nuclear activity. We find that the relative fraction of the sample classified as star forming versus AGN is a strong function of the integrated light enclosed by the spectroscopic aperture. We supplement our observations with a large database of nebular emission-line measurements of individual H II regions in the SINGS galaxies culled from the literature. We use these ancillary data to conduct a detailed analysis of the radial abundance gradients and average H II-region abundances of a large fraction of the sample. We combine these results with our new integrated spectra to estimate the central and characteristic (globally averaged) gas-phase oxygen abundances of all 75 SINGS galaxies. We conclude with an in-depth discussion of the absolute uncertainty in the nebular oxygen abundance scale.

  20. EXTINCTION IN STAR-FORMING DISK GALAXIES FROM INCLINATION-DEPENDENT COMPOSITE SPECTRA

    International Nuclear Information System (INIS)

    Yip, Ching-Wa; Szalay, Alex S.; Wyse, Rosemary F. G.; Budavari, Tamas; Dobos, Laszlo; Csabai, Istvan

    2010-01-01

    Extinction in galaxies affects their observed properties. In scenarios describing the distribution of dust and stars in individual disk galaxies, the amplitude of the extinction can be modulated by the inclination of the galaxies. In this work, we investigate the inclination dependency in composite spectra of star-forming disk galaxies from the Sloan Digital Sky Survey Data Release 5. In a volume-limited sample within a redshift range 0.065-0.075 and a r-band Petrosian absolute magnitude range -19.5 to -22 mag which exhibits a flat distribution of inclination, the inclined relative to face-on extinction in the stellar continuum is found empirically to increase with inclination in the g, r, and i bands. Within the central 0.5 intrinsic half-light radius of the galaxies, the g-band relative extinction in the stellar continuum for the highly inclined objects (axis ratio b/a = 0.1) is 1.2 mag, agreeing with previous studies. The extinction curve of the disk galaxies is given in the rest-frame wavelengths 3700-8000 A, identified with major optical emission and absorption lines in diagnostics. The Balmer decrement, Hα/Hβ, remains constant with inclination, suggesting a different kind of dust configuration and/or reddening mechanism in the H II region from that in the stellar continuum. One factor is shown to be the presence of spatially non-uniform interstellar extinction, presumably caused by clumped dust in the vicinity of the H II region.

  1. El medio interestelar en los alrededores de la region HII Sh2-183

    Science.gov (United States)

    Cichowolski, S.; Cappa, C. E.; Blanco, A.; Eppens, L.; Ertini, K.; Leiva, M. M.

    2017-10-01

    We present a multiwavelength study of the HII region Sh2-183, located at (,) = (123.3,+3.0) at a distance of 7.0 1.5 kpc from the Sun. Based on the radio continuum data we estimated the amount of ionized gas, the electronic density, and the number of ionizing photons needed to keep the region ionized, which is important since the star/s responsible of the region was/were not detected yet. On the other hand, based on IRAS data we have analyzed the dust temperature and distribution. The Hi line data allowed the detection of a shell-like structure surrounding the ionized gas and the CO data revealed the presence of 6 molecular clouds probably related to Sh2-183, which harbor several young stellar object candidates.

  2. A Distributed Public Key Infrastructure Based on Threshold Cryptography for the HiiMap Next Generation Internet Architecture

    Directory of Open Access Journals (Sweden)

    Oliver Hanka

    2011-02-01

    Full Text Available In this article, a security extension for the HiiMap Next Generation Internet Architecture is presented. We regard a public key infrastructure which is integrated into the mapping infrastructure of the locator/identifier-split addressing scheme. The security approach is based on Threshold Cryptography which enables a sharing of keys among the mapping servers. Hence, a more trustworthy and fair approach for a Next Generation Internet Architecture as compared to the state of the art approach is fostered. Additionally, we give an evaluation based on IETF AAA recommendations for security-related systems.

  3. Multicolor photometry of the nearby galaxy cluster A119

    International Nuclear Information System (INIS)

    Tian Jintao; Zhou Xu; Jiang Zhaoji; Ma Jun; Wu Zhenyu; Fan Zhou; Zhang Tianmeng; Zou Hu; Yuan Qirong; Wu Jianghua

    2012-01-01

    This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 (z = 0.0442) with the Beijing-Arizona-Taiwan-Connecticut system of 15 intermediate bands. Within the BATC field of view of 58' × 58', there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies (called sample I). Based on the spectral energy distributions of 1376 galaxies brighter than i BATC = 19.5, the photometric redshift technique and the color-magnitude relation of early-type galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample (called sample II) of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynamically complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidence for morphology or luminosity segregations is found in either sample. With the PEGASE evolutionary synthesis model, the environmental effect on the properties of star formation is confirmed. Faint galaxies in the low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities in their interstellar medium, which is in agreement with the context of the hierarchical cosmological scenario. (research papers)

  4. Observational hints of radial migration in disc galaxies from CALIFA

    Science.gov (United States)

    Ruiz-Lara, T.; Pérez, I.; Florido, E.; Sánchez-Blázquez, P.; Méndez-Abreu, J.; Sánchez-Menguiano, L.; Sánchez, S. F.; Lyubenova, M.; Falcón-Barroso, J.; van de Ven, G.; Marino, R. A.; de Lorenzo-Cáceres, A.; Catalán-Torrecilla, C.; Costantin, L.; Bland-Hawthorn, J.; Galbany, L.; García-Benito, R.; Husemann, B.; Kehrig, C.; Márquez, I.; Mast, D.; Walcher, C. J.; Zibetti, S.; Ziegler, B.; Califa Team

    2017-07-01

    Context. According to numerical simulations, stars are not always kept at their birth galactocentric distances but they have a tendency to migrate. The importance of this radial migration in shaping galactic light distributions is still unclear. However, if radial migration is indeed important, galaxies with different surface brightness (SB) profiles must display differences in their stellar population properties. Aims: We investigate the role of radial migration in the light distribution and radial stellar content by comparing the inner colour, age, and metallicity gradients for galaxies with different SB profiles. We define these inner parts, avoiding the bulge and bar regions and up to around three disc scale lengths (type I, pure exponential) or the break radius (type II, downbending; type III, upbending). Methods: We analysed 214 spiral galaxies from the CALIFA survey covering different SB profiles. We made use of GASP2D and SDSS data to characterise the light distribution and obtain colour profiles of these spiral galaxies. The stellar age and metallicity profiles were computed using a methodology based on full-spectrum fitting techniques (pPXF, GANDALF, and STECKMAP) to the Integral Field Spectroscopic CALIFA data. Results: The distributions of the colour, stellar age, and stellar metallicity gradients in the inner parts for galaxies displaying different SB profiles are unalike as suggested by Kolmogorov-Smirnov and Anderson-Darling tests. We find a trend in which type II galaxies show the steepest profiles of all, type III show the shallowest, and type I display an intermediate behaviour. Conclusions: These results are consistent with a scenario in which radial migration is more efficient for type III galaxies than for type I systems, where type II galaxies present the lowest radial migration efficiency. In such a scenario, radial migration mixes the stellar content, thereby flattening the radial stellar properties and shaping different SB profiles. However

  5. Anisotropic magnification distortion of the 3D galaxy correlation. I. Real space

    International Nuclear Information System (INIS)

    Hui, Lam; LoVerde, Marilena; Gaztanaga, Enrique

    2007-01-01

    It has long been known that gravitational lensing, primarily via magnification bias, modifies the observed galaxy (or quasar) clustering. Such discussions have largely focused on the 2D angular correlation function. Here and in paper II [L. Hui, E. Gaztanaga, and M. LoVerde, arXiv:0710.4191] we explore how magnification bias distorts the 3D correlation function and power spectrum, as first considered by Matsubara [Astrophys. J. Lett. 537, L77 (2000).]. The interesting point is that the distortion is anisotropic. Magnification bias in general preferentially enhances the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. For instance, at a LOS separation of ∼100 Mpc/h, where the intrinsic galaxy-galaxy correlation is rather weak, the observed correlation can be enhanced by lensing by a factor of a few, even at a modest redshift of z∼0.35. This effect presents an interesting opportunity as well as a challenge. The opportunity: this lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification, and magnification-magnification correlations, without measuring galaxy shapes. The anisotropy is distinguishable from the well-known distortion due to peculiar motions, as will be discussed in paper II. The challenge: the magnification distortion of the galaxy correlation must be accounted for in interpreting data as precision improves. For instance, the ∼100 Mpc/h baryon acoustic oscillation scale in the correlation function is shifted by up to ∼3% in the LOS orientation, and up to ∼0.6% in the monopole, depending on the galaxy bias, redshift, and number count slope. The corresponding shifts in the inferred Hubble parameter and angular diameter distance, if ignored, could significantly bias measurements of the dark energy equation of state. Lastly, magnification distortion offers a plausible explanation for the well-known excess correlations seen in pencil beam surveys

  6. The concerted impact of galaxies and QSOs on the ionization and thermal state of the intergalactic medium

    Science.gov (United States)

    Kakiichi, Koki; Graziani, Luca; Ciardi, Benedetta; Meiksin, Avery; Compostella, Michele; Eide, Marius B.; Zaroubi, Saleem

    2017-07-01

    We present a detailed analysis of the ionization and thermal structure of the intergalactic medium (IGM) around a high-redshift (z = 10) QSO, using a large suite of cosmological, multifrequency radiative transfer simulations, exploring the contribution from galaxies as well as the QSO, and the effect of X-rays and secondary ionization. We show that in high-z QSO environments both the central QSO and the surrounding galaxies concertedly control the reionization morphology of hydrogen and helium and have a non-linear impact on the thermal structure of the IGM. A QSO imprints a distinctive morphology on H II regions if its total ionizing photon budget exceeds that of the surrounding galaxies since the onset of hydrogen reionization; otherwise, the morphology shows little difference from that of H II regions produced only by galaxies. In addition, the spectral shape of the collective radiation field from galaxies and QSOs controls the thickness of the I-fronts. While a UV-obscured QSO can broaden the I-front, the contribution from other UV sources, either galaxies or unobscured QSOs, is sufficient to maintain a sharp I-front. X-ray photons from the QSO are responsible for a prominent extended tail of partial ionization ahead of the I-front. QSOs leave a unique imprint on the morphology of He II/He III regions. We suggest that, while the physical state of the IGM is modified by QSOs, the most direct test to understand the role of galaxies and QSOs during reionization is to perform galaxy surveys in a region of sky imaged by 21 cm tomography.

  7. SHOCKED SUPERWINDS FROM THE z {approx} 2 CLUMPY STAR-FORMING GALAXY, ZC406690

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Shapiro Griffin, Kristen [Aerospace Research Laboratories, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Davies, Ric; Foerster-Schreiber, Natascha M.; Tacconi, Linda J.; Kurk, Jaron; Wuyts, Stijn; Genel, Shy; Buschkamp, Peter; Eisenhauer, Frank; Lutz, Dieter [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr.1, D-85748 Garching (Germany); Lilly, Simon J.; Carollo, C. Marcella [Institute of Astronomy, Department of Physics, Eidgenoessische Technische Hochschule, ETH Zuerich CH-8093 (Switzerland); Renzini, Alvio; Mancini, Chiara [Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, Padova I-35122 (Italy); Bouche, Nicolas [Department of Physics and Astronomy, University of California, Santa Barbara, Santa Barbara, CA 93106 (United States); Burkert, Andreas [Department fuer Physik, Universitaets-Sternwarte Ludwig-Maximilians-Universitaet (USM), Scheinerstr. 1, Muenchen, D-81679 (Germany); Cresci, Giovanni [Istituto Nazionale di AstrofisicaOsservatorio Astronomico di Arcetri, Largo Enrico Fermi 5, I 50125 Firenze (Italy); Hicks, Erin, E-mail: sfnewman@berkeley.edu [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); and others

    2012-06-20

    We have obtained high-resolution data of the z {approx} 2 ring-like, clumpy star-forming galaxy (SFG) ZC406690 using the VLT/SINFONI with adaptive optics (in K band) and in seeing-limited mode (in H and J bands). Our data include all of the main strong optical emission lines: [O II], [O III], H{alpha}, H{beta}, [N II], and [S II]. We find broad, blueshifted H{alpha} and [O III] emission line wings in the spectra of the galaxy's massive, star-forming clumps ({sigma} {approx} 85 km s{sup -1}) and even broader wings (up to 70% of the total H{alpha} flux, with {sigma} {approx} 290 km s{sup -1}) in regions spatially offset from the clumps by {approx}2 kpc. The broad emission likely originates from large-scale outflows with mass outflow rates from individual clumps that are 1-8 Multiplication-Sign the star formation rate (SFR) of the clumps. Based on emission line ratio diagnostics ([N II]/H{alpha} and [S II]/H{alpha}) and photoionization and shock models, we find that the emission from the clumps is due to a combination of photoionization from the star-forming regions and shocks generated in the outflowing component, with 5%-30% of the emission deriving from shocks. In terms of the ionization parameter (6 Multiplication-Sign 10{sup 7} to 10{sup 8} cm s{sup -1}, based on both the SFR and the O{sub 32} ratio), density (local electron densities of 300-1800 cm{sup -3} in and around the clumps, and ionized gas column densities of 1200-8000 M{sub Sun }pc{sup -2}), and SFR (10-40 M{sub Sun} yr{sup -1}), these clumps more closely resemble nuclear starburst regions of local ultraluminous infrared galaxies and dwarf irregulars than H II regions in local galaxies. However, the star-forming clumps are not located in the nucleus as in local starburst galaxies but instead are situated in a ring several kpc from the center of their high-redshift host galaxy, and have an overall disk-like morphology. The two brightest clumps are quite different in terms of their internal

  8. R-process enrichment from a single event in an ancient dwarf galaxy.

    Science.gov (United States)

    Ji, Alexander P; Frebel, Anna; Chiti, Anirudh; Simon, Joshua D

    2016-03-31

    Elements heavier than zinc are synthesized through the rapid (r) and slow (s) neutron-capture processes. The main site of production of the r-process elements (such as europium) has been debated for nearly 60 years. Initial studies of trends in chemical abundances in old Milky Way halo stars suggested that these elements are produced continually, in sites such as core-collapse supernovae. But evidence from the local Universe favours the idea that r-process production occurs mainly during rare events, such as neutron star mergers. The appearance of a plateau of europium abundance in some dwarf spheroidal galaxies has been suggested as evidence for rare r-process enrichment in the early Universe, but only under the assumption that no gas accretes into those dwarf galaxies; gas accretion favours continual r-process enrichment in these systems. Furthermore, the universal r-process pattern has not been cleanly identified in dwarf spheroidals. The smaller, chemically simpler, and more ancient ultrafaint dwarf galaxies assembled shortly after the first stars formed, and are ideal systems with which to study nucleosynthesis events such as the r-process. Reticulum II is one such galaxy. The abundances of non-neutron-capture elements in this galaxy (and others like it) are similar to those in other old stars. Here, we report that seven of the nine brightest stars in Reticulum II, observed with high-resolution spectroscopy, show strong enhancements in heavy neutron-capture elements, with abundances that follow the universal r-process pattern beyond barium. The enhancement seen in this 'r-process galaxy' is two to three orders of magnitude higher than that detected in any other ultrafaint dwarf galaxy. This implies that a single, rare event produced the r-process material in Reticulum II. The r-process yield and event rate are incompatible with the source being ordinary core-collapse supernovae, but consistent with other possible sources, such as neutron star mergers.

  9. Impact of climate change on the Hii River basin and salinity in Lake Shinji: a case study using the SWAT model and a regression curve

    Science.gov (United States)

    The impacts of climate change on water resources were analysed for the Hii River basin and downstream Lake Shinji. The variation between saline and fresh water within these systems means that they encompass diverse ecosystems. Changes in evapotranspiration (ET), snow water equivalent, discharge into...

  10. Internal Variations in Empirical Oxygen Abundances for Giant H II Regions in the Galaxy NGC 2403

    Science.gov (United States)

    Mao, Ye-Wei; Lin, Lin; Kong, Xu

    2018-02-01

    This paper presents a spectroscopic investigation of 11 {{H}} {{II}} regions in the nearby galaxy NGC 2403. The {{H}} {{II}} regions are observed with a long-slit spectrograph mounted on the 2.16 m telescope at XingLong station of National Astronomical Observatories of China. For each of the {{H}} {{II}} regions, spectra are extracted at different nebular radii along the slit-coverage. Oxygen abundances are empirically estimated from the strong-line indices R23, N2O2, O3N2, and N2 for each spectrophotometric unit, with both observation- and model-based calibrations adopted into the derivation. Radial profiles of these diversely estimated abundances are drawn for each nebula. In the results, the oxygen abundances separately estimated with the prescriptions on the basis of observations and models, albeit from the same spectral index, systematically deviate from each other; at the same time, the spectral indices R23 and N2O2 are distributed with flat profiles, whereas N2 and O3N2 exhibit apparent gradients with the nebular radius. Because our study naturally samples various ionization levels, which inherently decline at larger radii within individual {{H}} {{II}} regions, the radial distributions indicate not only the robustness of R23 and N2O2 against ionization variations but also the sensitivity of N2 and O3N2 to the ionization parameter. The results in this paper provide observational corroboration of the theoretical prediction about the deviation in the empirical abundance diagnostics. Our future work is planned to investigate metal-poor {{H}} {{II}} regions with measurable T e, in an attempt to recalibrate the strong-line indices and consequently disclose the cause of the discrepancies between the empirical oxygen abundances.

  11. DISSECTING THE RED SEQUENCE. II. STAR FORMATION HISTORIES OF EARLY-TYPE GALAXIES THROUGHOUT THE FUNDAMENTAL PLANE

    International Nuclear Information System (INIS)

    Graves, Genevieve J.; Faber, S. M.; Schiavon, Ricardo P.

    2009-01-01

    This analysis uses spectra of ∼16,000 nearby Sloan Digital Sky Survey quiescent galaxies to track variations in galaxy star formation histories (SFHs) along and perpendicular to the fundamental plane (FP). We sort galaxies by their FP properties (σ, R e , and I e ) and construct high signal-to-noise ratio mean galaxy spectra that span the breadth and thickness of the FP. From these spectra, we determine mean luminosity-weighted ages, [Fe/H], [Mg/H], and [Mg/Fe] based on single stellar population models using the method described in Graves and Schiavon. In agreement with previous work, the SFHs of early-type galaxies are found to form a two-parameter family. The major trend is that mean age, [Fe/H], [Mg/H], and [Mg/Fe] all increase with σ. However, no stellar population property shows any dependence on R e at fixed σ, suggesting that σ and not dynamical mass (M dyn ∝ σ 2 R e ) is the better predictor of past SFH. In addition to the main trend with σ, galaxies also show a range of population properties at fixed σ that are strongly correlated with surface brightness residuals from the FP (Δlog I e ), such that higher surface brightness galaxies have younger mean ages, higher [Fe/H], higher [Mg/H], and lower [Mg/Fe] than lower surface brightness galaxies. These latter trends are a major new constraint on SFHs.

  12. INTERACTIONS OF GALAXIES IN THE GALAXY CLUSTER ENVIRONMENT

    International Nuclear Information System (INIS)

    Park, Changbom; Hwang, Ho Seong

    2009-01-01

    We study the dependence of galaxy properties on the clustercentric radius and the environment attributed to the nearest neighbor galaxy using the Sloan Digital Sky Survey galaxies associated with the Abell galaxy clusters. We find that there exists a characteristic scale where the properties of galaxies suddenly start to depend on the clustercentric radius at fixed neighbor environment. The characteristic scale is 1-3 times the cluster virial radius depending on galaxy luminosity. Existence of the characteristic scale means that the local galaxy number density is not directly responsible for the morphology-density relation in clusters because the local density varies smoothly with the clustercentric radius and has no discontinuity in general. What is really working in clusters is the morphology-clustercentric radius-neighbor environment relation, where the neighbor environment means both neighbor morphology and the local mass density attributed to the neighbor. The morphology-density relation appears working only because of the statistical correlation between the nearest neighbor distance and the local galaxy number density. We find strong evidence that the hydrodynamic interactions with nearby early-type galaxies is the main drive to quenching star formation activity of late-type galaxies in clusters. The hot cluster gas seems to play at most a minor role down to one tenth of the cluster virial radius. We also find that the viable mechanisms which can account for the clustercentric radius dependence of the structural and internal kinematics parameters are harassment and interaction of galaxies with the cluster potential. The morphology transformation of the late-type galaxies in clusters seems to have taken place through both galaxy-galaxy hydrodynamic interactions and galaxy-cluster/galaxy-galaxy gravitational interactions.

  13. INTERACTIONS OF GALAXIES IN THE GALAXY CLUSTER ENVIRONMENT

    Energy Technology Data Exchange (ETDEWEB)

    Park, Changbom; Hwang, Ho Seong [School of Physics, Korea Institute for Advanced Study, Seoul 130-722 (Korea, Republic of)], E-mail: cbp@kias.re.kr, E-mail: hshwang@kias.re.kr

    2009-07-10

    We study the dependence of galaxy properties on the clustercentric radius and the environment attributed to the nearest neighbor galaxy using the Sloan Digital Sky Survey galaxies associated with the Abell galaxy clusters. We find that there exists a characteristic scale where the properties of galaxies suddenly start to depend on the clustercentric radius at fixed neighbor environment. The characteristic scale is 1-3 times the cluster virial radius depending on galaxy luminosity. Existence of the characteristic scale means that the local galaxy number density is not directly responsible for the morphology-density relation in clusters because the local density varies smoothly with the clustercentric radius and has no discontinuity in general. What is really working in clusters is the morphology-clustercentric radius-neighbor environment relation, where the neighbor environment means both neighbor morphology and the local mass density attributed to the neighbor. The morphology-density relation appears working only because of the statistical correlation between the nearest neighbor distance and the local galaxy number density. We find strong evidence that the hydrodynamic interactions with nearby early-type galaxies is the main drive to quenching star formation activity of late-type galaxies in clusters. The hot cluster gas seems to play at most a minor role down to one tenth of the cluster virial radius. We also find that the viable mechanisms which can account for the clustercentric radius dependence of the structural and internal kinematics parameters are harassment and interaction of galaxies with the cluster potential. The morphology transformation of the late-type galaxies in clusters seems to have taken place through both galaxy-galaxy hydrodynamic interactions and galaxy-cluster/galaxy-galaxy gravitational interactions.

  14. Direct Measurement of the Supernova Rate in Starburst Galaxies

    Science.gov (United States)

    Bregman, Jesse D.; Temi, Pasquale; Rank, David; DeVincenzi, Donald L. (Technical Monitor)

    1999-01-01

    Supernovae play a key role in the dynamics, structure, and chemical evolution of galaxies. The massive stars that end their lives as supernovae live for short times. Many are still associated with dusty star formation regions when they explode, making them difficult to observe at visible wavelengths. In active star forming regions (galactic nuclei and starburst regions), dust extintion is especially severe. Thus, determining the supernova rate in the active star forming regions of galaxies, where the supernova rate can be one or two orders of magnitude higher than the average, has proven to be difficult. From observations of SN1987A, we know that the [NiII] 6.63 micron emission line was the strongest line in the infrared spectrum for a period of a year and a half after the explosion. Since dust extintion is much less at 6.63 pm than at visible wavelengths (A(sub 6.63)/A(sub V) = 0.025), the NiII line can be used as a sensitive probe for the detection of recent supernovae. We have observed a sample of starburst galaxies at 6.63 micron using ISOCAM to search for the NiII emission line characteristic of recent supernovae. We did not detect any NiII line emission brighter than a 5sigma limit of 5 mJy. We can set upper limits to the supernova rate in our sample, scaled to the rate in M82, of less than 0.3 per year at the 90% confidence level using Bayesian methods. Assuming that a supernova would have a NiII with the same luminosity as observed in SN1987A, we find less than 0.09 and 0.15 per year at the 50% and 67% confidence levels. These rates are somewhat less if a more normal type II supernovae has a NiII line luminosity greater than the line in SN1987A.

  15. THE FATE OF DWARF GALAXIES IN CLUSTERS AND THE ORIGIN OF INTRACLUSTER STARS. II. COSMOLOGICAL SIMULATIONS

    International Nuclear Information System (INIS)

    Martel, Hugo; Barai, Paramita; Brito, William

    2012-01-01

    We combine an N-body simulation algorithm with a subgrid treatment of galaxy formation, mergers, and tidal destruction, and an observed conditional luminosity function Φ(L|M), to study the origin and evolution of galactic and extragalactic light inside a cosmological volume of size (100 Mpc) 3 , in a concordance ΛCDM model. This algorithm simulates the growth of large-scale structures and the formation of clusters, the evolution of the galaxy population in clusters, the destruction of galaxies by mergers and tides, and the evolution of the intracluster light (ICL). We find that destruction of galaxies by mergers dominates over destruction by tides by about an order of magnitude at all redshifts. However, tidal destruction is sufficient to produce ICL fractions f ICL that are sufficiently high to match observations. Our simulation produces 18 massive clusters (M cl > 10 14 M ☉ ) with values of f ICL ranging from 1% to 58% at z = 0. There is a weak trend of f ICL to increase with cluster mass. The bulk of the ICL (∼60%) is provided by intermediate galaxies of total masses 10 11 -10 12 M ☉ and stellar masses 6 × 10 8 M ☉ to 3 × 10 10 M ☉ that were tidally destroyed by even more massive galaxies. The contribution of low-mass galaxies to the ICL is small and the contribution of dwarf galaxies is negligible, even though, by numbers, most galaxies that are tidally destroyed are dwarfs. Tracking clusters back in time, we find that their values of f ICL tend to increase over time, but can experience sudden changes that are sometimes non-monotonic. These changes occur during major mergers involving clusters of comparable masses but very different intracluster luminosities. Most of the tidal destruction events take place in the central regions of clusters. As a result, the ICL is more centrally concentrated than the galactic light. Our results support tidal destruction of intermediate-mass galaxies as a plausible scenario for the origin of the ICL.

  16. Source-plane reconstruction of the giant gravitational arc in A2667: A candidate Wolf-Rayet galaxy at z ∼ 1

    International Nuclear Information System (INIS)

    Cao, Shuo; Zhu, Zong-Hong; Federico II, Via Cinthia, I-80126 Napoli (Italy))" data-affiliation=" (Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Via Cinthia, I-80126 Napoli (Italy))" >Covone, Giovanni; Jullo, Eric; Richard, Johan; Izzo, Luca

    2015-01-01

    We present a new analysis of Hubble Space Telescope, Spitzer Space Telescope, and Very Large Telescope imaging and spectroscopic data of a bright lensed galaxy at z = 1.0334 in the lensing cluster A2667. Using this high-resolution imaging, we present an updated lens model that allows us to fully understand the lensing geometry and reconstruct the lensed galaxy in the source plane. This giant arc gives a unique opportunity to view the structure of a high-redshift disk galaxy. We find that the lensed galaxy of A2667 is a typical spiral galaxy with a morphology similar to the structure of its counterparts at higher redshift, z ∼ 2. The surface brightness of the reconstructed source galaxy in the z 850 band reveals the central surface brightness I(0) = 20.28 ± 0.22 mag arcsec –2 and a characteristic radius r s = 2.01 ± 0.16 kpc at redshift z ∼ 1. The morphological reconstruction in different bands shows obvious negative radial color gradients for this galaxy. Moreover, the redder central bulge tends to contain a metal-rich stellar population, rather than being heavily reddened by dust due to high and patchy obscuration. We analyze the VIMOS/integral field unit spectroscopic data and find that, in the given wavelength range (∼1800-3200 Å), the combined arc spectrum of the source galaxy is characterized by a strong continuum emission with strong UV absorption lines (Fe II and Mg II) and shows the features of a typical starburst Wolf-Rayet galaxy, NGC 5253. More specifically, we have measured the equivalent widths of Fe II and Mg II lines in the A2667 spectrum, and obtained similar values for the same wavelength interval of the NGC 5253 spectrum. Marginal evidence for [C III] 1909 emission at the edge of the grism range further confirms our expectation.

  17. Low-Surface-Brightness Galaxies: Hidden Galaxies Revealed

    Science.gov (United States)

    Bothun, G.; Impey, C.; McGaugh, S.

    1997-07-01

    In twenty years, low surface brightness (LSB) galaxies have evolved from being an idiosyncratic notion to being one of the major baryonic repositories in the Universe. The story of their discovery and the characterization of their properties is told here. Their recovery from the noise of the night sky background is a strong testament to the severity of surface brightness selection effects. LSB galaxies have a number of remarkable properties which distinguish them from the more familiar Hubble Sequence of spirals. The two most important are 1) they evolve at a significantly slower rate and may well experience star formation outside of the molecular cloud environment, 2) they are embedded in dark matter halos which are of lower density and more extended than the halos around high surface brightness (HSB) disk galaxies. Compared to HSB disks, LSB disks are strongly dark matter dominated at all radii and show a systematic increase in $M/L$ with decreasing central surface brightness. In addition, the recognition that large numbers of LSB galaxies actually exist has changed the form of the galaxy luminosity function and has clearly increased the space density of galaxies at z =0. Recent CCD surveys have uncovered a population of red LSB disks that may be related to the excess of faint blue galaxies detected at moderate redshifts. LSB galaxies offer us a new window into galaxy evolution and formation which is every bit as important as those processes which have produced easy to detect galaxies. Indeed, the apparent youth of some LSB galaxies suggest that galaxy formation is a greatly extended process. While the discovery of LSB galaxies have lead to new insights, it remains unwise to presume that we now have a representative sample which encompasses all galaxy types and forms. (SECTION: Invited Review Paper)

  18. Spectrophotometry of the nucleus of the Sy 2 galaxy Markarian 308

    International Nuclear Information System (INIS)

    Popov, V.N.; Khachikyan, Eh.E.

    1980-01-01

    The results of spectrophotometry of the Sy2 galaxy Markarian 308 are presented. The profiles of the emission lines [N II] lambda lambda 6583, 6548 A, Hsub(α), [O III] lambda lambda 5007, 4959 A and Hsub(β) are drawn. The electron density, electron temperature, mass and effective volume of the emitting gas are estimated. Markarian 308 shows now less activity compared with other Sy2 galaxies

  19. Spotted star light curve numerical modeling technique and its application to HII 1883 surface imaging

    Science.gov (United States)

    Kolbin, A. I.; Shimansky, V. V.

    2014-04-01

    We developed a code for imaging the surfaces of spotted stars by a set of circular spots with a uniform temperature distribution. The flux from the spotted surface is computed by partitioning the spots into elementary areas. The code takes into account the passing of spots behind the visible stellar limb, limb darkening, and overlapping of spots. Modeling of light curves includes the use of recent results of the theory of stellar atmospheres needed to take into account the temperature dependence of flux intensity and limb darkening coefficients. The search for spot parameters is based on the analysis of several light curves obtained in different photometric bands. We test our technique by applying it to HII 1883.

  20. Long-slit spectrophotometry of the multiple knots of the polar ring galaxy IIZw71

    Science.gov (United States)

    Pérez-Montero, E.; García-Benito, R.; Díaz, A. I.; Pérez, E.; Kehrig, C.

    2009-04-01

    companion galaxy IIZw70. Finally, we calculated the SFR in the different knots from the Hα luminosities. The combined SFR rate for the ring amounts to half of the integrated SFR for this galaxy reported by previous authors. The average surface SFR is also higher than the average reported value of HII in polar rings by more than an order of magnitude.

  1. Galaxies

    International Nuclear Information System (INIS)

    1989-01-01

    In studies of the large scale structure of the universe there is a continuing need for extensive galaxy redshift determinations. Optically selected redshift surveys are of particular importance, since flux-limited samples record much higher space densities of galaxies than samples of similar size selected in other wavebands. A considerable amount of the South African Astronomical Observatory (SAAO) observing time is currently being devoted to carrying out a large southern galaxy redshift survey. A recently completed study, the Durham-SAAO redshift survey suggests that the mean density of matter is well below the critical limit for a closed universe and also that the universe may be homogenous at very large scales. Other research conducted by the SAAO include studies on: the distribution of galaxies; Seyfert galaxies; starburst and IRAS galaxies; interacting and compact galaxies; a re-evaluation of the Cepheid distance to NGC 300, and a search for quasars behind galaxies. 1 fig

  2. HII 2407: AN ECLIPSING BINARY REVEALED BY K2 OBSERVATIONS OF THE PLEIADES

    Energy Technology Data Exchange (ETDEWEB)

    David, Trevor J.; Hillenbrand, Lynne A.; Zhang, Celia; Riddle, Reed L. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Stauffer, John; Rebull, L. M. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Cody, Ann Marie [NASA Ames Research Center, Mountain View, CA 94035 (United States); Conroy, Kyle; Stassun, Keivan G. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Pope, Benjamin; Aigrain, Suzanne; Gillen, Ed [Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Cameron, Andrew Collier [SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS (United Kingdom); Barrado, David [Centro de Astrobiología, INTA-CSIC, Dpto. Astrofísica, ESAC Campus, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain); Isaacson, Howard; Marcy, Geoffrey W. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Ziegler, Carl; Law, Nicholas M. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States); Baranec, Christoph, E-mail: tjd@astro.caltech.edu [Institute for Astronomy, University of Hawai‘i at Mānoa, Hilo, HI 96720-2700 (United States)

    2015-11-20

    The star HII 2407 is a member of the relatively young Pleiades star cluster and was previously discovered to be a single-lined spectroscopic binary. It is newly identified here within Kepler/K2 photometric time series data as an eclipsing binary system. Mutual fitting of the radial velocity and photometric data leads to an orbital solution and constraints on fundamental stellar parameters. While the primary has arrived on the main sequence, the secondary is still pre-main sequence and we compare our results for the M/M{sub ⊙} and R/R{sub ⊙} values with stellar evolutionary models. We also demonstrate that the system is likely to be tidally synchronized. Follow-up infrared spectroscopy is likely to reveal the lines of the secondary, allowing for dynamically measured masses and elevating the system to benchmark eclipsing binary status.

  3. Nebular excitation in z ∼ 2 star-forming galaxies from the SINS and LUCI surveys: The influence of shocks and active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Buschkamp, Peter; Förster Schreiber, Natascha M.; Kurk, Jaron; Rosario, David; Davies, Ric; Eisenhauer, Frank; Lutz, Dieter [Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching (Germany); Sternberg, Amiel [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Gnat, Orly [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Mancini, Chiara; Renzini, Alvio [Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Lilly, Simon J.; Carollo, C. Marcella [Institute of Astronomy, Department of Physics, Eidgenössische Technische Hochschule, ETH, CH-8093 Zürich (Switzerland); Burkert, Andreas [Universitäts-Sternwarte Ludwig-Maximilians-Universität (USM), Scheinerstr. 1, D-81679 München (Germany); Cresci, Giovanni [Istituto Nazionale di Astrofisica Osservatorio di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Shapiro Griffin, Kristen [Space Sciences Research Group, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Hicks, Erin K. S., E-mail: sfnewman@berkeley.edu [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); and others

    2014-01-20

    Based on high-resolution, spatially resolved data of 10 z ∼ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the 'composite' region of the z ∼ 0 [N II]/Hα versus [O III]/Hβ diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with H II regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [O III]/Hβ versus stellar mass plane, does not properly separate z ∼ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ∼ 2 mass-metallicity relation (i.e., to the mass they would have at z ∼ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [N II]/Hα are more biased by shocks and AGNs at high-z than the [O III]/Hβ/[N II]/Hα calibration.

  4. Direct HST Dust Lane Detection in Powerful Narrow-Line Radio Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez, Edgar A.; Aretxaga, Itziar [Instituto Nacional de Astrofísica, Óptica y Electrónica, Puebla (Mexico); Tadhunter, Clive N. [Department of Physics and Astronomy, University of Sheffield, Sheffield (United Kingdom); Lopez-Rodriguez, Enrique [NASA Ames Research Center, SOFIA Science Center, SOFIA/USRA, Mountain View, CA (United States); Department of Astronomy, University of Texas at Austin, Austin, TX (United States); McDonald Observatory, University of Texas at Austin, Austin, TX (United States); Packham, Chris, E-mail: e.ramirez@inaoep.mx [Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX (United States); National Astronomical Observatory of Japan, Tokyo (Japan)

    2017-11-22

    We present the analysis of near-infrared Hubble Space Telescope imaging of 10 Fanaroff Riley II powerful radio galaxies at low redshift (0.03 < z < 0.11) optically classified as narrow-line radio galaxies. The photometric properties of the host galaxy are measured using galfit, and compared with those from the literature. Our high resolution near-infrared observations provide new and direct information on the central kpc-scale dust lanes in our sample that could be connected to the pc-scale torus structure. Moreover, analyzing the infrared spectrograph Spitzer spectra of our sample, we suggest properties of the dust size of the torus.

  5. HI and Low Metal Ions at the Intersection of Galaxies and the CGM

    Science.gov (United States)

    Oppenheimer, Benjamin

    2017-08-01

    Over 1000 COS orbits have revealed a surprisingly complex picture of circumgalactic gas flows surrounding the diversity of galaxies in the evolved Universe. Cosmological hydrodynamic simulations have only begun to confront the vast amount of galaxy formation physics, chemistry, and dynamics revealed in the multi-ion CGM datasets. We propose the next generation of EAGLE zoom simulations, called EAGLE Cosmic Origins, to model HI and low metal ions (C II, Mg II, & Si II) throughout not just the CGM but also within the galaxies themselves. We will employ a novel, new chemistry solver, CHIMES, to follow time-dependent ionization, chemistry, and cooling of 157 ionic and molecular species, and include multiple ionization sources from the extra-galactic background, episodic AGN, and star formation. Our aim is to understand the complete baryon cycle of inflows, outflows, and gas recycling traced over 10 decades of HI column densities as well as the complex kinematic information encoded low ion absorption spectroscopy. This simulation project represents a pilot program for a larger suite of zoom simulations, which will be publicly released and lead to additional publications.

  6. Properties in the middle and far infrared radiation of spiral and irregular galaxies

    International Nuclear Information System (INIS)

    Contursi, Alessandra

    1998-01-01

    In the first part of this research thesis, the author reports the study in the middle infrared of H II regions belonging to Magellanic clouds. For this purpose, he presents different aspects of infrared emission by the interstellar medium: origin and evolution of interstellar grains, dust studied by astrophysical observations, dust models, infrared observations made by COBE and IRAS satellites, exploitation of the ISO satellite. He also presents the Small and Large Magellanic clouds, and reports the study of the H II N4 region of the large one, imagery and spectroscopy of the H II N66 region of the small one, and the study of silicate emission in the central region of N66. The second part reports the study of cluster normal spiral galaxies in the middle and far infrared. For this purpose, the author discusses the colours in the middle infrared of Virgo's and Coma's galaxies, discusses the properties in the infrared of spiral galaxies (Coma and A1367), based on observations made by ISO [fr

  7. SUBMILLIMETER FOLLOW-UP OF WISE-SELECTED HYPERLUMINOUS GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Wu Jingwen; Eisenhardt, Peter R. M.; Stern, Daniel; Assef, Roberto [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Tsai, Chao-Wei; Cutri, Roc; Griffith, Roger; Jarrett, Thomas [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Sayers, Jack; Bridge, Carrie [Division of Physics, Math and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Benford, Dominic [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Blain, Andrew [Department of Physics and Astronomy, University of Leicester, LE1 7RH Leicester (United Kingdom); Petty, Sara; Lake, Sean [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095 (United States); Bussmann, Shane [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS78, Cambridge, MA 02138 (United States); Comerford, Julia M.; Evans, Neal J. II [Department of Astronomy, University of Texas, Austin, TX 78731 (United States); Lonsdale, Carol [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Rho, Jeonghee [SETI Institute, 189 BERNARDO Avenue, Mountain View, CA 94043 (United States); Stanford, S. Adam, E-mail: jingwen.wu@jpl.nasa.gov [Department of Physics, University of California Davis, One Shields Avenue, Davis, CA 95616 (United States); and others

    2012-09-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare ({approx}1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 {mu}m, yet are clearly detected at 12 and 22 {mu}m. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 {mu}m, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 {mu}m, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10{sup 13} L{sub Sun }. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  8. SUBMILLIMETER FOLLOW-UP OF WISE-SELECTED HYPERLUMINOUS GALAXIES

    International Nuclear Information System (INIS)

    Wu Jingwen; Eisenhardt, Peter R. M.; Stern, Daniel; Assef, Roberto; Tsai, Chao-Wei; Cutri, Roc; Griffith, Roger; Jarrett, Thomas; Sayers, Jack; Bridge, Carrie; Benford, Dominic; Blain, Andrew; Petty, Sara; Lake, Sean; Bussmann, Shane; Comerford, Julia M.; Evans, Neal J. II; Lonsdale, Carol; Rho, Jeonghee; Stanford, S. Adam

    2012-01-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (∼1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 μm, yet are clearly detected at 12 and 22 μm. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 μm, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 μm, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature. We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10 13 L ☉ . These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe. We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  9. Submillimeter Follow-up of Wise-Selected Hyperluminous Galaxies

    Science.gov (United States)

    Wu, Jingwen; Tsai, Chao-Wei; Sayers, Jack; Benford, Dominic; Bridge, Carrie; Blain, Andrew; Eisenhardt, Peter R. M.; Stern, Daniel; Petty, Sara; Assef, Roberto; hide

    2013-01-01

    We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (approximately 1000 all-sky) population of galaxies at high redshift (peaks at zeta = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 micrometers, yet are clearly detected at 12 and 22 micrometers. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (zeta greater than 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 micrometers, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 micrometers, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature.We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10(exp 13) solar luminosity. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe.We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.

  10. THE SINS/zC-SINF SURVEY of z {approx} 2 GALAXY KINEMATICS: OUTFLOW PROPERTIES

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Foerster-Schreiber, Natascha M.; Buschkamp, Peter; Davies, Ric; Eisenhauer, Frank; Kurk, Jaron; Lutz, Dieter [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr.1, D-85748 Garching (Germany); Griffin, Kristen Shapiro [Space Sciences Research Group, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Mancini, Chiara; Renzini, Alvio [Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, Padova, I-35122 (Italy); Lilly, Simon J.; Carollo, C. Marcella; Peng, Yingjie [Institute of Astronomy, Department of Physics, Eidgenoessische Technische Hochschule, ETH Zuerich, CH-8093 (Switzerland); Bouche, Nicolas [Institut de Recherche en Astrophysique et Planetologie (IRAP), Universite de Toulouse, UPS-OMP, IRAP, 14, avenue Edouard Berlin, F-31400 Toulouse (France); Burkert, Andreas [Department fuer Physik, Universitaets-Sternwarte Ludwig-Maximilians-Universitaet (USM), Scheinerstr. 1, Muenchen, D-81679 (Germany); Cresci, Giovanni [Istituto Nazionale di AstrofisicaOsservatorio Astronomico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hicks, Erin K. S. [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); Naab, Thorsten, E-mail: sfnewman@berkeley.edu [Max-Planck Institute for Astrophysics, Karl Schwarzschildstrasse 1, D-85748 Garching (Germany); and others

    2012-12-10

    Using SINFONI H{alpha}, [N II], and [S II] AO data of 27 z {approx} 2 star-forming galaxies (SFGs) from the SINS and zC-SINF surveys, we explore the dependence of outflow strength (via the broad flux fraction) on various galaxy parameters. For galaxies that have evidence for strong outflows, we find that the broad emission is spatially extended to at least the half-light radius ({approx}a few kpc). Decomposition of the [S II] doublet into broad and narrow components suggests that this outflowing gas probably has a density of {approx}10-100 cm{sup -3}, less than that of the star-forming gas (600 cm{sup -3}). There is a strong correlation of the H{alpha} broad flux fraction with the star formation surface density of the galaxy, with an apparent threshold for strong outflows occurring at 1 M{sub Sun} yr{sup -1} kpc{sup -2}. Above this threshold, we find that SFGs with log m{sub *} > 10 have similar or perhaps greater wind mass-loading factors ({eta} = M-dot{sub out}/SFR) and faster outflow velocities than lower mass SFGs, suggesting that the majority of outflowing gas at z {approx} 2 may derive from high-mass SFGs. The mass-loading factor is also correlated with the star formation rate (SFR), galaxy size, and inclination, such that smaller, more star-forming, and face-on galaxies launch more powerful outflows. We propose that the observed threshold for strong outflows and the observed mass loading of these winds can be explained by a simple model wherein break-out of winds is governed by pressure balance in the disk.

  11. Experimental study of the vapour-liquid equilibria of HI-I-2-H2O ternary mixtures, Part 2: Experimental results at high temperature and pressure

    International Nuclear Information System (INIS)

    Larousse, B.; Lovera, P.; Borgard, J.M.; Roehrich, G.; Mokrani, N.; Maillault, C.; Doizi, D.; Dauvois, V.; Roujou, J.L.; Lorin, V.; Fauvet, P.; Carles, P.; Hartmann, J.M.

    2009-01-01

    In order to assess the choice of the sulphur-iodine thermochemical cycle for massive hydrogen production, a precise knowledge of the concentrations of the gaseous species (HI, I 2 , and H 2 O) in thermodynamic equilibrium with the liquid phase of the HI-I 2 -H 2 O ternary mixture is required, in a wide range of concentrations and for temperatures and pressures up to 300 degrees C and 50 bar. In the companion paper (Part 1) the experimental device was described, which enables the measurement of the total pressure and concentrations of the vapour phase (and thus the knowledge of the partial pressures of the different gaseous species) for the HI-I 2 -H 2 O mixture in the 20-140 degrees C range and up to 2 bar. This (Part 2) article describes the experimental device which enables similar measurements but now in the process domain. The results concerning concentrations in the vapour phase for the HI-I 2 -H 2 O initial mixture (with a global composition) in the 120-270 degrees C temperature range and up to 30 bar are presented. As previously, optical online diagnostics are used, based on recordings of infrared transmission spectra for HI and H 2 O and on UV/visible spectrometry for I 2 . The concentrations measured in the vapour phase are the first to describe the vapour composition under thermophysical conditions close to those of the distillation column. The experimental results are compared with a thermodynamic model and will help us to scale up and optimize the reactive distillation column we promote for the HI section of the sulphur-iodine cycle. (authors)

  12. THE ZURICH ENVIRONMENTAL STUDY OF GALAXIES IN GROUPS ALONG THE COSMIC WEB. I. WHICH ENVIRONMENT AFFECTS GALAXY EVOLUTION?

    Energy Technology Data Exchange (ETDEWEB)

    Carollo, C. Marcella; Cibinel, Anna; Lilly, Simon J.; Miniati, Francesco; Cameron, Ewan; Peng, Yingjie; Pipino, Antonio; Rudick, Craig S. [Institute for Astronomy, ETH Zurich, CH-8093 Zurich (Switzerland); Norberg, Peder [Department of Physics, Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Silverman, John D. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Chiba 277-8583 (Japan); Van Gorkom, Jacqueline [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Finoguenov, Alexis, E-mail: marcella@phys.ethz.ch [Max-Planck-Institut für extraterrestrische Physik, D-84571 Garching (Germany)

    2013-10-20

    The Zurich Environmental Study (ZENS) is based on a sample of ∼1500 galaxy members of 141 groups in the mass range ∼10{sup 12.5-14.5} M{sub ☉} within the narrow redshift range 0.05 < z < 0.0585. ZENS adopts novel approaches, described here, to quantify four different galactic environments, namely: (1) the mass of the host group halo; (2) the projected halo-centric distance; (3) the rank of galaxies as central or satellites within their group halos; and (4) the filamentary large-scale structure density. No self-consistent identification of a central galaxy is found in ∼40% of <10{sup 13.5} M{sub ☉} groups, from which we estimate that ∼15% of groups at these masses are dynamically unrelaxed systems. Central galaxies in relaxed and unrelaxed groups generally have similar properties, suggesting that centrals are regulated by their mass and not by their environment. Centrals in relaxed groups have, however, ∼30% larger sizes than in unrelaxed groups, possibly due to accretion of small satellites in virialized group halos. At M > 10{sup 10} M{sub ☉}, satellite galaxies in relaxed and unrelaxed groups have similar size, color, and (specific) star formation rate distributions; at lower galaxy masses, satellites are marginally redder in relaxed relative to unrelaxed groups, suggesting quenching of star formation in low-mass satellites by physical processes active in relaxed halos. Overall, relaxed and unrelaxed groups show similar stellar mass populations, likely indicating similar stellar mass conversion efficiencies. In the enclosed ZENS catalog, we publish all environmental diagnostics as well as the galaxy structural and photometric measurements described in companion ZENS papers II and III.

  13. Galaxy collisions

    International Nuclear Information System (INIS)

    Combes, F.

    1987-01-01

    Galaxies are not isolated systems of stars and gas, ''independent universes'' as believed by astronomers about ten years ago, but galaxies are formed and evolve by interaction with their environment, and in particular with their nearest neighbors. Gravitational interactions produce enormous tides in the disk of spiral galaxies, generate spiral arms and trigger bursts of star formation. Around elliptical galaxies, the collision with a small companion produces a series of waves, or shells. A galaxy interaction leads, in most cases, to the coalescence of the two coliders; therefore all galaxies are not formed just after the Big-Bang, when matter recombines: second generation galaxies are still forming now by galaxy mergers, essentially elliptical galaxies, but also compact dwarfs. Collisions between galaxies could also trigger activity in nuclei for radiogalaxies and quasars [fr

  14. THE FATE OF DWARF GALAXIES IN CLUSTERS AND THE ORIGIN OF INTRACLUSTER STARS. II. COSMOLOGICAL SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Martel, Hugo [Departement de physique, de genie physique et d' optique, Universite Laval, Quebec, QC (Canada); Barai, Paramita [Osservatorio Astronomico di Trieste, I-34143 Trieste (Italy); Brito, William [Centre de Recherche en Astrophysique du Quebec, C.P. 6128, Succ. Centre-Ville, Montreal, QC (Canada)

    2012-09-20

    We combine an N-body simulation algorithm with a subgrid treatment of galaxy formation, mergers, and tidal destruction, and an observed conditional luminosity function {Phi}(L|M), to study the origin and evolution of galactic and extragalactic light inside a cosmological volume of size (100 Mpc){sup 3}, in a concordance {Lambda}CDM model. This algorithm simulates the growth of large-scale structures and the formation of clusters, the evolution of the galaxy population in clusters, the destruction of galaxies by mergers and tides, and the evolution of the intracluster light (ICL). We find that destruction of galaxies by mergers dominates over destruction by tides by about an order of magnitude at all redshifts. However, tidal destruction is sufficient to produce ICL fractions f{sub ICL} that are sufficiently high to match observations. Our simulation produces 18 massive clusters (M{sub cl} > 10{sup 14} M{sub Sun }) with values of f{sub ICL} ranging from 1% to 58% at z = 0. There is a weak trend of f{sub ICL} to increase with cluster mass. The bulk of the ICL ({approx}60%) is provided by intermediate galaxies of total masses 10{sup 11}-10{sup 12} M{sub Sun} and stellar masses 6 Multiplication-Sign 10{sup 8} M{sub Sun} to 3 Multiplication-Sign 10{sup 10} M{sub Sun} that were tidally destroyed by even more massive galaxies. The contribution of low-mass galaxies to the ICL is small and the contribution of dwarf galaxies is negligible, even though, by numbers, most galaxies that are tidally destroyed are dwarfs. Tracking clusters back in time, we find that their values of f{sub ICL} tend to increase over time, but can experience sudden changes that are sometimes non-monotonic. These changes occur during major mergers involving clusters of comparable masses but very different intracluster luminosities. Most of the tidal destruction events take place in the central regions of clusters. As a result, the ICL is more centrally concentrated than the galactic light. Our results

  15. MEASURING STAR FORMATION RATES AND FAR-INFRARED COLORS OF HIGH-REDSHIFT GALAXIES USING THE CO(7–6) AND [N II] 205 μm LINES

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Nanyao; Zhao, Yinghe; Xu, C. Kevin; Howell, Justin; Mazzarella, Joseph M.; Schulz, Bernhard [Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125 (United States); Gao, Yu; Liu, Lijie [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Díaz-Santos, Tanio; Armus, Lee [Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125 (United States); Charmandaris, Vassilis [Department of Physics, University of Crete, GR-71003 Heraklion (Greece); Inami, Hanae [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Privon, George C. [Departamento de Astronomía, Universidad de Concepción, Casilla 160 C, Concepción (Chile); Lord, Steven D. [The SETI Institute, 189 Bernardo Avenue Suite 100, Mountain View, CA 94043 (United States); Sanders, David B. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Van der Werf, Paul P., E-mail: lu@ipac.caltech.edu [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

    2015-03-20

    To better characterize the global star formation activity in a galaxy, one needs to know not only the star formation rate (SFR) but also the rest-frame, far-infrared color (e.g., the 60–100 μm color, C(60/100)) of the dust emission. The latter probes the average intensity of the dust heating radiation field and scales statistically with the effective SFR surface density in star-forming galaxies including (ultra-)luminous infrared galaxies ((U)LIRGs). To this end, here we exploit a new spectroscopic approach involving only two emission lines: CO(7–6) at 372 μm and [N ii] at 205 μm([N ii]{sub 205μm}). For local (U)LIRGs, the ratios of the CO(7–6) luminosity (L{sub CO(7–6)}) to the total infrared luminosity (L{sub IR}; 8–1000 μm) are fairly tightly distributed (to within ∼0.12 dex) and show little dependence on C(60/100). This makes L{sub CO(7–6)} a good SFR tracer, which is less contaminated by active galactic nuclei than L{sub IR} and may also be much less sensitive to metallicity than L{sub CO(1–0)}. Furthermore, the logarithmic [N ii]{sub 205μm}/CO(7–6) luminosity ratio depends fairly strongly (at a slope of ∼ −1.4) on C(60/100), with a modest scatter (∼0.23 dex). This makes it a useful estimator on C(60/100) with an implied uncertainty of ∼0.15 (or ≲4 K in the dust temperature (T{sub dust}) in the case of a graybody emission with T{sub dust} ≳ 30 K and a dust emissivity index β ≥ 1). Our locally calibrated SFR and C(60/100) estimators are shown to be consistent with the published data of (U)LIRGs of z up to ∼6.5.

  16. IPHAS: Surveying the North Galactic Plane in H-alpha

    NARCIS (Netherlands)

    Drew, J.E.; Groot, P.J.; Morales-Rueda, L.; Roelofs, G.H.A.

    2005-01-01

    H-alpha emission is ubiquitous in our Galaxy. It traces ionised gas of assorted nebulae such as HII regions, planetary nebulae, Wolf-Rayet nebulae, and supernova remnants. It is a strong signature of active stars, interacting binaries, very massive stars (especially supergiants, Luminous Blue

  17. How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos

    Science.gov (United States)

    Tumlinson, Jason

    2009-07-01

    We propose to address two of the biggest open questions in galaxy formation - how galaxies acquire their gas and how they return it to the IGM - with a concentrated COS survey of diffuse multiphase gas in the halos of SDSS galaxies at z = 0.15 - 0.35. Our chief science goal is to establish a basic set of observational facts about the physical state, metallicity, and kinematics of halo gas, including the sky covering fraction of hot and cold material, the metallicity of infall and outflow, and correlations with galaxy stellar mass, type, and color - all as a function of impact parameter from 10 - 150 kpc. Theory suggests that the bimodality of galaxy colors, the shape of the luminosity function, and the mass-metallicity relation are all influenced at a fundamental level by accretion and feedback, yet these gas processes are poorly understood and cannot be predicted robustly from first principles. We lack even a basic observational assessment of the multiphase gaseous content of galaxy halos on 100 kpc scales, and we do not know how these processes vary with galaxy properties. This ignorance is presently one of the key impediments to understanding galaxy formation in general. We propose to use the high-resolution gratings G130M and G160M on the Cosmic Origins Spectrograph to obtain sensitive column density measurements of a comprehensive suite of multiphase ions in the spectra of 43 z sound map of the physical state and metallicity of gaseous halos, and subsets of the data with cuts on galaxy mass, color, and SFR will seek out predicted variations of gas properties with galaxy properties. Our interpretation of these data will be aided by state-of-the-art hydrodynamic simulations of accretion and feedback, in turn providing information to refine and test such models. We will also use Keck, MMT, and Magellan {as needed} to obtain optical spectra of the QSOs to measure cold gas with Mg II, and optical spectra of the galaxies to measure SFRs and to look for outflows. In

  18. Dwarf spheroidal galaxies: Keystones of galaxy evolution

    Science.gov (United States)

    Gallagher, John S., III; Wyse, Rosemary F. G.

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  19. AN ULTRA-DEEP NEAR-INFRARED SPECTRUM OF A COMPACT QUIESCENT GALAXY AT z = 2.2

    International Nuclear Information System (INIS)

    Kriek, Mariska; Van Dokkum, Pieter G.; Marchesini, Danilo; Labbe, Ivo; Franx, Marijn; Quadri, Ryan F.; Illingworth, Garth D.

    2009-01-01

    Several recent studies have shown that about half of the massive galaxies at z ∼ 2 are in a quiescent phase. Moreover, these galaxies are commonly found to be ultra-compact with half-light radii of ∼1 kpc. We have obtained a ∼29 hr spectrum of a typical quiescent, ultra-dense galaxy at z = 2.1865 with the Gemini Near-Infrared Spectrograph. The spectrum exhibits a strong optical break and several absorption features, which have not previously been detected in z > 2 quiescent galaxies. Comparison of the spectral energy distribution with stellar population synthesis models implies a low star formation rate (SFR) of 1-3 M sun yr -1 , an age of 1.3-2.2 Gyr, and a stellar mass of ∼2 x 10 11 M sun . We detect several faint emission lines, with emission-line ratios of [N II]/Hα, [S II]/Hα, and [O II]/[O III] typical of low-ionization nuclear emission-line regions. Thus, neither the stellar continuum nor the nebular emission implies active star formation. The current SFR is <1% of the past average SFR. If this galaxy is representative of compact quiescent galaxies beyond z = 2, it implies that quenching of star formation is extremely efficient and also indicates that low luminosity active galactic nuclei (AGNs) could be common in these objects. Nuclear emission is a potential concern for the size measurement. However, we show that the AGN contributes ∼<8% to the rest-frame optical emission. A possible post-starburst population may affect size measurements more strongly; although a 0.5 Gyr old stellar population can make up ∼<10% of the total stellar mass, it could account for up to ∼40% of the optical light. Nevertheless, this spectrum shows that this compact galaxy is dominated by an evolved stellar population.

  20. An Unusual Transient in the Extremely Metal-Poor Galaxy SDSS J094332.35+332657.6 (Leoncino Dwarf)

    Science.gov (United States)

    Filho, Mercedes E.; Sánchez Almeida, J.

    2018-05-01

    We have serendipitously discovered that Leoncino Dwarf, an ultra-faint, low-metallicity record-holder dwarf galaxy, may have hosted a transient source, and possibly exhibited a change in morphology, a shift in the center of brightness, and peak variability of the main (host) source in images taken approximately 40 yr apart; it is highly likely that these phenomena are related. Scenarios involving a Solar System object, a stellar cluster, dust enshrouding, and accretion variability have been considered, and discarded, as the origin of the transient. Although a combination of time-varying strong and weak lensing effects, induced by an intermediate mass black hole (104 - 5 × 105 M⊙) moving within the Milky Way halo (0.1 - 4 kpc), can conceivably explain all of the observed variable galaxy properties, it is statistically highly unlikely according to current theoretical predictions, and, therefore, also discarded. A cataclysmic event such as a supernova/hypernova could have occurred, as long as the event was observed towards the later/late-stage descent of the light curve, but this scenario fails to explain the absence of a post-explosion source and/or host HII region in recent optical images. An episode related to the giant eruption of a luminous blue variable star, a stellar merger or a nova, observed at, or near, peak magnitude may explain the transient source and possibly the change in morphology/center of brightness, but can not justify the main source peak variability, unless stellar variability is evoked.

  1. COMPLEX GAS KINEMATICS IN COMPACT, RAPIDLY ASSEMBLING STAR-FORMING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Amorin, R.; Vilchez, J. M.; Perez-Montero, E. [Instituto de Astrofisica de Andalucia-CSIC, Glorieta de la Astronomia S/N, E-18008 Granada (Spain); Haegele, G. F.; Firpo, V. [Facultad de Ciencias Astronomicas y Geofisicas, Universidad de la Plata, Paseo del Bosque S/N, 1900 La Plata (Argentina); Papaderos, P., E-mail: amorin@iaa.es [Centro de Astrofisica and Faculdade de Ciencias, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)

    2012-08-01

    Deep, high-resolution spectroscopic observations have been obtained for six compact, strongly star-forming galaxies at redshift z {approx} 0.1-0.3, most of them also known as green peas. Remarkably, these galaxies show complex emission-line profiles in the spectral region including H{alpha}, [N II] {lambda}{lambda}6548, 6584, and [S II] {lambda}{lambda}6717, 6731, consisting of the superposition of different kinematical components on a spatial extent of few kiloparsecs: a very broad line emission underlying more than one narrower component. For at least two of the observed galaxies some of these multiple components are resolved spatially in their two-dimensional spectra, whereas for another one a faint detached H{alpha} blob lacking stellar continuum is detected at the same recessional velocity {approx}7 kpc away from the galaxy. The individual narrower H{alpha} components show high intrinsic velocity dispersion ({sigma} {approx} 30-80 km s{sup -1}), suggesting together with unsharped masking Hubble Space Telescope images that star formation proceeds in an ensemble of several compact and turbulent clumps, with relative velocities of up to {approx}500 km s{sup -1}. The broad underlying H{alpha} components indicate in all cases large expansion velocities (full width zero intensity {>=}1000 km s{sup -1}) and very high luminosities (up to {approx}10{sup 42} erg s{sup -1}), probably showing the imprint of energetic outflows from supernovae. These intriguing results underline the importance of green peas for studying the assembly of low-mass galaxies near and far.

  2. The dependence of galactic outflows on the properties and orientation of zCOSMOS galaxies at z ∼ 1

    International Nuclear Information System (INIS)

    Bordoloi, R.; Lilly, S. J.; Hardmeier, E.; Carollo, C. M.; Contini, T.; Kneib, J.-P.; Fevre, O. Le; Garilli, B.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Zamorani, G.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Caputi, K.; Cucciati, O.; De la Torre, S.; De Ravel, L.; Iovino, A.

    2014-01-01

    We present an analysis of cool outflowing gas around galaxies, traced by Mg II absorption lines in the coadded spectra of a sample of 486 zCOSMOS galaxies at 1 ≤ z ≤ 1.5. These galaxies span a range of stellar masses (9.45 ≤ log 10 [M * /M ☉ ] ≤ 10.7) and star formation rates (0.14 ≤ log 10 [SFR/M ☉ yr –1 ] ≤ 2.35). We identify the cool outflowing component in the Mg II absorption and find that the equivalent width of the outflowing component increases with stellar mass. The outflow equivalent width also increases steadily with the increasing star formation rate of the galaxies. At similar stellar masses, the blue galaxies exhibit a significantly higher outflow equivalent width as compared to red galaxies. The outflow equivalent width shows strong correlation with the star formation surface density (Σ SFR ) of the sample. For the disk galaxies, the outflow equivalent width is higher for the face-on systems as compared to the edge-on ones, indicating that for the disk galaxies, the outflowing gas is primarily bipolar in geometry. Galaxies typically exhibit outflow velocities ranging from –150 km s –1 ∼–200 km s –1 and, on average, the face-on galaxies exhibit higher outflow velocity as compared to the edge-on ones. Galaxies with irregular morphologies exhibit outflow equivalent width as well as outflow velocities comparable to face on disk galaxies. These galaxies exhibit mass outflow rates >5-7 M ☉ yr –1 and a mass loading factor (η = M-dot out /SFR) comparable to the star formation rates of the galaxies.

  3. The circumnuclear environment of nearby non-interacting Seyfert galaxies

    International Nuclear Information System (INIS)

    Pogge, R.W.

    1988-01-01

    An investigation into the physical conditions prevailing in the regions immediately surrounding the active nuclei in 20 nearby, non-interacting Seyfert galaxies is reported. CCD interference-band images isolating the bright emission lines of Hα + [N II] λλ6548, 6583 and [O III] λ5007 have been obtained to search for spatially extended circumnuclear emission regions. Long-slit, low resolution spectrophotometry of interesting cases was used to probe the ionization state of the extended emission regions. For comparison, a CCD Hα + [N II] interference-band imaging survey of a statistically significant sample of 91 bright non-Seyfert spiral galaxies meeting the same non-interaction criteria has been carried out. Only three out of nine Seyfert 1s have spatially extended ionized gas regions compared with eight out of eleven Seyfert 2s. Enhanced circumnuclear star formation is uncommon to both Seyfert 1s and 2s. Extended emission in Seyfert 1s has essentially the same morphology in both Hα + [N II] and [O III] emission. In the Seyfert 2s, the Hα + [N II] and [O III] images show different extended emission morphologies. The [O III] emission regions appear as either one- or two-sided structures, four of which are resolved into two distinct cones of high-ionization gas emanating from the active nucleus. The morphology and ionization of these regions suggest collimation of the nuclear ionizing radiation field. The 91 non-interacting non-Seyfert spiral galaxies exhibit a rich variety of nuclear and circumnuclear emission-line structures ranging from no emission detected to bright stellar nuclei with complicated circumnuclear emission regions extending for many kiloparsecs

  4. THE UVJ SELECTION OF QUIESCENT AND STAR-FORMING GALAXIES: SEPARATING EARLY- AND LATE-TYPE GALAXIES AND ISOLATING EDGE-ON SPIRALS

    International Nuclear Information System (INIS)

    Patel, Shannon G.; Franx, Marijn; Holden, Bradford P.; Illingworth, Garth D.; Kelson, Daniel D.; Van der Wel, Arjen

    2012-01-01

    We utilize for the first time Hubble Space Telescope Advanced Camera for Surveys imaging to examine the structural properties of galaxies in the rest-frame U – V versus V – J diagram (i.e., the UVJ diagram) using a sample at 0.6 ☉ >10.25). The use of the UVJ diagram as a tool to distinguish quiescent galaxies from star-forming galaxies (SFGs) is becoming more common due to its ability to separate red quiescent galaxies from reddened SFGs. Quiescent galaxies occupy a small and distinct region of UVJ color space and we find most of them to have concentrated profiles with high Sérsic indices (n > 2.5) and smooth structure characteristic of early-type systems. SFGs populate a broad but well-defined sequence of UVJ colors and are comprised of objects with a mix of Sérsic indices. Interestingly, most UVJ-selected SFGs with high Sérsic indices also display structure due to dust and star formation typical of the n < 2.5 SFGs and late-type systems. Finally, we find that the position of an SFG on the sequence of UVJ colors is determined to a large degree by the mass of the galaxy and its inclination. Systems that are closer to edge-on generally display redder colors and lower [O II]λ3727 luminosity per unit mass as a consequence of the reddening due to dust within the disks. We conclude that the two main features seen in UVJ color space correspond closely to the traditional morphological classes of early- and late-type galaxies.

  5. Clusters of galaxies associated with quasars. I. 3C 206

    International Nuclear Information System (INIS)

    Ellingson, E.; Yee, H.K.C.; Green, R.F.; Kinman, T.D.

    1989-01-01

    Multislit spectroscopy and three-color CCD photometry of the galaxies in the cluster associated with the quasar 3C 206 (PKS 0837-12) at z = 0.198 are presented. This cluster is the richest environment of any low-redshift quasar observed in an Abell richness class 1 cluster. The cluster has a very flattened structure and a very concentrated core about the quasar. Most of the galaxies in this field have colors and luminosities consistent with normal galaxies at this redshift. The background-corrected blue fraction of galaxies is consistent with values for other rich clusters. The existence of several blue galaxies in the concentrated cluster core is an anomaly for a region of such high galaxy density, however, suggesting the absence of a substantial intracluster medium. This claim is supported by the Fanaroff-Riley (1974) class II morphology of the radio source. The velocity dispersion calculated from 11 spectroscopically confirmed cluster members is 500 + or - 110 km/s, which is slightly lower than the average for Abell class 1 clusters. A high frequency of interaction between the quasar host galaxy and cluster core members at low relative velocities, and a low intracluster gas pressure, may comprise a favorable environment for quasar activity. The properties of the cluster of galaxies associated with 3C 206 are consistent with this model. 59 refs

  6. Gravitational potential energy of a disk-sphere pair of galaxies

    International Nuclear Information System (INIS)

    Ballabh, G.M.

    1975-01-01

    Algebraic expressions are obtained for the interaction potential energy of a pair of galaxies in which one is disk shaped and the other spherical. The density distribution in the disk galaxy is represented by a polynomial in ascending powers of the distance from the centre of the disk while the density distribution in the spherical galaxy is represented by the superposition of spherical polytropes of integral indices. The basic functions required for obtaining the interaction potential energy of a coplanar disk-sphere pair of galaxies are tabulated. The forces of attraction between a coplanar disk-sphere pair of galaxies are shown graphically for two density models of disk and spherical galaxies. An overlapping coplanar disk-sphere pair of galaxies attract just like two mass-points at a certain separation, rsub(c), of their centres. The force of attraction is less than that of two mass-points having masses equal to the masses of the two galaxies, if the separation of the centres is less than rsub(c), and greater if the separation is greater than rsub(c). For a typical coplanar disk-sphere pair of galaxies (the density of the disk is represented by Model II and of the sphere by a polytropic index n=4) of equal radii, the following is noted. At a separation of 0.79 R, R being the common radius of the two galaxies, the force of attraction between the pair is the same as if the entire mass of each galaxy is concentrated at its centre. The mass-point model for the two galaxies will overestimate the force of attraction by more than a factor of 10 if the separation is less than 0.36 R. For separation greater than the radii of the galaxies the mass-point model will underestimate the force but the departure in this case is less than 33%. (Auth.)

  7. The galaxy major merger fraction to {z} 1

    Science.gov (United States)

    López-Sanjuan, C.; Balcells, M.; Pérez-González, P. G.; Barro, G.; García-Dabó, C. E.; Gallego, J.; Zamorano, J.

    2009-07-01

    Aims: The importance of disc-disc major mergers in galaxy evolution remains uncertain. We study the major merger fraction in a SPITZER/IRAC-selected catalogue in the GOODS-S field up to z 1 for luminosity- and mass-limited samples. Methods: We select disc-disc merger remnants on the basis of morphological asymmetries/distortions, and address three main sources of systematic errors: (i) we explicitly apply morphological K-corrections; (ii) we measure asymmetries in galaxies artificially redshifted to zd = 1.0 to deal with loss of morphological information with redshift; and (iii) we take into account the observational errors in z and A, which tend to overestimate the merger fraction, though use of maximum likelihood techniques. Results: We obtain morphological merger fractions (f_m^mph) below 0.06 up to z 1. Parameterizing the merger fraction evolution with redshift as f_m^mph(z) = f_m^mph(0) (1+z)^m, we find that m = 1.8 ± 0.5 for MB ≤ -20 galaxies, while m = 5.4 ± 0.4 for Mstar ≥ 1010 M⊙ galaxies. When we translate our merger fractions to merger rates (Re_m^mph), their evolution, parameterized as Re_m^mph(z) = Re_m^mph(0) (1+z)^n, is quite similar in both cases: n = 3.3 ± 0.8 for MB ≤ -20 galaxies, and n = 3.5 ± 0.4 for Mstar ≥ 1010 M⊙ galaxies. Conclusions: Our results imply that only 8% of today's Mstar ≥ 1010 M⊙ galaxies have undergone a disc-disc major merger since z 1. In addition, 21% of Mstar ≥ 1010 M⊙ galaxies at z 1 have undergone one of these mergers since z 1.5. This suggests that disc-disc major mergers are not the dominant process in the evolution of Mstar ≥ 1010 M⊙ galaxies since z 1, with only 0.2 disc-disc major mergers per galaxy, but may be an important process at z > 1, with ˜1 merger per galaxy at 1 < z < 3.

  8. H I IMAGING OBSERVATIONS OF SUPERTHIN GALAXIES. II. IC 2233 AND THE BLUE COMPACT DWARF NGC 2537

    International Nuclear Information System (INIS)

    Matthews, Lynn D.; Uson, Juan M.

    2008-01-01

    We have used the Very Large Array to image the H I 21 cm line emission in the edge-on Sd galaxy IC 2233 and the blue compact dwarf NGC 2537. We also present new optical B, R, and Hα imaging of IC 2233 obtained with the WIYN telescope. Despite evidence of localized massive star formation in the form of prominent H II regions and shells, supergiant stars, and a blue integrated color, IC 2233 is a low surface brightness system with a very low global star formation rate (∼ sun yr -1 ), and we detect no significant 21 cm radio continuum emission from the galaxy. The H I and ionized gas disks of IC 2233 are clumpy and vertically distended, with scale heights comparable to that of the young stellar disk. Both the stellar and H I disks of IC 2233 appear flared, and we also find a vertically extended, rotationally anomalous component of H I extending to ∼ 2.4d 10 kpc from the midplane. The H I disk exhibits a mild lopsidedness as well as a global corrugation pattern with a period of ∼7d 10 kpc and an amplitude of ∼150d 10 pc. To our knowledge, this is the first time corrugations of the gas disk have been reported in an external galaxy; these undulations may be linked to bending instabilities or to underlying spiral structure and suggest that the disk is largely self-gravitating. Lying at a projected distance of 16'.7 from IC 2233, NGC 2537 has an H I disk with a bright, tilted inner ring and a flocculent, dynamically cold outer region that extends to ∼3.5 times the extent of the stellar light (D 25 ). Although NGC 2537 is rotationally-dominated, we measure H I velocity dispersions as high as σ V.HI ∼25 km s -1 near its center, indicative of significant turbulent motions. The inner rotation curve rises steeply, implying a strong central mass concentration. Our data indicate that IC 2233 and NGC 2537 do not constitute a bound pair and most likely lie at different distances. We also find no compelling evidence of a recent minor merger in either IC 2233 or NGC

  9. VizieR Online Data Catalog: Diffuse ionized gas database DIGEDA (Flores-Fajardo+ 2009)

    Science.gov (United States)

    Flores-Fajardo, N.; Morisset, C.; Binette, L.

    2009-09-01

    DIGEDA is a comprehensive database comprising 1061 DIG and HII region spectroscopic observations of 29 different galaxies (25 spiral galaxies and 4 irregulars) from 18 bibliographic references. This survey contains galaxies with significant spread in star formation rates, Halpha luminosities, distances, disk inclinations, slit positions and slit orientations. The 1061 observations obtained from these references were extracted by digitalization of published figures or tables. The data were subsequently normalized and incorporated in DIGEDA. This resulted in a table of 26 columns containing 1061 data lines or records (DIGEDA.dat file). We have not performed any reddening by dust correction or for the presence of underlying absorption lines, although we did use the reddening corrected ratios when made available by the authors. Missing entries are represented by (-1) in the corresponding data field. In DIGEDA the observed areas are classificated in three possible emission region types: HII region, transition zones or DIG. When this classification was not reported (no matter the criterion) for the authors, we introduce our own classification taking into account the value of |z| as described in the paper. (4 data files).

  10. The association between gas and galaxies - II. The two-point correlation function

    Science.gov (United States)

    Wilman, R. J.; Morris, S. L.; Jannuzi, B. T.; Davé, R.; Shone, A. M.

    2007-02-01

    We measure the two-point correlation function, ξAG, between galaxies and quasar absorption-line systems at z 1017cm-2. For CIV absorbers, the peak strength of ξAG is roughly comparable to that of HI absorbers with NHI > 1016.5cm-2, consistent with the finding that the CIV absorbers are associated with strong HI absorbers. We do not reproduce the differences reported by Chen et al. between 1D ξAG measurements using galaxy subsamples of different spectral types. However, the full impact on the measurements of systematic differences in our samples is hard to quantify. We compare the observations with smoothed particle hydrodynamical (SPH) simulations and discover that in the observations ξAG is more concentrated to the smallest separations than in the simulations. The latter also display a `finger of god' elongation of ξAG along the LOS in redshift space, which is absent from our data, but similar to that found by Ryan-Weber for the cross-correlation of quasar absorbers and HI-emission-selected galaxies. The physical origin of these `fingers of god' is unclear, and we thus highlight several possible areas for further investigation.

  11. Rest-Frame Optical Spectra of Three Strongly Lensed Galaxies at z ~ 2

    Science.gov (United States)

    Hainline, Kevin N.; Shapley, Alice E.; Kornei, Katherine A.; Pettini, Max; Buckley-Geer, Elizabeth; Allam, Sahar S.; Tucker, Douglas L.

    2009-08-01

    We present Keck II NIRSPEC rest-frame optical spectra for three recently discovered lensed galaxies: the Cosmic Horseshoe (z = 2.38), the Clone (z = 2.00), and SDSS J090122.37+181432.3 (z = 2.26). The boost in signal-to-noise ratio (S/N) from gravitational lensing provides an unusually detailed view of the physical conditions in these objects. A full complement of high S/N rest-frame optical emission lines is measured, spanning from rest frame 3600 to 6800 Å, including robust detections of fainter lines such as Hγ, [S II]λ6717,6732, and in one instance [Ne III]λ3869. SDSS J090122.37+181432.3 shows evidence for active galactic nucleus activity, and therefore we focus our analysis on star-forming regions in the Cosmic Horseshoe and the Clone. For these two objects, we estimate a wide range of physical properties. Current lensing models for the Cosmic Horseshoe and the Clone allow us to correct the measured Hα luminosity and calculated star formation rate. Metallicities have been estimated with a variety of indicators, which span a range of values of 12+ log(O/H) = 8.3-8.8, between ~0.4 and ~1.5 of the solar oxygen abundance. Dynamical masses were computed from the Hα velocity dispersions and measured half-light radii of the reconstructed sources. A comparison of the Balmer lines enabled measurement of dust reddening coefficients. Variations in the line ratios between the different lensed images are also observed, indicating that the spectra are probing different regions of the lensed galaxies. In all respects, the lensed objects appear fairly typical of ultraviolet-selected star-forming galaxies at z ~ 2. The Clone occupies a position on the emission-line diagnostic diagram of [O III]/Hβ versus [N II]/Hα that is offset from the locations of z ~ 0 galaxies. Our new NIRSPEC measurements may provide quantitative insights into why high-redshift objects display such properties. From the [S II] line ratio, high electron densities (~1000 cm-3) are inferred compared

  12. A near infrared spectroscopic study of the interstellar gas in the starburst core of M82

    International Nuclear Information System (INIS)

    Lester, D.F.; Carr, J.; Joy, M.; Gaffney, N.

    1990-01-01

    Researchers used the McDonald Observatory Infrared Grating Spectrometer, to complete a program of spatially resolved spectroscopy of M82. The inner 300 pc of the starburst was observed with 4 inch (50 pc) resolution. Complete J, H and K band spectra with resolution 0.0035 micron (lambda/delta lambda=620 at K) were measured at the near-infrared nucleus of the galaxy. Measurements of selected spectral features including lines of FeII, HII and H2 were observed along the starburst ridge-line, so the relative distribution of the diagnostic features could be understood. This information was used to better define the extinction towards the starburst region, the excitation conditions in the gas, and to characterize the stellar populations there

  13. A near infrared spectroscopic study of the interstellar gas in the starburst core of M82

    Science.gov (United States)

    Lester, Dan F.; Carr, John; Joy, Marshall; Gaffney, Niall

    1990-01-01

    Researchers used the McDonald Observatory Infrared Grating Spectrometer, to complete a program of spatially resolved spectroscopy of M82. The inner 300 pc of the starburst was observed with 4 inch (50 pc) resolution. Complete J, H and K band spectra with resolution 0.0035 micron (lambda/delta lambda=620 at K) were measured at the near-infrared nucleus of the galaxy. Measurements of selected spectral features including lines of FeII, HII and H2 were observed along the starburst ridge-line, so the relative distribution of the diagnostic features could be understood. This information was used to better define the extinction towards the starburst region, the excitation conditions in the gas, and to characterize the stellar populations there.

  14. Galaxy bias from galaxy-galaxy lensing in the DES Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Prat, J.; et al.

    2016-09-26

    We present a measurement of galaxy-galaxy lensing around a magnitude-limited ($i_{AB} < 22.5$) sample of galaxies selected from the Dark Energy Survey Science Verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias $b$ and cross-correlation coefficient between the galaxy and dark matter overdensity fields $r$ in each bin, using scales above 4 Mpc/$h$ comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering (Crocce et al. 2016) and CMB lensing (Giannantonio et al. 2016) for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al. (2016), while, in the lowest redshift bin ($z\\sim0.3$), they show some tension with the findings in Giannantonio et al. (2016). Our results are found to be rather insensitive to a large range of systematic effects. We measure $b\\cdot r$ to be $0.87\\pm 0.11$, $1.12 \\pm 0.16$ and $1.24\\pm 0.23$, respectively for the three redshift bins of width $\\Delta z = 0.2$ in the range $0.2galaxy sample, except possibly at the lowest redshift bin ($z\\sim 0.3$), where we find $r = 0.71 \\pm 0.11$ when using TPZ, and $0.83 \\pm 0.12$ with BPZ, assuming the difference between the results from the two probes can be solely attributed to the cross-correlation parameter.

  15. GALAXY CLUSTERS IN THE LINE OF SIGHT TO BACKGROUND QUASARS. III. MULTI-OBJECT SPECTROSCOPY

    International Nuclear Information System (INIS)

    Andrews, H.; Barrientos, L. F.; Padilla, N.; Lacerna, I.; López, S.; Lira, P.; Maureira, M. J.; Gilbank, D. G.; Ellingson, E.; Gladders, M. D.; Yee, H. K. C.

    2013-01-01

    We present Gemini/GMOS-S multi-object spectroscopy of 31 galaxy cluster candidates at redshifts between 0.2 and 1.0 and centered on QSO sight lines taken from López et al. The targets were selected based on the presence of an intervening Mg II absorption system at a similar redshift to that of a galaxy cluster candidate lying at a projected distance 71 -1 Mpc from the QSO sight line (a p hotometric hit ) . The absorption systems span rest-frame equivalent widths between 0.015 and 2.028 Å. Our aim was three-fold: (1) to identify the absorbing galaxies and determine their impact parameters, (2) to confirm the galaxy cluster candidates in the vicinity of each quasar sightline, and (3) to determine whether the absorbing galaxies reside in galaxy clusters. In this way, we are able to characterize the absorption systems associated with cluster members. Our main findings are as follows. (1) We identified 10 out of 24 absorbing galaxies with redshifts between 0.2509 ≤ z gal ≤ 1.0955, up to an impact parameter of 142 h 71 -1 kpc and a maximum velocity difference of 280 km s –1 . (2) We spectroscopically confirmed 20 out of 31 cluster/group candidates, with most of the confirmed clusters/groups at z –1 from galaxy clusters/groups, in addition to two new ones related to galaxy group environments. These numbers imply efficiencies of 71% in finding such systems with MOS spectroscopy. This is a remarkable result since we defined a photometric hit as those cluster-absorber pairs having a redshift difference Δz = 0.1. The general population of our confirmed absorbing galaxies have luminosities L B ∼L B * and mean rest-frame colors (R c – z') typical of S cd galaxies. From this sample, absorbing cluster galaxies hosting weak absorbers are consistent with lower star formation activity than the rest, which produce strong absorption and agree with typical Mg II absorbing galaxies found in the literature. Our spectroscopic confirmations lend support to the selection of

  16. Dark matter halo properties from galaxy-galaxy lensing

    International Nuclear Information System (INIS)

    Brimioulle, Fabrice

    2013-01-01

    The scientific results over the past years have shown that the Universe is by far not only composed of baryonic matter. In fact the major energy content of 72% of the Universe appears to be represented by so-called dark energy, while even from the remaining components only about one fifth is of baryonic origin, whereas 80% have to be attributed to dark matter. Originally appearing in observations of spiral galaxy rotation curves, the need for dark matter has also been verified investigating elliptical galaxies and galaxy clusters. In fact, it appears that dark matter played a major role during structure formation in the early Universe. Shortly after the Big Bang, when the matter distribution was almost homogeneous, initially very small inhomogeneities in the matter distribution formed the seeds for the gravitational collapse of the matter structures. Numerical n-body simulations, for instance, clearly indicate that the presently observable evolutionary state and complexity of the matter structure in the Universe would not have been possible without dark matter, which significantly accelerated the structure collapse due to its gravitational interaction. As dark matter does not interact electromagnetically and therefore is non-luminous but only interacts gravitationally, the gravitational lens effect provides an excellent opportunity for its detection and estimation of its amount. Weak gravitational lensing is a technique that makes use of the random orientation of the intrinsic galaxy ellipticities and thus their uniform distribution. Gravitational tidal forces introduce a coherent distortion of the background object shapes, leading to a deviation from the uniform distribution which depends on the lens galaxy properties and therefore can be used to study them. This thesis describes the galaxy-galaxy lensing analysis of 89deg 2 of optical data, observed within the CFHTLS-WIDE survey. In the framework of this thesis the data were used in order to create photometric

  17. DISSECTION OF H{alpha} EMITTERS : LOW-z ANALOGS OF z > 4 STAR-FORMING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Hyunjin [Department of Earth Science Education, Kyungpook National University (Korea, Republic of); Chary, Ranga-Ram, E-mail: hjshim@knu.ac.kr [U.S. Planck Data Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125 (United States)

    2013-03-01

    Strong H{alpha} emitters (HAEs) dominate the z {approx} 4 Lyman-break galaxy (LBG) population. We have identified local analogs of these HAEs using the Sloan Digital Sky Survey. At z < 0.4, only 0.04% of the galaxies are classified as HAEs with H{alpha} equivalent widths ({approx}> 500 A) comparable to that of z {approx} 4 HAEs. Local HAEs have lower stellar mass and lower ultraviolet (UV) luminosity than z {approx} 4 HAEs, yet the H{alpha}-to-UV luminosity ratio, as well as their specific star formation rate, is consistent with that of z {approx} 4 HAEs, indicating that they are scaled-down versions of high-z star-forming galaxies. Compared to the previously studied local analogs of LBGs selected using rest-frame UV properties, local HAEs show similar UV luminosity surface density, weaker D{sub n} (4000) break, lower metallicity, and lower stellar mass. This implies that the local HAEs are less evolved galaxies than the traditional Lyman break analogs. In the stacked spectrum, local HAEs show a significant He II {lambda}4686 emission line suggesting a population of hot, massive stars similar to that seen in some Wolf-Rayet galaxies. Low [N II]/[O III] line flux ratios imply that local HAEs are inconsistent with being systems that host bright active galactic nuclei. Instead, it is highly likely that local HAEs are galaxies with an elevated ionization parameter, either due to a high electron density or large escape fraction of hydrogen ionizing photons as in the case of Wolf-Rayet galaxies.

  18. EXPLORING THE LOW-MASS END OF THE MBH-σ* RELATION WITH ACTIVE GALAXIES

    International Nuclear Information System (INIS)

    Xiao Ting; Barth, Aaron J.; Greene, Jenny E.; Ludwig, Randi R.; Ho, Luis C.; Bentz, Misty C.; Jiang Yanfei

    2011-01-01

    We present new measurements of stellar velocity dispersions, using spectra obtained with the Keck Echellette Spectrograph and Imager (ESI) and the Magellan Echellette (MagE), for 76 Seyfert 1 galaxies from the recent catalog of Greene and Ho. These objects were selected from the Sloan Digital Sky Survey (SDSS) to have estimated black hole (BH) masses below 2 x 10 6 M sun . Combining our results with previous ESI observations of similar objects, we obtain an expanded sample of 93 galaxies and examine the relation between BH mass and velocity dispersion (the M BH -σ * relation) for active galaxies with low BH masses. The low-mass active galaxies tend to follow the extrapolation of the M BH -σ * relation of inactive galaxies. Including results for active galaxies of higher BH mass from the literature, we find a zero point α = 7.68 ± 0.08 and slope of β = 3.32 ± 0.22 for the M BH -σ * relation (in the form log M BH = α + βlog (σ * /200 km s -1 )), with intrinsic scatter of 0.46 ± 0.03 dex. This result is consistent, within the uncertainties, with the slope of the M BH -σ * relation for reverberation-mapped active galaxies with BH masses from 10 6 to 10 9 M sun . For the subset of our sample having morphological information from Hubble Space Telescope images, we examine the slope of the M BH -σ * relation separately for subsamples of barred and unbarred host galaxies, and find no significant evidence for a difference in slope. We do find a mild offset between low-inclination and high-inclination disk galaxies, such that more highly inclined galaxies tend to have larger σ * at a given value of BH mass, presumably due to the contribution of disk rotation within the spectroscopic aperture. We also find that the velocity dispersion of the ionized gas, measured from narrow emission lines including [N II] λ6583, [S II] λλ6716, 6731, and the core of [O III] λ5007 (with the blueshifted wing removed), trace the stellar velocity dispersion well for this large

  19. Redshifts for fainter galaxies in the first CfA survey slice. II

    Science.gov (United States)

    Wegner, Gary; Thorstensen, John R.; Kurtz, Michael J.; Geller, Margaret J.; Huchra, John P.

    1990-01-01

    Redshifts were measured for 96 galaxies in right ascension alpha between 8h and 17h declination delta between 30 and 31 deg, and with m(Zwicky) in the range 15.6-15.7. These correspond to 94 of the 96 entries in the Zwicky-Nilson merged catalog. The declination range delta between 29 deg and 31 deg is now complete to m(Zwicky) = 15.7. The structures in the first 6-deg-wide slice of the Center for Astrophysics redshift survey slice (delta between 26.5 and 32.5 deg are clearly defined in the 2-deg-wide slightly deeper sample; the fainter galaxies trace the structures defined by the brighter ones.

  20. Imprints of local lightcone \\ projection effects on the galaxy bispectrum. Part II

    Energy Technology Data Exchange (ETDEWEB)

    Jolicoeur, Sheean; Umeh, Obinna; Maartens, Roy; Clarkson, Chris, E-mail: beautifulheart369@gmail.com, E-mail: umeobinna@gmail.com, E-mail: roy.maartens@gmail.com, E-mail: chris.clarkson@qmul.ac.uk [Department of Physics and Astronomy, University of the Western Cape, Cape Town 7535 (South Africa)

    2017-09-01

    General relativistic imprints on the galaxy bispectrum arise from observational (or projection) effects. The lightcone projection effects include local contributions from Doppler and gravitational potential terms, as well as lensing and other integrated contributions. We recently presented for the first time, the correction to the galaxy bispectrum from all local lightcone projection effects up to second order in perturbations. Here we provide the details underlying this correction, together with further results and illustrations. For moderately squeezed shapes, the correction to the Newtonian prediction is ∼ 30% on equality scales at z ∼ 1. We generalise our recent results to include the contribution, up to second order, of magnification bias (which affects some of the local terms) and evolution bias.

  1. Radiative Transfer Simulations of Cosmic Reionization With Pop II and III Stars

    Science.gov (United States)

    Trac, Hy; Cen, Renyue

    2008-03-01

    We have simulated 3 large volume, high resolution realizations of cosmic reionization using a hybrid code that combines a N-body algorithm for dark matter, prescriptions for baryons and star formation, and a radiative transfer algorithm for ionizing photons. Our largest simulation, with 24 billion particles in a 100 Mpc/h box, simultaneously provides (1) the mass resolution needed to resolve dark matter halos down to a virial temperatures of 104 K and (2) the volume needed to fairly sample highly biased sources and large HII regions. We model the stellar initial mass function (IMF) by following the spatially dependent gas metallicity evolution, and distinguish between the first generation (Population III) stars and the second generation (Population II) stars. The Population III stars, with a top-heavy IMF, produce an order of magnitude more ionizing photons at high redshifts z>~10, resulting in a more extended reionization. In our simulations, complete overlap of HII regions occurs at z~6.5 and the computed mass and volume weighted residual HI fractions at 5measurements from SDSS. The values for the Thomson optical depth are consistent within 1-σ of the current best-fit value from the WMAP Year 3 data release.

  2. [FeII] as a tracer supernova rate

    International Nuclear Information System (INIS)

    Rosenberg, M J F; Van der Werf, P P; Israel, F P

    2012-01-01

    Supernovae play an integral role in the feedback of processed material into the ISM of galaxies and are responsible for most of the chemical enrichment of the universe. The rate of supernovae can also reveal the star formation histories. Supernova rate is usually measured through the non-thermal radio continuum luminosity, but in this paper we establish a quantitative relationship between the [FeII] 1.26 luminosity and supernova rate in a sample of 11 near-by starburst galaxies. SINFONI data cubes are used to perform a pixel pixel analysis of this correlation. Using Bry equivalent width and luminosity as the only observational inputs into Starburst 99, the supernova rate is derived at each pixel and a map of supernova rate is created. This is then compared morphologically and quantitatively to [FeII] 1.26 luminosity map. We find a strong linear and morphological correlation between supernova rate and [FeII] 1.26 on a pixel-pixel basis. The Starburst 99 derived supernova rates are also in good agreement with the radio derived supernova rates, which further demonstrates the strength of [FeII] as a tracer of supernova rate. With the strong correlation found in this sample of galaxies, we now qualitatively use [FeII] 1.26 to derive supernova rate on either a pixel-pixel or integrated galactic basis.

  3. The IRX-β dust attenuation relation in cosmological galaxy formation simulations

    Science.gov (United States)

    Narayanan, Desika; Davé, Romeel; Johnson, Benjamin D.; Thompson, Robert; Conroy, Charlie; Geach, James

    2018-02-01

    We utilize a series of galaxy formation simulations to investigate the relationship between the ultraviolet (UV) slope, β, and the infrared excess (IRX) in the spectral energy distributions (SEDs) of galaxies. Our main goals are to understand the origin of and scatter in the IRX-β relation; to assess the efficacy of simplified stellar population synthesis screen models in capturing the essential physics in the IRX-β relation; and to understand systematic deviations from the canonical local IRX-β relations in particular populations of high-redshift galaxies. Our main results follow. Young galaxies with relatively cospatial UV and IR emitting regions and a Milky Way-like extinction curve fall on or near the standard Meurer relation. This behaviour is well captured by simplified screen models. Scatter in the IRX-β relation is dominated by three major effects: (i) older stellar populations drive galaxies below the relations defined for local starbursts due to a reddening of their intrinsic UV SEDs; (ii) complex geometries in high-z heavily star-forming galaxies drive galaxies towards blue UV slopes owing to optically thin UV sightlines; (iii) shallow extinction curves drive galaxies downwards in the IRX-β plane due to lowered near-ultraviolet/far-ultraviolet extinction ratios. We use these features of the UV slopes of galaxies to derive a fitting relation that reasonably collapses the scatter back towards the canonical local relation. Finally, we use these results to develop an understanding for the location of two particularly enigmatic populations of galaxies in the IRX-β plane: z ˜ 2-4 dusty star-forming galaxies and z > 5 star-forming galaxies.

  4. On the interaction of the PKS B1358–113 radio galaxy with the A1836 cluster

    Energy Technology Data Exchange (ETDEWEB)

    Stawarz, Ł.; Simionescu, A.; Hagino, K. [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Szostek, A.; Kozieł-Wierzbowska, D.; Ostrowski, M. [Astronomical Observatory, Jagiellonian University, ulica Orla 171, 30-244 Kraków (Poland); Cheung, C. C. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Siemiginowska, A.; Harris, D. E. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Werner, N. [KIPAC, Stanford University, 452 Lomita Mall, Stanford, CA 94305 (United States); Madejski, G. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Begelman, M. C., E-mail: stawarz@astro.isas.jaxa.jp [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309-0440 (United States)

    2014-10-20

    Here we present the analysis of multifrequency data gathered for the Fanaroff-Riley type-II (FR II) radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy in the center of A1836. The galaxy harbors one of the most massive black holes known to date, and our analysis of the acquired optical data reveals that this black hole is only weakly active, with a mass accretion rate M-dot {sub acc}∼2×10{sup −4} M-dot {sub Edd}∼0.02 M{sub ⊙} yr{sup –1}. Based on analysis of new Chandra and XMM-Newton X-ray observations and archival radio data, and assuming the well-established model for the evolution of FR II radio galaxies, we derive the preferred range for the jet kinetic luminosity L {sub j} ∼ (1-6) × 10{sup –3} L {sub Edd} ∼ (0.5-3) × 10{sup 45} erg s{sup –1}. This is above the values implied by various scaling relations proposed for radio sources in galaxy clusters, being instead very close to the maximum jet power allowed for the given accretion rate. We also constrain the radio source lifetime as τ{sub j} ∼ 40-70 Myr, meaning the total amount of deposited jet energy E {sub tot} ∼ (2-8) × 10{sup 60} erg. We argue that approximately half of this energy goes into shock heating of the surrounding thermal gas, and the remaining 50% is deposited into the internal energy of the jet cavity. The detailed analysis of the X-ray data provides indication for the presence of a bow shock driven by the expanding radio lobes into the A1836 cluster environment. We derive the corresponding shock Mach number in the range M{sub sh}∼2--4, which is one of the highest claimed for clusters or groups of galaxies. This, together with the recently growing evidence that powerful FR II radio galaxies may not be uncommon in the centers of clusters at higher redshifts, supports the idea that jet-induced shock heating may indeed play an important role in shaping the properties of clusters, galaxy groups, and galaxies in formation. In this context, we speculate on

  5. Galaxy And Mass Assembly (GAMA): Gas Fueling of Spiral Galaxies in the Local Universe. I. The Effect of the Group Environment on Star Formation in Spiral Galaxies

    Science.gov (United States)

    Grootes, M. W.; Tuffs, R. J.; Popescu, C. C.; Norberg, P.; Robotham, A. S. G.; Liske, J.; Andrae, E.; Baldry, I. K.; Gunawardhana, M.; Kelvin, L. S.; Madore, B. F.; Seibert, M.; Taylor, E. N.; Alpaslan, M.; Brown, M. J. I.; Cluver, M. E.; Driver, S. P.; Bland-Hawthorn, J.; Holwerda, B. W.; Hopkins, A. M.; Lopez-Sanchez, A. R.; Loveday, J.; Rushton, M.

    2017-03-01

    We quantify the effect of the galaxy group environment (for group masses of 1012.5-1014.0 M ⊙) on the current star formation rate (SFR) of a pure, morphologically selected sample of disk-dominated (I.e., late-type spiral) galaxies with redshift ≤0.13. The sample embraces a full representation of quiescent and star-forming disks with stellar mass M * ≥ 109.5 M ⊙. We focus on the effects on SFR of interactions between grouped galaxies and the putative intrahalo medium (IHM) of their host group dark matter halos, isolating these effects from those induced through galaxy-galaxy interactions, and utilizing a radiation transfer analysis to remove the inclination dependence of derived SFRs. The dependence of SFR on M * is controlled for by measuring offsets Δlog(ψ *) of grouped galaxies about a single power-law relation in specific SFR, {\\psi }* \\propto {M}* -0.45+/- 0.01, exhibited by non-grouped “field” galaxies in the sample. While a small minority of the group satellites are strongly quenched, the group centrals and a large majority of satellites exhibit levels of ψ * statistically indistinguishable from their field counterparts, for all M *, albeit with a higher scatter of 0.44 dex about the field reference relation (versus 0.27 dex for the field). Modeling the distributions in Δlog(ψ *), we find that (I) after infall into groups, disk-dominated galaxies continue to be characterized by a similar rapid cycling of gas into and out of their interstellar medium shown prior to infall, with inflows and outflows of ˜1.5-5 x SFR and ˜1-4 x SFR, respectively; and (II) the independence of the continuity of these gas flow cycles on M * appears inconsistent with the required fueling being sourced from gas in the circumgalactic medium on scales of ˜100 kpc. Instead, our data favor ongoing fueling of satellites from the IHM of the host group halo on ˜Mpc scales, I.e., from gas not initially associated with the galaxies upon infall. Consequently, the color

  6. Chemical evolution of the Galaxy at the initial rapid-collapse phase

    Energy Technology Data Exchange (ETDEWEB)

    Caimmi, R [Padua Univ. (Italy). Istituto di Astronomia

    1978-04-01

    Equations for the chemical evolution of the Galaxy are derived, accounting for (i) the dynamical evolution of the Galaxy (i.e. the collapse of the proto-galaxy) and (ii) either a variable mass-spectrum in the birth-rate stellar function of the type B(m,t) = psi(t)phi(m,t), or a constant mass-spectrum with variable lower mass limit for star birth: msub(mf) = msub(mf)(Z). Simple equations are adopted for the collapse of the proto-galaxy, accounting for the experimental data (i.e. axial ratio and major semi-axis) relative to the halo and to the disk, and best fitted for a rapid collapse; gas density is assumed to be always uniform. Numerical computations of several cases show that there is qualitative agreement with the experimental data relative to the Z(t) function when: (i) the mass-spectrum is nearly constant in time: phi(m,t) approximately phi(m) = msup(-2.35); (ii) the efficiency phi(t) proportional to rhosup(..cap alpha..) is sufficiently high; moreover, the super metallic effect (SME) takes place for ..cap alpha.. greater than a given value (..cap alpha.. > approximately 1.5); (iii) the shorter the collapse time Tsub(c), the more rapid is the initial increase of metallicity, the asymptotic value being left nearly unaltered. The theoretical results are not in complete agreement with the observed data bearing on the Nsub(n)(Z) function (Nsub(n) is the number of stars whose Main-Sequence lifetime is not less than the age of the Galaxy), while a hypothesis of star formation with different efficiencies in different zones of the Galaxy, and successive stellar mixing from zone to zone, is not inconsistent with such data.

  7. Chemical evolution of the Galaxy at the initial rapid-collapse phase

    International Nuclear Information System (INIS)

    Caimmi, R.

    1978-01-01

    Equations for the chemical evolution of the Galaxy are derived, accounting for (i) the dynamical evolution of the Galaxy (i.e. the collapse of the proto-galaxy) and (ii) either a variable mass-spectrum in the birth-rate stellar function of the type B(m,t) = psi(t)phi(m,t), or a constant mass-spectrum with variable lower mass limit for star birth: msub(mf) = msub(mf)(Z). Simple equations are adopted for the collapse of the proto-galaxy, accounting for the experimental data (i.e. axial ratio and major semi-axis) relative to the halo and to the disk, and best fitted for a rapid collapse; gas density is assumed to be always uniform. Numerical computations of several cases show that there is qualitative agreement with the experimental data relative to the Z(t) function when: (i) the mass-spectrum is nearly constant in time: phi(m,t) approximately phi(m) = msup(-2.35); (ii) the efficiency phi(t) proportional to rhosup(α) is sufficiently high; moreover, the super metallic effect (SME) takes place for α greater than a given value (α > approximately 1.5); (iii) the shorter the collapse time Tsub(c), the more rapid is the initial increase of metallicity, the asymptotic value being left nearly unaltered. The theoretical results are not in complete agreement with the observed data bearing on the Nsub(n)(Z) function (Nsub(n) is the number of stars whose Main-Sequence lifetime is not less than the age of the Galaxy), while a hypothesis of star formation with different efficiencies in different zones of the Galaxy, and successive stellar mixing from zone to zone, is not inconsistent with such data. (Auth.)

  8. The GBT Diffuse Ionized Gas Survey (GDIGS)

    Science.gov (United States)

    Luisi, Matteo; Anderson, Loren Dean; Liu, Bin; Bania, Thomas; Balser, Dana; Wenger, Trey; Haffner, Lawrence Matthew

    2018-01-01

    Diffuse ionized gas in the Galactic mid-plane known as the "Warm Ionized Medium" (WIM) makes up ~20% of the gas mass of the Milky Way and >90% of its ionized gas. It is the last major component of the interstellar medium (ISM) that has not yet been studied at high spatial and spectral resolution, and therefore many of its fundamental properties remain unclear. The Green Bank Telescope (GBT) Diffuse Ionized Gas Survey (GDIGS) is a new large survey of the Milky Way disk at C-band (4-8 GHz). The main goals of GDIGS are to investigate the properties of the WIM and to determine the connection between the WIM and high-mass star formation over the Galactic longitude and latitude range of 32 deg > l > -5 deg, |b| resolution of 0.5 km/s and rms sensitivities of ~3 mJy per beam. GDIGS observations are currently underway and are expected to be completed by late 2018. These data will allow us to: 1) Study for the first time the inner-Galaxy WIM unaffected by confusion from discrete HII regions, 2) determine the distribution of the inner Galaxy WIM, 3) investigate the ionization state of the WIM, 4) explore the connection between the WIM and HII regions, and 5) analyze the effect of leaked photons from HII regions on ISM dust temperatures.

  9. Isolated galaxies, pairs, and groups of galaxies

    International Nuclear Information System (INIS)

    Kuneva, I.; Kalinkov, M.

    1990-01-01

    The authors searched for isolated galaxies, pairs and groups of galaxies in the CfA survey (Huchra et al. 1983). It was assumed that the distances to galaxies are given by R = V/H sub o, where H sub o = 100 km s(exp -1) Mpc(exp -1) and R greater than 6 Mpc. The searching procedure is close to those, applied to find superclusters of galaxies (Kalinkov and Kuneva 1985, 1986). A sphere with fixed radius r (asterisk) is described around each galaxy. The mean spatial density in the sphere is m. Let G 1 be any galaxy and G 2 be its nearest neighbor at a distance R 2 . If R sub 2 exceeds the 95 percent quintile in the distribution of the distances of the second neighbors, then G 1 is an isolated galaxy. Let the midpoint of G 1 and G 2 be O 2 and r 2 =R 2 2. For the volume V 2 , defined with the radius r 2 , the density D 2 less than k mu, the galaxy G 2 is a single one and the procedure for searching for pairs and groups, beginning with this object is over and we have to pass to another object. Here the authors present the groups - isolated and nonisolated - with n greater than 3, found in the CfA survey in the Northern galactic hemisphere. The parameters used are k = 10 and r (asterisk) = 5 Mpc. Table 1 contains: (1) the group number, (2) the galaxy, nearest to the multiplet center, (3) multiplicity n, (4) the brightest galaxy if it is not listed in (2); (5) and (6) are R.A. and Dec. (1950), (7) - mean distance D in Mpc. Further there are the mean density rho (8) of the multiplet (galaxies Mpc (exp -3)), (9) the density rho (asterisk) for r (asterisk) = 5 Mpc and (10) the density rho sub g for the group with its nearest neighbor. The parenthesized digits for densities in the last three columns are powers of ten

  10. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

    Galaxy formation is an enormously complex discipline due to the many physical processes that play a role in shaping galaxies. The objective of this thesis is to study galaxy formation with two different approaches: First, numerical simulations are used to study the structure of dark matter and how...... galaxies form stars throughout the history of the Universe, and secondly it is shown that observations of gamma-ray bursts (GRBs) can be used to probe galaxies with active star formation in the early Universe. A conclusion from the hydrodynamical simulations is that the galaxies from the stateof...... is important, since it helps constraining chemical evolution models at high redshift. A new project studying how the population of galaxies hosting GRBs relate to other galaxy population is outlined in the conclusion of this thesis. The core of this project will be to quantify how the stellar mass function...

  11. Boosting Lyα and He II λ1640 Line Fluxes from Population III Galaxies: Stochastic IMF Sampling and Departures from Case-B

    Science.gov (United States)

    Mas-Ribas, Lluís; Dijkstra, Mark; Forero-Romero, Jaime E.

    2016-12-01

    We revisit calculations of nebular hydrogen Lyα and He II λ1640 line strengths for Population III (Pop III) galaxies, undergoing continuous, and bursts of, star formation. We focus on initial mass functions (IMFs) motivated by recent theoretical studies, which generally span a lower range of stellar masses than earlier works. We also account for case-B departures and the stochastic sampling of the IMF. In agreement with previous work, we find that departures from case-B can enhance the Lyα flux by a factor of a few, but we argue that this enhancement is driven mainly by collisional excitation and ionization, and not due to photoionization from the n = 2 state of atomic hydrogen. The increased sensitivity of the Lyα flux to the high-energy end of the galaxy spectrum makes it more subject to stochastic sampling of the IMF. The latter introduces a dispersion in the predicted nebular line fluxes around the deterministic value by as much as a factor of ˜4. In contrast, the stochastic sampling of the IMF has less impact on the emerging Lyman Werner photon flux. When case-B departures and stochasticity effects are combined, nebular line emission from Pop III galaxies can be up to one order of magnitude brighter than predicted by “standard” calculations that do not include these effects. This enhances the prospects for detection with future facilities such as the James Webb Space Telescope and large, ground-based telescopes.

  12. Stellar mass estimation based on IRAC photometry for Spitzer SWIRE-field galaxies

    International Nuclear Information System (INIS)

    Zhu Yinan; Wu Hong; Li Haining; Cao Chen

    2010-01-01

    We analyze the feasibility of estimating the stellar mass of galaxies by mid-infrared luminosities based on a large sample of galaxies cross-identified from Spitzer SWIRE fields and the SDSS spectrographic survey. We derived the formulae to calculate the stellar mass by using IRAC 3.6 μm and 4.5 μm luminosities. The mass-to-luminosity ratios of IRAC 3.6 μm and 4.5 μm luminosities are more sensitive to the star formation history of galaxies than to other factors, such as the intrinsic extinction, metallicity and star formation rate. To remove the effect of star formation history, we used g - r color to recalibrate the formulae and obtain a better result. Researchers must be more careful when estimating the stellar mass of low metallicity galaxies using our formulae. Due to the emission from dust heated by the hottest young stars, luminous infrared galaxies present higher IRAC 4.5 μm luminosities compared to IRAC 3.6 μm luminosities. For most of type-II AGNs, the nuclear activity cannot enhance 3.6 μm and 4.5 μm luminosities compared with normal galaxies. Star formation in our AGN-hosting galaxies is also very weak, almost all of which are early-type galaxies.

  13. Galaxy Zoo: dust in spiral galaxies

    Science.gov (United States)

    Masters, Karen L.; Nichol, Robert; Bamford, Steven; Mosleh, Moein; Lintott, Chris J.; Andreescu, Dan; Edmondson, Edward M.; Keel, William C.; Murray, Phil; Raddick, M. Jordan; Schawinski, Kevin; Slosar, Anže; Szalay, Alexander S.; Thomas, Daniel; Vandenberg, Jan

    2010-05-01

    We investigate the effect of dust on spiral galaxies by measuring the inclination dependence of optical colours for 24276 well-resolved Sloan Digital Sky Survey (SDSS) galaxies visually classified via the Galaxy Zoo project. We find clear trends of reddening with inclination which imply a total extinction from face-on to edge-on of 0.7, 0.6, 0.5 and 0.4mag for the ugri passbands (estimating 0.3mag of extinction in z band). We split the sample into `bulgy' (early-type) and `discy' (late-type) spirals using the SDSS fracdeV (or fDeV) parameter and show that the average face-on colour of `bulgy' spirals is redder than the average edge-on colour of `discy' spirals. This shows that the observed optical colour of a spiral galaxy is determined almost equally by the spiral type (via the bulge-disc ratio and stellar populations), and reddening due to dust. We find that both luminosity and spiral type affect the total amount of extinction, with discy spirals at Mr ~ -21.5mag having the most reddening - more than twice as much as both the lowest luminosity and most massive, bulge-dominated spirals. An increase in dust content is well known for more luminous galaxies, but the decrease of the trend for the most luminous has not been observed before and may be related to their lower levels of recent star formation. We compare our results with the latest dust attenuation models of Tuffs et al. We find that the model reproduces the observed trends reasonably well but overpredicts the amount of u-band attenuation in edge-on galaxies. This could be an inadequacy in the Milky Way extinction law (when applied to external galaxies), but more likely indicates the need for a wider range of dust-star geometries. We end by discussing the effects of dust on large galaxy surveys and emphasize that these effects will become important as we push to higher precision measurements of galaxy properties and their clustering. This publication has been made possible by the participation of more than

  14. Isolated galaxies

    International Nuclear Information System (INIS)

    Einasto, Maret

    1990-01-01

    To test for the possible presence of really isolated galaxies, which form a randomly distributed population in voids, we compare the distribution of most isolated galaxies in an observed sample with distributions of the same number of random points using the nearest neighbour test. The results show that the random population of really isolated galaxies does not exist - even the most isolated galaxies are connected with systems of galaxies, forming their outlying parts. (author)

  15. CHEMICAL SIGNATURES OF THE FIRST GALAXIES: CRITERIA FOR ONE-SHOT ENRICHMENT

    International Nuclear Information System (INIS)

    Frebel, Anna; Bromm, Volker

    2012-01-01

    We utilize metal-poor stars in the local, ultra-faint dwarf galaxies (UFDs; L tot ≤ 10 5 L ☉ ) to empirically constrain the formation process of the first galaxies. Since UFDs have much simpler star formation histories than the halo of the Milky Way, their stellar populations should preserve the fossil record of the first supernova (SN) explosions in their long-lived, low-mass stars. Guided by recent hydrodynamical simulations of first galaxy formation, we develop a set of stellar abundance signatures that characterize the nucleosynthetic history of such an early system if it was observed in the present-day universe. Specifically, we argue that the first galaxies are the product of chemical 'one-shot' events, where only one (long-lived) stellar generation forms after the first, Population III, SN explosions. Our abundance criteria thus constrain the strength of negative feedback effects inside the first galaxies. We compare the stellar content of UFDs with these one-shot criteria. Several systems (Ursa Major II, and also Coma Berenices, Bootes I, Leo IV, Segue 1) largely fulfill the requirements, indicating that their high-redshift predecessors did experience strong feedback effects that shut off star formation. We term the study of the entire stellar population of a dwarf galaxy for the purpose of inferring details about the nature and origin of the first galaxies 'dwarf galaxy archaeology'. This will provide clues to the connection of the first galaxies, the surviving, metal-poor dwarf galaxies, and the building blocks of the Milky Way.

  16. Quasar Probing Galaxies: New Constraints on Cold Gas Accretion at Z=0.2

    Science.gov (United States)

    Ho, Stephanie H.

    2017-07-01

    Galactic disks grow by accreting cooling gas from the circumgalactic medium, and yet direct observations of inflowing gas remain sparse. We observed quasars behind star-forming galaxies and measured the kinematics of circumgalactic absorption. Near the galaxy plane, the Mg II Doppler shifts share the same sign as the galactic rotation, which implies the gas co-rotates with the galaxy disk. However, a rotating disk model fails to explain the observed broad velocity range. Gas spiraling inward near the disk plane offers a plausible explanation for the lower velocity gas. We will discuss the sizes of these circumgalactic disks, the properties of their host galaxies, and predictions for the spiral arms. Our results provide direct evidence for cold gas accretion at redshift z=0.2.

  17. MID-INFRARED PROPERTIES OF OH MEGAMASER HOST GALAXIES. I. SPITZER IRS LOW- AND HIGH-RESOLUTION SPECTROSCOPY

    International Nuclear Information System (INIS)

    Willett, Kyle W.; Darling, Jeremy; Spoon, Henrik W. W.; Charmandaris, Vassilis; Armus, Lee

    2011-01-01

    We present mid-infrared spectra and photometry from the Infrared Spectrograph on the Spitzer Space Telescope for 51 OH megamasers (OHMs), along with 15 galaxies confirmed to have no megamaser emission above L OH = 10 2.3 L sun . The majority of galaxies display moderate-to-deep 9.7 μm amorphous silicate absorption, with OHM galaxies showing stronger average absorption and steeper 20-30 μm continuum emission than non-masing galaxies. Emission from multiple polycyclic aromatic hydrocarbons (PAHs), especially at 6.2, 7.7, and 11.3 μm, is detected in almost all systems. Fine-structure atomic emission (including [Ne II], [Ne III], [S III], and [S IV]) and multiple H 2 rotational transitions are observed in more than 90% of the sample. A subset of galaxies show emission from rarer atomic lines, such as [Ne V], [O IV], and [Fe II]. Fifty percent of the OHMs show absorption from water ice and hydrogenated amorphous carbon grains, while absorption features from CO 2 , HCN, C 2 H 2 , and crystalline silicates are also seen in several OHMs. Column densities of OH derived from 34.6 μm OH absorption are similar to those derived from 1667 MHz OH absorption in non-masing galaxies, indicating that the abundance of masing molecules is similar for both samples. This data paper presents full mid-infrared spectra for each galaxy, along with measurements of line fluxes and equivalent widths, absorption feature depths, and spectral indices.

  18. Mid-Infrared Properties of OH Megamaser Host Galaxies. I. Spitzer IRS Low- and High-Resolution Spectroscopy

    Science.gov (United States)

    Willett, Kyle W.; Darling, Jeremy; Spoon, Henrik W. W.; Charmandaris, Vassilis; Armus, Lee

    2011-03-01

    We present mid-infrared spectra and photometry from the Infrared Spectrograph on the Spitzer Space Telescope for 51 OH megamasers (OHMs), along with 15 galaxies confirmed to have no megamaser emission above L OH = 102.3 L sun. The majority of galaxies display moderate-to-deep 9.7 μm amorphous silicate absorption, with OHM galaxies showing stronger average absorption and steeper 20-30 μm continuum emission than non-masing galaxies. Emission from multiple polycyclic aromatic hydrocarbons (PAHs), especially at 6.2, 7.7, and 11.3 μm, is detected in almost all systems. Fine-structure atomic emission (including [Ne II], [Ne III], [S III], and [S IV]) and multiple H2 rotational transitions are observed in more than 90% of the sample. A subset of galaxies show emission from rarer atomic lines, such as [Ne V], [O IV], and [Fe II]. Fifty percent of the OHMs show absorption from water ice and hydrogenated amorphous carbon grains, while absorption features from CO2, HCN, C2H2, and crystalline silicates are also seen in several OHMs. Column densities of OH derived from 34.6 μm OH absorption are similar to those derived from 1667 MHz OH absorption in non-masing galaxies, indicating that the abundance of masing molecules is similar for both samples. This data paper presents full mid-infrared spectra for each galaxy, along with measurements of line fluxes and equivalent widths, absorption feature depths, and spectral indices.

  19. UVES Abundances of Stars in Nearby Dwarf Spheroidal Galaxies

    Science.gov (United States)

    Tolstoy, Eline; Venn, Kim; Shetrone, Matt; Primas, Francesca; Hill, Vanessa; Kaufer, Andreas; Szeifert, Thomas

    2002-07-01

    It is a truth universally acknowledged, that a galaxy in possession of a good quantity of gas must want to form stars. It is the details of how and why that baffle us all. The simplest theories either would have this process a carefully self-regulated affair, or one that goes completely out of control and is capable of wrecking the galaxy which hosts it. Of course the majority of galaxies seem to amble along somewhere between these two extremes, and the mean properties tend to favour a quiescent self-regulated evolutionary scenario. But there area variety of observations which require us to invoke transitory ‘bursts’ of star-formation at one time or another in most galaxy types. Several nearby dwarf spheroidal galaxies have clearly determined star-formation histories with apparent periods of zero star formation followed by periods of fairly active star formation. If we are able to understand what separated these bursts we would understand several important phenomena in galaxy evolution. Were these galaxies able to clear out their gas reservoir in a burst of star formation? How did this gas return? or did it? Have these galaxies receieved gas from the IGM instead? Could stars from these types of galaxy contribute significantly to the halo population in our Galaxy? To answer these questions we need to combine accurate stellar photometry and Colour-Magnitude Diagram interpretation with detailed metal abundances to combine a star-formation rate versus time with a range of element abundances with time. Different elements trace different evolutionary process (e.g., relative contributions of type I and II supernovae). We often aren't even sure of the abundance spread in these galaxies. We have collected detailed high resolution UVES spectra of four nearby dwarf spheroidal galaxies (Sculptor, Fornax, Leo I & Carina) to begin to answer these questions. This is a precursor study to a more complete study with FLAMES. We presented at this meeting the initial results for

  20. The effects of assembly bias on the inference of matter clustering from galaxy-galaxy lensing and galaxy clustering

    Science.gov (United States)

    McEwen, Joseph E.; Weinberg, David H.

    2018-04-01

    The combination of galaxy-galaxy lensing (GGL) and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modeling can extend the approach down to nonlinear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with large scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older halos affects the cutoff of the mean occupation function for central galaxies, with halos in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We introduce an extended, environment dependent HOD (EDHOD) prescription to describe these results and fit galaxy correlation measurements. Crucially, we find that the galaxy-matter cross-correlation coefficient, rgm(r) ≡ ξgm(r) . [ξmm(r)ξgg(r)]-1/2, is insensitive to assembly bias on scales r ≳ 1 h^{-1} Mpc, even though ξgm(r) and ξgg(r) are both affected individually. We can therefore recover the correct ξmm(r) from the HW13 galaxy-galaxy and galaxy-matter correlations using either a standard HOD or EDHOD fitting method. For Mr ≤ -19 or Mr ≤ -20 samples the recovery of ξmm(r) is accurate to 2% or better. For a sample of red Mr ≤ -20 galaxies we achieve 2% recovery at r ≳ 2 h^{-1} Mpc with EDHOD modeling but lower accuracy at smaller scales or with a standard HOD fit. Most of our mock galaxy samples are consistent with rgm = 1 down to r = 1h-1Mpc, to within the uncertainties set by our finite simulation volume.

  1. The effects of assembly bias on the inference of matter clustering from galaxy-galaxy lensing and galaxy clustering

    Science.gov (United States)

    McEwen, Joseph E.; Weinberg, David H.

    2018-07-01

    The combination of galaxy-galaxy lensing and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modelling can extend the approach down to non-linear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with the large-scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older haloes affects the cutoff of the mean occupation function ⟨Ncen(Mmin)⟩ for central galaxies, with haloes in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We introduce an extended, environment-dependent HOD (EDHOD) prescription to describe these results and fit galaxy correlation measurements. Crucially, we find that the galaxy-matter cross-correlation coefficient, rgm(r) ≡ ξgm(r) . [ξmm(r)ξgg(r)]-1/2, is insensitive to assembly bias on scales r ≳ 1 h-1 Mpc, even though ξgm(r) and ξgg(r) are both affected individually. We can therefore recover the correct ξmm(r) from the HW13 galaxy-galaxy and galaxy-matter correlations using either a standard HOD or EDHOD fitting method. For Mr ≤ -19 or Mr ≤ -20 samples the recovery of ξmm(r) is accurate to 2 per cent or better. For a sample of red Mr ≤ -20 galaxies, we achieve 2 per cent recovery at r ≳ 2 h-1 Mpc with EDHOD modelling but lower accuracy at smaller scales or with a standard HOD fit. Most of our mock galaxy samples are consistent with rgm = 1 down to r = 1 h-1 Mpc, to within the uncertainties set by our finite simulation volume.

  2. GHASP: an Hα kinematical survey of spiral galaxies - XI. Distribution of luminous and dark matter in spiral and irregular nearby galaxies using WISE photometry.

    Science.gov (United States)

    Korsaga, M.; Carignan, C.; Amram, P.; Epinat, B.; Jarrett, T. H.

    2018-04-01

    We present the mass distribution of a sample of 121 nearby galaxies with high quality optical velocity fields and available infra-red WISE 3.4 μm data. Contrary to previous studies, this sample covers all morphological types and is not biased toward late-type galaxies. These galaxies are part of the Fabry-Perot kinematical GHASP survey of spirals and irregular nearby galaxies. Combining the kinematical data to the WISE surface brightness data probing the emission from the old stellar population, we derive mass models allowing us to compare the luminous to the dark matter halo mass distribution in the optical regions of those galaxies. Dark matter (DM) models are constructed using the isothermal core profile and the Navarro-Frenk-White cuspy profile. We allow the M/L of the baryonic disc to vary or we keep it fixed, constrained by stellar evolutionary models (WISE W1-W2 color) and we carry out best fit (BFM) and pseudo-isothermal maximum disc (MDM) models. We found that the MDM provides M/L values four times higher than the BFM, suggesting that disc components, on average, tend to be maximal. The main results are: (i) the rotation curves of most galaxies are better fitted with core rather than cuspy profiles; (ii) the relation between the parameters of the DM and of the luminous matter components mostly depends on morphological types. More precisely, the distribution of the DM inside galaxies depends on whether or not the galaxy has a bulge.

  3. Galaxy mergers

    International Nuclear Information System (INIS)

    Roos, N.

    1981-01-01

    This thesis contains a series of four papers dealing with the effects of interactions among galaxies during the epoch of cluster formation. Galaxy interactions are investigated and the results incorporated in numerical simulations of the formation of groups and clusters of galaxies. The role of galaxy interactions is analysed in the more general context of simulations of an expanding universe. The evolution of galaxies in rich clusters is discussed. The results of the investigations are presented and their relation to other work done in the field are briefly reviewed and an attempt is made to link galaxy mergers to the occurrence of activity in galactic nuclei. (Auth.)

  4. Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies

    International Nuclear Information System (INIS)

    Seigar, Marc S.; Davis, Benjamin L.; Berrier, Joel; Kennefick, Daniel

    2014-01-01

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6 μm imaging data and observed Hα rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally, we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  5. Spectrophotometry of four galaxies of high surface brightness

    International Nuclear Information System (INIS)

    Arakelyan, M.A.; Magtesyan, A.P.

    1982-01-01

    Spectrophotometry has been performed for the emission lines in the nuclei of Arakelyan galaxies Nos. 428, 449, 454, 532. In the first two objects, H II clouds occur roughly-equal2 kpc out from the nucleus. No. 449 may contain another cloud moving at roughly-equal1500 km/sec radial velocity. radial

  6. The Lyman Continuum Escape Fraction of Emission Line-selected z ∼ 2.5 Galaxies Is Less Than 15%

    Energy Technology Data Exchange (ETDEWEB)

    Rutkowski, Michael J.; Hayes, Matthew [Department of Astronomy, AlbaNova University Centre, Stockholm University, SE-10691 Stockholm (Sweden); Scarlata, Claudia; Mehta, Vihang [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Henry, Alaina; Hathi, Nimish; Koekemoer, Anton M. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Cohen, Seth; Windhorst, Rogier [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85281 (United States); Teplitz, Harry I. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Haardt, Francesco [DiSAT, Università dellInsubria, via Valleggio 11, I-22100 Como (Italy); Siana, Brian [Department of Physics, University of California, Riverside, CA 92521 (United States)

    2017-06-01

    Recent work suggests that strong emission line, star-forming galaxies (SFGs) may be significant Lyman continuum leakers. We combine archival Hubble Space Telescope broadband ultraviolet and optical imaging (F275W and F606W, respectively) with emission line catalogs derived from WFC3 IR G141 grism spectroscopy to search for escaping Lyman continuum (LyC) emission from homogeneously selected z ∼ 2.5 SFGs. We detect no escaping Lyman continuum from SFGs selected on [O ii] nebular emission ( N = 208) and, within a narrow redshift range, on [O iii]/[O ii]. We measure 1 σ upper limits to the LyC escape fraction relative to the non-ionizing UV continuum from [O ii] emitters, f {sub esc} ≲ 5.6%, and strong [O iii]/[O ii] > 5 ELGs, f {sub esc} ≲ 14.0%. Our observations are not deep enough to detect f {sub esc} ∼ 10% typical of low-redshift Lyman continuum emitters. However, we find that this population represents a small fraction of the star-forming galaxy population at z ∼ 2. Thus, unless the number of extreme emission line galaxies grows substantially to z ≳ 6, such galaxies may be insufficient for reionization. Deeper survey data in the rest-frame ionizing UV will be necessary to determine whether strong line ratios could be useful for pre-selecting LyC leakers at high redshift.

  7. The Lyman Continuum Escape Fraction of Emission Line-selected z ∼ 2.5 Galaxies Is Less Than 15%

    International Nuclear Information System (INIS)

    Rutkowski, Michael J.; Hayes, Matthew; Scarlata, Claudia; Mehta, Vihang; Henry, Alaina; Hathi, Nimish; Koekemoer, Anton M.; Cohen, Seth; Windhorst, Rogier; Teplitz, Harry I.; Haardt, Francesco; Siana, Brian

    2017-01-01

    Recent work suggests that strong emission line, star-forming galaxies (SFGs) may be significant Lyman continuum leakers. We combine archival Hubble Space Telescope broadband ultraviolet and optical imaging (F275W and F606W, respectively) with emission line catalogs derived from WFC3 IR G141 grism spectroscopy to search for escaping Lyman continuum (LyC) emission from homogeneously selected z ∼ 2.5 SFGs. We detect no escaping Lyman continuum from SFGs selected on [O ii] nebular emission ( N = 208) and, within a narrow redshift range, on [O iii]/[O ii]. We measure 1 σ upper limits to the LyC escape fraction relative to the non-ionizing UV continuum from [O ii] emitters, f _e_s_c ≲ 5.6%, and strong [O iii]/[O ii] > 5 ELGs, f _e_s_c ≲ 14.0%. Our observations are not deep enough to detect f _e_s_c ∼ 10% typical of low-redshift Lyman continuum emitters. However, we find that this population represents a small fraction of the star-forming galaxy population at z ∼ 2. Thus, unless the number of extreme emission line galaxies grows substantially to z ≳ 6, such galaxies may be insufficient for reionization. Deeper survey data in the rest-frame ionizing UV will be necessary to determine whether strong line ratios could be useful for pre-selecting LyC leakers at high redshift.

  8. Unveiling the structure of barred galaxies at 3.6 μm with the Spitzer survey of stellar structure in galaxies (S4G). I. Disk breaks

    International Nuclear Information System (INIS)

    Kim, Taehyun; Lee, Myung Gyoon; Gadotti, Dimitri A.; Muñoz-Mateos, Juan-Carlos; Sheth, Kartik; Athanassoula, E.; Bosma, Albert; Madore, Barry F.; Ho, Luis C.; Elmegreen, Bruce; Knapen, Johan H.; Cisternas, Mauricio; Erroz-Ferrer, Santiago; Zaritsky, Dennis; Comerón, Sébastien; Laurikainen, Eija; Salo, Heikki; Holwerda, Benne; Hinz, Joannah L.; Buta, Ron

    2014-01-01

    We have performed two-dimensional multicomponent decomposition of 144 local barred spiral galaxies using 3.6 μm images from the Spitzer Survey of Stellar Structure in Galaxies. Our model fit includes up to four components (bulge, disk, bar, and a point source) and, most importantly, takes into account disk breaks. We find that ignoring the disk break and using a single disk scale length in the model fit for Type II (down-bending) disk galaxies can lead to differences of 40% in the disk scale length, 10% in bulge-to-total luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We find that for galaxies with B/T ≥ 0.1, the break radius to bar radius, r br /R bar , varies between 1 and 3, but as a function of B/T the ratio remains roughly constant. This suggests that in bulge-dominated galaxies the disk break is likely related to the outer Lindblad resonance of the bar and thus moves outward as the bar grows. For galaxies with small bulges, B/T < 0.1, r br /R bar spans a wide range from 1 to 6. This suggests that the mechanism that produces the break in these galaxies may be different from that in galaxies with more massive bulges. Consistent with previous studies, we conclude that disk breaks in galaxies with small bulges may originate from bar resonances that may be also coupled with the spiral arms, or be related to star formation thresholds.

  9. The nature of the ISM in galaxies during the star-formation activity peak of the Universe

    NARCIS (Netherlands)

    Popping, G.; Pérez-Beaupuits, J. P.; Spaans, M.; Trager, S. C.; Somerville, R. S.

    2014-01-01

    We combine a semi-analytic model of galaxy formation, tracking atomic and molecular phases of cold gas, with a three-dimensional radiative-transfer and line tracing code to study the sub-mm emission from atomic and molecular species (CO, HCN, [C I], [C II], [O I]) in galaxies. We compare the physics

  10. The H II galaxy Hubble diagram strongly favours Rh = ct over ΛCDM

    Science.gov (United States)

    Wei, Jun-Jie; Wu, Xue-Feng; Melia, Fulvio

    2016-12-01

    We continue to build support for the proposal to use H II galaxies (HIIGx) and giant extragalactic H II regions (GEHR) as standard candles to construct the Hubble diagram at redshifts beyond the current reach of Type Ia supernovae. Using a sample of 25 high-redshift HIIGx, 107 local HIIGx, and 24 GEHR, we confirm that the correlation between the emission-line luminosity and ionized-gas velocity dispersion is a viable luminosity indicator, and use it to test and compare the standard model ΛCDM and the Rh = ct universe by optimizing the parameters in each cosmology using a maximization of the likelihood function. For the flat ΛCDM model, the best fit is obtained with Ω _m= 0.40_{-0.09}^{+0.09}. However, statistical tools, such as the Akaike (AIC), Kullback (KIC) and Bayes (BIC) Information Criteria favour Rh = ct over the standard model with a likelihood of ≈94.8-98.8 per cent versus only ≈1.2-5.2 per cent. For wCDM (the version of ΛCDM with a dark-energy equation of state wde ≡ pde/ρde rather than wde = wΛ = -1), a statistically acceptable fit is realized with Ω _m=0.22_{-0.14}^{+0.16} and w_de= -0.51_{-0.25}^{+0.15} which, however, are not fully consistent with their concordance values. In this case, wCDM has two more free parameters than Rh = ct, and is penalized more heavily by these criteria. We find that Rh = ct is strongly favoured over wCDM with a likelihood of ≈92.9-99.6 per cent versus only 0.4-7.1 per cent. The current HIIGx sample is already large enough for the BIC to rule out ΛCDM/wCDM in favour of Rh = ct at a confidence level approaching 3σ.

  11. Anisotropic Galaxy-Galaxy Lensing in the Illustris-1 Simulation

    Science.gov (United States)

    Brainerd, Tereasa G.

    2017-06-01

    In Cold Dark Matter universes, the dark matter halos of galaxies are expected to be triaxial, leading to a surface mass density that is not circularly symmetric. In principle, this "flattening" of the dark matter halos of galaxies should be observable as an anisotropy in the weak galaxy-galaxy lensing signal. The degree to which the weak lensing signal is observed to be anisotropic, however, will depend strongly on the degree to which mass (i.e., the dark matter) is aligned with light in the lensing galaxies. That is, the anisotropy will be maximized when the major axis of the projected mass distribution is well aligned with the projected light distribution of the lens galaxies. Observational studies of anisotropic galaxy-galaxy lensing have found an anisotropic weak lensing signal around massive, red galaxies. Detecting the signal around blue, disky galaxies has, however, been more elusive. A possible explanation for this is that mass and light are well aligned within red galaxies and poorly aligned within blue galaxies (an explanation that is supported by studies of the locations of satellites of large, relatively isolated galaxies). Here we compute the weak lensing signal of isolated central galaxies in the Illustris-1 simulation. We compute the anisotropy of the weak lensing signal using two definitions of the geometry: [1] the major axis of the projected dark matter mass distribution and [2] the major axis of the projected stellar mass. On projected scales less than 15% of the virial radius, an anisotropy of order 10% is found for both definitions of the geometry. On larger scales, the anisotropy computed relative to the major axis of the projected light distribution is less than the anisotropy computed relative to the major axis of the projected dark matter. On projected scales of order the virial radius, the anisotropy obtained when using the major axis of the light is an order of magnitude less than the anisotropy obtained when using the major axis of the

  12. DUST-CORRECTED STAR FORMATION RATES OF GALAXIES. I. COMBINATIONS OF Hα AND INFRARED TRACERS

    International Nuclear Information System (INIS)

    Kennicutt, Robert C.; Hao, C.-N.; Johnson, Benjamin D.; Calzetti, Daniela; Moustakas, John; Dale, Daniel A.; Bendo, George; Engelbracht, Charles W.; Lee, Janice C.

    2009-01-01

    We combine Hα emission-line and infrared (IR) continuum measurements of two samples of nearby galaxies to derive dust attenuation-corrected star formation rates (SFRs). We use a simple energy balance based method that has been applied previously to H II regions in the Spitzer Infrared Nearby Galaxies Survey, and extend the methodology to integrated measurements of galaxies. We find that our composite Hα + IR based SFRs are in excellent agreement with attenuation-corrected SFRs derived from integrated spectrophotometry, over the full range of SFRs (0.01-80 M sun yr -1 ) and attenuations (0-2.5 mag) studied. We find that the combination of Hα and total IR luminosities provides the most robust SFR measurements, but combinations of Hα measurements with monochromatic luminosities at 24 μm and 8 μm perform nearly as well. The calibrations differ significantly from those obtained for H II regions, with the difference attributable to a more evolved population of stars heating the dust. Our results are consistent with a significant component of diffuse dust (the 'IR cirrus' component) that is heated by a non-star-forming population. The same methodology can be applied to [O II]λ3727 emission-line measurements, and the radio continuum fluxes of galaxies can be applied in place of IR fluxes when the latter are not available. We assess the precision and systematic reliability of all of these composite methods.

  13. Elemental gas-phase abundances of intermediate redshift type Ia supernova star-forming host galaxies

    Science.gov (United States)

    Moreno-Raya, M. E.; Galbany, L.; López-Sánchez, Á. R.; Mollá, M.; González-Gaitán, S.; Vílchez, J. M.; Carnero, A.

    2018-05-01

    The maximum luminosity of type Ia supernovae (SNe Ia) depends on the oxygen abundance of the regions of the host galaxies, where they explode. This metallicity dependence reduces the dispersion in the Hubble diagram (HD) when included with the traditional two-parameter calibration of SN Ia light-curve parameters and absolute magnitude. In this work, we use empirical calibrations to carefully estimate the oxygen abundance of galaxies hosting SNe Ia from the SDSS-II/SN (Sloan Digital Sky Survey-II Supernova) survey at intermediate redshift by measuring their emission-line intensities. We also derive electronic temperature with the direct method for a small fraction of objects for consistency. We find a trend of decreasing oxygen abundance with increasing redshift for the most massive galaxies. Moreover, we study the dependence of the HD residuals (HR) with galaxy oxygen abundance obtaining a correlation in line with those found in other works. In particular, the HR versus oxygen abundance shows a slope of -0.186 ± 0.123 mag dex-1 (1.52σ) in good agreement with theoretical expectations. This implies smaller distance modulii after corrections for SNe Ia in metal-rich galaxies. Based on our previous results on local SNe Ia, we propose this dependence to be due to the lower luminosity of the SNe Ia produced in more metal-rich environments.

  14. The Taipan Galaxy Survey: Scientific Goals and Observing Strategy

    Science.gov (United States)

    da Cunha, Elisabete; Hopkins, Andrew M.; Colless, Matthew; Taylor, Edward N.; Blake, Chris; Howlett, Cullan; Magoulas, Christina; Lucey, John R.; Lagos, Claudia; Kuehn, Kyler; Gordon, Yjan; Barat, Dilyar; Bian, Fuyan; Wolf, Christian; Cowley, Michael J.; White, Marc; Achitouv, Ixandra; Bilicki, Maciej; Bland-Hawthorn, Joss; Bolejko, Krzysztof; Brown, Michael J. I.; Brown, Rebecca; Bryant, Julia; Croom, Scott; Davis, Tamara M.; Driver, Simon P.; Filipovic, Miroslav D.; Hinton, Samuel R.; Johnston-Hollitt, Melanie; Jones, D. Heath; Koribalski, Bärbel; Kleiner, Dane; Lawrence, Jon; Lorente, Nuria; Mould, Jeremy; Owers, Matt S.; Pimbblet, Kevin; Tinney, C. G.; Tothill, Nicholas F. H.; Watson, Fred

    2017-10-01

    The Taipan galaxy survey (hereafter simply `Taipan') is a multi-object spectroscopic survey starting in 2017 that will cover 2π steradians over the southern sky (δ ≲ 10°, |b| ≳ 10°), and obtain optical spectra for about two million galaxies out to z growth rate of structure to 5%; (ii) to make the most extensive map yet constructed of the total mass distribution and motions in the local Universe, using peculiar velocities based on improved Fundamental Plane distances, which will enable sensitive tests of gravitational physics; and (iii) to deliver a legacy sample of low-redshift galaxies as a unique laboratory for studying galaxy evolution as a function of dark matter halo and stellar mass and environment. The final survey, which will be completed within 5 yrs, will consist of a complete magnitude-limited sample (i ⩽ 17) of about 1.2 × 106 galaxies supplemented by an extension to higher redshifts and fainter magnitudes (i ⩽ 18.1) of a luminous red galaxy sample of about 0.8 × 106 galaxies. Observations and data processing will be carried out remotely and in a fully automated way, using a purpose-built automated `virtual observer' software and an automated data reduction pipeline. The Taipan survey is deliberately designed to maximise its legacy value by complementing and enhancing current and planned surveys of the southern sky at wavelengths from the optical to the radio; it will become the primary redshift and optical spectroscopic reference catalogue for the local extragalactic Universe in the southern sky for the coming decade.

  15. Galaxy formation

    International Nuclear Information System (INIS)

    Gribbin, J.

    1979-01-01

    The current debate on the origin and evolution of galaxies is reviewed and evidence to support the so-called 'isothermal' and 'adiabatic' fluctuation models considered. It is shown that new theories have to explain the formation of both spiral and elliptical galaxies and the reason for their differences. It is stated that of the most recent models the best indicates that rotating spiral galaxies are formed naturally when gas concentrates in the centre of a great halo and forms stars while ellipticals are explained by later interactions between spiral galaxies and merging, which can cancel out the rotation while producing an elliptical galaxy in which the stars, coming from two original galaxies, follow very elliptical, anisotropic orbits. (UK)

  16. PAndAS' CUBS: DISCOVERY OF TWO NEW DWARF GALAXIES IN THE SURROUNDINGS OF THE ANDROMEDA AND TRIANGULUM GALAXIES

    International Nuclear Information System (INIS)

    Martin, Nicolas F.; McConnachie, Alan W.; Irwin, Mike; Chapman, Scott; Widrow, Lawrence M.; Ferguson, Annette M. N.; Ibata, Rodrigo A.; Dubinski, John; Babul, Arif; Navarro, Julio; Fardal, Mark; Lewis, Geraint F.; Rich, R. Michael

    2009-01-01

    We present the discovery of two new dwarf galaxies, Andromeda XXI and Andromeda XXII, located in the surroundings of the Andromeda and Triangulum galaxies (M31 and M33). These discoveries stem from the first year data of the Pan-Andromeda Archaeological Survey, a photometric survey of the M31/M33 group conducted with the Megaprime/MegaCam Wide-Field Camera mounted on the Canada-France-Hawaii Telescope. Both satellites appear as spatial overdensities of stars which, when plotted in a color-magnitude diagram, follow metal-poor, [Fe/H] = -1.8, red giant branches at the distance of M31/M33. Andromeda XXI is a moderately bright dwarf galaxy (M V = -9.9 ± 0.6), albeit with low surface brightness, emphasizing again that many relatively luminous M31 satellites still remain to be discovered. It is also a large satellite, with a half-light radius close to 1 kpc, making it the fourth largest Local Group dwarf spheroidal galaxy after the recently discovered Andromeda XIX, Andromeda II, and Sagittarius around the Milky Way, and supports the trend that M31 satellites are larger than their Milky Way counterparts. Andromeda XXII is much fainter (M V = -6.5 ± 0.8) and lies a lot closer in projection to M33 than it does to M31 (42 versus 224 kpc), suggesting that it could be the first Triangulum satellite to be discovered. Although this is a very exciting possibility in the context of a past interaction of M33 with M31 and the fate of its satellite system, a confirmation will have to await a good distance estimate to confirm its physical proximity to M33. Along with the dwarf galaxies found in previous surveys of the M31 surroundings, these two new satellites bring the number of dwarf spheroidal galaxies in this region to 20.

  17. Star formation and galactic evolution. I. General expressions and applications to our galaxy

    International Nuclear Information System (INIS)

    Kaufman, M.

    1979-01-01

    The study of galactic evolution involves three mechanisms for triggering star formation in interstellar clouds: (i) star formation triggered by a galactic spiral density wave, (ii) star formation triggered by shock waves from supernovae, and (iii) star formation triggered by an expanding H II region. Useful analytic approximations to the birthrate per unit mass are obtained by treating the efficiencies of these various mechanisms as time independent. In situations where shock waves from high-mass stars (either expanding H II regions or supernova explosions) are the only important star-forming mechanisms, the birthrate is exponential in time. This case is appropriate for the past evolution of an elliptical galaxy, nuclear bulge, or galactic halo. In the disk of a spiral galaxy where all three mechanisms operate, the birthrate consists of an exponential term plus a time-independent term. In both situations, the value of the time constant T in the exponential term is directly related to the efficiency of the shock waves from massive stars in initiating star formation.For our Galaxy, this simplified model is used to compute the radial distributions of young objects and low-mass stars in the disk, and the past and present birthrates in the solar-neighborhood shell

  18. Cosmological parameter constraints from galaxy-galaxy lensing and galaxy clustering with the SDSS DR7

    Science.gov (United States)

    Mandelbaum, Rachel; Slosar, Anže; Baldauf, Tobias; Seljak, Uroš; Hirata, Christopher M.; Nakajima, Reiko; Reyes, Reinabelle; Smith, Robert E.

    2013-06-01

    Recent studies have shown that the cross-correlation coefficient between galaxies and dark matter is very close to unity on scales outside a few virial radii of galaxy haloes, independent of the details of how galaxies populate dark matter haloes. This finding makes it possible to determine the dark matter clustering from measurements of galaxy-galaxy weak lensing and galaxy clustering. We present new cosmological parameter constraints based on large-scale measurements of spectroscopic galaxy samples from the Sloan Digital Sky Survey (SDSS) data release 7. We generalize the approach of Baldauf et al. to remove small-scale information (below 2 and 4 h-1 Mpc for lensing and clustering measurements, respectively), where the cross-correlation coefficient differs from unity. We derive constraints for three galaxy samples covering 7131 deg2, containing 69 150, 62 150 and 35 088 galaxies with mean redshifts of 0.11, 0.28 and 0.40. We clearly detect scale-dependent galaxy bias for the more luminous galaxy samples, at a level consistent with theoretical expectations. When we vary both σ8 and Ωm (and marginalize over non-linear galaxy bias) in a flat Λ cold dark matter model, the best-constrained quantity is σ8(Ωm/0.25)0.57 = 0.80 ± 0.05 (1σ, stat. + sys.), where statistical and systematic errors (photometric redshift and shear calibration) have comparable contributions, and we have fixed ns = 0.96 and h = 0.7. These strong constraints on the matter clustering suggest that this method is competitive with cosmic shear in current data, while having very complementary and in some ways less serious systematics. We therefore expect that this method will play a prominent role in future weak lensing surveys. When we combine these data with Wilkinson Microwave Anisotropy Probe 7-year (WMAP7) cosmic microwave background (CMB) data, constraints on σ8, Ωm, H0, wde and ∑mν become 30-80 per cent tighter than with CMB data alone, since our data break several parameter

  19. Galaxy angular momentum

    International Nuclear Information System (INIS)

    Thompson, L.A.

    1974-01-01

    In order to test the theories which purport to explain the origin of galaxy angular momentum, this study presents new data for about 1000 individual galaxies in eight rich clusters. The clusters which are studied include Virgo, A 119, A 400, A 1656 (Coma), A 2147, A 2151 (Hercules), A 2197, and A 2199. Selected samples of these data are used to investigate systematic alignment effects in clusters of galaxies and to investigate the intrinsic ellipticities of E, SO, and spiral galaxies. The following new results are reported: Galaxies in the cluster A 2197 show a significant alignment effect (chi 2 probability less than 0.0002), and the preferential direction of alignment corresponds approximately to the major axis of the overall cluster elongation. None of the other seven clusters show any significant alignment trends. The spiral galaxy samples in four clusters (Virgo, A 1656, A 2151, and A 2197) were large enough to analyze the number distributions of forward and reverse winding spirals. Large and small spiral galaxies have identical ellipticity distributions. Large E and SO galaxies tend to be more spherical, and small E and SO galaxies more flattened. The intrinsic ellipticities of E, SO, and spiral galaxies are the same for galaxies in the ''field'' and for galaxies in rich clusters. Six models of galaxy formation are reviewed, and the major []mphasis is placed on how each model explains the origin of galaxy angular momentum. (Diss. Abstr. Int., B)

  20. Quasars Probing Galaxies. I. Signatures of Gas Accretion at Redshift z ≈ 0.2

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Stephanie H.; Martin, Crystal L. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Kacprzak, Glenn G. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Churchill, Christopher W., E-mail: shho@physics.ucsb.edu, E-mail: cmartin@physics.ucsb.edu [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)

    2017-02-01

    We describe the kinematics of circumgalactic gas near the galactic plane, combining new measurements of galaxy rotation curves and spectroscopy of background quasars. The sightlines pass within 19–93 kpc of the target galaxy and generally detect Mg ii absorption. The Mg ii Doppler shifts have the same sign as the galactic rotation, so the cold gas co-rotates with the galaxy. Because the absorption spans a broader velocity range than disk rotation can explain, we explore simple models for the circumgalactic kinematics. Gas spiraling inwards (near the disk plane) offers a successful description of the observations. An appendix describes the addition of tangential and radial gas flows and illustrates how the sign of the disk inclination produces testable differences in the projected line-of-sight velocity range. This inflow interpretation implies that cold flow disks remain common down to redshift z ≈ 0.2 and prolong star formation by supplying gas to the disk.

  1. Two micron spectroscopy of the Blue Compact Dwarf Galaxy Haro 2

    International Nuclear Information System (INIS)

    Davidge, T.J.; Maillard, J.P.

    1990-01-01

    This paper discusses the results of 2-micron spectroscopic observations of the Blue Compact Dwarf Galaxy (BCDG) Haro 2, obtained with the 3.6-m Canada-France-Hawaii Telescope. The spectrum contains emission lines of H I, He I, Fe II, and H2 and strong absorption originating from Delta-v = 2 transitions of CO. The strengths of the various features are discussed and the extinction in the 2-micron region is estimated. The spectrum of Haro 2 is compared with those of other BCDGs and the starburst galaxies NGC 253 and M82. It is found that, in many respects, Haro 2 is a typical starburst galaxy and that its blue near-IR colors are not necessarily a sign of youth. 35 refs

  2. A model for the origin of bursty star formation in galaxies

    Science.gov (United States)

    Faucher-Giguère, Claude-André

    2018-01-01

    We propose a simple analytic model to understand when star formation is time steady versus bursty in galaxies. Recent models explain the observed Kennicutt-Schmidt relation between star formation rate and gas surface densities in galaxies as resulting from a balance between stellar feedback and gravity. We argue that bursty star formation occurs when such an equilibrium cannot be stably sustained, and identify two regimes in which galaxy-scale star formation should be bursty: (i) at high redshift (z ≳ 1) for galaxies of all masses, and (ii) at low masses (depending on gas fraction) for galaxies at any redshift. At high redshift, characteristic galactic dynamical time-scales become too short for supernova feedback to effectively respond to gravitational collapse in galactic discs (an effect recently identified for galactic nuclei), whereas in dwarf galaxies star formation occurs in too few bright star-forming regions to effectively average out. Burstiness is also enhanced at high redshift owing to elevated gas fractions in the early Universe. Our model can thus explain the bursty star formation rates predicted in these regimes by recent high-resolution galaxy formation simulations, as well as the bursty star formation histories observationally inferred in both local dwarf and high-redshift galaxies. In our model, bursty star formation is associated with particularly strong spatiotemporal clustering of supernovae. Such clustering can promote the formation of galactic winds and our model may thus also explain the much higher wind mass loading factors inferred in high-redshift massive galaxies relative to their z ∼ 0 counterparts.

  3. 4C radio sources in clusters of galaxies

    International Nuclear Information System (INIS)

    McHardy, I.M.

    1979-01-01

    Observations of a complete sample of 4C and 4CT radio sources in Abell clusters with the Cambridge One-Mile telescope are analysed. It is concluded that radio sources are strongly concentrated towards the cluster centres and are equally likely to be found in clusters of any richness. The probability of a galaxy of a given absolute magnitude producing a source above a given luminosity does not depend on cluster membership. 4C and 4CT radio sources in clusters, selected at 178 MHz, occur preferentially in Bautz-Morgan (BM) class 1 clusters, whereas those selected at 1.4 GHz do not. The most powerful radio source in the cluster is almost always associated with the optically brightest galaxy. The average spectrum of 4C sources in the range 408 to 1407 MHz is steeper in BM class 1 than in other classes. Spectra also steepen with cluster richness. the morphology of 4C sources in clusters depends strongly on BM class and, in particular, radio-trail sources occur only in BM classes II, II-III and III. (author)

  4. Discovery of an Ultra-diffuse Galaxy in the Pisces--Perseus Supercluster

    Science.gov (United States)

    Martínez-Delgado, David; Läsker, Ronald; Sharina, Margarita; Toloba, Elisa; Fliri, Jürgen; Beaton, Rachael; Valls-Gabaud, David; Karachentsev, Igor D.; Chonis, Taylor S.; Grebel, Eva K.; Forbes, Duncan A.; Romanowsky, Aaron J.; Gallego-Laborda, J.; Teuwen, Karel; Gómez-Flechoso, M. A.; Wang, Jie; Guhathakurta, Puragra; Kaisin, Serafim; Ho, Nhung

    2016-04-01

    We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10.°4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (μV = 24.8 mag arcsec-2), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (Re(V) = 12″) and proximity (15‧) to the well-known dwarf spheroidal galaxy And II. Its red color (V - I = 1.0), shallow Sérsic index (nV = 0.68), and the absence of detectable Hα emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6 m telescope (Vh = 5450 ± 40 km s-1) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (˜78 Mpc), DGSAT I would have an Re ˜ 4.7 kpc and MV ˜ -16.3. Its properties resemble those of the ultra-diffuse galaxies (UDGs) recently discovered in the Coma cluster. DGSAT I is the first case of these rare UDGs found in this galaxy cluster. Unlike the UDGs associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.

  5. Evidence for wide-spread active galactic nucleus-driven outflows in the most massive z ∼ 1-2 star-forming galaxies

    International Nuclear Information System (INIS)

    Genzel, R.; Förster Schreiber, N. M.; Rosario, D.; Lang, P.; Lutz, D.; Wisnioski, E.; Wuyts, E.; Wuyts, S.; Bandara, K.; Bender, R.; Berta, S.; Kurk, J.; Mendel, J. T.; Tacconi, L. J.; Wilman, D.; Beifiori, A.; Burkert, A.; Buschkamp, P.; Chan, J.; Brammer, G.

    2014-01-01

    In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M * /M ☉ ) ≥ 10.9) z ∼ 1-3 star-forming galaxies by increasing the sample size by a factor of six (to 44 galaxies above log(M * /M ☉ ) ≥ 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS 3D spectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Hα, [N II], and [S II] lines ∼450-5300 km s –1 ), with large [N II]/Hα ratios, above log(M * /M ☉ ) ∼ 10.9, with about two-thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z ∼ 1 and ∼2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGNs), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation.

  6. Simulating neutron star mergers as r-process sources in ultrafaint dwarf galaxies

    Science.gov (United States)

    Safarzadeh, Mohammadtaher; Scannapieco, Evan

    2017-10-01

    To explain the high observed abundances of r-process elements in local ultrafaint dwarf (UFD) galaxies, we perform cosmological zoom simulations that include r-process production from neutron star mergers (NSMs). We model star formation stochastically and simulate two different haloes with total masses ≈108 M⊙ at z = 6. We find that the final distribution of [Eu/H] versus [Fe/H] is relatively insensitive to the energy by which the r-process material is ejected into the interstellar medium, but strongly sensitive to the environment in which the NSM event occurs. In one halo, the NSM event takes place at the centre of the stellar distribution, leading to high levels of r-process enrichment such as seen in a local UFD, Reticulum II (Ret II). In a second halo, the NSM event takes place outside of the densest part of the galaxy, leading to a more extended r-process distribution. The subsequent star formation occurs in an interstellar medium with shallow levels of r-process enrichment that results in stars with low levels of [Eu/H] compared to Ret II stars even when the maximum possible r-process mass is assumed to be ejected. This suggests that the natal kicks of neutron stars may also play an important role in determining the r-process abundances in UFD galaxies, a topic that warrants further theoretical investigation.

  7. Clusters of Galaxies

    Science.gov (United States)

    Huchtmeier, W. K.; Richter, O. G.; Materne, J.

    1981-09-01

    The large-scale structure of the universe is dominated by clustering. Most galaxies seem to be members of pairs, groups, clusters, and superclusters. To that degree we are able to recognize a hierarchical structure of the universe. Our local group of galaxies (LG) is centred on two large spiral galaxies: the Andromeda nebula and our own galaxy. Three sr:naller galaxies - like M 33 - and at least 23 dwarf galaxies (KraanKorteweg and Tammann, 1979, Astronomische Nachrichten, 300, 181) can be found in the evironment of these two large galaxies. Neighbouring groups have comparable sizes (about 1 Mpc in extent) and comparable numbers of bright members. Small dwarf galaxies cannot at present be observed at great distances.

  8. Spatial distribution of H II regions in NGC 4321

    International Nuclear Information System (INIS)

    Anderson, S.; Hodge, P.; Kennicutt, R.C. Jr.

    1983-01-01

    A catalog of 286 H II regions in the giant Sc Virgo Cluster spiral galaxy NGC 4321 is used to analyze some aspects of this galaxy's spiral structure. The H II region distribution is rectified to face-on by least-squares fitting to a logarithmic spiral, and the radial distribution, the across-arm distribution, and the along-arm distribution of H II regions are determined. Comparison of the circular distribution with a simple shock wave model of the density wave theory does not clearly support the model. Arm 1 shows no obvious structure, and arm 2, although it has a clear peak, does not show the expected asymmetrical distribution. Agreement is reasonably good, however, with the somewhat more elaborate density wave model of Bash. Tests for clumping of the H II regions were negative

  9. Galaxy And Mass Assembly (GAMA): gas fuelling of spiral galaxies in the local Universe II. - direct measurement of the dependencies on redshift and host halo mass of stellar mass growth in central disc galaxies

    Science.gov (United States)

    Grootes, M. W.; Dvornik, A.; Laureijs, R. J.; Tuffs, R. J.; Popescu, C. C.; Robotham, A. S. G.; Liske, J.; Brown, M. J. I.; Holwerda, B. W.; Wang, L.

    2018-06-01

    We present a detailed analysis of the specific star formation rate-stellar mass (sSFR-M*) of z ≤ 0.13 disc central galaxies using a morphologically selected mass-complete sample (M* ≥ 109.5 M⊙). Considering samples of grouped and ungrouped galaxies, we find the sSFR-M* relations of disc-dominated central galaxies to have no detectable dependence on host dark-matter halo (DMH) mass, even where weak-lensing measurements indicate a difference in halo mass of a factor ≳ 5. We further detect a gradual evolution of the sSFR-M* relation of non-grouped (field) central disc galaxies with redshift, even over a Δz ≈ 0.04 (≈5 × 108 yr) interval, while the scatter remains constant. This evolution is consistent with extrapolation of the `main sequence of star-forming-galaxies' from previous literature that uses larger redshift baselines and coarser sampling. Taken together, our results present new constraints on the paradigm under which the SFR of galaxies is determined by a self-regulated balance between gas inflows and outflows, and consumption of gas by star formation in discs, with the inflow being determined by the product of the cosmological accretion rate and a fuelling efficiency - \\dot{M}_{b,halo}ζ. In particular, maintaining the paradigm requires \\dot{M}_{b,halo}ζ to be independent of the mass Mhalo of the host DMH. Furthermore, it requires the fuelling efficiency ζ to have a strong redshift dependence (∝(1 + z)2.7 for M* = 1010.3 M⊙ over z = 0-0.13), even though no morphological transformation to spheroids can be invoked to explain this in our disc-dominated sample. The physical mechanisms capable of giving rise to such dependencies of ζ on Mhalo and z for discs are unclear.

  10. BOOSTING LY α   AND He ii λ 1640 LINE FLUXES FROM POPULATION III GALAXIES: STOCHASTIC IMF SAMPLING AND DEPARTURES FROM CASE-B

    International Nuclear Information System (INIS)

    Mas-Ribas, Lluís; Dijkstra, Mark; Forero-Romero, Jaime E.

    2016-01-01

    We revisit calculations of nebular hydrogen Ly α and He ii λ 1640 line strengths for Population III (Pop III) galaxies, undergoing continuous, and bursts of, star formation. We focus on initial mass functions (IMFs) motivated by recent theoretical studies, which generally span a lower range of stellar masses than earlier works. We also account for case-B departures and the stochastic sampling of the IMF. In agreement with previous work, we find that departures from case-B can enhance the Ly α flux by a factor of a few, but we argue that this enhancement is driven mainly by collisional excitation and ionization, and not due to photoionization from the n  = 2 state of atomic hydrogen. The increased sensitivity of the Ly α flux to the high-energy end of the galaxy spectrum makes it more subject to stochastic sampling of the IMF. The latter introduces a dispersion in the predicted nebular line fluxes around the deterministic value by as much as a factor of ∼4. In contrast, the stochastic sampling of the IMF has less impact on the emerging Lyman Werner photon flux. When case-B departures and stochasticity effects are combined, nebular line emission from Pop III galaxies can be up to one order of magnitude brighter than predicted by “standard” calculations that do not include these effects. This enhances the prospects for detection with future facilities such as the James Webb Space Telescope and large, ground-based telescopes.

  11. The dynamics of aggregates of galaxies as related to their main galaxies

    International Nuclear Information System (INIS)

    Einasto, J.; Joeveer, M.; Kaasik, A.; Vennik, J.

    1976-01-01

    The dynamics of the aggregates of galaxies is compared with the dynamics of their member galaxies. It is demonstrated that within a factor 1.5-2 the dispersion of relative line-of-sight velocities is constant from the nuclei of main galaxies to the periphery of an aggregate. This isothermality of aggregates of galaxies is observed in all aggregates studied so far, from poor groups to rich clusters. The fact that the velocity dispersion of stars in galaxies is equal to that of galaxies in aggregates applies only to main galaxies. The stars in all companion galaxies have a smaller velocity dispersion of stars. The dynamical evolution of both galaxies and aggregates of galaxies is very slow. Thus the above data suggest that galaxies and their aggregates were formed together. (orig.) [de

  12. EVOLUTION AND DISTRIBUTION OF MAGNETIC FIELDS FROM ACTIVE GALACTIC NUCLEI IN GALAXY CLUSTERS. II. THE EFFECTS OF CLUSTER SIZE AND DYNAMICAL STATE

    International Nuclear Information System (INIS)

    Xu Hao; Li Hui; Collins, David C.; Li, Shengtai; Norman, Michael L.

    2011-01-01

    Theory and simulations suggest that magnetic fields from radio jets and lobes powered by their central super massive black holes can be an important source of magnetic fields in the galaxy clusters. This is Paper II in a series of studies where we present self-consistent high-resolution adaptive mesh refinement cosmological magnetohydrodynamic simulations that simultaneously follow the formation of a galaxy cluster and evolution of magnetic fields ejected by an active galactic nucleus. We studied 12 different galaxy clusters with virial masses ranging from 1 x 10 14 to 2 x 10 15 M sun . In this work, we examine the effects of the mass and merger history on the final magnetic properties. We find that the evolution of magnetic fields is qualitatively similar to those of previous studies. In most clusters, the injected magnetic fields can be transported throughout the cluster and be further amplified by the intracluster medium (ICM) turbulence during the cluster formation process with hierarchical mergers, while the amplification history and the magnetic field distribution depend on the cluster formation and magnetism history. This can be very different for different clusters. The total magnetic energies in these clusters are between 4 x 10 57 and 10 61 erg, which is mainly decided by the cluster mass, scaling approximately with the square of the total mass. Dynamically older relaxed clusters usually have more magnetic fields in their ICM. The dynamically very young clusters may be magnetized weakly since there is not enough time for magnetic fields to be amplified.

  13. THE SL2S GALAXY-SCALE LENS SAMPLE. II. COSMIC EVOLUTION OF DARK AND LUMINOUS MASS IN EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Ruff, Andrea J.; Marshall, Philip J.; Treu, Tommaso; Auger, Matthew W.; Gavazzi, Raphael; Brault, Florence

    2011-01-01

    We present a joint gravitational lensing and stellar-dynamical analysis of 11 early-type galaxies (median deflector redshift z d = 0.5) from Strong Lenses in the Legacy Survey (SL2S). Using newly measured redshifts and stellar velocity dispersions from Keck spectroscopy with lens models from Paper I, we derive the total mass-density slope inside the Einstein radius for each of the 11 lenses. The average total density slope is found to be (γ') = 2.16 +0.09 -0.09 (ρ tot ∝r -γ ' ), with an intrinsic scatter of 0.25 +0.10 -0.07 . We also determine the dark matter fraction for each lens within half the effective radius, R eff /2, and find the average-projected dark matter mass fraction to be 0.42 +0.08 -0.08 with a scatter of 0.20 +0.09 -0.07 for a Salpeter initial mass function. By combining the SL2S results with those from the Sloan Lens ACS Survey (median z d = 0.2) and the Lenses Structure and Dynamics Survey (median z d = 0.8), we investigate cosmic evolution of γ' and find a mild trend ∂(γ')/∂z d = -0.25 +0.10 -0.12 . This suggests that the total density profile of massive galaxies has become slightly steeper over cosmic time. If this result is confirmed by larger samples, it would indicate that dissipative processes played some role in the growth of massive galaxies since z ∼ 1.

  14. Wolf-Rayet stars featured in emission-line galaxies

    International Nuclear Information System (INIS)

    Kunth, D.

    1982-01-01

    In the galaxy Tololo 3 (NGC 3125) recent observations by the author and Sargent (1981) have revealed the presence of an unusual strong and broad He II 4686 emission. The origin of this line together with some nitrogen lines (e.g. N V 4620 and N III 4638) is attributed to Wolf-Rayet stars, mostly of WN types. (Auth.)

  15. Gas Removal in the Ursa Minor Galaxy: Linking Hydrodynamics and Chemical Evolution Models

    Energy Technology Data Exchange (ETDEWEB)

    Caproni, Anderson; Lanfranchi, Gustavo Amaral; Baio, Gabriel Henrique Campos; Kowal, Grzegorz [Núcleo de Astrofísica Teórica, Universidade Cruzeiro do Sul, R. Galvão Bueno 868, Liberdade, 01506-000, São Paulo, SP (Brazil); Falceta-Gonçalves, Diego, E-mail: anderson.caproni@cruzeirodosul.edu.br [Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Bettio 1000, CEP 03828-000 São Paulo (Brazil)

    2017-04-01

    We present results from a non-cosmological, three-dimensional hydrodynamical simulation of the gas in the dwarf spheroidal galaxy Ursa Minor. Assuming an initial baryonic-to-dark-matter ratio derived from the cosmic microwave background radiation, we evolved the galactic gas distribution over 3 Gyr, taking into account the effects of the types Ia and II supernovae. For the first time, we used in our simulation the instantaneous supernovae rates derived from a chemical evolution model applied to spectroscopic observational data of Ursa Minor. We show that the amount of gas that is lost in this process is variable with time and radius, being the highest rates observed during the initial 600 Myr in our simulation. Our results indicate that types Ia and II supernovae must be essential drivers of the gas loss in Ursa Minor galaxy (and probably in other similar dwarf galaxies), but it is ultimately the combination of galactic winds powered by these supernovae and environmental effects (e.g., ram-pressure stripping) that results in the complete removal of the gas content.

  16. Inferring physical properties of galaxies from their emission-line spectra

    Science.gov (United States)

    Ucci, G.; Ferrara, A.; Gallerani, S.; Pallottini, A.

    2017-02-01

    We present a new approach based on Supervised Machine Learning algorithms to infer key physical properties of galaxies (density, metallicity, column density and ionization parameter) from their emission-line spectra. We introduce a numerical code (called GAME, GAlaxy Machine learning for Emission lines) implementing this method and test it extensively. GAME delivers excellent predictive performances, especially for estimates of metallicity and column densities. We compare GAME with the most widely used diagnostics (e.g. R23, [N II] λ6584/Hα indicators) showing that it provides much better accuracy and wider applicability range. GAME is particularly suitable for use in combination with Integral Field Unit spectroscopy, both for rest-frame optical/UV nebular lines and far-infrared/sub-millimeter lines arising from photodissociation regions. Finally, GAME can also be applied to the analysis of synthetic galaxy maps built from numerical simulations.

  17. Unbiased contaminant removal for 3D galaxy power spectrum measurements

    Science.gov (United States)

    Kalus, B.; Percival, W. J.; Bacon, D. J.; Samushia, L.

    2016-11-01

    We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (I) removing the contaminant signal, (II) estimating the uncontaminated cosmological power spectrum and (III) debiasing the resulting estimates. For (I), we show that removing the best-fitting contaminant (mode subtraction) and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (II), performing a quadratic maximum likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large N_mode^2 matrices (Nmode being the total number of modes), which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (II) as proposed by Feldman, Kaiser & Peacock (FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require any large matrix calculations. We argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants, is less severe than that commonly ignored due to the survey window.

  18. Rotation curve of our galaxy; how well do we know it

    Energy Technology Data Exchange (ETDEWEB)

    Pismis, P [Universidad Nacional Autonoma de Mexico, Mexico City. Inst. de Astronomia

    1981-01-01

    Following an historical sketch of the relevant circumstances leading to the formulation of the rotation of the galaxy, the differential rotation formulae are recalled. The necessity of obtaining an overall rotation curve at the advent of radioastronomy is stressed; only through the knowledge of such a curve can the kinematic distances of H I profiles, H II regions and molecular clouds be obtained. The existence of the deviations from a smooth rotation curve are pointed out; in particular it is shown that the curve exhibits ''waves'', a phenomenon at present known to be rather common in spiral galaxies. Maxima and minima correspond to arm and interarm regions, respectively. The interpretation of these waves as population effects suggested earlier by this author is emphasized once again. Recent observations of H II regions and CO clouds suggest that the sun is located close to the minimum of a wave. Another irregularity, the presumed difference in the north and south rotation curves, is also briefly discussed. Based on a plausible assumption that the spiral structure can be represented by a pair of symmetrically located logarithmic spirals, it is shown that if waves do indeed exist - irrespective of the cause of such waves - the rotation curve in our galaxy and in others will be a function of direction from the galactic center. Unlike external galaxies, from the location of the sun we are not able to obtain the rotation velocity in all directions. An average rotation curve where the waves are smoothed out can be obtained from the mean over directions within a central angle of 180/sup 0/. However, from our eccentric position in the galaxy we can obtain information on the rotation law at best within a central angle of 120/sup 0/. Finally, it is emphazied that the rotation curve discussed usually is that of the fastest rotating system, the population I, which contains not more than 10% of the total mass of the galaxy. The rotation curve is, therefore, not unique.

  19. Powerful Radio Galaxies with Simbol-X: the Nuclear Environment

    Science.gov (United States)

    Torresi, E.; Grandi, P.; Malaguti, G.; Palumbo, G. G. C.; Bianchin, V.

    2009-05-01

    Fanaroff & Riley type II radio galaxies (FRII) are complex objects. In particular FRII Narrow Line Radio Galaxies (NLRG), optically classified as High Excitation Galaxies (HEG) show X-ray spectra very similar to their radio-quiet counterparts, the Seyfert 2 galaxies. They show 2-10 keV continua heavily obscured (NH~1023-24 cm-2) and intense FeKα lines, typical cold matter reprocessing features. Moreover recent Chandra and XMM-Newton observations suggest that the soft X-ray emission of HEG and Seyfert 2 have a common origin from photoionized gas, reinforcing the idea that not only their nuclear engine but also the circumnuclear gas (at least the warm phase) are similar. On the contrary, our knowledge of NLRG HEG above 10 keV is very poor when compared to brighter Seyfert 2. As a consequence, the physical properties of the cold phase of the circumnuclear gas (possibly linked to a dusty torus) are largely unknown. Thanks to its high sensitivity up to 80 keV, Simbol-X will provide very accurate spectra and will allow a direct comparison between the NLRG and Seyfert 2 cold environments.

  20. Superclusters and galaxy formation

    International Nuclear Information System (INIS)

    Einasto, J.; Joeveer, M.; Saar, E.

    1979-01-01

    The spatial distribution of Galaxies and Galaxy congestions in the southern galactic hemisphere is studied. The rich galaxy congestions, containing many elliptic Galaxies and radiogalaxies, are linked with each other by chains of scanty congestions with moderate content of elliptic Galaxies and radiogalaxies. The flat formation, linking the density pikes and the intermediate chains, can reasonably be called supercongestion. In the central region of supercongestions there is a thin layer of Galaxies consisting of only spiral Galaxies. The neighbouring supercongestions touch each other, while the intersupercongestion space contains no Galaxy congestions and almost no Galaxies. It is shown that such a structure was, apparently, formed before the formation of Galaxies

  1. Separating intrinsic alignment and galaxy-galaxy lensing

    International Nuclear Information System (INIS)

    Blazek, Jonathan; Seljak, Uroš; Mandelbaum, Rachel; Nakajima, Reiko

    2012-01-01

    The coherent physical alignment of galaxies is an important systematic for gravitational lensing studies as well as a probe of the physical mechanisms involved in galaxy formation and evolution. We develop a formalism for treating this intrinsic alignment (IA) in the context of galaxy-galaxy lensing and present an improved method for measuring IA contamination, which can arise when sources physically associated with the lens are placed behind the lens due to photometric redshift scatter. We apply the technique to recent Sloan Digital Sky Survey (SDSS) measurements of Luminous Red Galaxy lenses and typical ( ∼ L * ) source galaxies with photometric redshifts selected from the SDSS imaging data. Compared to previous measurements, this method has the advantage of being fully self-consistent in its treatment of the IA and lensing signals, solving for the two simultaneously. We find an IA signal consistent with zero, placing tight constraints on both the magnitude of the IA effect and its potential contamination to the lensing signal. While these constraints depend on source selection and redshift quality, the method can be applied to any measurement that uses photometric redshifts. We obtain a model-independent upper-limit of roughly 10% IA contamination for projected separations of r p ≈ 0.1–10 h −1 Mpc. With more stringent photo-z cuts and reasonable assumptions about the physics of intrinsic alignments, this upper limit is reduced to 1–2%. These limits are well below the statistical error of the current lensing measurements. Our results suggest that IA will not present intractable challenges to the next generation of galaxy-galaxy lensing experiments, and the methods presented here should continue to aid in our understanding of alignment processes and in the removal of IA from the lensing signal

  2. THE LICK AGN MONITORING PROJECT: THE M BH-σ* RELATION FOR REVERBERATION-MAPPED ACTIVE GALAXIES

    International Nuclear Information System (INIS)

    Woo, Jong-Hak; Treu, Tommaso; Bennert, Vardha N.; Barth, Aaron J.; Walsh, Jonelle L.; Bentz, Misty C.; Wright, Shelley A.; Filippenko, Alexei V.; Li, Weidong; Martini, Paul; Canalizo, Gabriela; Gates, Elinor; Greene, Jenny; Malkan, Matthew A.; Stern, Daniel; Minezaki, Takeo

    2010-01-01

    To investigate the black hole mass versus stellar velocity dispersion (M BH -σ * ) relation of active galaxies, we measured the velocity dispersions of a sample of local Seyfert 1 galaxies, for which we have recently determined black hole masses using reverberation mapping. For most objects, stellar velocity dispersions were measured from high signal-to-noise ratio optical spectra centered on the Ca II triplet region (∼8500 A), obtained at the Keck, Palomar, and Lick Observatories. For two objects, in which the Ca II triplet region was contaminated by nuclear emission, the measurement was based on high-quality H-band spectra obtained with the OH-Suppressing Infrared Imaging Spectrograph at the Keck-II telescope. Combining our new measurements with data from the literature, we assemble a sample of 24 active galaxies with stellar velocity dispersions and reverberation-based black hole mass measurements in the range of black hole mass 10 6 BH /M sun 9 . We use this sample to obtain reverberation-mapping constraints on the slope and intrinsic scatter of the M BH -σ * relation of active galaxies. Assuming a constant virial coefficient f for the reverberation-mapping black hole masses, we find a slope β = 3.55 ± 0.60 and the intrinsic scatter σ int = 0.43 ± 0.08 dex in the relation log(M BH /M sun ) = α + β log(σ * /200 km s -1 ), which are consistent with those found for quiescent galaxies. We derive an updated value of the virial coefficient f by finding the value which places the reverberation masses in best agreement with the M BH -σ * relation of quiescent galaxies; using the quiescent M BH -σ * relation determined by Gueltekin et al., we find log f = 0.72 +0.09 -0.10 with an intrinsic scatter of 0.44 ± 0.07 dex. No strong correlations between f and parameters connected to the physics of accretion (such as the Eddington ratio or line-shape measurements) are found. The uncertainty of the virial coefficient remains one of the main sources of the

  3. DISCOVERY OF AN ULTRA-DIFFUSE GALAXY IN THE PISCES-PERSEUS SUPERCLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Delgado, David; Grebel, Eva K. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12–14, D-69120 Heidelberg (Germany); Läsker, Ronald [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Sharina, Margarita; Karachentsev, Igor D. [Special Astrophysical Observatory, Russian Academy of Sciences (Russian Federation); Toloba, Elisa; Romanowsky, Aaron J. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Fliri, Jürgen [Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38200 La Laguna, Tenerife (Spain); Beaton, Rachael [The Observatories of the Carnegie Institutions for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Valls-Gabaud, David [LERMA, CNRS UMR 8112, Observatoire de Paris, 61 Avenue de l’Observatoire, F-75014 Paris (France); Chonis, Taylor S. [Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712 (United States); Forbes, Duncan A. [Center for Astrophysics and Supercomputing, Swinburne University, Hawthorn VIC 3122 (Australia); Gallego-Laborda, J. [Fosca Nit Observatory, Montsec Astronomical Park, Ager (Spain); Teuwen, Karel [Remote Observatories Southern Alpes, Verclause (France); Gómez-Flechoso, M. A. [Departamento de Matemática Aplicada (Biomatemática), Universidad Complutense de Madrid, E-28040 Madrid (Spain); and others

    2016-04-15

    We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10.°4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (μ{sub V} = 24.8 mag arcsec{sup −2}), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (R{sub e}(V) = 12″) and proximity (15′) to the well-known dwarf spheroidal galaxy And II. Its red color (V − I = 1.0), shallow Sérsic index (n{sub V} = 0.68), and the absence of detectable Hα emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6 m telescope (V{sub h} = 5450 ± 40 km s{sup −1}) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (∼78 Mpc), DGSAT I would have an R{sub e} ∼ 4.7 kpc and M{sub V} ∼ −16.3. Its properties resemble those of the ultra-diffuse galaxies (UDGs) recently discovered in the Coma cluster. DGSAT I is the first case of these rare UDGs found in this galaxy cluster. Unlike the UDGs associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.

  4. A WARM MOLECULAR HYDROGEN TAIL DUE TO RAM-PRESSURE STRIPPING OF A CLUSTER GALAXY

    International Nuclear Information System (INIS)

    Sivanandam, Suresh; Rieke, Marcia J.; Rieke, George H.

    2010-01-01

    We have discovered a remarkable warm (130-160 K) molecular hydrogen tail with a H 2 mass of approximately 4 x 10 7 M sun extending 20 kpc from a cluster spiral galaxy, ESO 137-001, in Abell 3627. At least half of this gas is lost permanently to the intracluster medium, as the tail extends beyond the tidal radius of the galaxy. We also detect a hot (400-550 K) component in the tail that is approximately 1% of the mass. The large H 2 line to IR continuum luminosity ratio in the tail indicates that star formation is not a major excitation source and that the gas is possibly shock-heated. This discovery confirms that the galaxy is currently undergoing ram-pressure stripping, as also indicated by its previously discovered X-ray and Hα tails. We estimate that the galaxy is losing its warm H 2 gas at a rate of ∼2-3 M sun yr -1 . The true mass-loss rate is likely higher if we account for cold molecular gas and atomic gas. We predict that the galaxy will lose most of its gas in a single pass through the core and place a strong upper limit on the ram-pressure timescale of 1 Gyr. We also study the star-forming properties of the galaxy and its tail. We identify most of the previously discovered external Hα sources within the tail in our 8 μm data but not in our 3.6 μm data; IRS spectroscopy of the region containing these Hα sources also reveals aromatic features typically associated with star formation. From the positions of these H II regions, it appears that star formation is not occurring throughout the molecular hydrogen tail but only immediately downstream of the galaxy. Some of these H II regions lie outside the tidal radius of the galaxy, indicating that ram-pressure stripping can be a source of intracluster stars.

  5. The hELENa project - II. Abundance distribution trends of early-type galaxies: from dwarfs to giants

    Science.gov (United States)

    Sybilska, A.; Kuntschner, H.; van de Ven, G.; Vazdekis, A.; Falcón-Barroso, J.; Peletier, R. F.; Lisker, T.

    2018-06-01

    In this second paper of The role of Environment in shaping Low-mass Early-type Nearby galaxies (hELENa) series we study [Mg/Fe] abundance distribution trends of early-type galaxies (ETGs) observed with the Spectrographic Areal Unit for Research on Optical Nebulae integral field unit, spanning a wide range in mass and local environment densities: 20 low-mass early types (dEs) of Sybilska et al. and 258 massive early types (ETGs) of the ATLAS3D project, all homogeneously reduced and analysed. We show that the [Mg/Fe] ratios scale with velocity dispersion (σ) at fixed [Fe/H] and that they evolve with [Fe/H] along similar paths for all early types, grouped in bins of increasing local and global σ, as well as the second velocity moment Vrms, indicating a common inside-out formation pattern. We then place our dEs on the [Mg/Fe] versus [Fe/H] diagram of Local Group galaxies and show that dEs occupy the same region and show a similar trend line slope in the diagram as the high-metallicity stars of the Milky Way and the Large Magellanic Cloud. This finding extends the similar trend found for dwarf spheroidal versus dwarf irregular galaxies and supports the notion that dEs have evolved from late-type galaxies that have lost their gas at a point of their evolution, which likely coincided with them entering denser environments.

  6. The effect of stellar evolution uncertainties on the rest-frame ultraviolet stellar lines of C IV and He II in high-redshift Lyman-break galaxies

    Science.gov (United States)

    Eldridge, John J.; Stanway, Elizabeth R.

    2012-01-01

    Young, massive stars dominate the rest-frame ultraviolet (UV) spectra of star-forming galaxies. At high redshifts (z > 2), these rest-frame UV features are shifted into the observed-frame optical and a combination of gravitational lensing, deep spectroscopy and spectral stacking analysis allows the stellar population characteristics of these sources to be investigated. We use our stellar population synthesis code Binary Population and Spectral Synthesis (BPASS) to fit two strong rest-frame UV spectral features in published Lyman-break galaxy spectra, taking into account the effects of binary evolution on the stellar spectrum. In particular, we consider the effects of quasi-homogeneous evolution (arising from the rotational mixing of rapidly rotating stars), metallicity and the relative abundance of carbon and oxygen on the observed strengths of He IIλ1640 Å and C IVλ1548, 1551 Å spectral lines. We find that Lyman-break galaxy spectra at z ˜ 2-3 are best fitted with moderately sub-solar metallicities, and with a depleted carbon-to-oxygen ratio. We also find that the spectra of the lowest metallicity sources are best fitted with model spectra in which the He II emission line is boosted by the inclusion of the effect of massive stars being spun-up during binary mass transfer so these rapidly rotating stars experience quasi-homogeneous evolution.

  7. H II region in NGC 6744: Spectrophotometry and chemical abundances

    International Nuclear Information System (INIS)

    Talent, D.L.

    1982-01-01

    Spectrophotometry of emission lines in the lambdalambda3700--6800 spectral range is presented for An H II region in an outer arm of NGC6744, a southern hemisphere galaxy of type SAB(r)bc II. The electron temperature, derived from the [O III] lines and assuming N/sub e/ = 100 cm -3 , was found to be 9,630 +- 450 K. Ionic abundances, derived in the usual fashion from the measured line strengths, were corrected to total relative number abundances by application of the standard ionization correction factor (ICF) scheme and by comparison to models. The derived abundances, relative to log Hequivalent12.00, are log He = 10.96 +- 0.06, log N = 7.34 +- 0.26, log O log O = 8.44 +- 0.10, log Ne = 7.80 +- 0.16, and log S = 6.75 +- 0.28. The NGC 6744 H II region abundances, and various ratios, are compared to similar data for H II regions in the SMC, LMC, and the Perseus arm of the Galaxy,. From the comparison it is suggested that the histories of nucleosynthesis in the outer regions of NGC 6744 and the Galaxy could have been quite similar

  8. Spitzer Observations of M33 & M83 and the Hot Star, Hii Region Connection

    Science.gov (United States)

    Rubin, R.; Simpson, J.; Colgan, S.; Dufour, R.; Citron, R.; Ray, K.; Erickson, E.; Haas, M.; Pauldrach, A.

    2007-05-01

    H II regions play a crucial role in the measurement of current interstellar abundances. They also serve as laboratories for atomic physics and provide fundamental data about heavy element abundances that serve to constrain models of galactic chemical evolution. We observed emission lines of [S IV] 10.5, H (7-6) 12.4, [Ne II] 12.8, [Ne III] 15.6, & [S III] 18.7 micron cospatially with the Spitzer Space Telescope using the Infrared Spectrograph (IRS) in short-high mode (SH). Here we concentrate on the galaxy M33 and compare the results with our earlier similar study of M83. In each of these substantially face-on spirals, we observed ˜25 H II regions, covering a full range of galactocentric radii (RG). For most of the M33 H II regions, we were able to measure the H (7-6) line while none were detectable in M83. This limited our M83 study to a determination of the Ne++/Ne+, /, and S3+/S++ abundance ratios vs. RG. Angular brackets denote fractional ionizations. As well as having the addition of fluxes for the H(7-6) line, the M33 H II regions are generally of much higher ionization than those in M83, resulting in larger Ne++/Ne+ and S3+/ S++ abundance ratios. For M33, in addition to what we derived for those nebulae in M83, we are also able to derive Ne/H, S/H and Ne/S vs. RG. Important advantages compared with prior optical studies are: 1) the IR lines have a weak and similar electron temperature (Te) dependence while optical lines vary exponentially with Te and 2) the IR lines suffer far less from interstellar extinction. Additionally, these data may be used as constraints on the ionizing spectral energy distribution for the stars exciting these nebulae by comparing the above ionic ratios with predictions using stellar atmosphere models from several different non-LTE model sets. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407

  9. COMBINED EFFECTS OF GALAXY INTERACTIONS AND LARGE-SCALE ENVIRONMENT ON GALAXY PROPERTIES

    International Nuclear Information System (INIS)

    Park, Changbom; Choi, Yun-Young

    2009-01-01

    We inspect the coupled dependence of physical parameters of the Sloan Digital Sky Survey galaxies on the small-scale (distance to and morphology of the nearest neighbor galaxy) and the large-scale (background density smoothed over 20 nearby galaxies) environments. The impacts of interaction on galaxy properties are detected at least out to the neighbor separation corresponding to the virial radius of galaxies, which is typically between 200 and 400 h -1 kpc for the galaxies in our sample. To detect these long-range interaction effects, it is crucial to divide galaxy interactions into four cases dividing the morphology of target and neighbor galaxies into early and late types. We show that there are two characteristic neighbor-separation scales where the galaxy interactions cause abrupt changes in the properties of galaxies. The first scale is the virial radius of the nearest neighbor galaxy r vir,nei . Many physical parameters start to deviate from those of extremely isolated galaxies at the projected neighbor separation r p of about r vir,nei . The second scale is at r p ∼ 0.05r vir,nei = 10-20 h -1 kpc, and is the scale at which the galaxies in pairs start to merge. We find that late-type neighbors enhance the star formation activity of galaxies while early-type neighbors reduce it, and that these effects occur within r vir,nei . The hot halo gas and cold disk gas must be participating in the interactions at separations less than the virial radius of the galaxy plus dark halo system. Our results also show that the role of the large-scale density in determining galaxy properties is minimal once luminosity and morphology are fixed. We propose that the weak residual dependence of galaxy properties on the large-scale density is due to the dependence of the halo gas property on the large-scale density.

  10. Joint analysis of galaxy-galaxy lensing and galaxy clustering: Methodology and forecasts for Dark Energy Survey

    International Nuclear Information System (INIS)

    Park, Y.; Krause, E.; Dodelson, S.; Jain, B.; Amara, A.

    2016-01-01

    Here, the joint analysis of galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth function of large-scale structure. Anticipating a near future application of this analysis to Dark Energy Survey (DES) measurements of galaxy positions and shapes, we develop a practical approach to modeling the assumptions and systematic effects affecting the joint analysis of small-scale galaxy-galaxy lensing and large-scale galaxy clustering. Introducing parameters that characterize the halo occupation distribution (HOD), photometric redshift uncertainties, and shear measurement errors, we study how external priors on different subsets of these parameters affect our growth constraints. Degeneracies within the HOD model, as well as between the HOD and the growth function, are identified as the dominant source of complication, with other systematic effects being subdominant. The impact of HOD parameters and their degeneracies necessitate the detailed joint modeling of the galaxy sample that we employ. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the Universe, conservatively/optimistically constraining the growth function to 7.9%/4.8% with its first-year data that cover over 1000 square degrees, and to 3.9%/2.3% with its full five-year data that will survey 5000 square degrees, including both statistical and systematic uncertainties.

  11. SDSS IV MaNGA - Properties of AGN Host Galaxies

    Science.gov (United States)

    Sánchez, S. F.; Avila-Reese, V.; Hernandez-Toledo, H.; Cortes-Suárez, E.; Rodríguez-Puebla, A.; Ibarra-Medel, H.; Cano-Díaz, M.; Barrera-Ballesteros, J. K.; Negrete, C. A.; Calette, A. R.; de Lorenzo-Cáceres, A.; Ortega-Minakata, R. A.; Aquino, E.; Valenzuela, O.; Clemente, J. C.; Storchi-Bergmann, T.; Riffel, R.; Schimoia, J.; Riffel, R. A.; Rembold, S. B.; Brownstein, J. R.; Pan, K.; Yates, R.; Mallmann, N.; Bitsakis, T.

    2018-04-01

    We present the characterization of the main properties of a sample of 98 AGN host galaxies, both type-II and type-I, in comparison with those of ≍2700 non-active galaxies observed by the MaNGA survey. We found that AGN hosts are morphologically early-type or early-spirals. AGN hosts are, on average, more massive, more compact, more centrally peaked and more pressure-supported systems. They are located in the intermediate/transition region between starforming and non-star-forming galaxies (i.e., the so-called green valley). We consider that they are in the process of halting/quenching the star formation. The analysis of the radial distributions of different properties shows that the quenching happens from inside-out involving both a decrease of the effciency of the star formation and a deficit of molecular gas. The data-products of the current analysis are distributed as a Value Added Catalog within the SDSS-DR14.

  12. CEPHEID VARIABLES IN THE MASER-HOST GALAXY NGC 4258

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Samantha L.; Macri, Lucas M., E-mail: lmacri@tamu.edu [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States)

    2015-06-15

    We present results of a ground-based survey for Cepheid variables in NGC 4258. This galaxy plays a key role in the Extragalactic Distance Scale due to its very precise and accurate distance determination via very long baseline interferometry observations of water masers. We imaged two fields within this galaxy using the Gemini North telescope and the Gemini Multi-Object Spectrograph, obtaining 16 epochs of data in the Sloan Digital Sky Survey gri bands over 4 yr. We carried out point-spread function photometry and detected 94 Cepheids with periods between 7 and 127 days, as well as an additional 215 variables which may be Cepheids or Population II pulsators. We used the Cepheid sample to test the absolute calibration of theoretical gri Period–Luminosity relations and found good agreement with the maser distance to this galaxy. The expected data products from the Large Synoptic Survey Telescope should enable Cepheid searches out to at least 10 Mpc.

  13. Spectroscopy of the galaxy components of N and Seyfert galaxies

    International Nuclear Information System (INIS)

    Boroson, T.A.; Oke, J.B.; Palomar Observatory, Pasadena, CA)

    1987-01-01

    Nuclear and off-nuclear spectra of nine active galaxies are presented. The sample consists of four Seyfert galaxies, two N galaxies, one Seyfert radio galaxy, and one liner/Seyfert 2 galaxy. All of the objects show continuum emission off the nucleus. Four clearly show absorption features from a stellar population. Velocities have been measured for the off-nuclear emission and absorption lines. In the case of I Zw 1, the absorption-line velocities are inconsistent with 21-cm H I measurements of this object. 26 references

  14. Luminosity distribution in galaxies. I. The elliptical galaxy NGC 3379 as a luminosity distribution standard

    International Nuclear Information System (INIS)

    de Vaucouleurs, G.; Capaccioli, M.

    1979-01-01

    A standard mean luminosity profile in the B band of the El galaxy NGC 3379 along its east-west x-axis is derived from four sets of medium- and low-resolution photographic and photoelectric McDonald data. The 154 mean points cover a range in excess of 11 mag down to μ/sub B/=27.8 mag arcsec -2 (x=7'.3), with possible detection out to x=16'.3 (μ/sub B/approx. =30.9).The profile is presented within +- 0.08 mag at all x>10'' by μ 1 =14.076+3.0083 x/sup 1/4/ (x in arcsec). Near the center the galaxy is brighter than μ 1 by up to 0.35 mag; the excess can be represented by a Gaussian core μ/sub II/=18.565+0.03965 r 2 (r in arcsec) contributing 19.8% of the integrated magnitude B=11.97 within r* =12'' and 4.0% of the total magnitude B/sub T/=10.225 of the galaxy.This two-component model convolved by the appropriate point spread function represents the data within a standard deviation of 0.04 mag over the whole range. Other analytical formulae give generally poorer fits. There is no evidence for a tidal cutoff or a tidal extension.The integrated magnitudes derived from the model agree with aperture photometry (47 values) within 0.05 mag

  15. POX 52: A Dwarf Seyfert 1 Galaxy with an Intermediate-Mass Black Hole

    Science.gov (United States)

    Barth, Aaron J.; Ho, Luis C.; Rutledge, Robert E.; Sargent, Wallace L. W.

    2004-05-01

    We describe new optical images and spectra of POX 52, a dwarf galaxy with an active nucleus that was originally detected in the POX objective-prism survey. While POX 52 was originally thought to be a Seyfert 2 galaxy, the new data reveal an emission-line spectrum very similar to that of the dwarf Seyfert 1 galaxy NGC 4395, with broad components to the permitted line profiles, and we classify POX 52 as a Seyfert 1 galaxy. The host galaxy appears to be a dwarf elliptical, and its brightness profile is best fit by a Sérsic model with an index of 3.6+/-0.2 and a total magnitude of MV=-17.6. Applying mass-luminosity-line width scaling relations to estimate the black hole mass from the broad Hβ line width and nonstellar continuum luminosity, we find MBH~1.6×105Msolar. The stellar velocity dispersion in the host galaxy, measured from the Ca II λ8498, 8542 lines, is 36+/-5 km s-1, also suggestive of a black hole mass of order 105Msolar. Further searches for active nuclei in dwarf galaxies can provide unique constraints on the demographics of black holes in the mass range below 106Msolar.

  16. SYSTEMATIC SEARCH FOR EXTREMELY METAL-POOR GALAXIES IN THE SLOAN DIGITAL SKY SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Luis, A. B.; Sanchez Almeida, J.; Aguerri, J. A. L.; Munoz-Tunon, C., E-mail: abml@iac.es, E-mail: jos@iac.es, E-mail: cmt@iac.es, E-mail: jalfonso@iac.es [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)

    2011-12-10

    We carry out a systematic search for extremely metal-poor (XMP) galaxies in the spectroscopic sample of Sloan Digital Sky Survey (SDSS) data release 7 (DR7). The XMP candidates are found by classifying all the galaxies according to the form of their spectra in a region 80 A wide around H{alpha}. Due to the data size, the method requires an automatic classification algorithm. We use k-means. Our systematic search renders 32 galaxies having negligible [N II] lines, as expected in XMP galaxy spectra. Twenty-one of them have been previously identified as XMP galaxies in the literature-the remaining 11 are new. This was established after a thorough bibliographic search that yielded only some 130 galaxies known to have an oxygen metallicity 10 times smaller than the Sun (explicitly, with 12 + log (O/H) {<=} 7.65). XMP galaxies are rare; they represent 0.01% of the galaxies with emission lines in SDSS/DR7. Although the final metallicity estimate of all candidates remains pending, strong-line empirical calibrations indicate a metallicity about one-tenth solar, with the oxygen metallicity of the 21 known targets being 12 + log (O/H) {approx_equal} 7.61 {+-} 0.19. Since the SDSS catalog is limited in apparent magnitude, we have been able to estimate the volume number density of XMP galaxies in the local universe, which turns out to be (1.32 {+-} 0.23) Multiplication-Sign 10{sup -4} Mpc{sup -3}. The XMP galaxies constitute 0.1% of the galaxies in the local volume, or {approx}0.2% considering only emission-line galaxies. All but four of our candidates are blue compact dwarf galaxies, and 24 of them have either cometary shape or are formed by chained knots.

  17. VizieR Online Data Catalog: Clusters of galaxies in SDSS-III (Wen+, 2012)

    Science.gov (United States)

    Wen, Z. L.; Han, J. L.; Liu, F. S.

    2012-06-01

    Wen et al. (2009, Cat. J/ApJS/183/197) identified 39668 galaxy clusters from the SDSS DR6 by the discrimination of member galaxies of clusters using photometric redshifts of galaxies. Wen & Han (2011ApJ...734...68W) improved the method and successfully identified the high-redshift clusters from the deep fields of the Canada-France-Hawaii Telescope (CFHT) Wide survey, the CHFT Deep survey, the Cosmic Evolution Survey, and the Spitzer Wide-area InfraRed Extragalactic survey. Here, we follow and improve the algorithm to identify clusters from SDSS-III (SDSS Data Release 8; Aihara et al. 2011ApJS..193...29A, see Cat. II/306). (1 data file).

  18. THE STAR-FORMATION-RATE-DENSITY RELATION AT 0.6 < z < 0.9 AND THE ROLE OF STAR-FORMING GALAXIES

    International Nuclear Information System (INIS)

    Patel, Shannon G.; Holden, Bradford P.; Illingworth, Garth D.; Kelson, Daniel D.; Franx, Marijn

    2011-01-01

    We study the star formation rates (SFRs) of galaxies as a function of local galaxy density at 0.6 z /(1 + z) ∼ 1% for galaxies with z AB 1.8 x 10 10 M sun (log M/M sun >10.25) to conduct our main analysis. With three different SFR indicators, (1) Spitzer MIPS 24 μm imaging, (2) spectral energy distribution (SED) fitting, and (3) [O II]λ3727 emission, we find the median specific SFR (SSFR) and SFR to decline from the low-density field to the cores of groups and a rich cluster. For the SED- and [O II]-based SFRs, the decline in SSFR is roughly an order of magnitude while for the MIPS-based SFRs, the decline is a factor of ∼4. We find approximately the same magnitude of decline in SSFR even after removing the sample of galaxies near the cluster. Galaxies in groups and a cluster at these redshifts therefore have lower star formation (SF) activity than galaxies in the field, as is the case at z ∼ 0. We investigated whether the decline in SFR with increasing density is caused by a change in the proportion of quiescent and star-forming galaxies (SFGs) or by a decline in the SFRs of SFGs. Using the rest-frame U - V and V - J colors to distinguish quiescent galaxies from SFGs (including both unattenuated blue galaxies and reddened ones), we find that the fraction of quiescent galaxies increases from ∼32% to 79% from low to high density. In addition, we find the SSFRs of SFGs, selected based on U - V and V - J colors, to decline with increasing density by factors of ∼5-6 for the SED- and [O II]-based SFRs. The MIPS-based SSFRs for SFGs decline with a shallower slope. The declining SFRs of SFGs with density are paralleled by a decline in the median A V , providing indirect evidence that the cold gas content that fuels future SF is diminished in higher density environments. The order of magnitude decline in the SSFR-density relation at 0.6 < z < 0.9 is therefore driven by both a combination of declining SFRs of SFGs as well as a changing mix of SFGs and quiescent

  19. Gamma-ray bursts, QSOs and active galaxies.

    Science.gov (United States)

    Burbidge, Geoffrey

    2007-05-15

    The similarity of the absorption spectra of gamma-ray burst (GRB) sources or afterglows with the absorption spectra of quasars (QSOs) suggests that QSOs and GRB sources are very closely related. Since most people believe that the redshifts of QSOs are of cosmological origin, it is natural to assume that GRBs or their afterglows also have cosmological redshifts. For some years a few of us have argued that there is much optical evidence suggesting a very different model for QSOs, in which their redshifts have a non-cosmological origin, and are ejected from low-redshift active galaxies. In this paper I extend these ideas to GRBs. In 2003, Burbidge (Burbidge 2003 Astrophys. J. 183, 112-120) showed that the redshift periodicity in the spectra of QSOs appears in the redshift of GRBs. This in turn means that both the QSOs and the GRB sources are similar objects ejected from comparatively low-redshift active galaxies. It is now clear that many of the GRBs of low redshift do appear in, or very near, active galaxies.A new and powerful result supporting this hypothesis has been produced by Prochter et al. (Prochter et al. 2006 Astrophys. J. Lett. 648, L93-L96). They show that in a survey for strong MgII absorption systems along the sightlines to long-duration GRBs, nearly every sightline shows at least one absorber. If the absorbers are intervening clouds or galaxies, only a small fraction should show absorption of this kind. The number found by Prochter et al. is four times higher than that normally found for the MgII absorption spectra of QSOs. They believe that this result is inconsistent with the intervening hypothesis and would require a statistical fluctuation greater than 99.1% probability. This is what we expect if the absorption is intrinsic to the GRBs and the redshifts are not associated with their distances. In this case, the absorption must be associated with gas ejected from the QSO. This in turn implies that the GRBs actually originate in comparatively low

  20. CONTINUUM OBSERVATIONS AT 350 MICRONS OF HIGH-REDSHIFT MOLECULAR EMISSION LINE GALAXIES

    International Nuclear Information System (INIS)

    Wu Jingwen; Evans, Neal J.; Dunham, Michael M.; Vanden Bout, Paul A.

    2009-01-01

    We report observations of 15 high-redshift (z = 1 - 5) galaxies at 350 μm using the Caltech Submillimeter Observatory and Submillimeter High Angular Resolution Camera II array detector. Emission was detected from eight galaxies, for which far-infrared luminosities, star formation rates (SFRs), total dust masses, and minimum source size estimates are derived. These galaxies have SFRs and star formation efficiencies comparable to other high-redshift molecular emission line galaxies. The results are used to test the idea that star formation in these galaxies occurs in a large number of basic units, the units being similar to star-forming clumps in the Milky Way. The luminosity of these extreme galaxies can be reproduced in a simple model with (0.9-30)x10 6 dense clumps, each with a luminosity of 5 x 10 5 L sun , the mean value for such clumps in the Milky Way. Radiative transfer models of such clumps can provide reasonable matches to the overall spectral energy distributions (SEDs) of the galaxies. They indicate that the individual clumps are quite opaque in the far-infrared. Luminosity-to-mass ratios vary over two orders of magnitude, correlating strongly with the dust temperature derived from simple fits to the SED. The gas masses derived from the dust modeling are in remarkable agreement with those from CO luminosities, suggesting that the assumptions going into both calculations are reasonable.

  1. Origins of ultra-diffuse galaxies in the Coma cluster - II. Constraints from their stellar populations

    Science.gov (United States)

    Ferré-Mateu, Anna; Alabi, Adebusola; Forbes, Duncan A.; Romanowsky, Aaron J.; Brodie, Jean; Pandya, Viraj; Martín-Navarro, Ignacio; Bellstedt, Sabine; Wasserman, Asher; Stone, Maria B.; Okabe, Nobuhiro

    2018-06-01

    In this second paper of the series we study, with new Keck/DEIMOS spectra, the stellar populations of seven spectroscopically confirmed ultra-diffuse galaxies (UDGs) in the Coma cluster. We find intermediate to old ages (˜ 7 Gyr), low metallicities ([Z/H]˜ - 0.7 dex) and mostly super-solar abundance patterns ([Mg/Fe] ˜ 0.13 dex). These properties are similar to those of low-luminosity (dwarf) galaxies inhabiting the same area in the cluster and are mostly consistent with being the continuity of the stellar mass scaling relations of more massive galaxies. These UDGs' star formation histories imply a relatively recent infall into the Coma cluster, consistent with the theoretical predictions for a dwarf-like origin. However, considering the scatter in the resulting properties and including other UDGs in Coma, together with the results from the velocity phase-space study of the Paper I in this series, a mixed-bag of origins is needed to explain the nature of all UDGs. Our results thus reinforce a scenario in which many UDGs are field dwarfs that become quenched through their later infall onto cluster environments, whereas some UDGs could be be genuine primordial galaxies that failed to develop due to an early quenching phase. The unknown proportion of dwarf-like to primordial-like UDGs leaves the enigma of the nature of UDGs still open.

  2. Galaxy and Mass Assembly (GAMA): small-scale anisotropic galaxy clustering and the pairwise velocity dispersion of galaxies

    Science.gov (United States)

    Loveday, J.; Christodoulou, L.; Norberg, P.; Peacock, J. A.; Baldry, I. K.; Bland-Hawthorn, J.; Brown, M. J. I.; Colless, M.; Driver, S. P.; Holwerda, B. W.; Hopkins, A. M.; Kafle, P. R.; Liske, J.; Lopez-Sanchez, A. R.; Taylor, E. N.

    2018-03-01

    The galaxy pairwise velocity dispersion (PVD) can provide important tests of non-standard gravity and galaxy formation models. We describe measurements of the PVD of galaxies in the Galaxy and Mass Assembly (GAMA) survey as a function of projected separation and galaxy luminosity. Due to the faint magnitude limit (r PVD to smaller scales (r⊥ = 0.01 h - 1 Mpc) than previous work. The measured PVD at projected separations r⊥ ≲ 1 h - 1 Mpc increases near monotonically with increasing luminosity from σ12 ≈ 200 km s - 1 at Mr = -17 mag to σ12 ≈ 600 km s - 1 at Mr ≈ -22 mag. Analysis of the Gonzalez-Perez et al. (2014) GALFORM semi-analytic model yields no such trend of PVD with luminosity: the model overpredicts the PVD for faint galaxies. This is most likely a result of the model placing too many low-luminosity galaxies in massive haloes.

  3. Formation of galaxies

    International Nuclear Information System (INIS)

    Szalay, A.S.

    1984-12-01

    The present theories of galaxy formation are reviewed. The relation between peculiar velocities and the correlation function of galaxies points to the possibility that galaxies do not form uniformly everywhere. Scale invariant properties of the cluster-cluster correlations are discussed. Comparing the correlation functions in a dimensionless way, galaxies appear to be stronger clustered, in contrast with the comparison of the dimensional amplitudes of the correlation functions. Theoretical implications of several observations as Lyman-α clouds, correlations of faint galaxies are discussed. None of the present theories of galaxy formation can account for all facts in a natural way. 29 references

  4. The intrinsic shape of galaxies in SDSS/Galaxy Zoo

    Science.gov (United States)

    Rodríguez, Silvio; Padilla, Nelson D.

    2013-09-01

    By modelling the axis ratio distribution of Sloan Digital Sky Survey (SDSS) Data Release 8 galaxies, we find the intrinsic 3D shapes of spirals and ellipticals. We use morphological information from the Galaxy Zoo project and assume a non-parametric distribution intrinsic of shapes, while taking into account dust extinction. We measure the dust extinction of the full sample of spiral galaxies and find a smaller value than previous estimations, with an edge-on extinction of E_0 = 0.284^{+0.015}_{-0.026} in the SDSS r band. We also find that the distribution of minor to major axis ratio has a mean value of 0.267 ± 0.009, slightly larger than previous estimates mainly due to the lower extinction used; the same affects the circularity of galactic discs, which are found to be less round in shape than in previous studies, with a mean ellipticity of 0.215 ± 0.013. For elliptical galaxies, we find that the minor to major axis ratio, with a mean value of 0.584 ± 0.006, is larger than previous estimations due to the removal of spiral interlopers present in samples with morphological information from photometric profiles. These interlopers are removed when selecting ellipticals using Galaxy Zoo data. We find that the intrinsic shapes of galaxies and their dust extinction vary with absolute magnitude, colour and physical size. We find that bright elliptical galaxies are more spherical than faint ones, a trend that is also present with galaxy size, and that there is no dependence of elliptical galaxy shape with colour. For spiral galaxies, we find that the reddest ones have higher dust extinction as expected, due to the fact that this reddening is mainly due to dust. We also find that the thickness of discs increases with luminosity and size, and that brighter, smaller and redder galaxies have less round discs.

  5. CHANDRA ACIS SURVEY OF X-RAY POINT SOURCES IN NEARBY GALAXIES. II. X-RAY LUMINOSITY FUNCTIONS AND ULTRALUMINOUS X-RAY SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Song; Qiu, Yanli; Liu, Jifeng [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Bregman, Joel N., E-mail: songw@bao.ac.cn, E-mail: jfliu@bao.ac.cn [University of Michigan, Ann Arbor, MI 48109 (United States)

    2016-09-20

    Based on the recently completed Chandra /ACIS survey of X-ray point sources in nearby galaxies, we study the X-ray luminosity functions (XLFs) for X-ray point sources in different types of galaxies and the statistical properties of ultraluminous X-ray sources (ULXs). Uniform procedures are developed to compute the detection threshold, to estimate the foreground/background contamination, and to calculate the XLFs for individual galaxies and groups of galaxies, resulting in an XLF library of 343 galaxies of different types. With the large number of surveyed galaxies, we have studied the XLFs and ULX properties across different host galaxy types, and confirm with good statistics that the XLF slope flattens from lenticular ( α ∼ 1.50 ± 0.07) to elliptical (∼1.21 ± 0.02), to spirals (∼0.80 ± 0.02), to peculiars (∼0.55 ± 0.30), and to irregulars (∼0.26 ± 0.10). The XLF break dividing the neutron star and black hole binaries is also confirmed, albeit at quite different break luminosities for different types of galaxies. A radial dependency is found for ellipticals, with a flatter XLF slope for sources located between D {sub 25} and 2 D {sub 25}, suggesting the XLF slopes in the outer region of early-type galaxies are dominated by low-mass X-ray binaries in globular clusters. This study shows that the ULX rate in early-type galaxies is 0.24 ± 0.05 ULXs per surveyed galaxy, on a 5 σ confidence level. The XLF for ULXs in late-type galaxies extends smoothly until it drops abruptly around 4 × 10{sup 40} erg s{sup −1}, and this break may suggest a mild boundary between the stellar black hole population possibly including 30 M {sub ⊙} black holes with super-Eddington radiation and intermediate mass black holes.

  6. Galaxy-galaxy weak gravitational lensing in f(R) gravity

    Science.gov (United States)

    Li, Baojiu; Shirasaki, Masato

    2018-03-01

    We present an analysis of galaxy-galaxy weak gravitational lensing (GGL) in chameleon f(R) gravity - a leading candidate of non-standard gravity models. For the analysis, we have created mock galaxy catalogues based on dark matter haloes from two sets of numerical simulations, using a halo occupation distribution (HOD) prescription which allows a redshift dependence of galaxy number density. To make a fairer comparison between the f(R) and Λ cold dark matter (ΛCDM) models, their HOD parameters are tuned so that the galaxy two-point correlation functions in real space (and therefore the projected two-point correlation functions) match. While the f(R) model predicts an enhancement of the convergence power spectrum by up to ˜ 30 per cent compared to the standard ΛCDM model with the same parameters, the maximum enhancement of GGL is only half as large and less than 5 per cent on separations above ˜1-2 h-1 Mpc, because the latter is a cross-correlation of shear (or matter, which is more strongly affected by modified gravity) and galaxy (which is weakly affected given the good match between galaxy autocorrelations in the two models) fields. We also study the possibility of reconstructing the matter power spectrum by combination of GGL and galaxy clustering in f(R) gravity. We find that the galaxy-matter cross-correlation coefficient remains at unity down to ˜2-3 h-1 Mpc at relevant redshifts even in f(R) gravity, indicating joint analysis of GGL and galaxy clustering can be a powerful probe of matter density fluctuations in chameleon gravity. The scale dependence of the model differences in their predictions of GGL can potentially allows us to break the degeneracy between f(R) gravity and other cosmological parameters such as Ωm and σ8.

  7. THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE 'GREEN PEA' GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Jaskot, A. E.; Oey, M. S. [Department of Astronomy, University of Michigan, 830 Dennison Building, Ann Arbor, MI 48109 (United States)

    2013-04-01

    Although Lyman-continuum (LyC) radiation from star-forming galaxies likely drove the reionization of the universe, observations of star-forming galaxies at low redshift generally indicate low LyC escape fractions. However, the extreme [O III]/[O II] ratios of the z = 0.1-0.3 Green Pea galaxies may be due to high escape fractions of ionizing radiation. To analyze the LyC optical depths and ionizing sources of these rare, compact starbursts, we compare nebular photoionization and stellar population models with observed emission lines in the Peas' Sloan Digital Sky Survey (SDSS) spectra. We focus on the six most extreme Green Peas, the galaxies with the highest [O III]/[O II] ratios and the best candidates for escaping ionizing radiation. The Balmer line equivalent widths and He I {lambda}3819 emission in the extreme Peas support young ages of 3-5 Myr, and He II {lambda}4686 emission in five extreme Peas signals the presence of hard ionizing sources. Ionization by active galactic nuclei or high-mass X-ray binaries is inconsistent with the Peas' line ratios and ages. Although stacked spectra reveal no Wolf-Rayet (WR) features, we tentatively detect WR features in the SDSS spectra of three extreme Peas. Based on the Peas' ages and line ratios, we find that WR stars, chemically homogeneous O stars, or shocks could produce the observed He II emission. If hot stars are responsible, then the Peas' optical depths are ambiguous. However, accounting for emission from shocks lowers the inferred optical depth and suggests that the Peas may be optically thin. The Peas' ages likely optimize the escape of LyC radiation; they are old enough for supernovae and stellar winds to reshape the interstellar medium, but young enough to possess large numbers of UV-luminous O or WR stars.

  8. Emulating galaxy clustering and galaxy-galaxy lensing into the deeply nonlinear regime: methodology, information, and forecasts

    OpenAIRE

    Wibking, Benjamin D.; Salcedo, Andrés N.; Weinberg, David H.; Garrison, Lehman H.; Ferrer, Douglas; Tinker, Jeremy; Eisenstein, Daniel; Metchnik, Marc; Pinto, Philip

    2017-01-01

    The combination of galaxy-galaxy lensing (GGL) with galaxy clustering is one of the most promising routes to determining the amplitude of matter clustering at low redshifts. We show that extending clustering+GGL analyses from the linear regime down to $\\sim 0.5 \\, h^{-1}$ Mpc scales increases their constraining power considerably, even after marginalizing over a flexible model of non-linear galaxy bias. Using a grid of cosmological N-body simulations, we construct a Taylor-expansion emulator ...

  9. Galaxy formation

    International Nuclear Information System (INIS)

    Silk, J.; Di Cintio, A.; Dvorkin, I.

    2014-01-01

    Galaxy formation is at the forefront of observation and theory in cosmology. An improved understanding is essential for improving our knowledge both of the cosmological parameters, of the contents of the universe, and of our origins. In these lectures intended for graduate students, galaxy formation theory is reviewed and confronted with recent observational issues. In lecture 1, the following topics are presented: star formation considerations, including IMF, star formation efficiency and star formation rate, the origin of the galaxy luminosity function, and feedback in dwarf galaxies. In lecture 2, we describe formation of disks and massive spheroids, including the growth of supermassive black holes, negative feedback in spheroids, the AGN-star formation connection, star formation rates at high redshift and the baryon fraction in galaxies.

  10. LOCAL LUMINOUS INFRARED GALAXIES. II. ACTIVE GALACTIC NUCLEUS ACTIVITY FROM SPITZER/INFRARED SPECTROGRAPH SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Alonso-Herrero, Almudena; Pereira-Santaella, Miguel [Centro de Astrobiologia, INTA-CSIC, E-28850 Torrejon de Ardoz, Madrid (Spain); Rieke, George H. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Rigopoulou, Dimitra [Astrophysics Department, University of Oxford, Oxford OX1 3RH (United Kingdom)

    2012-01-01

    We quantify the active galactic nucleus (AGN) contribution to the mid-infrared (mid-IR) and the total infrared (IR, 8-1000 {mu}m) emission in a complete volume-limited sample of 53 local luminous infrared galaxies (LIRGs, L{sub IR} = 10{sup 11}-10{sup 12} L{sub Sun }). We decompose the Spitzer Infrared Spectrograph low-resolution 5-38 {mu}m spectra of the LIRGs into AGN and starburst components using clumpy torus models and star-forming galaxy templates, respectively. We find that 50% (25/50) of local LIRGs have an AGN component detected with this method. There is good agreement between these AGN detections through mid-IR spectral decomposition and other AGN indicators, such as the optical spectral class, mid-IR spectral features, and X-ray properties. Taking all the AGN indicators together, the AGN detection rate in the individual nuclei of LIRGs is {approx}62%. The derived AGN bolometric luminosities are in the range L{sub bol}(AGN) = (0.4-50) Multiplication-Sign 10{sup 43} erg s{sup -1}. The AGN bolometric contribution to the IR luminosities of the galaxies is generally small, with 70% of LIRGs having L{sub bol}[AGN]/L{sub IR} {<=} 0.05. Only {approx_equal} 8% of local LIRGs have a significant AGN bolometric contribution L{sub bol}[AGN]/L{sub IR} > 0.25. From the comparison of our results with literature results of ultraluminous infrared galaxies (L{sub IR} = 10{sup 12}-10{sup 13} L{sub Sun }), we confirm that in the local universe the AGN bolometric contribution to the IR luminosity increases with the IR luminosity of the galaxy/system. If we add up the AGN bolometric luminosities we find that AGNs only account for 5%{sub -3%}{sup +8%} of the total IR luminosity produced by local LIRGs (with and without AGN detections). This proves that the bulk of the IR luminosity of local LIRGs is due to star formation activity. Taking the newly determined IR luminosity density of LIRGs in the local universe, we then estimate an AGN IR luminosity density of {Omega}{sup AGN

  11. THE LOCAL [C ii] 158 μ m EMISSION LINE LUMINOSITY FUNCTION

    Energy Technology Data Exchange (ETDEWEB)

    Hemmati, Shoubaneh; Yan, Lin; Capak, Peter; Faisst, Andreas; Masters, Daniel [Infrared Processing and Analysis Center, Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., Pasadena CA 91125 (United States); Diaz-Santos, Tanio [Nucleo de Astronomia de la Facultad de Ingenieria, Universidad Diego Portales, Av. Ejercito Libertador 441, Santiago (Chile); Armus, Lee, E-mail: shemmati@ipac.caltech.edu [Spitzer Science Center, Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States)

    2017-01-01

    We present, for the first time, the local [C ii] 158 μ m emission line luminosity function measured using a sample of more than 500 galaxies from the Revised Bright Galaxy Sample. [C ii] luminosities are measured from the Herschel PACS observations of the Luminous Infrared Galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey and estimated for the rest of the sample based on the far-infrared (far-IR) luminosity and color. The sample covers 91.3% of the sky and is complete at S{sub 60μm} > 5.24 Jy. We calculate the completeness as a function of [C ii] line luminosity and distance, based on the far-IR color and flux densities. The [C ii] luminosity function is constrained in the range ∼10{sup 7–9} L{sub ⊙} from both the 1/ V{sub max} and a maximum likelihood methods. The shape of our derived [C ii] emission line luminosity function agrees well with the IR luminosity function. For the CO(1-0) and [C ii] luminosity functions to agree, we propose a varying ratio of [C ii]/CO(1-0) as a function of CO luminosity, with larger ratios for fainter CO luminosities. Limited [C ii] high-redshift observations as well as estimates based on the IR and UV luminosity functions are suggestive of an evolution in the [C ii] luminosity function similar to the evolution trend of the cosmic star formation rate density. Deep surveys using the Atacama Large Millimeter Array with full capability will be able to confirm this prediction.

  12. STAR-FORMING GALAXIES IN THE HERCULES CLUSTER: Hα IMAGING OF A2151

    International Nuclear Information System (INIS)

    Cedres, Bernabe; Iglesias-Paramo, Jorge; VIlchez, Jose Manuel; Reverte, Daniel; Petropoulou, Vasiliki; Hernandez-Fernandez, Jonathan

    2009-01-01

    This paper presents the first results of an Hα imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in Hα, from which 41 were classified as secure members of the cluster and 2 as likely members based on spectroscopic and photometric redshift considerations. The remaining seven galaxies were classified as background contaminants and thus excluded from our study on the Hα properties of the cluster. The morphologies of the 43 Hα selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalactic H II regions, spanning a range of magnitudes of -21 ≤ M B ≤ -12.5 mag. From these 43 galaxies, 7 have been classified as active galactic nucleus (AGN) candidates. These AGN candidates follow the L(Hα) versus M B relationship of the normal galaxies, implying that the emission associated with the nuclear engine has a rather secondary impact on the total Hα emission of these galaxies. A comparison with the clusters Coma and A1367 and a sample of field galaxies has shown the presence of cluster galaxies with L(Hα) lower than expected for their M B , a consequence of the cluster environment. This fact results in differences in the L(Hα) versus EW(Hα) and L(Hα) distributions of the clusters with respect to the field, and in cluster-to-cluster variations of these quantities, which we propose are driven by a global cluster property as the total mass. In addition, the cluster Hα emitting galaxies tend to avoid the central regions of the clusters, again with different intensity depending on the cluster total mass. For the particular case of A2151, we find that most Hα emitting galaxies are located close to the regions with the higher galaxy density, offset from the main X-ray peak. Overall, we conclude that both the global cluster environment and the cluster merging history play a non-negligible role in the integral star formation properties of

  13. wft4galaxy: a workflow testing tool for galaxy.

    Science.gov (United States)

    Piras, Marco Enrico; Pireddu, Luca; Zanetti, Gianluigi

    2017-12-01

    Workflow managers for scientific analysis provide a high-level programming platform facilitating standardization, automation, collaboration and access to sophisticated computing resources. The Galaxy workflow manager provides a prime example of this type of platform. As compositions of simpler tools, workflows effectively comprise specialized computer programs implementing often very complex analysis procedures. To date, no simple way to automatically test Galaxy workflows and ensure their correctness has appeared in the literature. With wft4galaxy we offer a tool to bring automated testing to Galaxy workflows, making it feasible to bring continuous integration to their development and ensuring that defects are detected promptly. wft4galaxy can be easily installed as a regular Python program or launched directly as a Docker container-the latter reducing installation effort to a minimum. Available at https://github.com/phnmnl/wft4galaxy under the Academic Free License v3.0. marcoenrico.piras@crs4.it. © The Author 2017. Published by Oxford University Press.

  14. Rebuilding Spiral Galaxies

    Science.gov (United States)

    2005-01-01

    Major Observing Programme Leads to New Theory of Galaxy Formation Summary Most present-day large galaxies are spirals, presenting a disc surrounding a central bulge. Famous examples are our own Milky Way or the Andromeda Galaxy. When and how did these spiral galaxies form? Why do a great majority of them present a massive central bulge? An international team of astronomers [1] presents new convincing answers to these fundamental questions. For this, they rely on an extensive dataset of observations of galaxies taken with several space- and ground-based telescopes. In particular, they used over a two-year period, several instruments on ESO's Very Large Telescope. Among others, their observations reveal that roughly half of the present-day stars were formed in the period between 8,000 million and 4,000 million years ago, mostly in episodic burst of intense star formation occurring in Luminous Infrared Galaxies. From this and other evidence, the astronomers devised an innovative scenario, dubbed the "spiral rebuilding". They claim that most present-day spiral galaxies are the results of one or several merger events. If confirmed, this new scenario could revolutionise the way astronomers think galaxies formed. PR Photo 02a/05: Luminosity - Oxygen Abundance Relation for Galaxies (VLT) PR Photo 02b/05: The Spiral Rebuilding Scenario A fleet of instruments How and when did galaxies form? How and when did stars form in these island universes? These questions are still posing a considerable challenge to present-day astronomers. Front-line observational results obtained with a fleet of ground- and space-based telescopes by an international team of astronomers [1] provide new insights into these fundamental issues. For this, they embarked on an ambitious long-term study at various wavelengths of 195 galaxies with a redshift [2] greater than 0.4, i.e. located more than 4000 million light-years away. These galaxies were studied using ESO's Very Large Telescope, as well as the

  15. Cosmic reionization on computers. II. Reionization history and its back-reaction on early galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Gnedin, Nickolay Y. [Particle Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Kaurov, Alexander A., E-mail: gnedin@fnal.gov, E-mail: kaurov@uchicago.edu [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States)

    2014-09-20

    We compare the results from several sets of cosmological simulations of cosmic reionization, produced under the Cosmic Reionization On Computers project, with existing observational data on the high-redshift Lyα forest and the abundance of Lyα emitters. We find good consistency with the observational measurements and previous simulation work. By virtue of having several independent realizations for each set of numerical parameters, we are able to explore the effect of cosmic variance on observable quantities. One unexpected conclusion we are forced into is that cosmic variance is unusually large at z > 6, with both our simulations and, most likely, observational measurements still not fully converged for even such basic quantities as the average Gunn-Peterson optical depth or the volume-weighted neutral fraction. We also find that reionization has little effect on the early galaxies or on global cosmic star formation history, because galaxies whose gas content is affected by photoionization contain no molecular (i.e., star-forming) gas in the first place. In particular, measurements of the faint end of the galaxy luminosity function by the James Webb Space Telescope are unlikely to provide a useful constraint on reionization.

  16. STRUCTURES OF LOCAL GALAXIES COMPARED TO HIGH-REDSHIFT STAR-FORMING GALAXIES

    International Nuclear Information System (INIS)

    Petty, Sara M.; De Mello, DuIlia F.; Gallagher, John S.; Gardner, Jonathan P.; Lotz, Jennifer M.; Matt Mountain, C.; Smith, Linda J.

    2009-01-01

    The rest-frame far-ultraviolet morphologies of eight nearby interacting and starburst galaxies (Arp 269, M 82, Mrk 8, NGC 520, NGC 1068, NGC 3079, NGC 3310, and NGC 7673) are compared with 54 galaxies at z ∼ 1.5 and 46 galaxies at z ∼ 4 observed in the Great Observatories Origins Deep Survey (GOODS) taken with the Advanced Camera for Surveys onboard the Hubble Space Telescope. The nearby sample is artificially redshifted to z ∼ 1.5 and 4 by applying luminosity and size scaling. We compare the simulated galaxy morphologies to real z ∼ 1.5 and 4 UV-bright galaxy morphologies. We calculate the Gini coefficient (G), the second-order moment of the brightest 20% of the galaxy's flux (M 20 ), and the Sersic index (n). We explore the use of nonparametric methods with two-dimensional profile fitting and find the combination of M 20 with n an efficient method to classify galaxies as having merger, exponential disk, or bulge-like morphologies. When classified according to G and M 20 20/30% of real/simulated galaxies at z ∼ 1.5 and 37/12% at z ∼ 4 have bulge-like morphologies. The rest have merger-like or intermediate distributions. Alternatively, when classified according to the Sersic index, 70% of the z ∼ 1.5 and z ∼ 4 real galaxies are exponential disks or bulge-like with n>0.8, and ∼ 30% of the real galaxies are classified as mergers. The artificially redshifted galaxies have n values with ∼ 35% bulge or exponential at z ∼ 1.5 and 4. Therefore, ∼ 20%-30% of Lyman-break galaxies have structures similar to local starburst mergers, and may be driven by similar processes. We assume merger-like or clumpy star-forming galaxies in the GOODS field have morphological structure with values n 20 > - 1.7. We conclude that Mrk 8, NGC 3079, and NGC 7673 have structures similar to those of merger-like and clumpy star-forming galaxies observed at z ∼ 1.5 and 4.

  17. Near-IR search for lensed supernovae behind galaxy clusters. II. First detection and future prospects

    OpenAIRE

    Goobar, A.; Paech, K.; Stanishev, V.; Amanullah, R.; Dahlén, T.; Jönsson, J.; Kneib, J. P.; Lidman, C.; Limousin, M.; Mörtsell, E.; Nobili, S.; Richard, J.; Riehm, T.; von Strauss, M.

    2009-01-01

    Aims. Powerful gravitational telescopes in the form of massive galaxy clusters can be used to enhance the light collecting power over a limited field of view by about an order of magnitude in flux. This effect is exploited here to increase the depth of a survey for lensed supernovae at near-IR wavelengths. Methods. We present a pilot supernova search programme conducted with the ISAAC camera at VLT. Lensed galaxies behind the massive clusters A1689, A1835, and AC114 were observed for a tot...

  18. OXYGEN METALLICITY DETERMINATIONS FROM OPTICAL EMISSION LINES IN EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Athey, Alex E.; Bregman, Joel N.

    2009-01-01

    We measured the oxygen abundances of the warm (T ∼ 10 4 K) phase of gas in seven early-type galaxies through long-slit observations. A template spectra was constructed from galaxies void of warm gas and subtracted from the emission-line galaxies, allowing for a clean measurement of the nebular lines. The ratios of the emission lines are consistent with photoionization, which likely originates from the ultraviolet flux of postasymototic giant branch stars. We employ H II region photoionization models to determine a mean oxygen metallicity of 1.01 ± 0.50 solar for the warm interstellar medium (ISM) in this sample. This warm ISM 0.5-1.5 solar metallicity is consistent with modern determinations of the metallicity in the hot (T ∼ 10 6 -10 7 K) ISM and the upper range of this warm ISM metallicity is consistent with stellar population metallicity determinations. A solar metallicity of the warm ISM favors an internal origin for the warm ISM such as asymptotic giant branch mass loss within the galaxy.

  19. Emission-line diagnostics of nearby H II regions including interacting binary populations

    Science.gov (United States)

    Xiao, Lin; Stanway, Elizabeth R.; Eldridge, J. J.

    2018-06-01

    We present numerical models of the nebular emission from H II regions around young stellar populations over a range of compositions and ages. The synthetic stellar populations include both single stars and interacting binary stars. We compare these models to the observed emission lines of 254 H II regions of 13 nearby spiral galaxies and 21 dwarf galaxies drawn from archival data. The models are created using the combination of the BPASS (Binary Population and Spectral Synthesis) code with the photoionization code CLOUDY to study the differences caused by the inclusion of interacting binary stars in the stellar population. We obtain agreement with the observed emission line ratios from the nearby star-forming regions and discuss the effect of binary-star evolution pathways on the nebular ionization of H II regions. We find that at population ages above 10 Myr, single-star models rapidly decrease in flux and ionization strength, while binary-star models still produce strong flux and high [O III]/H β ratios. Our models can reproduce the metallicity of H II regions from spiral galaxies, but we find higher metallicities than previously estimated for the H II regions from dwarf galaxies. Comparing the equivalent width of H β emission between models and observations, we find that accounting for ionizing photon leakage can affect age estimates for H II regions. When it is included, the typical age derived for H II regions is 5 Myr from single-star models, and up to 10 Myr with binary-star models. This is due to the existence of binary-star evolution pathways, which produce more hot Wolf-Rayet and helium stars at older ages. For future reference, we calculate new BPASS binary maximal starburst lines as a function of metallicity, and for the total model population, and present these in Appendix A.

  20. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Vigroux, Laurent

    1979-01-01

    This research thesis addresses theories on the chemical evolution of galaxies which aim at explaining abundances of different elements in galaxies, and more particularly aims at improving the model by modifying hypotheses. After a description of the simple model and of its uncertainties, the author shows how it is possible to understand the evolution of the main elements. Predictions obtained with this model are then compared with the present knowledge on galaxies by considering them according to an increasing complexity: Sun's neighbourhood, our galaxy, other spiral galaxies, elliptical galaxies, and finally galaxy clusters. A specific attention is given to irregular galaxies which are the simplest systems [fr

  1. STELLAR ARCHAEOLOGY IN THE GALACTIC HALO WITH THE ULTRA-FAINT DWARFS. VI. URSA MAJOR II

    Energy Technology Data Exchange (ETDEWEB)

    Dall' Ora, M.; Ripepi, Vincenzo; Marconi, Marcella; Musella, Ilaria, E-mail: dallora@na.astro.it, E-mail: ripepi@na.astro.it, E-mail: marcella@na.astro.it, E-mail: ilaria@na.astro.it [INAF, Osservatorio Astronomico di Capodimonte, Napoli (Italy); and others

    2012-06-10

    We present a B, V color-magnitude diagram (CMD) of the Milky Way dwarf satellite Ursa Major II (UMa II), spanning the magnitude range from V {approx} 15 to V {approx} 23.5 mag and extending over an 18 Multiplication-Sign 18 arcmin{sup 2} area centered on the Galaxy. Our photometry goes down to about 2 mag below the Galaxy's main-sequence turnoff that we detected at V {approx} 21.5 mag. We have discovered a bona fide RR Lyrae variable star in UMa II, which we use to estimate a conservative dereddened distance modulus for the galaxy of (m - M){sub 0} = 17.70 {+-} 0.04 {+-} 0.12 mag, where the first error accounts for the uncertainties of the calibrated photometry, and the second reflects our lack of information on the metallicity of the star. The corresponding distance to UMa II is 34.7{sup +0.6}{sub -0.7}({sup +2.0}{sub -1.9}) kpc. Our photometry shows evidence of a spread in the Galaxy's subgiant branch, compatible with a spread in metal abundance in the range between Z = 0.0001 and Z = 0.001. Based on our estimate of the distance, a comparison of the fiducial lines of the Galactic globular clusters M68 and M5 ([Fe/H] = -2.27 {+-} 0.04 dex and -1.33 {+-} 0.02 dex, respectively), with the position on the CMD of spectroscopically confirmed Galaxy members, may suggest the existence of stellar populations of different metal abundance/age in the central region of UMa II.

  2. Physical properties of emission-line galaxies at z ∼ 2 from near-infrared spectroscopy with Magellan fire

    Energy Technology Data Exchange (ETDEWEB)

    Masters, Daniel; Siana, Brian; Mobasher, Bahram; Domínguez, Alberto [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); McCarthy, Patrick; Blanc, Guillermo; Dressler, Alan [Carnegie Observatories, Pasadena, CA 91101 (United States); Malkan, Mathew; Ross, Nathaniel R. [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095 (United States); Atek, Hakim [Laboratoire d' Astrophysique Ecole Polytechnique Fédérale, CH-1290 Sauverny (Switzerland); Henry, Alaina [Astrophysics Science Division, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Martin, Crystal L. [Department of Physics, Universitey of California, Santa Barbara, CA 93106 (United States); Rafelski, Marc; Colbert, James [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Hathi, Nimish P. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Scarlata, Claudia [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States); Bunker, Andrew J. [Department of Physics, University of Oxford (United Kingdom); Bedregal, Alejandro G. [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Teplitz, Harry [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States)

    2014-04-20

    We present results from near-infrared spectroscopy of 26 emission-line galaxies at z ∼ 2.2 and z ∼ 1.5 obtained with the Folded-port InfraRed Echellette (FIRE) spectrometer on the 6.5 m Magellan Baade telescope. The sample was selected from the WFC3 Infrared Spectroscopic Parallels survey, which uses the near-infrared grism of the Hubble Space Telescope Wide Field Camera 3 (WFC3) to detect emission-line galaxies over 0.3 ≲ z ≲ 2.3. Our FIRE follow-up spectroscopy (R ∼ 5000) over 1.0-2.5 μm permits detailed measurements of the physical properties of the z ∼ 2 emission-line galaxies. Dust-corrected star formation rates for the sample range from ∼5-100 M {sub ☉} yr{sup –1} with a mean of 29 M {sub ☉} yr{sup –1}. We derive a median metallicity for the sample of 12 + log(O/H) = 8.34 or ∼0.45 Z {sub ☉}. The estimated stellar masses range from ∼10{sup 8.5}-10{sup 9.5} M {sub ☉}, and a clear positive correlation between metallicity and stellar mass is observed. The average ionization parameter measured for the sample, log U ≈ –2.5, is significantly higher than what is found for most star-forming galaxies in the local universe, but similar to the values found for other star-forming galaxies at high redshift. We derive composite spectra from the FIRE sample, from which we measure typical nebular electron densities of ∼100-400 cm{sup –3}. Based on the location of the galaxies and composite spectra on diagnostic diagrams, we do not find evidence for significant active galactic nucleus activity in the sample. Most of the galaxies, as well as the composites, are offset diagram toward higher [O III]/Hβ at a given [N II]/Hα, in agreement with other observations of z ≳ 1 star-forming galaxies, but composite spectra derived from the sample do not show an appreciable offset from the local star-forming sequence on the [O III]/Hβ versus [S II]/Hα diagram. We infer a high nitrogen-to-oxygen abundance ratio from the composite spectrum, which

  3. A probabilistic approach to emission-line galaxy classification

    Science.gov (United States)

    de Souza, R. S.; Dantas, M. L. L.; Costa-Duarte, M. V.; Feigelson, E. D.; Killedar, M.; Lablanche, P.-Y.; Vilalta, R.; Krone-Martins, A.; Beck, R.; Gieseke, F.

    2017-12-01

    We invoke a Gaussian mixture model (GMM) to jointly analyse two traditional emission-line classification schemes of galaxy ionization sources: the Baldwin-Phillips-Terlevich (BPT) and WH α versus [N II]/H α (WHAN) diagrams, using spectroscopic data from the Sloan Digital Sky Survey Data Release 7 and SEAGal/STARLIGHT data sets. We apply a GMM to empirically define classes of galaxies in a three-dimensional space spanned by the log [O III]/H β, log [N II]/H α and log EW(H α) optical parameters. The best-fitting GMM based on several statistical criteria suggests a solution around four Gaussian components (GCs), which are capable to explain up to 97 per cent of the data variance. Using elements of information theory, we compare each GC to their respective astronomical counterpart. GC1 and GC4 are associated with star-forming galaxies, suggesting the need to define a new starburst subgroup. GC2 is associated with BPT's active galactic nuclei (AGN) class and WHAN's weak AGN class. GC3 is associated with BPT's composite class and WHAN's strong AGN class. Conversely, there is no statistical evidence - based on four GCs - for the existence of a Seyfert/low-ionization nuclear emission-line region (LINER) dichotomy in our sample. Notwithstanding, the inclusion of an additional GC5 unravels it. The GC5 appears associated with the LINER and passive galaxies on the BPT and WHAN diagrams, respectively. This indicates that if the Seyfert/LINER dichotomy is there, it does not account significantly to the global data variance and may be overlooked by standard metrics of goodness of fit. Subtleties aside, we demonstrate the potential of our methodology to recover/unravel different objects inside the wilderness of astronomical data sets, without lacking the ability to convey physically interpretable results. The probabilistic classifications from the GMM analysis are publicly available within the COINtoolbox at https://cointoolbox.github.io/GMM_Catalogue/.

  4. Cosmological constraints from galaxy clustering and the mass-to-number ratio of galaxy clusters: marginalizing over the physics of galaxy formation

    Energy Technology Data Exchange (ETDEWEB)

    Reddick, Rachel M.; Wechsler, Risa H.; Lu, Yu [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, Stanford, CA 94305 (United States); Tinker, Jeremy L., E-mail: rmredd@stanford.edu, E-mail: rwechsler@stanford.edu [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States)

    2014-03-10

    Many approaches to obtaining cosmological constraints rely on the connection between galaxies and dark matter. However, the distribution of galaxies is dependent on their formation and evolution as well as on the cosmological model, and galaxy formation is still not a well-constrained process. Thus, methods that probe cosmology using galaxies as tracers for dark matter must be able to accurately estimate the cosmological parameters. This can be done without knowing details of galaxy formation a priori as long as the galaxies are well represented by a halo occupation distribution (HOD). We apply this reasoning to the method of obtaining Ω {sub m} and σ{sub 8} from galaxy clustering combined with the mass-to-number ratio of galaxy clusters. To test the sensitivity of this method to variations due to galaxy formation, we consider several different models applied to the same cosmological dark matter simulation. The cosmological parameters are then estimated using the observables in each model, marginalizing over the parameters of the HOD. We find that for models where the galaxies can be well represented by a parameterized HOD, this method can successfully extract the desired cosmological parameters for a wide range of galaxy formation prescriptions.

  5. Cosmological constraints from galaxy clustering and the mass-to-number ratio of galaxy clusters: marginalizing over the physics of galaxy formation

    International Nuclear Information System (INIS)

    Reddick, Rachel M.; Wechsler, Risa H.; Lu, Yu; Tinker, Jeremy L.

    2014-01-01

    Many approaches to obtaining cosmological constraints rely on the connection between galaxies and dark matter. However, the distribution of galaxies is dependent on their formation and evolution as well as on the cosmological model, and galaxy formation is still not a well-constrained process. Thus, methods that probe cosmology using galaxies as tracers for dark matter must be able to accurately estimate the cosmological parameters. This can be done without knowing details of galaxy formation a priori as long as the galaxies are well represented by a halo occupation distribution (HOD). We apply this reasoning to the method of obtaining Ω m and σ 8 from galaxy clustering combined with the mass-to-number ratio of galaxy clusters. To test the sensitivity of this method to variations due to galaxy formation, we consider several different models applied to the same cosmological dark matter simulation. The cosmological parameters are then estimated using the observables in each model, marginalizing over the parameters of the HOD. We find that for models where the galaxies can be well represented by a parameterized HOD, this method can successfully extract the desired cosmological parameters for a wide range of galaxy formation prescriptions.

  6. OBSERVATIONAL LIMITS ON THE GAS MASS OF A z = 4.9 GALAXY

    International Nuclear Information System (INIS)

    Livermore, R. C.; Swinbank, A. M.; Smail, Ian; Bower, R. G.; Coppin, K. E. K.; Edge, A. C.; Geach, J. E.; Richard, J.; Crain, R. A.

    2012-01-01

    We present the results of a search for molecular gas emission from a star-forming galaxy at z = 4.9. The galaxy benefits from magnification of 22 ± 5 × due to strong gravitational lensing by the foreground cluster MS1358+62. We target the CO(5-4) emission at a known position and redshift from existing Hubble Space Telescope/Advanced Camera for Surveys imaging and Gemini/NIFS [O II]3727 imaging spectroscopy, and obtain a tentative detection at the 4.3σ level with a flux of 0.104 ± 0.024 Jy km s –1 . From the CO line luminosity and assuming a CO-to-H 2 conversion factor α = 2, we derive a gas mass M gas ∼ 1 +1 –0.6 × 10 9 M ☉ . Combined with the existing data, we derive a gas fraction M gas /(M gas + M * ) = 0.59 +0.11 –0.06 . The faint line flux of this galaxy highlights the difficulty of observing molecular gas in representative galaxies at this epoch, and suggests that routine detections of similar galaxies in the absence of gravitational lensing will remain challenging even with ALMA in full science operations.

  7. Nearby supernova host galaxies from the CALIFA survey. II. Supernova environmental metallicity

    NARCIS (Netherlands)

    Galbany, L.; Stanishev, V.; Mourão, A. M.; Rodrigues, M.; Flores, H.; Walcher, C. J.; Sánchez, S. F.; García-Benito, R.; Mast, D.; Badenes, C.; González Delgado, R. M.; Kehrig, C.; Lyubenova, M.; Marino, R. A.; Mollá, M.; Meidt, S.; Pérez, E.; van de Ven, G.; Vílchez, J. M.

    2016-01-01

    The metallicity of a supernova progenitor, together with its mass, is one of the main parameters that can rule the progenitor's fate. We present the second study of nearby supernova (SN) host galaxies (0.005 ⊙) > 10 dex) by targeted searches. We neither found evidence that the metallicity at the SN

  8. Quantifying the impact of mergers on the angular momentum of simulated galaxies

    Science.gov (United States)

    Lagos, Claudia del P.; Stevens, Adam R. H.; Bower, Richard G.; Davis, Timothy A.; Contreras, Sergio; Padilla, Nelson D.; Obreschkow, Danail; Croton, Darren; Trayford, James W.; Welker, Charlotte; Theuns, Tom

    2018-02-01

    We use EAGLE to quantify the effect galaxy mergers have on the stellar specific angular momentum of galaxies, jstars. We split mergers into dry (gas-poor)/wet (gas-rich), major/minor and different spin alignments and orbital parameters. Wet (dry) mergers have an average neutral gas-to-stellar mass ratio of 1.1 (0.02), while major (minor) mergers are those with stellar mass ratios ≥0.3 (0.1-0.3). We correlate the positions of galaxies in the jstars-stellar mass plane at z = 0 with their merger history, and find that galaxies of low spins suffered dry mergers, while galaxies of normal/high spins suffered predominantly wet mergers, if any. The radial jstars profiles of galaxies that went through dry mergers are deficient by ≈0.3 dex at r ≲ 10 r50 (with r50 being the half-stellar mass radius), compared to galaxies that went through wet mergers. Studying the merger remnants reveals that dry mergers reduce jstars by ≈30 per cent, while wet mergers increase it by ≈10 per cent, on average. The latter is connected to the build-up of the bulge by newly formed stars of high rotational speed. Moving from minor to major mergers accentuates these effects. When the spin vectors of the galaxies prior to the dry merger are misaligned, jstars decreases by a greater magnitude, while in wet mergers corotation and high orbital angular momentum efficiently spun-up galaxies. We predict what would be the observational signatures in the jstars profiles driven by dry mergers: (i) shallow radial profiles and (ii) profiles that rise beyond ≈10 r50, both of which are significantly different from spiral galaxies.

  9. Measuring Extinction in Local Group Galaxies Using Background Galaxies

    Science.gov (United States)

    Wyder, T. K.; Hodge, P. W.

    1999-05-01

    Knowledge of the distribution and quantity of dust in galaxies is important for understanding their structure and evolution. The goal of our research is to measure the total extinction through Local Group galaxies using measured properties of background galaxies. Our method relies on the SExtractor software as an objective and automated method of detecting background galaxies. In an initial test, we have explored two WFPC2 fields in the SMC and two in M31 obtained from the HST archives. The two pointings in the SMC are fields around the open clusters L31 and B83 while the two M31 fields target the globular clusters G1 and G170. Except for the G1 observations of M31, the fields chosen are very crowded (even when observed with HST) and we chose them as a particularly stringent test of the method. We performed several experiments using a series of completeness tests that involved superimposing comparison fields, adjusted to the equivalent exposure time, from the HST Medium-Deep and Groth-Westphal surveys. These tests showed that for crowded fields, such as the two in the core of the SMC and the one in the bulge of M31, this automated method of detecting galaxies can be completely dominated by the effects of crowding. For these fields, only a small fraction of the added galaxies was recovered. However, in the outlying G1 field in M31, almost all of the added galaxies were recovered. The numbers of actual background galaxies in this field are consistent with zero extinction. As a follow-up experiment, we used image processing techniques to suppress stellar objects while enhancing objects with non-stellar, more gradual luminosity profiles. This method yielded significant numbers of background galaxies in even the most crowded fields, which we are now analyzing to determine the total extinction and reddening caused by the foreground galaxy.

  10. Shocked POststarburst Galaxy Survey. II. The Molecular Gas Content and Properties of a Subset of SPOGs

    Science.gov (United States)

    Alatalo, Katherine; Lisenfeld, Ute; Lanz, Lauranne; Appleton, Philip N.; Ardila, Felipe; Cales, Sabrina L.; Kewley, Lisa J.; Lacy, Mark; Medling, Anne M.; Nyland, Kristina; Rich, Jeffrey A.; Urry, C. Meg

    2016-08-01

    We present CO(1-0) observations of objects within the Shocked POststarburst Galaxy Survey taken with the Institut de Radioastronomie Millimétrique 30 m single dish and the Combined Array for Research for Millimeter Astronomy interferometer. Shocked poststarburst galaxies (SPOGs) represent a transitioning population of galaxies, with deep Balmer absorption ({{EW}}{{H}δ }\\gt 5 {\\mathring{{A}}} ), consistent with an intermediate-age (A-star) stellar population, and ionized gas line ratios inconsistent with pure star formation. The CO(1-0) subsample was selected from SPOGs detected by the Wide-field Infrared Survey Explorer with 22 μm flux detected at a signal-to-noise ratio (S/N) > 3. Of the 52 objects observed in CO(1-0), 47 are detected with S/N > 3. A large fraction (37%-46% ± 7%) of our CO-SPOG sample were visually classified as morphologically disrupted. The H2 masses detected were between {10}8.7-10.8 {M}⊙ , consistent with the gas masses found in normal galaxies, though approximately an order of magnitude larger than the range seen in poststarburst galaxies. When comparing the 22 μm and CO(1-0) fluxes, SPOGs diverge from the normal star-forming relation, having 22 μm fluxes in excess of the relation by a factor of ={4.91}-0.39+0.42, suggestive of the presence of active galactic nuclei (AGNs). The Na I D characteristics of CO-SPOGs show that it is likely that many of these objects host interstellar winds. Objects with large Na I D enhancements also tend to emit in the radio, suggesting possible AGN driving of neutral winds.

  11. Looking Wider and Further: The Evolution of Galaxies Inside Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yuanyuan [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-01-01

    Galaxy clusters are rare objects in the universe, but on-going wide field optical surveys are identifying many thousands of them to redshift 1.0 and beyond. Using early data from the Dark Energy Survey (DES) and publicly released data from the Sloan Digital Sky Survey (SDSS), this dissertation explores the evolution of cluster galaxies in the redshift range from 0 to 1.0. As it is common for deep wide field sky surveys like DES to struggle with galaxy detection efficiency at cluster core, the first component of this dissertation describes an efficient package that helps resolving the issue. The second part focuses on the formation of cluster galaxies. The study quantifies the growth of cluster bright central galaxies (BCGs), and argues for the importance of merging and intra-cluster light production during BCG evolution. An analysis of cluster red sequence galaxy luminosity function is also performed, demonstrating that the abundance of these galaxies is mildly dependent on cluster mass and redshift. The last component of the dissertation characterizes the properties of galaxy filaments to help understanding cluster environments

  12. Galaxy And Mass Assembly (GAMA): the galaxy stellar mass function to z = 0.1 from the r-band selected equatorial regions

    Science.gov (United States)

    Wright, A. H.; Robotham, A. S. G.; Driver, S. P.; Alpaslan, M.; Andrews, S. K.; Baldry, I. K.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Colless, M.; da Cunha, E.; Davies, L. J. M.; Graham, Alister W.; Holwerda, B. W.; Hopkins, A. M.; Kafle, P. R.; Kelvin, L. S.; Loveday, J.; Maddox, S. J.; Meyer, M. J.; Moffett, A. J.; Norberg, P.; Phillipps, S.; Rowlands, K.; Taylor, E. N.; Wang, L.; Wilkins, S. M.

    2017-09-01

    We derive the low-redshift galaxy stellar mass function (GSMF), inclusive of dust corrections, for the equatorial Galaxy And Mass Assembly (GAMA) data set covering 180 deg2. We construct the mass function using a density-corrected maximum volume method, using masses corrected for the impact of optically thick and thin dust. We explore the galactic bivariate brightness plane (M⋆-μ), demonstrating that surface brightness effects do not systematically bias our mass function measurement above 107.5 M⊙. The galaxy distribution in the M-μ plane appears well bounded, indicating that no substantial population of massive but diffuse or highly compact galaxies are systematically missed due to the GAMA selection criteria. The GSMF is fitted with a double Schechter function, with M^\\star =10^{10.78± 0.01± 0.20} M_{⊙}, φ ^\\star _1=(2.93± 0.40)× 10^{-3} h_{70}^3 Mpc-3, α1 = -0.62 ± 0.03 ± 0.15, φ ^\\star _2=(0.63± 0.10)× 10^{-3} h_{70}^3 Mpc-3 and α2 = -1.50 ± 0.01 ± 0.15. We find the equivalent faint end slope as previously estimated using the GAMA-I sample, although we find a higher value of M^\\star. Using the full GAMA-II sample, we are able to fit the mass function to masses as low as 107.5 M⊙, and assess limits to 106.5 M⊙. Combining GAMA-II with data from G10-COSMOS, we are able to comment qualitatively on the shape of the GSMF down to masses as low as 106 M⊙. Beyond the well-known upturn seen in the GSMF at 109.5, the distribution appears to maintain a single power-law slope from 109 to 106.5. We calculate the stellar mass density parameter given our best-estimate GSMF, finding Ω _\\star = 1.66^{+0.24}_{-0.23}± 0.97 h^{-1}_{70} × 10^{-3}, inclusive of random and systematic uncertainties.

  13. Galaxy Zoo: dust in spiral galaxies star

    OpenAIRE

    Masters, Karen L.; Nichol, Robert; Bamford, Steven; Mosleh, Moein; Lintott, Chris J.; Andreescu, Dan; Edmondson, Edward M.; Keel, William C.; Murray, Phil; Raddick, M. Jordan; Schawinski, Kevin; Slosar, Anze; Szalay, Alexander S.; Thomas, Daniel; Vandenberg, Jan

    2010-01-01

    We investigate the effect of dust on spiral galaxies by measuring the inclination dependence of optical colours for 24 276 well-resolved Sloan Digital Sky Survey (SDSS) galaxies visually classified via the Galaxy Zoo project. We find clear trends of reddening with inclination which imply a total extinction from face-on to edge-on of 0.7, 0.6, 0.5 and 0.4 mag for the ugri passbands (estimating 0.3 mag of extinction in z band). We split the sample into ‘bulgy’ (early-type) and ‘discy’ (late-typ...

  14. Optical-to-virial velocity ratios of local disc galaxies from combined kinematics and galaxy-galaxy lensing

    Science.gov (United States)

    Reyes, R.; Mandelbaum, R.; Gunn, J. E.; Nakajima, R.; Seljak, U.; Hirata, C. M.

    2012-10-01

    In this paper, we measure the optical-to-virial velocity ratios Vopt/V200c of disc galaxies in the Sloan Digital Sky Survey (SDSS) at a mean redshift of = 0.07 and with stellar masses 109 < M* < 1011 M⊙. Vopt/V200c, the ratio of the circular velocity measured at the optical radius of the disc (˜10 kpc) to that at the virial radius of the dark matter halo (˜150 kpc), is a powerful observational constraint on disc galaxy formation. It links galaxies to their dark matter haloes dynamically and constrains the total mass profile of disc galaxies over an order of magnitude in length scale. For this measurement, we combine Vopt derived from the Tully-Fisher relation (TFR) from Reyes et al. with V200c derived from halo masses measured with galaxy-galaxy lensing. In anticipation of this combination, we use similarly selected galaxy samples for both the TFR and lensing analysis. For three M* bins with lensing-weighted mean stellar masses of 0.6, 2.7 and 6.5 × 1010 M⊙, we find halo-to-stellar mass ratios M200c/M* = 41, 23 and 26, with 1σ statistical uncertainties of around 0.1 dex, and Vopt/V200c = 1.27 ± 0.08, 1.39 ± 0.06 and 1.27 ± 0.08 (1σ), respectively. Our results suggest that the dark matter and baryonic contributions to the mass within the optical radius are comparable, if the dark matter halo profile has not been significantly modified by baryons. The results obtained in this work will serve as inputs to and constraints on disc galaxy formation models, which will be explored in future work. Finally, we note that this paper presents a new and improved galaxy shape catalogue for weak lensing that covers the full SDSS Data Release 7 footprint.

  15. GAS OUTFLOWS IN SEYFERT GALAXIES: EFFECTS OF STAR FORMATION VERSUS AGN FEEDBACK

    Energy Technology Data Exchange (ETDEWEB)

    Melioli, C.; Pino, E. M. de Gouveia Dal, E-mail: claudio.melioli@iag.usp.br, E-mail: dalpino@iag.usp.br [Department of Astronomy (IAG-USP), University of Sao Paulo (Brazil)

    2015-10-20

    Large-scale, weakly collimated outflows are very common in galaxies with large infrared luminosities. In complex systems in particular, where intense star formation (SF) coexists with an active galactic nucleus (AGN), it is not clear yet from observations whether the SF, the AGN, or both are driving these outflows. Accreting supermassive black holes are expected to influence their host galaxies through kinetic and radiative feedback processes, but in a Seyfert galaxy, where the energy emitted in the nuclear region is comparable to that of the body of the galaxy, it is possible that stellar activity is also playing a key role in these processes. In order to achieve a better understanding of the mechanisms driving the gas evolution especially at the nuclear regions of these galaxies, we have performed high-resolution three-dimensional hydrodynamical simulations with radiative cooling considering the feedback from both SF regions, including supernova (Type I and II) explosions and an AGN jet emerging from the central region of the active spiral galaxy. We computed the gas mass lost by the system, separating the role of each of these injection energy sources on the galaxy evolution, and found that at scales within 1 kpc an outflow can be generally established considering intense nuclear SF only. The jet alone is unable to drive a massive gas outflow, although it can sporadically drag and accelerate clumps of the underlying outflow to very high velocities.

  16. Photometric redshift requirements for lens galaxies in galaxy-galaxy lensing analyses

    Science.gov (United States)

    Nakajima, R.; Mandelbaum, R.; Seljak, U.; Cohn, J. D.; Reyes, R.; Cool, R.

    2012-03-01

    Weak gravitational lensing is a valuable probe of galaxy formation and cosmology. Here we quantify the effects of using photometric redshifts (photo-z) in galaxy-galaxy lensing, for both sources and lenses, both for the immediate goal of using galaxies with photo-z as lenses in the Sloan Digital Sky Survey (SDSS) and as a demonstration of methodology for large, upcoming weak lensing surveys that will by necessity be dominated by lens samples with photo-z. We calculate the bias in the lensing mass calibration as well as consequences for absolute magnitude (i.e. k-corrections) and stellar mass estimates for a large sample of SDSS Data Release 8 (DR8) galaxies. The redshifts are obtained with the template-based photo-z code ZEBRA on the SDSS DR8 ugriz photometry. We assemble and characterize the calibration samples (˜9000 spectroscopic redshifts from four surveys) to obtain photometric redshift errors and lensing biases corresponding to our full SDSS DR8 lens and source catalogues. Our tests of the calibration sample also highlight the impact of observing conditions in the imaging survey when the spectroscopic calibration covers a small fraction of its footprint; atypical imaging conditions in calibration fields can lead to incorrect conclusions regarding the photo-z of the full survey. For the SDSS DR8 catalogue, we find σΔz/(1+z)= 0.096 and 0.113 for the lens and source catalogues, with flux limits of r= 21 and 21.8, respectively. The photo-z bias and scatter is a function of photo-z and template types, which we exploit to apply photo-z quality cuts. By using photo-z rather than spectroscopy for lenses, dim blue galaxies and L* galaxies up to z˜ 0.4 can be used as lenses, thus expanding into unexplored areas of parameter space. We also explore the systematic uncertainty in the lensing signal calibration when using source photo-z, and both lens and source photo-z; given the size of existing training samples, we can constrain the lensing signal calibration (and

  17. Extragalactic Ultra-High Energy Cosmic-Rays - Part One - Contribution from Hot Spots in Fr-II Radio Galaxies

    Science.gov (United States)

    Rachen, J. P.; Biermann, P. L.

    1993-05-01

    The hot spots of Fanaroff-Riley class II radio galaxies, considered as working surfaces of highly collimated plasma jets, are proposed to be the dominant sources of the cosmic rays at energies above 1 EeV^a^. We apply the model of first order Fermi acceleration at strong, nonrelativistic shock waves to the hot spot region. The strength of the model has been demonstrated by Biermann & Strittmatter (1987) and by Meisenheimer et al. (1989), who explain their radio-to optical spectra and infer the physical conditions of the radiating plasma. Using synchrotron radiating electrons as a trace, we can calculate the spectrum and the maximum energy of protons accelerated under the same conditions. For simplicity, we disregard heavy nuclei, but their probable role is discussed. The normalization of proton flux injected in extragalactic space is performed by using estimates from Rawlings & Saunders (1991) for the total energy stored in relativistic particles inside the jets and radio galaxy evolution models given by Peacock (1985). We calculate the spectral modifications due to interactions of the protons with the microwave background photons in an evolving universe, following Berezinsky & Grigor'eva (1988). Constraints on the extragalactic magnetic field can be imposed, since it must permit an almost homogeneous filling of the universe with energetic protons. The observed ultra-high energy cosmic ray spectrum is reproduced in slope and flux, limited at high energies by the Greisen-cutoff at about 80 EeV. The requirements on the content of relativistic protons in jets and the constraints to the extragalactic magnetic field are consistent with common estimates. The data beyond the Greisen cutoff for protons may be explained by including heavy nuclei in our model, since they can propagate over cosmological distances up to more than 100 EeV.

  18. Visibility of galaxies

    International Nuclear Information System (INIS)

    Disney, M.J.

    1976-01-01

    It is stated that counts of galaxies could be seriously biased by selection effects, largely influenced by the brightness of the night sky. To illustrate this suppose the Earth were situated near the center of a giant elliptical galaxy. The mean surface brightness of the sky would then appear some 8 to 9 mag. brighter than is observed from our position in the Galaxy. Extragalactic space would then appear to be empty void; spiral and irregular galaxies would be invisible, and all that could be easily detected would be the core regions of galaxy ellipticals very similar to our own. Much of the Universe would be blinded by the surface brightness of the parent galaxy. This blinding, however, is a relative matter and the question arises as to what extent we are blinded by the spiral galaxy in which we exist. Strong indirect evidence exists that our knowledge of galaxies is heavily biased by the sky background, and the true population of extragalactic space may be very different from that seen. Other relevant work is also discussed, and further investigational work is indicated. (U.K.)

  19. Strong bimodality in the host halo mass of central galaxies from galaxy-galaxy lensing

    Science.gov (United States)

    Mandelbaum, Rachel; Wang, Wenting; Zu, Ying; White, Simon; Henriques, Bruno; More, Surhud

    2016-04-01

    We use galaxy-galaxy lensing to study the dark matter haloes surrounding a sample of locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey. We measure mean halo mass as a function of the stellar mass and colour of the central galaxy. Mock catalogues constructed from semi-analytic galaxy formation simulations demonstrate that most LBGs are the central objects of their haloes, greatly reducing interpretation uncertainties due to satellite contributions to the lensing signal. Over the full stellar mass range, 10.3 10.7. Tests using the mock catalogues and on the data themselves clarify the effects of LBG selection and show that it cannot artificially induce a systematic dependence of halo mass on LBG colour. The bimodality in halo mass at fixed stellar mass is reproduced by the astrophysical model underlying our mock catalogue, but the sign of the effect is inconsistent with recent, nearly parameter-free age-matching models. The sign and magnitude of the effect can, however, be reproduced by halo occupation distribution models with a simple (few-parameter) prescription for type dependence.

  20. The star formation histories of local group dwarf galaxies. II. Searching for signatures of reionization

    Energy Technology Data Exchange (ETDEWEB)

    Weisz, Daniel R. [Department of Astronomy, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States); Skillman, Evan D. [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Holtzman, Jon [Department of Astronomy, New Mexico State University, Box 30001, 1320 Frenger Street, Las Cruces, NM 88003 (United States); Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F., E-mail: drw@ucsc.edu [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

    2014-07-10

    We search for signatures of reionization in the star formation histories (SFHs) of 38 Local Group dwarf galaxies (10{sup 4} < M{sub *} < 10{sup 9} M{sub ☉}). The SFHs are derived from color-magnitude diagrams using archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. Only five quenched galaxies (And V, And VI, And XIII, Leo IV, and Hercules) are consistent with forming the bulk of their stars before reionization, when full uncertainties are considered. Observations of 13 of the predicted 'true fossils' identified by Bovill and Ricotti show that only two (Hercules and Leo IV) indicate star formation quenched by reionization. However, both are within the virial radius of the Milky Way and evidence of tidal disturbance complicates this interpretation. We argue that the late-time gas capture scenario posited by Ricotti for the low mass, gas-rich, and star-forming fossil candidate Leo T is observationally indistinguishable from simple gas retention. Given the ambiguity between environmental effects and reionization, the best reionization fossil candidates are quenched low mass field galaxies (e.g., KKR 25).

  1. THE STELLAR HALOS OF MASSIVE ELLIPTICAL GALAXIES. II. DETAILED ABUNDANCE RATIOS AT LARGE RADIUS

    Energy Technology Data Exchange (ETDEWEB)

    Greene, Jenny E.; Murphy, Jeremy D.; Graves, Genevieve J.; Gunn, James E.; Raskutti, Sudhir [Department of Astrophysics, Princeton University, Princeton, NJ 08540 (United States); Comerford, Julia M.; Gebhardt, Karl [Department of Astronomy, UT Austin, 1 University Station C1400, Austin, TX 71712 (United States)

    2013-10-20

    We study the radial dependence in stellar populations of 33 nearby early-type galaxies with central stellar velocity dispersions σ{sub *} ∼> 150 km s{sup –1}. We measure stellar population properties in composite spectra, and use ratios of these composites to highlight the largest spectral changes as a function of radius. Based on stellar population modeling, the typical star at 2R{sub e} is old (∼10 Gyr), relatively metal-poor ([Fe/H] ≈ –0.5), and α-enhanced ([Mg/Fe] ≈ 0.3). The stars were made rapidly at z ≈ 1.5-2 in shallow potential wells. Declining radial gradients in [C/Fe], which follow [Fe/H], also arise from rapid star formation timescales due to declining carbon yields from low-metallicity massive stars. In contrast, [N/Fe] remains high at large radius. Stars at large radius have different abundance ratio patterns from stars in the center of any present-day galaxy, but are similar to average Milky Way thick disk stars. Our observations are thus consistent with a picture in which the stellar outskirts are built up through minor mergers with disky galaxies whose star formation is truncated early (z ≈ 1.5-2)

  2. The hydrogen-poor superluminous supernova iPTF 13ajg and its host galaxy in absorption and emission

    Energy Technology Data Exchange (ETDEWEB)

    Vreeswijk, Paul M.; Gal-Yam, Avishay; De Cia, Annalisa; Rubin, Adam; Yaron, Ofer; Tal, David; Ofek, Eran O. [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 7610001 (Israel); Savaglio, Sandra [Max Planck Institute for Extraterrestrial Physics, D-85748 Garching bei München (Germany); Quimby, Robert M. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); Sullivan, Mark [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Cenko, S. Bradley; Filippenko, Alexei V.; Clubb, Kelsey I. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Perley, Daniel A.; Cao, Yi [Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Taddia, Francesco; Sollerman, Jesper; Leloudas, Giorgos [Department of Astronomy, The Oskar Klein Center, Stockholm University, AlbaNova 10691 Stockholm (Sweden); Arcavi, Iair [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Kasliwal, Mansi M., E-mail: paul.vreeswijk@weizmann.ac.il [The Observatories, Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); and others

    2014-12-10

    We present imaging and spectroscopy of a hydrogen-poor superluminous supernova (SLSN) discovered by the intermediate Palomar Transient Factory, iPTF 13ajg. At a redshift of z = 0.7403, derived from narrow absorption lines, iPTF 13ajg peaked at an absolute magnitude of M {sub u,} {sub AB} = –22.5, one of the most luminous supernovae to date. The observed bolometric peak luminosity of iPTF 13ajg is 3.2 × 10{sup 44} erg s{sup –1}, while the estimated total radiated energy is 1.3 × 10{sup 51} erg. We detect narrow absorption lines of Mg I, Mg II, and Fe II, associated with the cold interstellar medium in the host galaxy, at two different epochs with X-shooter at the Very Large Telescope. From Voigt profile fitting, we derive the column densities log N(Mg I) =11.94 ± 0.06, log N(Mg II) =14.7 ± 0.3, and log N(Fe II) =14.25 ± 0.10. These column densities, as well as the Mg I and Mg II equivalent widths of a sample of hydrogen-poor SLSNe taken from the literature, are at the low end of those derived for gamma-ray bursts (GRBs) whose progenitors are also thought to be massive stars. This suggests that the environments of hydrogen-poor SLSNe and GRBs are different. From the nondetection of Fe II fine-structure absorption lines, we derive a lower limit on the distance between the supernova and the narrow-line absorbing gas of 50 pc. The neutral gas responsible for the absorption in iPTF 13ajg exhibits a single narrow component with a low velocity width, ΔV = 76 km s{sup –1}, indicating a low-mass host galaxy. No host galaxy emission lines are detected, leading to an upper limit on the unobscured star formation rate (SFR) of SFR{sub [O} {sub II]}<0.07M{sub ⊙}yr{sup −1}. Late-time imaging shows the iPTF 13ajg host galaxy to be faint, with g {sub AB} ≈ 27.0 and R {sub AB} ≥ 26.0 mag, corresponding to M {sub B,} {sub Vega} ≳ –17.7 mag.

  3. DETECTION OF OUTFLOWING AND EXTRAPLANAR GAS IN DISKS IN AN ASSEMBLING GALAXY CLUSTER AT z = 0.37

    International Nuclear Information System (INIS)

    Freeland, Emily; Tran, Kim-Vy H.; Irwin, Trevor; Giordano, Lea; Saintonge, Amélie; Gonzalez, Anthony H.; Zaritsky, Dennis; Just, Dennis

    2011-01-01

    We detect ionized gas characteristics indicative of winds in three disk-dominated galaxies that are members of a super-group at z = 0.37 that will merge to form a Coma-mass cluster. All three galaxies are IR luminous (L IR > 4 × 10 10 L ☉ , SFR > 8 M ☉ yr –1 ) and lie outside the X-ray cores of the galaxy groups. We find that the most IR-luminous galaxy has strong blueshifted and redshifted emission lines with velocities of ∼ ± 200 km s –1 and a third, blueshifted (∼900 km s –1 ) component. This galaxy's line widths (Hβ, [O III]λ5007, [N II], Hα) correspond to velocities of 100-1000 km s –1 . We detect extraplanar gas in two of the three galaxies with SFR >8 M ☉ yr –1 whose orientations are approximately edge-on and which have integral field unit (IFU) spaxels off the stellar disk. IFU maps reveal that the extraplanar gas extends to r h ∼ 10 kpc; [N II] and Hα line widths correspond to velocities of ∼200-400 km s –1 in the disk and decrease to ∼50-150 km s –1 above the disk. Multi-wavelength observations indicate that the emission is dominated by star formation. Including the most IR-luminous galaxy we find that 18% of supergroup members with SFR >8 M ☉ yr –1 show ionized gas characteristics indicative of outflows. This is a lower limit as showing that gas is outflowing in the remaining, moderately inclined, galaxies requires a non-trivial decoupling of contributions to the emission lines from rotational and turbulent motion. Ionized gas mass loss in these winds is ∼0.1 M ☉ yr –1 for each galaxy, although the winds are likely to entrain significantly larger amounts of mass in neutral and molecular gases.

  4. Ultraviolet Extinction in Backlit Galaxies - from Galaxy Zoo to GALEX

    Science.gov (United States)

    Keel, William C.; Manning, A.; Holwerda, B. W.; Lintott, C.; Schawinski, K.; Galaxy Zoo Team

    2012-01-01

    We examine the ultraviolet extinction of galaxies on large scales, combining optical and GALEX UV data on backlit galaxies (most found in the Galaxy Zoo citizen-science project). We analyze the images in matching ways, modelling both foreground and background galaxies by symmetry or elliptical isophote families as appropriate, and using the non-overlapping regions of the galaxies to estimate errors in the derived transmission T=e-κ. Spirals appear less symmetric in the UV, as star-forming regions become more dominant, so that our most reliable results are mean values across multiple regions and multiple galaxies. Our mean effective extinction curve is dominated by the contribution of luminous spirals,and shows a fairly flat gray" extinction law into the ultraviolet. For example, the median of κNUV/κB in spiral arms is only 1.3. Along with previous high-resolution HST studies of a few nearby backlit galaxies, this suggests that on kpc scales the effective extinction is dominated by the dust clumping rather than the intrinsic reddening law. This implies that extrapolation of local properties to short wavelengths, a step toward the history of dust in galaxies through comparison of local properties with a similar analysis in deep HST fields, can be done without introducing much additional error. This work was supported by NASA Astrophysics Data Analysis Program grant NNX10AD54G.

  5. THE AGORA HIGH-RESOLUTION GALAXY SIMULATIONS COMPARISON PROJECT. II. ISOLATED DISK TEST

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji-hoon [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Agertz, Oscar [Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH (United Kingdom); Teyssier, Romain; Feldmann, Robert [Centre for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Zurich, 8057 (Switzerland); Butler, Michael J. [Max-Planck-Institut für Astronomie, D-69117 Heidelberg (Germany); Ceverino, Daniel [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, D-69120 Heidelberg (Germany); Choi, Jun-Hwan [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Keller, Ben W. [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada); Lupi, Alessandro [Institut d’Astrophysique de Paris, Sorbonne Universites, UPMC Univ Paris 6 et CNRS, F-75014 Paris (France); Quinn, Thomas; Wallace, Spencer [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Revaz, Yves [Institute of Physics, Laboratoire d’Astrophysique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Gnedin, Nickolay Y. [Particle Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Leitner, Samuel N. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Shen, Sijing [Kavli Institute for Cosmology, University of Cambridge, Cambridge, CB3 0HA (United Kingdom); Smith, Britton D., E-mail: me@jihoonkim.org [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Collaboration: AGORA Collaboration; and others

    2016-12-20

    Using an isolated Milky Way-mass galaxy simulation, we compare results from nine state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt–Schmidt relations. Quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly formed stellar clump mass functions show more significant variation (difference by up to a factor of ∼3). Systematic differences exist, for example, between mesh-based and particle-based codes in the low-density region, and between more diffusive and less diffusive schemes in the high-density tail of the density distribution. Yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. Our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes.

  6. ALFALFA DISCOVERY OF THE MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691

    Energy Technology Data Exchange (ETDEWEB)

    Hirschauer, Alec S.; Salzer, John J.; Rhode, Katherine L., E-mail: ash@astro.indiana.edu, E-mail: slaz@astro.indiana.edu, E-mail: krhode@indiana.edu [Department of Astronomy, Indiana University, 727 East Third Street, Bloomington, IN 47405 (United States); and others

    2016-05-10

    We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part of the Survey of H i in Extremely Low-Mass Dwarfs project, which is a multi-wavelength study of galaxies with H i masses in the range of 10{sup 6}–10{sup 7.2} M {sub ⊙}, discovered by the Arecibo Legacy Fast ALFA (ALFALFA) survey. We have obtained spectra of the lone H ii region in AGC 198691 with the new high-throughput KPNO Ohio State Multi-Object Spectrograph on the Mayall 4 m, as well as with the Blue Channel spectrograph on the MMT 6.5 m telescope. These observations enable the measurement of the temperature-sensitive [O iii] λ 4363 line and hence the determination of a “direct” oxygen abundance for AGC 198691. We find this system to be an extremely metal-deficient (XMD) system with an oxygen abundance of 12+log(O/H) = 7.02 ± 0.03, making AGC 198691 the lowest-abundance star-forming galaxy known in the local universe. Two of the five lowest-abundance galaxies known have been discovered by the ALFALFA blind H i survey; this high yield of XMD galaxies represents a paradigm shift in the search for extremely metal-poor galaxies.

  7. FAR-INFRARED LINE SPECTRA OF SEYFERT GALAXIES FROM THE HERSCHEL-PACS SPECTROMETER

    International Nuclear Information System (INIS)

    Spinoglio, Luigi; Pereira-Santaella, Miguel; Busquet, Gemma; Dasyra, Kalliopi M.; Calzoletti, Luca; Malkan, Matthew A.; Tommasin, Silvia

    2015-01-01

    We observed the far-IR fine-structure lines of 26 Seyfert galaxies with the Herschel-PACS spectrometer. These observations are complemented with Spitzer Infrared Spectrograph and Herschel SPIRE spectroscopy. We used the ionic lines to determine electron densities in the ionized gas and the [C I] lines, observed with SPIRE, to measure the neutral gas densities, while the [O I] lines measure the gas temperature, at densities below ∼10 4  cm –3 . Using the [O I]145 μm/63 μm and [S III]33/18 μm line ratios, we find an anti-correlation of the temperature with the gas density. Various fine-structure line ratios show density stratifications in these active galaxies. On average, electron densities increase with the ionization potential of the ions. The infrared lines arise partly in the narrow line region, photoionized by the active galactic nucleus (AGN), partly in H II regions photoionized by hot stars, and partly in photo-dissociated regions. We attempt to separate the contributions to the line emission produced in these different regions by comparing our observed emission line ratios to theoretical values. In particular, we tried to separate the contribution of AGNs and star formation by using a combination of Spitzer and Herschel lines, and we found that besides the well-known mid-IR line ratios, the line ratio of [O III]88 μm/[O IV]26 μm can reliably discriminate the two emission regions, while the far-IR line ratio of [C II]157 μm/[O I]63 μm is only able to mildly separate the two regimes. By comparing the observed [C II]157 μm/[N II]205 μm ratio with photoionization models, we also found that most of the [C II] emission in the galaxies we examined is due to photodissociation regions

  8. FAR-INFRARED LINE SPECTRA OF SEYFERT GALAXIES FROM THE HERSCHEL-PACS SPECTROMETER

    Energy Technology Data Exchange (ETDEWEB)

    Spinoglio, Luigi; Pereira-Santaella, Miguel; Busquet, Gemma [Istituto di Astrofisica e Planetologia Spaziali, INAF, Via Fosso del Cavaliere 100, I-00133 Roma (Italy); Dasyra, Kalliopi M. [Observatoire de Paris, LERMA (CNRS:UMR8112), 61 Av. de l' Observatoire, F-75014, Paris (France); Calzoletti, Luca [Agenzia Spaziale Italiana (ASI) Science Data Center, I-00044 Frascati (Roma) (Italy); Malkan, Matthew A. [Astronomy Division, University of California, Los Angeles, CA 90095-1547 (United States); Tommasin, Silvia, E-mail: luigi.spinoglio@iaps.inaf.it [Weizmann Institute of Science, Department of Neurobiology, Rehovot 76100 (Israel)

    2015-01-20

    We observed the far-IR fine-structure lines of 26 Seyfert galaxies with the Herschel-PACS spectrometer. These observations are complemented with Spitzer Infrared Spectrograph and Herschel SPIRE spectroscopy. We used the ionic lines to determine electron densities in the ionized gas and the [C I] lines, observed with SPIRE, to measure the neutral gas densities, while the [O I] lines measure the gas temperature, at densities below ∼10{sup 4} cm{sup –3}. Using the [O I]145 μm/63 μm and [S III]33/18 μm line ratios, we find an anti-correlation of the temperature with the gas density. Various fine-structure line ratios show density stratifications in these active galaxies. On average, electron densities increase with the ionization potential of the ions. The infrared lines arise partly in the narrow line region, photoionized by the active galactic nucleus (AGN), partly in H II regions photoionized by hot stars, and partly in photo-dissociated regions. We attempt to separate the contributions to the line emission produced in these different regions by comparing our observed emission line ratios to theoretical values. In particular, we tried to separate the contribution of AGNs and star formation by using a combination of Spitzer and Herschel lines, and we found that besides the well-known mid-IR line ratios, the line ratio of [O III]88 μm/[O IV]26 μm can reliably discriminate the two emission regions, while the far-IR line ratio of [C II]157 μm/[O I]63 μm is only able to mildly separate the two regimes. By comparing the observed [C II]157 μm/[N II]205 μm ratio with photoionization models, we also found that most of the [C II] emission in the galaxies we examined is due to photodissociation regions.

  9. Optical Variability of Narrow-line and Broad-line Seyfert 1 Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Rakshit, Suvendu; Stalin, C. S., E-mail: suvenduat@gmail.com [Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034 (India)

    2017-06-20

    We studied the optical variability (OV) of a large sample of narrow-line Seyfert 1 (NLSy1) and broad-line Seyfert 1 (BLSy1) galaxies with z < 0.8 to investigate any differences in their OV properties. Using archival optical V -band light curves from the Catalina Real Time Transient Survey that span 5–9 years and modeling them using damped random walk, we estimated the amplitude of variability. We found that NLSy1 galaxies as a class show lower amplitude of variability than their broad-line counterparts. In the sample of both NLSy1 and BLSy1 galaxies, radio-loud sources are found to have higher variability amplitude than radio-quiet sources. Considering only sources that are detected in the X-ray band, NLSy1 galaxies are less optically variable than BLSy1 galaxies. The amplitude of variability in the sample of both NLSy1 and BLSy1 galaxies is found to be anti-correlated with Fe ii strength but correlated with the width of the H β line. The well-known anti-correlation of variability–luminosity and the variability–Eddington ratio is present in our data. Among the radio-loud sample, variability amplitude is found to be correlated with radio-loudness and radio-power, suggesting that jets also play an important role in the OV in radio-loud objects, in addition to the Eddington ratio, which is the main driving factor of OV in radio-quiet sources.

  10. Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. II: anisotropy

    International Nuclear Information System (INIS)

    Blasi, Pasquale; Amato, Elena

    2012-01-01

    In this paper we investigate the effects of stochasticity in the spatial and temporal distribution of supernova remnants on the anisotropy of cosmic rays observed at Earth. The calculations are carried out for different choices of the diffusion coefficient D(E) experienced by cosmic rays during propagation in the Galaxy. The propagation and spallation of nuclei (with charge 1 ≤ Z ≤ 26) are taken into account. At high energies (E > 1 TeV) we assume that D(E)∝(E/Z) δ , with δ = 1/3 and δ = 0.6 being the reference scenarios. The large scale distribution of supernova remnants in the Galaxy is modeled following the distribution of pulsars with and without accounting for the spiral structure of the Galaxy. Our calculations allow us to determine the contribution to anisotropy resulting from both the large scale distribution of SNRs in the Galaxy and the random distribution of the nearest remnants. The naive expectation that the anisotropy amplitude scales as δ A ∝D(E) is shown to be a wild oversimplification of reality which does not reflect in the predicted anisotropy for any realistic distribution of the sources. The fluctuations in the anisotropy pattern are dominated by nearby sources, so that predicting or explaining the observed anisotropy amplitude and phase becomes close to impossible. Nevertheless, the results of our calculations, when compared to the data, allow us to draw interesting conclusions in terms of the propagation scenario to be preferred both in terms of the energy dependence of the diffusion coefficient and of the size of the halo. We find that the very weak energy dependence of the anisotropy amplitude below 10 5 GeV, as observed by numerous experiments, as well as the rise at higher energies, can best be explained if the diffusion coefficient is D(E)∝E 1/3 . Faster diffusion, for instance with δ = 0.6, leads in general to an exceedingly large anisotropy amplitude. The spiral structure introduces interesting trends in the energy

  11. A NEARBY GAMMA-RAY BURST HOST PROTOTYPE FOR z ∼ 7 LYMAN-BREAK GALAXIES: SPITZER-IRS AND X-SHOOTER SPECTROSCOPY OF THE HOST GALAXY OF GRB 031203

    International Nuclear Information System (INIS)

    Watson, D.; French, J.; Hjorth, J.; Malesani, D.; Fynbo, J. P. U.; Castro Cerón, J. M.; Christensen, L.; O'Halloran, B.; Michałowski, M.; Gordon, K. D.; Covino, S.; Reinfrank, R. F.

    2011-01-01

    Gamma-ray burst (GRB) host galaxies have been studied extensively in optical photometry and spectroscopy. Here we present the first mid-infrared spectrum of a GRB host, HG 031203. It is one of the nearest GRB hosts at z = 0.1055, allowing both low- and high-resolution spectroscopy with the Spitzer Infrared Spectrograph (IRS). Medium-resolution UV to K-band spectroscopy with the X-shooter spectrograph on the Very Large Telescope is also presented, along with Spitzer IRAC and MIPS photometry, as well as radio and submillimeter observations. These data allow us to construct a UV to radio spectral energy distribution with almost complete spectroscopic coverage from 0.3 to 35 μm of a GRB host galaxy for the first time, potentially valuable as a template for future model comparisons. The IRS spectra show strong, high-ionization fine structure line emission indicative of a hard radiation field in the galaxy—in particular the [S IV]/[S III] and [Ne III]/[Ne II] ratios—suggestive of strong ongoing star formation and a very young stellar population. The absence of any polycyclic aromatic hydrocarbon emission supports these conclusions, as does the probable hot peak dust temperature, making HG 031203 similar to the prototypical blue compact dwarf galaxy (BCD), II Zw 40. The selection of HG 031203 via the presence of a GRB suggests that it might be a useful analog of very young star-forming galaxies in the early universe, and hints that local BCDs may be used as more reliable analogs of star formation in the early universe than typical local starbursts. We look at the current debate on the ages of the dominant stellar populations in z ∼ 7 and z ∼ 8 galaxies in this context. The nebular line emission is so strong in HG 031203 that at z ∼ 7, it can reproduce the spectral energy distributions of z-band dropout galaxies with elevated IRAC 3.6 and 4.5 μm fluxes without the need to invoke a 4000 Å break. Indeed, photometry of HG 031203 shows elevation of the broadband V

  12. THE PROPAGATION OF UNCERTAINTIES IN STELLAR POPULATION SYNTHESIS MODELING. II. THE CHALLENGE OF COMPARING GALAXY EVOLUTION MODELS TO OBSERVATIONS

    International Nuclear Information System (INIS)

    Conroy, Charlie; Gunn, James E.; White, Martin

    2010-01-01

    Models for the formation and evolution of galaxies readily predict physical properties such as star formation rates, metal-enrichment histories, and, increasingly, gas and dust content of synthetic galaxies. Such predictions are frequently compared to the spectral energy distributions of observed galaxies via the stellar population synthesis (SPS) technique. Substantial uncertainties in SPS exist, and yet their relevance to the task of comparing galaxy evolution models to observations has received little attention. In the present work, we begin to address this issue by investigating the importance of uncertainties in stellar evolution, the initial stellar mass function (IMF), and dust and interstellar medium (ISM) properties on the translation from models to observations. We demonstrate that these uncertainties translate into substantial uncertainties in the ultraviolet, optical, and near-infrared colors of synthetic galaxies. Aspects that carry significant uncertainties include the logarithmic slope of the IMF above 1 M sun , dust attenuation law, molecular cloud disruption timescale, clumpiness of the ISM, fraction of unobscured starlight, and treatment of advanced stages of stellar evolution including blue stragglers, the horizontal branch, and the thermally pulsating asymptotic giant branch. The interpretation of the resulting uncertainties in the derived colors is highly non-trivial because many of the uncertainties are likely systematic, and possibly correlated with the physical properties of galaxies. We therefore urge caution when comparing models to observations.

  13. Crashing galaxies, cosmic fireworks

    International Nuclear Information System (INIS)

    Keel, W.C.

    1989-01-01

    The study of binary systems is reviewed. The history of the study of interacting galaxies, the behavior of gas in binary systems, studies to identify the processes that occur when galaxies interact, and the relationship of Seyfert galaxies and quasars to binary systems are discussed. The development of an atlas of peculiar galaxies (Arp, 1966) and methods for modeling galaxy interactions are examined

  14. ISO far-infrared observations of rich galaxy clusters II. Sersic 159-03

    DEFF Research Database (Denmark)

    Hansen, Lene; Jørgensen, H.E.; Nørgaard-Nielsen, Hans Ulrik

    2000-01-01

    In a series of papers we investigate far-infrared emission from rich galaxy clusters. Maps have been obtained by ISO at 60 mu m, 100 mu m, 135 mu m, and 200 mu m using the PHT-C camera. Ground based imaging and spectroscopy were also acquired. Here we present the results for the cooling flow...

  15. SPATIAL ANISOTROPY OF GALAXY KINEMATICS IN SLOAN DIGITAL SKY SURVEY GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Skielboe, Andreas; Wojtak, Radosław; Pedersen, Kristian; Rozo, Eduardo; Rykoff, Eli S.

    2012-01-01

    Measurements of galaxy cluster kinematics are important in understanding the dynamical state and evolution of clusters of galaxies, as well as constraining cosmological models. While it is well established that clusters exhibit non-spherical geometries, evident in the distribution of galaxies on the sky, azimuthal variations of galaxy kinematics within clusters have yet to be observed. Here we measure the azimuthal dependence of the line-of-sight velocity dispersion profile in a stacked sample of 1743 galaxy clusters from the Sloan Digital Sky Survey (SDSS). The clusters are drawn from the SDSS DR8 redMaPPer catalog. We find that the line-of-sight velocity dispersion of galaxies lying along the major axis of the central galaxy is larger than those that lie along the minor axis. This is the first observational detection of anisotropic kinematics of galaxies in clusters. We show that the result is consistent with predictions from numerical simulations. Furthermore, we find that the degree of projected anisotropy is strongly dependent on the line-of-sight orientation of the galaxy cluster, opening new possibilities for assessing systematics in optical cluster finding.

  16. Tidal interaction of galaxies

    International Nuclear Information System (INIS)

    Kozlov, N.N.; Syunyaev, R.A.; Ehneev, T.M.

    1974-01-01

    One of the hypotheses explaining the occurrence of anomalous details in interacting galaxies has been investigated. Pairs of galaxies with 'tails' oppositely directed or neighbouring galaxies with cofferdams 'bridges', as if connecting the galaxies, are called interacting galaxies. The hypothesis connects the origin of cofferdams and 'tails' of interacting galaxies with tidal effects ; the action of power gravitational forces in the intergalactic space. A source of such forces may be neighbouring stellar systems or invisible bodies, for instance, 'dead' quasars after a gravitational collapse. The effect of large masses of matter on the galaxy evolution has been investigated in the Institute of Applied Mathematics of the Academy of Sciences of the USSSR in 1971-1972 by numerical simulation of the process on a digital computer with the subsequent data transmission on a display. Different versions of a massive body flight relative to a galaxy disk are considered. Photographs of a display screen at different moments of time are presented. As a result of mathematical simulation of galaxies gravitational interactions effects are discovered which resemble real structures in photographs of galaxies. It seems to be premature to state that namely these mechanisms cause the formation of 'tails' and cofferdams between galaxies. However, even now it is clear that the gravitational interaction strongly affects the dynamics of the stellar system evolution. Further studies should ascertain a true scale of this effect and its genuine role in galaxy evolution

  17. Nearby Galaxies: Templates for Galaxies Across Cosmic Time

    OpenAIRE

    Lockman, F. J.; Ott, J.

    2009-01-01

    Studies of nearby galaxies including the Milky Way have provided fundamental information on the evolution of structure in the Universe, the existence and nature of dark matter, the origin and evolution of galaxies, and the global features of star formation. Yet despite decades of work, many of the most basic aspects of galaxies and their environments remain a mystery. In this paper we describe some outstanding problems in this area and the ways in which large radio facilities will contribute ...

  18. GALAXY ENVIRONMENTS OVER COSMIC TIME: THE NON-EVOLVING RADIAL GALAXY DISTRIBUTIONS AROUND MASSIVE GALAXIES SINCE z = 1.6

    International Nuclear Information System (INIS)

    Tal, Tomer; Van Dokkum, Pieter G.; Leja, Joel; Franx, Marijn; Wake, David A.; Whitaker, Katherine E.

    2013-01-01

    We present a statistical study of the environments of massive galaxies in four redshift bins between z = 0.04 and z = 1.6, using data from the Sloan Digital Sky Survey and the NEWFIRM Medium Band Survey. We measure the projected radial distribution of galaxies in cylinders around a constant number density selected sample of massive galaxies and utilize a statistical subtraction of contaminating sources. Our analysis shows that massive primary galaxies typically live in group halos and are surrounded by 2-3 satellites with masses more than one-tenth of the primary galaxy mass. The cumulative stellar mass in these satellites roughly equals the mass of the primary galaxy itself. We further find that the radial number density profile of galaxies around massive primaries has not evolved significantly in either slope or overall normalization in the past 9.5 Gyr. A simplistic interpretation of this result can be taken as evidence for a lack of mergers in the studied groups and as support for a static evolution model of halos containing massive primaries. Alternatively, there exists a tight balance between mergers and accretion of new satellites such that the overall distribution of galaxies in and around the halo is preserved. The latter interpretation is supported by a comparison to a semi-analytic model, which shows a similar constant average satellite distribution over the same redshift range.

  19. EARLY-TYPE GALAXIES AT z ∼ 1.3. II. MASSES AND AGES OF EARLY-TYPE GALAXIES IN DIFFERENT ENVIRONMENTS AND THEIR DEPENDENCE ON STELLAR POPULATION MODEL ASSUMPTIONS

    International Nuclear Information System (INIS)

    Raichoor, A.; Mei, S.; Huertas-Company, M.; Nakata, F.; Kodama, T.; Stanford, S. A.; Rettura, A.; Jee, M. J.; Holden, B. P.; Illingworth, G.; Postman, M.; White, R. L.; Rosati, P.; Blakeslee, J. P.; Demarco, R.; Eisenhardt, P.; Tanaka, M.

    2011-01-01

    We have derived masses and ages for 79 early-type galaxies (ETGs) in different environments at z ∼ 1.3 in the Lynx supercluster and in the GOODS/CDF-S field using multi-wavelength (0.6-4.5 μm; KPNO, Palomar, Keck, Hubble Space Telescope, Spitzer) data sets. At this redshift the contribution of the thermally pulsing asymptotic giant branch (TP-AGB) phase is important for ETGs, and the mass and age estimates depend on the choice of the stellar population model used in the spectral energy distribution fits. We describe in detail the differences among model predictions for a large range of galaxy ages, showing the dependence of these differences on age. Current models still yield large uncertainties. While recent models from Maraston and Charlot and Bruzual offer better modeling of the TP-AGB phase with respect to less recent Bruzual and Charlot models, their predictions do not often match. The modeling of this TP-AGB phase has a significant impact on the derived parameters for galaxies observed at high redshift. Some of our results do not depend on the choice of the model: for all models, the most massive galaxies are the oldest ones, independent of the environment. When using the Maraston and Charlot and Bruzual models, the mass distribution is similar in the clusters and in the groups, whereas in our field sample there is a deficit of massive (M ∼> 10 11 M sun ) ETGs. According to those last models, ETGs belonging to the cluster environment host on average older stars with respect to group and field populations. This difference is less significant than the age difference in galaxies of different masses.

  20. Galaxy Formation

    CERN Document Server

    Longair, Malcolm S

    2008-01-01

    This second edition of Galaxy Formation is an up-to-date text on astrophysical cosmology, expounding the structure of the classical cosmological models from a contemporary viewpoint. This forms the background to a detailed study of the origin of structure and galaxies in the Universe. The derivations of many of the most important results are derived by simple physical arguments which illuminate the results of more advanced treatments. A very wide range of observational data is brought to bear upon these problems, including the most recent results from WMAP, the Hubble Space Telescope, galaxy surveys like the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey, studies of Type 1a supernovae, and many other observations.