WorldWideScience

Sample records for cluster-influenced spiral galaxy

  1. Nuclear spirals in galaxies

    OpenAIRE

    Maciejewski, Witold

    2006-01-01

    Recent high-resolution observations indicate that nuclear spirals are often present in the innermost few hundred parsecs of disc galaxies. My models show that nuclear spirals form naturally as a gas response to non-axisymmetry in the gravitational potential. Some nuclear spirals take the form of spiral shocks, resulting in streaming motions in the gas, and in inflow comparable to the accretion rates needed to power local Active Galactic Nuclei. Recently streaming motions of amplitude expected...

  2. Superluminous Spiral Galaxies

    CERN Document Server

    Ogle, Patrick M; Nader, Cyril; Helou, George

    2015-01-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity L_r=8-14L* (4.3-7.5E44 erg/s). These super spiral galaxies are also giant and massive, with diameter D=57-134 kpc and stellar mass M_stars=0.3-3.4E11 M_sun. We find 53 super spirals out of a complete sample of 1,616 SDSS galaxies with redshift z8L*. The closest example is found at z=0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and WISE colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5-65 M_sun/yr place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers--a possible clue to their formation. We su...

  3. SUPERLUMINOUS SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Ogle, Patrick M.; Lanz, Lauranne; Nader, Cyril; Helou, George, E-mail: ogle@ipac.caltech.edu [IPAC, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States)

    2016-02-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity L{sub r} = 8–14L* (4.3–7.5 × 10{sup 44} erg s{sup −1}). These super spiral galaxies are also giant and massive, with diameter D = 57–134 kpc and stellar mass M{sub stars} = 0.3–3.4 × 10{sup 11}M{sub ⊙}. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and L{sub r} > 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5–65 M{sub ⊙} yr{sup −1} place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.

  4. Genesis of spiral galaxies

    CERN Document Server

    Kiselev, Valery V

    2013-01-01

    Enigmatic spiral structure of many galaxies and its huge orbital momentum originated due to the capture of lightweight bare black hole by gravity of heavy primordial gas cloud at large impact parameter. The rotating of black hole caused the formation of accretion disc from the cloud and the transfer of orbital momentum to the disc, while during the fall to the center of mass, the spiral trace of black hole in the disc did create the spiral front line of sound waves in the gas, that further evolved into the stellar spiral arms. This mechanism opens the way to study features of spiral galaxy formation, say, an influence and a significance of dark matter in this process.

  5. Investigating Dwarf Spiral Galaxies

    Science.gov (United States)

    Weerasooriya, Sachithra; Dunn, Jacqueline M.

    2017-01-01

    Several studies have proposed that dwarf elliptical / spheroidal galaxies form through the transformation of dwarf irregular galaxies. Early and late type dwarfs resemble each other in terms of their observed colors and light distributions (each can often be represented by exponential disks), providing reason to propose an evolutionary link between the two types. The existence of dwarf spirals has been largely debated. However, more and more recent studies are using the designation of dwarf spiral to describe their targets of interest. This project seeks to explore where dwarf spirals fit into the above mentioned evolutionary sequence, if at all. Optical colors will be compared between a sample of dwarf irregular, dwarf elliptical, and dwarf spiral galaxies. The dwarf irregular and dwarf elliptical samples have previously been found to overlap in both optical color and surface brightness profile shape when limiting the samples to their fainter members. A preliminary comparison including the dwarf spiral sample will be presented here, along with a comparison of available ultraviolet and near-infrared data. Initial results indicate a potential evolutionary link that merits further investigation.

  6. 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

  7. Galaxy Zoo: Passive Red Spirals

    CERN Document Server

    Masters, Karen L; Romer, A Kathy; Nichol, Robert C; Bamford, Steven P; Schawinski, Kevin; Lintott, Chris J; Andreescu, Dan; Campbell, Heather C; Crowcroft, Ben; Doyle, Isabelle; Edmondson, Edward M; Murray, Phil; Raddick, M Jordan; Slosar, Anze; Szalay, Alexander S; Vandenberg, Jan

    2009-01-01

    We study the spectroscopic properties and environments of red spiral galaxies found by the Galaxy Zoo project. By carefully selecting face-on, disk dominated spirals we construct a sample of truly passive disks (not dust reddened, nor dominated by old stellar populations in a bulge). As such, our red spirals represent an interesting set of possible transition objects between normal blue spirals and red early types. We use SDSS data to investigate the physical processes which could have turned these objects red without disturbing their morphology. Red spirals prefer intermediate density regimes, however there are no obvious correlations between red spiral properties and environment - environment alone is not sufficient to determine if a galaxy will become a red spiral. Red spirals are a small fraction of spirals at low masses, but dominate at large stellar masses - massive galaxies are red independent of morphology. We confirm that red spirals have older stellar populations and less recent star formation than ...

  8. Satellites of spiral galaxies

    Science.gov (United States)

    Zaritsky, Dennis; Smith, Rodney; Frenk, Carlos; White, Simon D. M.

    1993-01-01

    We present a survey of satellites around a homogeneous set of late-type spirals with luminosity similar to that of the Milky Way. On average, we find fewer than 1.5 satellites per primary, but we argue that we can treat the survey as an ensemble and so derive the properties of the halo of a 'typical' isolated spiral. The projected density profile of the ensemble falls off approximately as 1/r. Within 50 kpc the azimuthal distribution of satellites shows some evidence for the 'Holmberg effect', an excess near the minor axis of the primary; however, at larger projected distances, the distribution appears isotropic. There is a weak but significant correlation between the size of a satellite and its distance from its primary, as expected if satellites are tidally truncated. Neither Hubble type nor spectral characteristics correlate with apparent separation. The ensemble of satellites appears to be rotating at about 30 km/s in the same direction as the galactic disk. Satellites on prograde orbits tend to be brighter than those on retrograde orbits. The typical velocity difference between a satellite and its primary shows no clear dependence either on apparent separation, or on the rotation speed of the primary. Thus our survey demonstrates that isolated spiral galaxies have massive halos that extend to many optical radii.

  9. Galaxy Zoo: Dust in Spirals

    CERN Document Server

    Masters, Karen L; 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 SDSS galaxies visually classified in Galaxy Zoo. 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 magnitudes for the ugri passbands. We split the sample into "bulgy" (early-type) and "disky" (late-type) spirals using the SDSS fracdeV (or f_DeV) parameter and show that the average face-on colour of "bulgy" spirals is redder than the average edge-on colour of "disky" spirals. This shows that the observed optical colour of a spiral galaxy is determined almost equally by the spiral type (via the bulge-disk ratio and stellar populations), and reddening due to dust. We find that both luminosity and spiral type affect the total amount of extinction, with "disky" spirals at M_r ~ -21.5 mags having the most reddening. This decrease of reddening for the most luminous spirals has not been observed before ...

  10. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with

  11. Magnetic Fields in Spiral Galaxies

    CERN Document Server

    Beck, Rainer

    2015-01-01

    Radio synchrotron emission is a powerful tool to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30\\mu G) and in central starburst regions (50-100\\mu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15\\mu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the interg...

  12. Quantitative analysis of spirality in elliptical galaxies

    CERN Document Server

    Dojcsak, Levente

    2013-01-01

    We use an automated galaxy morphology analysis method to quantitatively measure the spirality of galaxies classified manually as elliptical. The data set used for the analysis consists of 60,518 galaxy images with redshift obtained by the Sloan Digital Sky Survey (SDSS) and classified manually by Galaxy Zoo, as well as the RC3 and NA10 catalogues. We measure the spirality of the galaxies by using the Ganalyzer method, which transforms the galaxy image to its radial intensity plot to detect galaxy spirality that is in many cases difficult to notice by manual observation of the raw galaxy image. Experimental results using manually classified elliptical and S0 galaxies with redshift <0.3 suggest that galaxies classified manually as elliptical and S0 exhibit a nonzero signal for the spirality. These results suggest that the human eye observing the raw galaxy image might not always be the most effective way of detecting spirality and curves in the arms of galaxies.

  13. Spiral Galaxies as Chiral Objects?

    CERN Document Server

    Capozziello, S; Capozziello, Salvatore; Lattanzi, Alessandra

    2005-01-01

    Spiral galaxies show axial symmetry and an intrinsic 2D-chirality. Environmental effects can influence the chirality of originally isolated stellar systems and a progressive loss of chirality can be recognised in the Hubble sequence. We point out a preferential modality for genetic galaxies as in microscopic systems like aminoacids, sugars or neutrinos. This feature could be the remnant of a primordial symmetry breaking characterizing systems at all scales.

  14. Simulations of Normal Spiral Galaxies

    CERN Document Server

    Bottema, R

    2003-01-01

    Results are presented of numerical simulations of normal isolated late type spiral galaxies. Specifically the galaxy NGC 628 is used as a template. The method employs a TREESPH code including stellar particles, gas particles, cooling and heating of the gas, star formation according to a Jeans criterion, and Supernova feedback. A regular spiral disc can be generated as an equilibrium situation of two opposing actions. On the one hand cooling and dissipation of the gas, on the other hand gas heating by the FUV field of young stars and SN mechanical forcing. The disc exhibits small and medium scale spiral structure of which the multiplicity increases as a function of radius. The theory of swing amplification can explain, both qualitatively and quantitatively, the emerging spiral structure. In addition, swing amplification predicts that the existence of a grand design m=2 spiral is only possible if the disc is massive. The simulations show that the galaxy is then unstable to bar formation. A general criterion is ...

  15. Lopsided Spiral Galaxies

    CERN Document Server

    Jog, Chanda J

    2008-01-01

    The light distribution in the disks of many galaxies is non-axisymmetric or `lopsided' with a spatial extent much larger along one half of a galaxy than the other, as in M101. Recent near-IR observations show that lopsidedness is common. The stellar disks in nearly 30 % of galaxies have significant lopsidedness, greater than 10 % measured as the Fourier amplitude of the m=1 component normalized to the average value. This asymmetry is traced particularly well by the atomic hydrogen gas distribution lying in the outer parts. The lopsidedness also occurs in the nuclear regions, where the nucleus is offset with respect to the outer isophotes. The galaxies in a group environment show higher lopsidedness. The origin of lopsidedness could be due to the disk response to a tidally distorted halo, or via gas accretion. The lopsidedness has a large impact on the dynamics of the galaxy, its evolution, the star formation in it, and on the growth of the central black hole and on the nuclear fueling, merging of binary black...

  16. Scale height determination of spiral galaxies

    Institute of Scientific and Technical Information of China (English)

    计朝晖; 商朝晖; 彭秋和

    1997-01-01

    The method adopted here is based on the rigorous solution of Poison’s equation for logarithmic disturbance density within finite thickness galaxies. After their spiral arms are fitted directly with logarithmic spirals, the morphological parameters, scale heights and their relative errors for 32 spiral galaxies, such as NGC4814, are ob-tained.

  17. On Three-Dimensional Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    LUO Xin-Lian; PENG Qiu-He; LONG Min; PENG Fang; ZOU Zhi-Gang

    2000-01-01

    Density waves in 3D spiral galaxies are studied. In order to eliminate the forbidden region near the corotation in the grand-design galaxies, we assume that the perturbation satisfies the stable condition Q(r) > 1 over all the disk except that at the corotation. Then, a new method is put forward here to determine some basic parameters of spiral galaxies. We apply it to our Galaxy, and the results are in good agreement with the previous results.

  18. ANGULAR-MOMENTUM IN BINARY SPIRAL GALAXIES

    NARCIS (Netherlands)

    OOSTERLOO, T

    1993-01-01

    In order to investigate the relative orientations of spiral galaxies in pairs, the distribution of the angle between the spin-vectors for a new sample of 40 binary spiral galaxies is determined. From this distribution it is found, contrary to an earlier result obtained by Helou (1984), that there is

  19. Scale heights of 84 northern spiral galaxies

    Institute of Scientific and Technical Information of China (English)

    马骏; 彭秋和

    1997-01-01

    Using the method proposed by Peng (1988) on the basis of density waves theory and the solution of three-dimensional Poisson s equation for a logarithmic disturbance of density,and analyzing the spiral patterns,the scale heights of 84 northern spiral galaxies,whose images are taken from the Digitized Sky Survey at Xinglong Observational Station of Beijing Observatory,are measured.The spiral arms of all these galaxies have been fitted on their photographs with some logarithmic spiral curves for getting their correct inclinations.

  20. Simulations of dual morphology in spiral galaxies

    CERN Document Server

    Berman, S L

    2003-01-01

    Gas and stars in spiral galaxies are modelled with the DUAL code, using hydrodynamic and N-body techniques. The simulations reveal morphological differences mirroring the dual morphologies seen in B and K' band observations of many spiral galaxies. In particular, the gaseous images are more flocculent with lower pitch angles than the stellar images, and the stellar arm-interarm contrast correlates with the degree of morphological decoupling.

  1. Uncovering spiral structure in flocculent galaxies

    CERN Document Server

    Thornley, M D

    1996-01-01

    We present K'(2.1 micron) observations of four nearby flocculent spirals, which clearly show low-level spiral structure and suggest that kiloparsec-scale spiral structure is more prevalent in flocculent spirals than previously supposed. In particular, the prototypical flocculent spiral NGC 5055 is shown to have regular, two-arm spiral structure to a radius of 4 kpc in the near infrared, with an arm-interarm contrast of 1.3. The spiral structure in all four galaxies is weaker than that in grand design galaxies. Taken in unbarred galaxies with no large, nearby companions, these data are consistent with the modal theory of spiral density waves, which maintains that density waves are intrinsic to the disk. As an alternative, mechanisms for driving spiral structure with non-axisymmetric perturbers are also discussed. These observations highlight the importance of near infrared imaging for exploring the range of physical environments in which large-scale dynamical processes, such as density waves, are important.

  2. Arm Structure in Anemic Spiral Galaxies

    CERN Document Server

    Elmegreen, D M; Frogel, J A; Eskridge, P B; Pogge, R W; Gallagher, A; Iams, J; Elmegreen, Debra Meloy; Elmegreen, Bruce G.; Frogel, Jay A.; Eskridge, Paul B.; Pogge, Richard W.; Gallagher, Andrew; Iams, Joel

    2002-01-01

    Anemic galaxies have less prominent star formation than normal galaxies of the same Hubble type. Previous studies showed they are deficient in total atomic hydrogen but not in molecular hydrogen. Here we compare the combined surface densities of HI and H2 at mid-disk radii with the Kennicutt threshold for star formation. The anemic galaxies are below threshold, which explains their lack of prominent star formation, but they are not much different than other early type galaxies, which also tend to be below threshold. The spiral wave amplitudes of anemic and normal galaxies were also compared, using images in B and J passbands from the OSU Bright Spiral Galaxy Survey. Anemic galaxies have normal spiral wave properties too, with the same amplitudes and radial dependencies as other galaxies of the same arm class. Because of the lack of gas, spiral waves in early type galaxies and anemics do not have a continuous supply of stars with low velocity dispersions to maintain a marginally stable disk. As a result, they ...

  3. Fast magnetohydrodynamic density waves in spiral galaxies

    Science.gov (United States)

    Lou, Yu-Qing; Han, J. L.; Fan, Zuhui

    1999-09-01

    The newly observed large-scale structures of a southern grand-design spiral galaxy NGC 2997 in total and polarized radio-continuum emission together with their overall correlations with the known optical spiral structure are physically interpreted in terms of fast magnetohydrodynamic (MHD) density waves in contrast to slow MHD density waves in NGC 6946. The global spiral pattern of such fast MHD density waves extends from the very centre, where the disc rotates almost rigidly within ~0.5arcmin, all the way to the outer disc with a more or less flat rotation curve. To strengthen the case, several known features of spiral galaxies M51 and IC 342 are referred to and their pattern identifications discussed. It is emphasized that the nature of a magnetized spiral galaxy would be much better appreciated by examining large-scale structures in optical, atomic hydrogen Hi, total and polarized radio-continuum and infrared emission together. As various star-formation processes occur concurrently and/or sequentially in spiral arms of high gas concentration, relatively broad and fuzzy Hi arms, roughly coincident with optical arms in the inner disc, are expected to extend from the extremities of fading optical arms further into the outer gas disc. We predict that the south-east `magnetic arm', apparently isolated from any optical features, in total and polarized radio-continuum intensity maps of NGC 2997 should be associated with an Hi gas arm yet to be detected in 21-cm line emission.

  4. Radial transport of dust in spiral galaxies

    CERN Document Server

    Vorobyov, E I; Shchekinov, Yu. A.

    2006-01-01

    Motivated by recent observations which detect dust at large galactocentric distances in the disks of spiral galaxies, we propose a mechanism of outward radial transport of dust by spiral stellar density waves. We consider spiral galaxies in which most of dust formation is localized inside the corotation radius. We show that in the disks of such spiral galaxies, the dust grains can travel over radial distances that exceed the corotation radius by roughly 25%. A fraction of the dust grains can be trapped on kidney-shaped stable orbits between the stellar spiral arms and thus can escape the destructive effect of supernova explosions. These grains form diffuse dusty spiral arms, which stretch 4-5 kpc from the sites of active star formation. About 10% of dust by mass injected inside corotation, can be transported over radial distances 3-4 kpc during approximately 1.0 Gyr. This is roughly an order of magnitude more efficient than can be provided by the turbulent motions.

  5. Are spiral galaxies optically thin or thick?

    CERN Document Server

    Xilouris, E M; Kylafis, N D; Paleologou, E V; Papamastorakis, J

    1999-01-01

    The opacity of spiral galaxies is examined by modelling the dust and stellar content of individual galaxies. The model is applied to five late-type spiral galaxies (NGC 4013, IC 2531, UGC 1082, NGC 5529 and NGC 5907). Having analyzed a total of seven galaxies thus far, the five galaxies mentioned above plus UGC 2048 and NGC 891 presented in (Xilouris et al. 1997, 1998), we are able to draw some general conclusions, the most significant of which are: 1) The face-on central optical depth is less than one in all optical bands indicating that typical spiral galaxies like the ones that we have modelled would be completely transparent if they were to be seen face-on. 2) The dust scaleheight is about half that of the stars, which means that the dust is more concentrated near the plane of the disk. 3) The dust scalelength is about 1.4 times larger than that of the stars and the dust is more radially extended than the stars. 4) The dust mass is found to be about an order of a magnitude more than previously measured us...

  6. Short WSRT HI observations of spiral galaxies

    NARCIS (Netherlands)

    Rhee, MH; vanAlbada, TS

    1996-01-01

    We have obtained short HI observations of 60 late type spiral galaxies with the Westerbork Synthesis Radio Telescope (WSRT). Several HI properties are presented, including the radial surface density distribution of HI and a position-velocity map. When possible these are compared to those measured fr

  7. The Milky Way and other spiral galaxies

    Directory of Open Access Journals (Sweden)

    Wang J.L.

    2012-02-01

    Full Text Available Cosmologists have often considered the Milky Way as a typical spiral galaxy, and its properties have considerably influenced the current scheme of galaxy formation. Here we compare the general properties of the Milky Way disk and halo with those of galaxies selected from the SDSS. Assuming the recent measurements of its circular velocity results in the Milky Way being offset by ~2σ from the fundamental scaling relations. On the basis of their location in the (MK, Rd, Vflat volume, the fraction of SDSS spirals like the MilkyWay is only 1.2% in sharp contrast with M31, which appears to be quite typical. Comparison of the Milky Way with M31 and with other spirals is also discussed to investigate whether or not there is a fundamental discrepancy between their mass assembly histories. Possibly the Milky Way is one of the very few local galaxies that could be a direct descendant of very distant, z = 2-3 galaxies, thanks to its quiescent history since thick disk formation.

  8. Modelling Neutral Hydrogen Discs of Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    林伟鹏; 洪碧海

    2002-01-01

    We present an analytical model of a neutral hydrogen disc in a spiral galaxy. The gas disc of the spiral galaxy isassumed to have an exponential surface density profile and to be ionized by the cosmic ultraviolet background.To compare with observations, we consider the disc position angle and inclination angle for a line of sight goingthrough the galaxy disc. The HI column densities depend on the strength of ionizing field and disc position andinclination. The model was applied to NGC 3198 and the results were compared with observational data. TheHI disc profile at large disc radii can be tested by further HI observations using radio telescopes with a largeraperture than the present facilities. This HI disc model can be used to predict quasar absorption line systems bygalaxy discs if quasar lines of sight go through the discs.

  9. Magnetic fields in spiral galaxies

    Science.gov (United States)

    Krause, Marita

    2015-03-01

    The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At λ6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).

  10. The Geometry of the Galaxy's Spiral Arms

    Science.gov (United States)

    Steiman-Cameron, Thomas Y.; Wolfire, M.; Hollenbach, D.

    2008-05-01

    We present a new model for the spiral structure of the Milky Way based upon an analysis of the essentially all-sky spectral data obtained by the Far Infrared Absolute Spectrophotometer (FIRAS) instrument of the Cosmic Background Explorer (COBE) satellite. The model provides the volume emissivities of the [C II] 128 µm and [N II] 205 µm lines, as a function of position within the Galaxy. These lines are important coolants of the interstellar medium and strong tracers of the spiral structure. Despite decades of work, there is still no full agreement on the number of spiral arms in the Milky Way, much less the details of their geometry. Motivated, in part, by this fact, we conducted a systematic search for 2-arm, 3-arm, and 4-arm models that maximize agreement with the COBE data. We find that only a four-arm model, with arms defined by logarithmic spiral forms and pitch angles ranging from 13.5 to 15.6 degrees, is consistent with the observations. The arms are neither evenly spaced nor identical in form. The resultant volume emissivity models for C+ and N+, when convolved with the FIRAS beam and integrated over the Galaxy, reproduce the COBE [C II] 128 µm and [N II] 205 µm intensity maps extremely well. We also examine all models for the Galaxy's spiral structure that have been proposed over the past half century in the context of the same COBE observations. A significant fraction of these models, including many recent ones, appear to be incompatible with the data. However, several four-arm models from the literature are consistent with the COBE observations.

  11. A Photometrically and Spectroscopically Confirmed Population of Passive Spiral Galaxies

    CERN Document Server

    Fraser-McKelvie, Amelia; Pimbblet, Kevin A; Dolley, Tim; Crossett, Jacob P; Bonne, Nicolas J

    2016-01-01

    We have identified a population of passive spiral galaxies from photometry and integral field spectroscopy. We selected z<0.035 spiral galaxies that have WISE colours consistent with little mid-infrared emission from warm dust. Matched aperture photometry of 51 spiral galaxies in ultraviolet, optical and mid-infrared show these galaxies have colours consistent with passive galaxies. Six galaxies form a spectroscopic pilot study and were observed using the Wide-Field Spectrograph (WiFeS) to check for signs of nebular emission from star formation. We see no evidence of substantial nebular emission found in previous red spiral samples. These six galaxies possess absorption-line spectra with 4000\\AA\\ breaks consistent with an average luminosity-weighted age of 2.3 Gyr. Our photometric and IFU spectroscopic observations confirm the existence of a population of local passive spiral galaxies, implying that transformation into early-type morphologies is not required for the quenching of star formation.

  12. The cold interstellar medium - An HI view of spiral galaxies

    NARCIS (Netherlands)

    Sancisi, R; Bender, R; Davies, RL

    1996-01-01

    An HI view of spiral galaxies is presented. In the first part the standard picture of isolated, normal spiral galaxies is briefly reviewed. In the second part attention is drawn to all those phenomena, such as tidal interactions, accretion and mergers, that depend on the galaxy environment and seem

  13. Lopsided spiral galaxies: evidence for gas accretion

    CERN Document Server

    Bournaud, F; Jog, C J; Puerari, I

    2005-01-01

    We quantify the degree of lopsidedness for a sample of 149 galaxies observed in the near-infrared from the OSUBGS sample, and try to explain the physical origin for the observed disk lopsidedness. We confirm previous studies, but now for a larger sample, that a large fraction of galaxies show significant lopsidedness in their stellar disks, measured as the Fourier amplitude of the m=1 component, normalised to the average or m=0 component, in the surface density. Late-type galaxies are found to be more lopsided, while the presence of m=2 spiral arms and bars is correlated. The m=1 amplitude is found to be uncorrelated with the tidal forces acting on a galaxy via nearby companions. Numerical simulations are carried out to study the generation of m=1 via different processes: galaxy tidal encounters, galaxy mergers, and external gas accretion and subsequent star formation. The simulations show that galaxy interactions and mergers can trigger strong lopsidedness, but do not explain several independent statistical ...

  14. A Unified Scaling Law in Spiral Galaxies.

    Science.gov (United States)

    Koda; Sofue; Wada

    2000-03-01

    We investigate the origin of a unified scaling relation in spiral galaxies. Observed spiral galaxies are spread on a plane in the three-dimensional logarithmic space of luminosity L, radius R, and rotation velocity V. The plane is expressed as L~&parl0;VR&parr0;alpha in the I passband, where alpha is a constant. On the plane, observed galaxies are distributed in an elongated region which looks like the shape of a surfboard. The well-known scaling relations L-V (Tully-Fisher [TF] relation), V-R (also the TF relation), and R-L (Freeman's law) can be understood as oblique projections of the surfboard-like plane into two-dimensional spaces. This unified interpretation of the known scaling relations should be a clue to understand the physical origin of all the relations consistently. Furthermore, this interpretation can also explain why previous studies could not find any correlation between TF residuals and radius. In order to clarify the origin of this plane, we simulate formation and evolution of spiral galaxies with the N-body/smoothed particle hydrodynamics method, including cooling, star formation, and stellar feedback. Initial conditions are set to 14 isolated spheres with two free parameters, such as mass and angular momentum. The cold dark matter (h=0.5, Omega0=1) cosmology is considered as a test case. The simulations provide the following two conclusions: (1) The slope of the plane is well reproduced but the zero point is not. This zero-point discrepancy could be solved in a low-density (Omega00.5) cosmology. (2) The surfboard-shaped plane can be explained by the control of galactic mass and angular momentum.

  15. Halpha Morphologies and Environmental Effects in Virgo Cluster Spiral Galaxies

    CERN Document Server

    Koopmann, R A

    2004-01-01

    We describe the various Halpha morphologies of Virgo Cluster and isolated spiral galaxies, and associate the Halpha morphologies with the types of environmental interactions which have altered the cluster galaxies. The spatial distributions of Halpha and R-band emission are used to divide the star formation morphologies of the 52 Virgo Cluster spirals into several categories: normal (37%), anemic (6%), enhanced (6%), and (spatially) truncated (52%). Truncated galaxies are further subdivided based on their inner star formation rates into truncated/normal (37%), truncated/compact (6%), truncated/anemic (8%), and truncated/enhanced (2%). The fraction of anemic galaxies is relatively small (6-13%) in both environments, suggesting that starvation is not a major factor in the reduced star formation rates of Virgo spirals. The majority of Virgo spiral galaxies have their Halpha disks truncated (52%), whereas truncated Halpha disks are rarer in isolated galaxies (12%). Most of the Halpha-truncated galaxies have relat...

  16. The Nature of Red-Sequence Cluster Spiral Galaxies

    Science.gov (United States)

    Kashur, Lane; Barkhouse, Wayne; Sultanova, Madina; Kalawila Vithanage, Sandanuwa; Archer, Haylee; Foote, Gregory; Mathew, Elijah; Rude, Cody; Lopez-Cruz, Omar

    2017-01-01

    Preliminary analysis of the red-sequence galaxy population from a sample of 57 low-redshift galaxy clusters observed using the KPNO 0.9m telescope and 74 clusters from the WINGS dataset, indicates that a small fraction of red-sequence galaxies have a morphology consistent with spiral systems. For spiral galaxies to acquire the color of elliptical/S0s at a similar luminosity, they must either have been stripped of their star-forming gas at an earlier epoch, or contain a larger than normal fraction of dust. To test these ideas we have compiled a sample of red-sequence spiral galaxies and examined their infrared properties as measured by 2MASS, WISE, Spitzer, and Herschel. These IR data allows us to estimate the amount of dust in each of our red-sequence spiral galaxies. We compare the estimated dust mass in each of these red-sequence late-type galaxies with spiral galaxies located in the same cluster field but having colors inconsistent with the red-sequence. We thus provide a statistical measure to discriminate between purely passive spiral galaxy evolution and dusty spirals to explain the presence of these late-type systems in cluster red-sequences.

  17. BVRI Surface Photometry of Isolated Spiral Galaxies

    CERN Document Server

    Hernandez-Toledo, H; Avila-Reese, V

    2007-01-01

    A release of multicolor broad band (BVRI) photometry for a subsample of 44 isolated spirals drawn from the Catalogue of Isolated Galaxies (CIG) is presented. Total magnitudes and colors at various circular apertures, as well as some global structural/morphological parameters are estimated. Morphology is reevaluated through optical and sharp/filtered R band images, (B-I) color index maps, and archive near-IR JHK images from the Two-Micron Survey. The CAS structural parameters (Concentration, Asymmetry, and Clumpiness) were calculated from the images in each one of the bands. The fraction of galaxies with well identified optical/near-IR bars (SB) is 63%, while a 17% more shows evidence of weak or suspected bars (SAB). The sample average value of the maximum bar ellipticity is 0.4. Half of the galaxies in the sample shows rings. We identify two candidates for isolated galaxies with disturbed morphology. The structural CAS parameters change with the observed band, and the tendencies they follow with the morpholog...

  18. Scale Heights of Non-Edge-on Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    Tao Hu; Qiu-He Peng; Ying-He Zhao

    2006-01-01

    We present a method of calculating the scale height of non-edge-on spiral galaxies, together with a formula for errors. The method is based on solving Poisson's equation for a logarithmic disturbance of matter density in spiral galaxies. We show that the spiral arms can not extend to inside the "forbidden radius" γ0, due to the effect of the finite thickness of the disk. The method is tested by re-calculating the scale heights of 71 northern spiral galaxies previously calculated by Ma, Peng & Gu.Our results differ from theirs by less than 9%. We also present the scale heights of a further 23 non-edge-on spiral galaxies.

  19. THE SURFACE BRIGHTNESS OF OUR GALAXY AND OTHER SPIRALS

    NARCIS (Netherlands)

    VANDERKRUIT, PC

    1990-01-01

    In this review I discuss some aspects of the luminosity distributions in our Galaxy and external spiral galaxies. The major conclusions are the following: (1) the radial scale length of the luminosity distribution in the disk of our Galaxy is 5.0 +/- 0.5 kpc, (2) on this basis the Hubble constant ne

  20. Galaxy Zoo: star formation versus spiral arm number

    Science.gov (United States)

    Hart, Ross E.; Bamford, Steven P.; Casteels, Kevin R. V.; Kruk, Sandor J.; Lintott, Chris J.; Masters, Karen L.

    2017-06-01

    Spiral arms are common features in low-redshift disc galaxies, and are prominent sites of star formation and dust obscuration. However, spiral structure can take many forms: from galaxies displaying two strong 'grand design' arms to those with many 'flocculent' arms. We investigate how these different arm types are related to a galaxy's star formation and gas properties by making use of visual spiral arm number measurements from Galaxy Zoo 2. We combine ultraviolet and mid-infrared (MIR) photometry from GALEX and WISE to measure the rates and relative fractions of obscured and unobscured star formation in a sample of low-redshift SDSS spirals. Total star formation rate has little dependence on spiral arm multiplicity, but two-armed spirals convert their gas to stars more efficiently. We find significant differences in the fraction of obscured star formation: an additional ˜10 per cent of star formation in two-armed galaxies is identified via MIR dust emission, compared to that in many-armed galaxies. The latter are also significantly offset below the IRX-β relation for low-redshift star-forming galaxies. We present several explanations for these differences versus arm number: variations in the spatial distribution, sizes or clearing time-scales of star-forming regions (i.e. molecular clouds), or contrasting recent star formation histories.

  1. Self-Perpetuating Spiral Arms in Disk Galaxies

    CERN Document Server

    D'Onghia, Elena; Hernquist, Lars

    2012-01-01

    The precise nature of spiral structure in galaxies remains uncertain. Recent studies suggest that spiral arms result from interactions between disks and satellite galaxies. Instead, leaving aside the grand bisymmetric spirals, here we consider the possibility that the multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can survive at least in a statistical sense long after the original perturbing influence has been removed. Our findings thus motivate a ...

  2. IR STAR FORMING KNOTS IN GRAND DESIGN SPIRAL GALAXIES: SPIRAL STRUCTURE STAR FORMATION CONNECTION

    Directory of Open Access Journals (Sweden)

    H. Dottori

    2009-01-01

    Full Text Available We are studying 46 Grand Design spirals widely spread in types, which have been imaged in the K-band with the ESO NTT telescope. Eleven objects show knots strongly associated to the m=2 Fourier component of the spiral structure. Corotation ressonance (CR for the two-armed pattern have been derived for ve galaxies.

  3. IC3328 a "dwarf elliptical galaxy" with spiral structure

    CERN Document Server

    Jerjen, H; Binggeli, B; Jerjen, Helmut; Kalnajs, Agris; Binggeli, Bruno

    2000-01-01

    We present the 2-D photometric decomposition of the Virgo galaxy IC3328. The analysis of the global light distribution of this morphologically classified nucleated dwarf elliptical galaxy (dE1,N) reveals a tightly wound, bi-symmetric spiral structure with a diameter of 4.5 kpc, precisely centered on the nucleus of the dwarf. The amplitude of the spiral is only three percent of the dwarf's surface brightness making it the faintest and smallest spiral ever found in a galaxy. In terms of pitch angle and arm winding the spiral is similar to the intermediate-type galaxy M51, but it lacks the dust and prominent HII regions which signal the presence of gas. The visual evidence of a spiral pattern in an early-type dwarf galaxy reopens the question on whether these dwarfs are genuine rotationally supported or anisotropic stellar systems. In the case of IC3328, we argue for a nearly face-on disk (dS0) galaxy with an estimated maximum rotation velocity of v_c,max = 55kms-1. The faintness of the spiral and the small moti...

  4. The formation of molecular clouds in spiral galaxies

    CERN Document Server

    Dobbs, C L

    2006-01-01

    We present Smoothed Particle Hydrodynamics (SPH) simulations of molecular cloud formation in spiral galaxies. These simulations model the response of a non-self-gravitating gaseous disk to a galactic potential. The formation of molecular gas occurs when cold ($T \\le 100$ K) gas is compressed during the passage of a spiral arm. The spiral arms display considerable structure and the molecular gas accumulates into dense clouds. We identify the formation of these structures as due to the dynamics of clumpy shocks, which perturb the orbits of particles passing through the spiral arm. In addition, the spiral shocks induce a large velocity dispersion in the spiral arms, comparable with the magnitude of the velocity dispersion observed in molecular clouds. The molecular clouds are largely confined to the spiral arms, since most molecular gas is photodissociated to atomic hydrogen upon leaving the arms. However a low photodissociation rate increases the amount of interarm molecular gas, and the possibility of molecula...

  5. The Emission Line Sequence of Normal Spiral Galaxies

    CERN Document Server

    Sodré, L; Stasinska, Grazyna

    1999-01-01

    We have analyzed the emission line properties in the integrated spectra of 15 normal spiral galaxies. We show that very clear trends appear when plotting relevant emission line ratios or equivalent widths as a function of galaxy spectral types, obtained with a Principal Component Analysis of the continua and absorption features of spectra. The equivalent widths of all the lines analyzed correlate extremely well with spectral types, implying that each of them can be considered a good indicator of the spectral type in normal galaxies. The position of most galaxies of our sample in classical emission line diagnostic diagrams follows that of individual giant HII regions in spiral galaxies, but for the earliest type galaxies, the emission line pattern resembles more that of LINERs. Therefore, the direct interpretation of equivalent widths in terms of star formation rates would be misleading in such cases. The observed trends in the emission line ratios as a function of galaxy spectral type suggest a decrease of O/...

  6. An investigation into the prominence of spiral galaxy bulges

    CERN Document Server

    Graham, A W

    2001-01-01

    From a diameter-limited sample of 86 `face-on' spiral galaxies, the bulge-to-disk size and luminosity ratios, and other quantitative measurements for the prominence of the bulge are derived. The bulge and disk parameters have been estimated using a seeing convolved Sersic r^(1/n) bulge and a seeing convolved exponential disk. In general, early-type spiral galaxy bulges have Sersic values of n>1, and late-type spiral galaxy bulges have values of n 3-sigma) for the early-type spirals than the late-type spirals. This apparent contradiction with the r_e/h values can be explained with an iceberg-like scenario, in which the bulges in late-type spiral galaxies are relatively submerged in their disk. This can be achieved by varying the relative bulge/disk stellar density while maintaining the same effective bulge-to-disk size ratio. The absolute bulge magnitude - log(n) diagram is used as a diagnostic tool for comparative studies with dwarf elliptical and ordinary elliptical galaxies. At least in the B-band, these ob...

  7. Gas mass fractions and the evolution of spiral galaxies

    NARCIS (Netherlands)

    McGaugh, SS; DeBlok, WJG

    1997-01-01

    We show that the gas mass fraction of spiral galaxies is strongly correlated with luminosity and surface brightness. It is not correlated with linear size. Gas fraction varies with luminosity and surface brightness at the same rate, indicating evolution at fixed size. Dim galaxies are clearly less e

  8. Turbulence and Star Formation in a Sample of Spiral Galaxies

    Science.gov (United States)

    Maier, Erin; Chien, Li-Hsin; Hunter, Deidre A.

    2016-11-01

    We investigate turbulent gas motions in spiral galaxies and their importance to star formation in far outer disks, where the column density is typically far below the critical value for spontaneous gravitational collapse. Following the methods of Burkhart et al. on the Small Magellanic Cloud, we use the third and fourth statistical moments, as indicators of structures caused by turbulence, to examine the neutral hydrogen (H i) column density of a sample of spiral galaxies selected from The H i Nearby Galaxy Survey. We apply the statistical moments in three different methods—the galaxy as a whole, divided into a function of radii and then into grids. We create individual grid maps of kurtosis for each galaxy. To investigate the relation between these moments and star formation, we compare these maps with their far-ultraviolet images taken by the Galaxy Evolution Explorer satellite.We find that the moments are largely uniform across the galaxies, in which the variation does not appear to trace any star-forming regions. This may, however, be due to the spatial resolution of our analysis, which could potentially limit the scale of turbulent motions that we are sensitive to greater than ∼700 pc. From comparison between the moments themselves, we find that the gas motions in our sampled galaxies are largely supersonic. This analysis also shows that the Burkhart et al. methods may be applied not just to dwarf galaxies but also to normal spiral galaxies.

  9. Dust Attenuation in Hydrodynamic Simulations of Spiral Galaxies

    CERN Document Server

    Rocha, M; Primack, J R; Cox, T J; Rocha, Miguel; Jonsson, Patrik; Primack, Joel R.

    2007-01-01

    We study the effects of dust in hydrodynamic simulations of spiral galaxies when different radial metallicity gradients are assumed. SUNRISE, a Monte-Carlo radiative-transfer code, is used to make detailed calculations of the internal extinction of disk galaxies caused by their dust content. SUNRISE is used on eight different Smooth Particle Hydrodynamics (SPH) simulations of isolated spiral galaxies. These galaxies vary mainly in mass and hence luminosity, spanning a range in luminosities from -16 to -22 magnitudes in the B band. We focus on the attenuation in different wavelength bands as a function of the disk inclination and the luminosity of the models, and compare this to observations. Observations suggest different metallicity gradients for galaxies of different luminosities. These metallicity gradients were explored in our different models, finding that the resulting dust attenuation matches observations for edge-on galaxies, but do not show a linear behaviour in log axis ratio as some observations ha...

  10. The rotation curve of spiral galaxies and its cosmological implications

    CERN Document Server

    Florido, E

    2000-01-01

    We review the topic of rotation curves of spiral galaxies emphasizing the standard interpretation as evidence for the existence of dark matter halos. Galaxies other than spirals and late-type dwarfs may also possess great amounts of dark matter, and therefore ellipticals, dwarf spirals, lenticulars and polar ring galaxies are also considered. Furthermore, other methods for determining galactic dark matter, such as those provided by binaries, satellites or globular clusters, have to be included. Cold dark matter hierarchical models constitute the standard way to explain rotation curves, and thus the problem becomes just one aspect of a more general theory explaining structure and galaxy formation. Alternative theories also are included. In the magnetic model, rotation curves could also be a particular aspect of the whole history of cosmic magnetism during different epochs of the Universe. Modifications of Newtonian Dynamics provide another interesting possibility which is discussed here.

  11. The formation of spiral arms and rings in barred galaxies

    CERN Document Server

    Romero-Gomez, M; Masdemont, J J; García-Gomez, C

    2007-01-01

    We propose a new theory to explain the formation of spiral arms and of all types of outer rings in barred galaxies. We have extended and applied the technique used in celestial mechanics to compute transfer orbits. Thus, our theory is based on the chaotic orbital motion driven by the invariant manifolds associated to the periodic orbits around the hyperbolic equilibrium points. In particular, spiral arms and outer rings are related to the presence of heteroclinic or homoclinic orbits. Thus, R1 rings are associated to the presence of heteroclinic orbits, while R1R2 rings are associated to the presence of homoclinic orbits. Spiral arms and R2 rings, however, appear when there exist neither heteroclinic nor homoclinic orbits. We examine the parameter space of three realistic, yet simple, barred galaxy models and discuss the formation of the different morphologies according to the properties of the galaxy model. The different morphologies arise from differences in the dynamical parameters of the galaxy.

  12. A Survey of nearby, nearly face-on spiral galaxies

    Science.gov (United States)

    Garmire, Gordon

    2014-09-01

    This is a continuation of a survey of nearby, nearly face-on spiral galaxies. The main purpose is to search for evidence of collisions with small galaxies that show up in X-rays by the generation of hot shocked gas from the collision. Secondary objectives include study of the spatial distribution point sources in the galaxy and to detect evidence for a central massive blackhole.

  13. Gas Ejection from Spiral Galaxy Disks

    Science.gov (United States)

    Durelle, Jeremy

    We present the results of three proposed mechanisms for ejection of gas from a spiral arm into the halo. The mechanisms were modelled using magnetohydrodynamics (MHD) as a theoretical template. Each mechanism was run through simulations using a Fortran code: ZEUS-3D, an MHD equation solver. The first mechanism modelled the gas dynamics with a modified Hartmann flow which describes the fluid flow between two parallel plates. We initialized the problem based on observation of lagging halos; that is, that the rotational velocity falls to a zero at some height above the plane of the disk. When adopting a density profile which takes into account the various warm and cold H I and HII molecular clouds, the system evolves very strangely and does not reproduce the steady velocity gradient observed in edge-on galaxies. This density profile, adopted from Martos and Cox (1998), was used in the remaining models. However, when treating a system with a uniform density profile, a stable simulation can result. Next we considered supernova (SN) blasts as a possible mechanism for gas ejection. While a single SN was shown to be insufficient to promote vertical gas structures from the disk, multiple SN explosions proved to be enough to promote gas ejection from the disk. In these simulations, gas ejected to a height of 0.5 kpc at a velocity of 130 km s--1 from 500 supernovae, extending to an approximate maximum height of 1 kpc at a velocity of 6.7 x 103 km s--1 from 1500 supernovae after 0.15 Myr, the approximate time of propagation of a supernova shock wave. Finally, we simulated gas flowing into the spiral arm at such a speed to promote a jump in the disk gas, termed a hydraulic jump. The height of the jump was found to be slightly less than a kiloparsec with a flow velocity of 41 km s--1 into the halo after 167 Myr. The latter models proved to be effective mechanisms through which gas is ejected from the disk whereas the Hartmann flow (or toy model) mechanism remains unclear as the

  14. Scalable Automated Detection of Spiral Galaxy Arm Segments

    CERN Document Server

    Davis, Darren R

    2014-01-01

    Given an approximately centered image of a spiral galaxy, we describe an entirely automated method that finds, centers, and sizes the galaxy and then automatically extracts structural information about the spiral arms. For each arm segment found, we list the pixels in that segment and perform a least-squares fit of a logarithmic spiral arc to the pixels in the segment. The algorithm takes about 1 minute per galaxy, and can easily be scaled using parallelism. We have run it on all ~644,000 Sloan objects classified as "galaxy" and large enough to observe some structure. Our algorithm is stable in the sense that the statistics across a large sample of galaxies vary smoothly based on algorithmic parameters, although results for individual galaxies can sometimes vary in a non-smooth but easily understood manner. We find a very good correlation between our quantitative description of spiral structure and the qualitative description provided by humans via Galaxy Zoo. In addition, we find that pitch angle often varie...

  15. Star Formation Activity of Barred Spiral Galaxies

    Science.gov (United States)

    Kim, Eunbin; Hwang, Ho Seong; Chung, Haeun; Lee, Gwang-Ho; Park, Changbom; Cervantes Sodi, Bernardo; Kim, Sungsoo S.

    2017-08-01

    We study the star formation activity of nearby galaxies with bars using a sample of late-type galaxies at 0.02≤slant z≤slant 0.05489 and {M}rmass and redshift distributions similar to barred galaxies. We find that the star formation activity of strongly barred galaxies probed by starburstiness, g-r, {NUV}-r, and mid-infrared [3.4]-[12] colors is, on average, lower than that of non-barred galaxies. However, weakly barred galaxies do not show such a difference between barred and non-barred galaxies. The amounts of atomic and molecular gas in strongly barred galaxies are smaller than those in non-barred galaxies, and the gas metallicity is higher in strongly barred galaxies than in non-barred galaxies. The gas properties of weakly barred galaxies again show no difference from those of non-barred galaxies. We stack the optical spectra of barred and non-barred galaxies in several mass bins and fit to the stacked spectra with a spectral fitting code, STARLIGHT. We find no significant difference in stellar populations between barred and non-barred galaxies for both strongly and weakly barred galaxies. Our results are consistent with the idea that the star formation activity of barred galaxies was enhanced in the past along with significant gas consumption, and is currently lower than or similar to that of non-barred galaxies. The past star formation enhancement depends on the strength of bars.

  16. Spiral structure in nearby galaxies II. comparative analysis and conclusions

    CERN Document Server

    Kendall, S; Kennicutt, R C

    2014-01-01

    This paper presents a detailed analysis of two-armed spiral structure in a sample of galax- ies from the Spitzer Infrared Nearby Galaxies Survey (SINGS), with particular focus on the relationships between the properties of the spiral pattern in the stellar disc and the global struc- ture and environment of the parent galaxies. Following Paper I we have used a combination of Spitzer Space Telescope mid-infrared imaging and visible multi-colour imaging to isolate the spiral pattern in the underlying stellar discs, and we examine the systematic behaviours of the observed amplitudes and shapes (pitch angles) of these spirals. In general, spiral morphology is found to correlate only weakly at best with morphological parameters such as stellar mass, gas fraction, disc/bulge ratio, and vflat. In contrast to weak correlations with galaxy structure a strong link is found between the strength of the spiral arms and tidal forcing from nearby companion galaxies. This appears to support the longstanding suggestion that ei...

  17. Environment Dependence of Disk Morphology of Spiral Galaxies

    CERN Document Server

    Ann, H B

    2014-01-01

    We analyze the dependence of disk morphology (arm class, Hubble type, bar type) of nearby spiral galaxies on the galaxy environment by using local background density ($\\Sigma_{n}$), projected distance ($r_{p}$), and tidal index ($TI$) as measures of the environment. There is a strong dependence of arm class and Hubble type on the galaxy environment, while the bar type exhibits a weak dependence with a high frequency of SB galaxies in high density regions. Grand design fractions and early-type fractions increase with increasing $\\Sigma_{n}$, $1/r_{p}$, and $TI$, while fractions of flocculent spirals and late-type spirals decrease. Multiple-arm and intermediate-type spirals exhibit nearly constant fractions with weak trends similar to grand design and early-type spirals. While bar types show only a marginal dependence on $\\Sigma_{n}$, they show a fairly clear dependence on $r_{p}$ with a high frequency of SB galaxies at small $r_{p}$. The arm class also exhibits a stronger correlation with $r_{p}$ than $\\Sigma_...

  18. Star formation in galaxies: the role of spiral arms

    CERN Document Server

    Dobbs, Clare

    2013-01-01

    Studying star formation in spiral arms tells us not only about the evolution of star formation, and molecular clouds, but can also tell us about the nature of spiral structure in galaxies. I will address both these topics using the results of recent simulations and observations. Galactic scale simulations are beginning to examine in detail the evolution of GMCs as they form in spiral arms, and then disperse by stellar feedback or shear. The overall timescale for this process appears comparable to the crossing time of the GMCs, a few Myrs for $10^5$ M$_{\\odot}$ clouds, 20 Myr or so for more massive GMCs. Both simulations and observations show that the massive clouds are found in the spiral arms, likely as a result of cloud-cloud collisions. Simulations including stars should also tell us about the stellar age distribution in GMCs, and across spiral arms. More generally, recent work on spiral galaxies suggests that the dynamics of gas flows in spiral arms are different in longlived and transient spiral arms, re...

  19. Tidal Origin of Spiral Arms in Galaxies Orbiting a Cluster

    Science.gov (United States)

    Semczuk, Marcin; Łokas, Ewa L.; del Pino, Andrés

    2017-01-01

    One of the scenarios for the formation of grand-design spiral arms in disky galaxies involves their interactions with a satellite or another galaxy. Here we consider another possibility, where the perturbation is instead due to the potential of a galaxy cluster. Using N-body simulations we investigate the formation and evolution of spiral arms in a Milky-Way-like galaxy orbiting a Virgo-like cluster. The galaxy is placed on a few orbits of different size but similar eccentricity and its evolution are followed for 10 Gyr. The tidally induced, two-armed, approximately logarithmic spiral structure forms on each of them during the pericenter passages. The spiral arms dissipate and wind up with time, to be triggered again at the next pericenter passage. We confirm this transient and recurrent nature of the arms by analyzing the time evolution of the pitch angle and the arm strength. We find that the strongest arms are formed on the tightest orbit; however, they wind up rather quickly and are disturbed by another pericenter passage. The arms on the most extended orbit, which we analyze in more detail, wind up slowly and survive for the longest time. Measurements of the pattern speed of the arms indicate that they are kinematic density waves. We attempt a comparison with observations by selecting grand-design spiral galaxies in the Virgo cluster. Among those, we find nine examples bearing no sign of recent interactions or the presence of companions. For three of them we present close structural analogues among our simulated spiral galaxies.

  20. Rotation curves of 967 spiral galaxies: implications for dark matter.

    Science.gov (United States)

    Persic, M.; Salucci, P.; Stel, F.

    1996-02-01

    The authors present the rotation curves of 967 spiral galaxies, obtained by deprojecting and folding the raw Hα data published by Mathewson et al. (1992). Of these, 80 meet objective excellence criteria and are suitable for individual detailed mass modelling, while 820 are suitable for statistical studies. A preliminary analysis of their properties confirms that rotation curves are a universal function of luminosity and that the dark matter fraction in spirals increases with decreasing luminosity.

  1. Spiral Galaxies - classical description of spiral arms and rotational velocity pattern - toy model

    CERN Document Server

    Lobodzinski, Bogdan

    2014-01-01

    We propose an explanation of features of spiral galaxies: spiral arms and observed flat rotation curves, without the presence of an exotic form of matter. The formalism is based on Boltzmanns transport equation for the collisional matter and the very-low-velocity post-Newtonian approximation of the general relativity equations expressed in the Maxwell-like form. The Maxwell-like formulation provides the base for the explanation of the above phenomena in the language of dynamically created gravitoelectromagnetic fields by the movement of mass streams in the plane of the galaxy disc. In the model we use radical simplifications expressed as neglect of the gravitational interaction between neighbors and approximation of the incompressible mass flow. In this frame we show that if the galaxy is fuelled constantly by mass from an external gas reservoir, then the amplification of the gravitomagnetic field can be large enough to create the rotational velocity pattern and spiral arms without the necessity of introducin...

  2. Arm classification and velocity gradients in spiral galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Biviano, A.; Girardi, M.; Giuricin, G.; Mardirossian, F.; Mezzetti, M. (Trieste Univ. (Italy) Scuola Internazionale Superiore di Studi Avanzati (Italy) Scuola Internazionale Superiore di Studi Avanzati, Trieste (Italy) Scuola Internazionale Superiore di Studi Avanzati (Italy) Centro Interuniversitario Regionale di Astrofisica e Cosmologia (Italy))

    1991-08-01

    On the basis of published rotation curves, velocity gradients are compiled for 94 galaxies. A significant correlation is found in this sample of galaxies between their gradients and arm classes (as given by Elmegreen and Elmegreen, 1982); galaxies with steeper curves tend to have a flocculent arm structure, and galaxies with flatter curves tend to have a grand design morphology. The correlation is true, since it is not induced by other correlations. The present result is in agreement with previous suggestions by Whitmore (1984) and with the recent result by Elmegreen and Elmegreen; it is also consistent with the predictions of density wave theory for the formation of the spiral structure. 89 refs.

  3. Self-perpetuating Spiral Arms in Disk Galaxies

    Science.gov (United States)

    D'Onghia, Elena; Vogelsberger, Mark; Hernquist, Lars

    2013-03-01

    The causes of spiral structure in galaxies remain uncertain. Leaving aside the grand bisymmetric spirals with their own well-known complications, here we consider the possibility that multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can thus survive at least in a statistical sense long after the original perturbing influence has been removed.

  4. Rotation and mass in the Milky Way and spiral galaxies

    Science.gov (United States)

    Sofue, Yoshiaki

    2017-02-01

    Rotation curves are the basic tool for deriving the distribution of mass in spiral galaxies. In this review, we describe various methods to measure rotation curves in the Milky Way and spiral galaxies. We then describe two major methods to calculate the mass distribution using the rotation curve. By the direct method, the mass is calculated from rotation velocities without employing mass models. By the decomposition method, the rotation curve is deconvolved into multiple mass components by model fitting assuming a black hole, bulge, exponential disk, and dark halo. The decomposition is useful for statistical correlation analyses among the dynamical parameters of the mass components. We also review recent observations and derived results.

  5. The spiral structure of our Milky Way Galaxy

    CERN Document Server

    Hou, L G; Shi, W B

    2009-01-01

    The spiral structure of our Milky Way Galaxy is not yet known. HII regions and Giant molecular clouds are the most prominent spiral tracers. The 2-, 3- and 4-arm models have previously been proposed to outline the structure of our Galaxy. Recently, new data of spiral tracers covering a larger region of the Galactic disk have been published in literature. We wish to obtain the updated spiral structure of the Milky way using all tracer data. We collected the spiral tracer data of our Milky Way from literature, namely, HII regions and giant molecular clouds (GMCs). With the weighting factors based on the excitation parameters of HII regions or the masses of GMCs, we fitted the distribution of these tracers with the models of two-, three-, four-spiral-arms or polynomial spiral arms. The distances of tracers, if not available from stellar or direct measurements, were estimated kinetically from the standard rotation curve of Brand & Blitz (1993) with R_0=8.5 kpc, and \\Theta_0 =220 km s^{-1} or the newly fitted ...

  6. An HST Archival Survey of Feathers in Spiral Galaxies

    CERN Document Server

    La Vigne, M A; Ostriker, E C; Vigne, Misty A. La; Vogel, Stuart N.; Ostriker, Eve C.

    2006-01-01

    We present a survey of spiral arm extinction substructure referred to as feathers in 223 spiral galaxies using HST WFPC2 images. The sample includes all galaxies in the RC3 catalog with cz < 5000 km/s, B_T < 15, i < 60 degrees, and types Sa--Sd with well-exposed broadband WFPC2 images. The detection frequency of delineated, periodic feathers in this sample is 20% (45 of 223). This work is consistent with Lynds (1970), who concluded that feathers are common in prototypical Sc galaxies; we find that feathers are equally common in Sb galaxies. Sb--Sc galaxies without clear evidence for feathers either had poorer quality images, or flocculent or complex structure. We did not find clearly defined feathers in any Scd--Sd galaxy. The probability of detecting feathers was highest (83%) for spirals with well-defined primary dust lanes (PDLs; the lanes which line the inner edge of an arm); well-defined PDLs were only noted in Sab--Sc galaxies. Consistent with earlier work, we find that neighboring feathers ten...

  7. Enhanced Abundances in Spiral Galaxies of the Pegasus I Cluster

    CERN Document Server

    Robertson, Paul; Blanc, Guillermo A

    2011-01-01

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to ISM-ICM interaction, albeit to a lesser degree. Based on the abundances of 3 H I deficient spirals and 2 H I normal spirals, we observe a heavy element abundance offset of +0.13\\pm0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log(O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our resul...

  8. Tidal origin of spiral arms in galaxies orbiting a cluster

    CERN Document Server

    Semczuk, Marcin; del Pino, Andres

    2016-01-01

    One of the scenarios for the formation of grand-design spiral arms in disky galaxies involves their interactions with a satellite or another galaxy. Here we consider another possibility, where the perturbation is instead due to the potential of a galaxy cluster. Using $N$-body simulations we investigate the formation and evolution of spiral arms in a Milky Way-like galaxy orbiting a Virgo-like cluster. The galaxy is placed on a few orbits of different size but similar eccentricity and its evolution is followed for 10 Gyr. The tidally induced, two-armed, approximately logarithmic spiral structure forms on each of them during the pericenter passages. The spiral arms dissipate and wind up with time, to be triggered again at the next pericenter passage. We confirm this transient and recurrent nature of the arms by analyzing the time evolution of the pitch angle and the arm strength. We find that the strongest arms are formed on the tightest orbit, however they wind up rather quickly and are disturbed by another p...

  9. Environmental Dependence of Warps in Spiral Galaxies

    Science.gov (United States)

    Ann, Hong Bae; Bae, Hyun Jeong

    2016-12-01

    We determined the warp parameters of 192 warped galaxies which are selected from 340 edge-on galaxies using color images as well as r-band isophotal maps. We derive the local background density (Σ_{n}) to examine the dependence of the warp amplitudes on the galaxy environment. We find a clear trend that strongly warped galaxies are likely to be found in high density regions where tidal interactions are supposed to be frequent. However, the correlation between α_{w} and Σ_{n} is too weak for weakly warped galaxies (α_{w} decisive role in the formation of weak warps.}

  10. Arm & Interarm Star Formation in Spiral Galaxies

    CERN Document Server

    Foyle, Kelly; Walter, Fabian; Leroy, Adam

    2010-01-01

    We investigate the relationship between spiral arms and star formation in the grand-design spirals NGC 5194 and NGC 628 and in the flocculent spiral NGC 6946. Filtered maps of near-IR (3.6 micron) emission allow us to identify "arm regions" that should correspond to regions of stellar mass density enhancements. The two grand-design spirals show a clear two-armed structure, while NGC 6946 is more complex. We examine these arm and interarm regions, looking at maps that trace recent star formation - far-ultraviolet (GALEX NGS) and 24 micron emission (Spitzer, SINGS) - and cold gas - CO (Heracles) and HI (Things). We find the star formation tracers and CO more concentrated in the spiral arms than the stellar 3.6 micron flux. If we define the spiral arms as the 25% highest pixels in the filtered 3.6 micron images, we find that the majority (60%) of star formation tracers occurs in the interarm regions; this result persists qualitatively even when considering the potential impact of finite data resolution and diffu...

  11. Detection of spiral magnetic fields in two flocculent galaxies

    CERN Document Server

    Knapik, J; Dettmar, R J; Beck, R; Urbanik, M

    2000-01-01

    Two flocculent galaxies NGC 3521 and NGC 5055 has been observed at 10.55GHz with the Effelsberg 100m telescope. In both cases polarized emission reveals substantial radial component of regular magnetic field - similar to that in grand-designed spirals. Comparison with H_alpha distribution obtained at Lowell Observatory is presented. Polarization models discussed, support modern non-standard dynamo concepts for magnetic field generation in galaxies.

  12. Kinematic classification of non-interacting spiral galaxies

    CERN Document Server

    Wiegert, Theresa

    2013-01-01

    Using neutral hydrogen (HI) rotation curves of 79 galaxies, culled from the literature, as well as measured from HI data, we present a method for classifying disk galaxies by their kinematics. In order to investigate fundamental kinematic properties we concentrate on non-interacting spiral galaxies. We employ a simple parameterized form for the rotation curve in order to derive the three parameters: the maximum rotational velocity, the turnover radius and a measure of the slope of the rotation curve beyond the turnover radius. Our approach uses the statistical Hierarchical Clustering method to guide our division of the resultant 3D distribution of galaxies into five classes. Comparing the kinematic classes in this preliminary classification scheme to a number of galaxy properties we find that our class containing galaxies with the largest rotational velocities has a mean morphological type of Sb/Sbc while the other classes tend to later types. Other trends also generally agree with those described by previous...

  13. Ultraviolet Halos Around Spiral Galaxies. I. Morphology

    CERN Document Server

    Hodges-Kluck, Edmund; Bregman, Joel

    2016-01-01

    We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that UV halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlation between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 1-10 million solar masses of dust within 2-10 kpc of the disk, whose properties may change with height in starburst galaxies.

  14. Magnetic field evolution and reversals in spiral galaxies

    Science.gov (United States)

    Dobbs, C. L.; Price, D. J.; Pettitt, A. R.; Bate, M. R.; Tricco, T. S.

    2016-10-01

    We study the evolution of galactic magnetic fields using 3D smoothed particle magnetohydrodynamics (SPMHD) simulations of galaxies with an imposed spiral potential. We consider the appearance of reversals of the field, and amplification of the field. We find that magnetic field reversals occur when the velocity jump across the spiral shock is above ≈20 km s-1, occurring where the velocity change is highest, typically at the inner Lindblad resonance in our models. Reversals also occur at corotation, where the direction of the velocity field reverses in the corotating frame of a spiral arm. They occur earlier with a stronger amplitude spiral potential, and later or not at all with weaker or no spiral arms. The presence of a reversal at radii of around 4-6 kpc in our fiducial model is consistent with a reversal identified in the Milky Way, though we caution that alternative Galaxy models could give a similar reversal. We find that relatively high resolution, a few million particles in SPMHD, is required to produce consistent behaviour of the magnetic field. Amplification of the magnetic field occurs in the models, and while some may be genuinely attributable to differential rotation or spiral arms, some may be a numerical artefact. We check our results using ATHENA, finding reversals but less amplification of the field, suggesting that some of the amplification of the field with SPMHD is numerical.

  15. Determining the Co-Rotation Radius of Nearby Spiral Galaxies Using Spiral Arm Overlays

    Science.gov (United States)

    Shameer Abdeen, Mohamed; Kennefick, Daniel; Kennefick, Julia D.; Pour Imani, Hamed; Shields, Douglas W.; Eufrasio, Rafael; Berlanga Medina, Jazmin; Monson, Erik

    2017-01-01

    Density wave theory, originally proposed by C.C. Lin and Frank Shu (Lin & Shu 1964), views the spiral arm structures in spiral galaxies as density waves that propagates through the galactic disk. Resonances within orbits create standing wave patterns of density waves that we observe as spiral arms. The theory predicts the existence of a radius known as the co-rotation radius in which the spiral arm pattern speed matches the velocities of the stars within the disk. We introduce a novel way of determining the co-rotation radius, based on an image overlaying technique, which involves tracing the arms of spiral galaxies on images observed from different wavelengths. For the purpose of this study, 12 nearby galaxies were analyzed from four different wavelengths using pitch angle measurements from a previous study (Hamed et al. 2016). We used optical wavelength images (B-Band,440 nm), two infrared wavelength (Infrared; 3.6 µm and 8 µm) Spitzer Space Telescope images and ultraviolet images from GALEX. The results were verified by checking against results compiled from the literature.

  16. Spiral galaxy distance indicators based on near-infrared photometry

    NARCIS (Netherlands)

    Grijs, R. de; Peletier, R. F.

    1999-01-01

    We compare two methods of distance determination to spiral galaxies using optical/near-infrared (NIR) observations, the (I-K) versus M-K colour-absolute magnitude (CM) relation and the I- and K-band Tully-Fisher relation (TFR). Dust-free colours and NIR absolute magnitudes greatly enhance the

  17. Quintessence-like Dark Matter in Spiral Galaxies

    CERN Document Server

    Matos, T; Núñez, D; Ramírez, E

    2000-01-01

    Through the geodesic analysis of a static and axially symmetric space time,we present conditions over the state equation of an isotropic perfect fluid$p=\\omega d$, when it is considered as dark matter in spiral galaxies. The mainconclusion is that it can be an exotic fluid ($-1<\\omega <-1/3$) as it is foundfor Quintessence at cosmological scale.

  18. Turbulence and Star Formation in a Sample of Spiral Galaxies

    CERN Document Server

    Maier, Erin; Hunter, Deidre A

    2016-01-01

    We investigate turbulent gas motions in spiral galaxies and their importance to star formation in far outer disks, where the column density is typically far below the critical value for spontaneous gravitational collapse. Following the methods of Burkhart et al. (2010) on the Small Magellanic Cloud, we use the third and fourth statistical moments, as indicators of structures caused by turbulence, to examine the neutral hydrogen (HI) column density of a sample of spiral galaxies selected from The HI Nearby Galaxy Survey (THINGS, Walter et al. 2008). We apply the statistical moments in three different methods- the galaxy as a whole, divided into a function of radii and then into grids. We create individual grid maps of kurtosis for each galaxy. To investigate the relation between these moments and star formation, we compare these maps with their far-ultraviolet images taken by the Galaxy Evolution Explorer (GALEX) satellite. We find that the moments are largely uniform across the galaxies, in which the variatio...

  19. Magnetic Fields in a Sample of Nearby Spiral Galaxies

    CERN Document Server

    Van Eck, Cameron; Shukurov, Anvar; Fletcher, Andrew

    2014-01-01

    Both observations and modelling of magnetic fields in the diffuse interstellar gas of spiral galaxies are well developed but the theory has been confronted with observations for only a handful of individual galaxies. There is now sufficient data to consider statistical properties of galactic magnetic fields. We have collected data from the literature on the magnetic fields and interstellar media (ISM) of 20 spiral galaxies, and tested for various physically motivated correlations between magnetic field and ISM parameters. Clear correlations emerge between the total magnetic field strength and molecular gas density as well as the star formation rate. The magnetic pitch angle exhibits correlations with the total gas density, the star formation rate and the strength of the axisymmetric component of the mean magnetic field. The total and mean magnetic field strengths exhibit noticeable degree of correlation, suggesting a universal behaviour of the degree of order in galactic magnetic fields. We also compare the p...

  20. Photometric asymmetry between clockwise and counterclockwise spiral galaxies in SDSS

    CERN Document Server

    Shamir, Lior

    2016-01-01

    While galaxies with clockwise and counterclockwise handedness are visually different, they are expected to be symmetric in all of their other characteristics. Previous experiments using both manual analysis and machine vision have shown that the handedness of Sloan Digital Sky Survey (SDSS) galaxies can be predicted with accuracy significantly higher than mere chance using its photometric data alone, showing that SDSS photometry pipeline is sensitive to the handedness of the galaxy. However, some of these previous experiments were based on manually classified galaxies, and the results may therefore be subjected to bias originated from the human perception. This paper describes an experiment based on a set of 162,514 celestial objects classified as clockwise and counterclockwise spiral galaxies in a fully automatic process, showing that the source of the asymmetry is more than the human perception bias. The results are compared to two smaller datasets, and confirm the observation that the handedness of SDSS ga...

  1. New Low Surface Brightness Dwarf Galaxies Detected Around Nearby Spirals

    CERN Document Server

    Karachentsev, I D; Zilch, T; Blauensteiner, M; Elvov, M; Hochleitner, P; Hubl, B; Kerschhuber, G; Küppers, S; Neyer, F; Pölzl, R; Remmel, P; Schneider, O; Sparenberg, R; Trulson, U; Willems, G; Ziegler, H

    2015-01-01

    We conduct a survey of low surface brightness (LSB) satellite galaxies around the Local Volume massive spirals using long exposures with small amateur telescopes. We identified 27 low and very low surface brightness objects around the galaxies NGC,672, 891, 1156, 2683, 3344, 4258, 4618, 4631, and 5457 situated within 10 Mpc from us, and found nothing new around NGC,2903, 3239, 4214, and 5585. Assuming that the dwarf candidates are the satellites of the neighboring luminous galaxies, their absolute magnitudes are in the range of -8.6 > M_B > -13.3, their effective diameters are 0.4-4.7 kpc, and the average surface brightness is 26.1 mag/sq arcsec. The mean linear projected separation of the satellite candidates from the host galaxies is 73 kpc. Our spectroscopic observations of two LSB dwarfs with the Russian 6-meter telescope confirm their physical connection to the host galaxies NGC,891 and NGC,2683.

  2. Magnetic field evolution and reversals in spiral galaxies

    CERN Document Server

    Dobbs, C L; Pettitt, A R; Bate, M R; Tricco, T

    2016-01-01

    We study the evolution of galactic magnetic fields using 3D smoothed particle magnetohydrodynamics (SPMHD) simulations of galaxies with an imposed spiral potential. We consider the appearance of reversals of the field, and amplification of the field. We find magnetic field reversals occur when the velocity jump across the spiral shock is above $\\approx$20km s$^{-1}$, occurring where the velocity change is highest, typically at the inner Lindblad resonance (ILR) in our models. Reversals also occur at corotation, where the direction of the velocity field reverses in the co-rotating frame of a spiral arm. They occur earlier with a stronger amplitude spiral potential, and later or not at all with weaker or no spiral arms. The presence of a reversal at a radii of around 4--6 kpc in our fiducial model is consistent with a reversal identified in the Milky Way, though we caution that alternative Galaxy models could give a similar reversal. We find that relatively high resolution, a few million particles in SPMHD, is ...

  3. The Properties of Spiral Galaxies in Semi-Analytic Galaxy Formation Models

    OpenAIRE

    2000-01-01

    We examine the present-day galaxy disk colors and star formation rates (SFRs) in the semi-analytic model of Cole et al. (2000). We find that the fiducial model is a good match to Kennicutt's (1998) observed global star formation law, the color-based metallicity-magnitude correlation and the colors of low-luminosity galaxies. The main limitation of the model, from the point of view of present-day spirals, is that the optical colors of the disks of very luminous spiral galaxies are too blue, ev...

  4. The Ultraviolet Attenuation Law in Backlit Spiral Galaxies

    CERN Document Server

    Keel, William C; Holwerda, Benne W; Lintott, Chris J; Schawinski, Kevin

    2014-01-01

    (Abridged) The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use GALEX, XMM Optical Monitor, and HST data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with candidates provided by Galaxy Zoo participants. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law close to the Calzetti et al. (1994) form; the UV slope for the overall sample is substantially shallower than found by Wild et al. (2011), a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives accuracy almost equal ...

  5. Photometric Asymmetry Between Clockwise and Counterclockwise Spiral Galaxies in SDSS

    Science.gov (United States)

    Shamir, Lior

    2017-02-01

    While galaxies with clockwise and counterclockwise handedness are visually different, they are expected to be symmetric in all of their other characteristics. Previous experiments using both manual analysis and machine vision have shown that the handedness of Sloan Digital Sky Survey galaxies can be predicted with accuracy significantly higher than mere chance using its photometric data alone. However, some of these previous experiments were based on manually classified galaxies, and the results may therefore be subjected to bias originated from the human perception. This paper describes an experiment based on a set of 162,514 galaxies classified automatically to clockwise and counterclockwise spiral galaxies, showing that the source of the asymmetry in Sloan Digital Sky Survey (SDSS) database is not the human perception bias. The results are compared to two smaller datasets, and confirm the observation that the handedness of SDSS galaxies can be predicted by their photometry. The experiment also shows statistically significant differences in the measured magnitude of SDSS galaxies, according which galaxies with clockwise patterns are brighter than galaxies with counterclockwise patterns. The magnitude of that difference changes across RA ranges, and exhibits a strong correlation with the cosine of the right ascension.

  6. Signatures of Galaxy-Cluster Interactions Spiral Galaxy Rotation Curve Asymmetry, Shape, and Extent

    CERN Document Server

    Dale, D A; Haynes, M P; Hardy, E; Campusano, L E; Dale, Daniel A.; Giovanelli, Riccardo; Haynes, Martha P.; Hardy, Eduardo; Campusano, Luis E.

    2001-01-01

    The environmental dependencies of the characteristics of spiral galaxy rotation curves are studied in this work. We use our large, homogeneously collected sample of 510 cluster spiral galaxy rotation curves to test the claim that the shape of a galaxy's rotation curve strongly depends on its location within the cluster, and thus presumably on the strength of the local intracluster medium and on the frequency and strength of tidal interactions with the cluster and cluster galaxies. Our data do not corroborate such a scenario, consistent with the fact that Tully-Fisher residuals are independent of galaxy location within the cluster; while the average late-type spiral galaxy shows more rise in the outer parts of its rotation curve than does the typical early-type spiral galaxy, there is no apparent trend for either subset with cluster environment. We also investigate as a function of cluster environment rotation curve asymmetry and the radial distribution of H II region tracers within galactic disks. Mild trends...

  7. Extended HI disks in nearby spiral galaxies

    Science.gov (United States)

    Bosma, Albert

    2017-03-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a ``tilted ring model'' allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  8. Extended HI disks in nearby spiral galaxies

    CERN Document Server

    Bosma, A

    2016-01-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a "tilted ring model" allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  9. Rotation and Mass in the Milky Way and Spiral Galaxies

    CERN Document Server

    Sofue, Yoshiaki

    2016-01-01

    [PASJ Review Paper] Rotation curves are the basic tool for deriving the distribution of mass in spiral galaxies. In this review, we describe various methods to measure rotation curves in the Milky Way and spiral galaxies. We then describe two major methods to calculate the mass distribution using the rotation curve. By the direct method, the mass is calculated from rotation velocities without employing mass models. By the decomposition method, the rotation curve is deconvolved into multiple mass components by model fitting assuming a black hole, bulge, exponential disk and dark halo. The decomposition is useful for statistical correlation analyses among the dynamical parameters of the mass components. We also review recent observations and derived results. ( Full resolution copy is available at URL: http://www.ioa.s.u-tokyo.ac.jp/~sofue/htdocs/PASJreview2016/ )

  10. Molecular gas temperature and density in spiral galaxies

    Science.gov (United States)

    Wall, W. F.; Jaffe, D. T.; Bash, F. N.; Israel, F. P.; Maloney, P. R.; Baas, F.

    1993-01-01

    We combine beam-matched CO-13, CO-12 J = 3 yields 2 and J = 2 yields 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of infrared-bright external galaxies: NGC253, IC342, M 83, Maffei 2, and NGC6946. Additional observations of the J = 1 yields 0 lines of C-18O and CO-13 set limits on the opacity of the CO-13 J = 1 yields 0 line averaged over the central kiloparsec of these spiral galaxies.

  11. The (C II) 158 micron line mapping of spiral galaxies

    Science.gov (United States)

    Stacey, Gordon J.; Geis, N.; Genzel, Reinhard; Jackson, J. M.; Poglitsch, Albrecht; Townes, Charles H.

    1990-01-01

    Large scale maps of the face of spiral galaxies M51, M83, and NGC 6946 in the 158 micron (C II) fine structure line. The maps are obtained from the Far-infrared Imaging Fabry-Perot Interferometer (FIFI) during its first series of flights on board the Kuiper Airborne Observatory. The (C II) line emission is ubiquitous and easily traced over the mapped regions of each of the galaxies. The (C II) maps are compared with those obtained with similar sized beams in the CO line. The data available from these maps is interpreted.

  12. Internal Extinction in Spiral Galaxies in the Near Infrared

    CERN Document Server

    Masters, K L; Haynes, M P; Masters, Karen L.; Giovanelli, Riccardo; Haynes, Martha P.

    2003-01-01

    In order to study the effects of internal extinction in spiral galaxies we search for correlations of near infrared (NIR) photometric parameters with inclination. We use data from the 2 Micron All-Sky Survey (2MASS) Extended Source Catalog (XSC) on 15,224 spiral galaxies for which we also have redshifts. For 3035 of the galaxies, I-band photometry is available which is included in the analysis. From the simple dependence of reddening on inclination we derive a lower limit to the difference in magnitude between the face-on and edge-on aspect of 0.9, 0.3 and 0.1 magnitudes in I (0.81 um), J (1.25 um) and H (1.65 um) bands. We find that the faintest isophotal radius reported in the XSC (at the 21st mag/arc sq level) is closer to the centers of the galaxies than other common isophotal measures (e.g. the 23.5 mag/arc sq radius in I-band), and argue that it should not be assumed to represent an outer isophote at which galaxies are transparent at all viewing angles. A simple linear extinction law (i.e. Delta M = gam...

  13. Tidally Induced Offset Disks in Magellanic Spiral Galaxies

    Science.gov (United States)

    Pardy, Stephen A.; D'Onghia, Elena; Athanassoula, E.; Wilcots, Eric M.; Sheth, Kartik

    2016-08-01

    Magellanic spiral galaxies are a class of one-armed systems that often exhibit an offset stellar bar and are rarely found around massive spiral galaxies. Using a set of N-body and hydrodynamic simulations, we consider a dwarf-dwarf galaxy interaction as the driving mechanism for the formation of this peculiar class of systems. We investigate here the relation between the dynamical, stellar, and gaseous disk center and the bar. In all our simulations the bar center always coincides with the dynamical center, while the stellar disk becomes highly asymmetric during the encounter, causing the photometric center of the Magellanic galaxy disk to become mismatched with both the bar and the dynamical center. The disk asymmetries persist for almost 2 Gyr, the time that it takes for the disk to be recentered with the bar, and well after the companion has passed. This explains the nature of the offset bar found in many Magellanic-type galaxies, including the Large Magellanic Cloud (LMC) and NGC 3906. In particular, these results, once applied to the LMC, suggest that the dynamical center should reside in the bar center instead of the H i center as previously assumed, pointing to a variation in the current estimate of the north component of the LMC proper motion.

  14. On the apparent coupling of neutral hydrogen and dark matter in spiral galaxies

    NARCIS (Netherlands)

    Hoekstra, H; van Albada, TS; Sancisi, R

    2001-01-01

    We have studied a mass model for spiral galaxies in which the dark matter surface density is a scaled version of the observed H I surface density. Applying this mass model to a sample of 24 spiral galaxies with reliable rotation curves, one obtains good fits for most galaxies. The scaling factors cl

  15. The warm ionized medium in spiral galaxies

    CERN Document Server

    Haffner, L M; Beckman, J E; Wood, K; Slavin, J D; Giammanco, C; Madsen, G J; Zurita, A; Reynolds, R J

    2009-01-01

    This article reviews observations and models of the diffuse ionized gas that permeates the disk and halo of our Galaxy and others. It was inspired by a series of invited talks presented during an afternoon scientific session of the 65th birthday celebration for Professor Carl Heiles held at Arecibo Observatory in August 2004. This review is in recognition of Carl's long standing interest in and advocacy for studies of the ionized as well as the neutral components of the interstellar medium.

  16. Branch, Spur, and Feather Formation in Spiral Galaxies

    CERN Document Server

    Chakrabarti, S; Shu, F H

    2003-01-01

    We use hydrodynamical simulations to investigate the response of geometrically thin, self-gravitating, singular isothermal disks of gas to imposed rigidly rotating spiral potentials. By minimizing reflection-induced feedback from boundaries, and by restricting our attention to models where the swing parameter $X sim 10$, we minimize the swing amplification of global normal modes even in models where Toomre's $Q_g sim 1-2$ in the gas disk. We perform two classes of simulations: short-term ones over a few galactic revolutions where the background spiral forcing is large, and long-term ones over many galactic revolutions where the spiral forcing is considerably smaller. In both classes of simulations, the initial response of the gas disk is smooth and mimics the driving spiral field. At late times, many of the models evince substructure akin to the so-called branches, spurs, and feathers observed in real spiral galaxies. We comment on the parts played respectively by ultraharmonic resonances, reflection off inte...

  17. Dynamics of Non-Steady Spiral Arms in Disk Galaxies

    CERN Document Server

    Baba, Junichi; Wada, Keiichi

    2012-01-01

    In order to understand the physical mechanisms underlying non-steady stellar spiral arms in disk galaxies, we analyzed the growing and damping phases of their spiral arms using three-dimensional $N$-body simulations. We confirmed that the spiral arms are formed due to a swing amplification mechanism that reinforces density enhancement as a seeded wake. In the damping phase, the Coriolis force exerted on a portion of the arm surpasses the gravitational force that acts to shrink the portion. Consequently, the stars in the portion escape from the arm, and subsequently they form a new arm at a different location. The time-dependent nature of the spiral arms are originated in the continual repetition of this non-linear phenomenon. Since a spiral arm does not rigidly rotate, but follows the galactic differential rotation, the stars in the arm rotate at almost the same rate as the arm. In other words, every single position in the arm can be regarded as the co-rotation point. Due to interaction with their host arms, ...

  18. Prominent spiral arms in the gaseous outer galaxy disks

    CERN Document Server

    Bertin, G

    2009-01-01

    Context: Several spiral galaxies, as beautifully exhibited by the case of NGC 6946, display a prominent large-scale spiral structure in their gaseous outer disk. Such structure is often thought to pose a dynamical puzzle, because grand-design spiral structure is traditionally interpreted as the result of density waves carried mostly in the stellar disk. Aims. Here we argue that the outer spiral arms in the cold gas outside the bright optical disk actually have a natural interpretation as the manifestation of the mechanism that excites grand-design spiral structure in the main, star-dominated body of the disk: the excitation is driven by angular momentum transport to the outer regions, through trailing density waves outside the corotation circle that can penetrate beyond the Outer Lindblad Resonance in the gaseous component of the disk. Methods: Because of conservation of the density wave action, these outgoing waves are likely to become more prominent in the outer disk and eventually reach non-linear amplitud...

  19. A diversity of progenitors and histories for isolated spiral galaxies

    CERN Document Server

    Martig, Marie; Croton, Darren J; Dekel, Avishai; Teyssier, Romain

    2012-01-01

    We analyze a suite of 33 cosmological simulations following the evolution of Milky Way-mass galaxies in low-density environments. Our sample at z = 0 comprises galaxies with a broad range of Hubble types, from nearly bulgeless disks to bulge-dominated galaxies. The bulges are typically pseudo-bulges, with a Sersic index lower than 2, and 70% of the galaxies have bars. Despite the fact that a large fraction of the bulge is typically in place by z = 1, we find no significant correlation between the morphology at z = 1 and at z = 0. The progenitors of disk galaxies span a whole range of morphologies at z = 1, including smooth disks, unstable disks, interacting galaxies and bulge-dominated systems. By z = 0.5, the progenitor morphology is correlated with the z = 0 morphology, with spiral arms and bars largely in place at z = 0.5. From this sample we analyze the formation histories of galaxies with a bulge-to-total ratio below 0.3 (typically Sb and later types). They do form in our simulations, but with a lower ab...

  20. HST detection of spiral structure in two Coma Cluster dwarf galaxies

    CERN Document Server

    Graham, A W; Guzmán, R; Graham, Alister W.; Jerjen, Helmut; Guzman, Rafael

    2003-01-01

    We report the discovery of (stellar) spiral-like structure in Hubble Space Telescope images of two dwarf galaxies (GMP 3292 and GMP 3629) belonging to the Coma cluster. GMP 3629 is the faintest such galaxy detected in a cluster environment, and it is the first such galaxy observed in the dense Coma cluster. The large bulge and the faintness of the broad spiral-like pattern in GMP 3629 suggests that its disk may have been largely depleted. >We may therefore have found an example of the ``missing link'' in theories of galaxy evolution which have predicted that dwarf spiral galaxies, particularly in clusters, evolve into dwarf elliptical galaxies.

  1. Magnetic fields and rotation of spiral galaxies

    CERN Document Server

    Battaner, E; Florido, E

    1998-01-01

    We present a simplified model in which we suggest that two important galactic problems -the magnetic field configuration at large scales and the flat rotation curve- may be simultaneously explained. A highly convective disc produces a high turbulent magnetic diffusion in the vertical direction, stablishing a merging of extragalactic and galactic magnetic fields. The outer disc may then adquire a magnetic energy gradient very close to the gradient required to explain the rotation curve, without the hypothesis of galactic dark matter. Our model predicts symmetries of the galactic field in noticeable agreement with the large scale structure of our galaxy.

  2. Stellar populations of the bulges of four spiral galaxies

    CERN Document Server

    Morelli, L; Corsini, E M; Bontà, E Dalla; Coccato, L; Méndez-Abreu, J; Parmiggiani, M

    2015-01-01

    Key information to understand the formation and evolution of disk galaxies are imprinted in the stellar populations of their bulges. This paper has the purpose to make available new measurements of the stellar population properties of the bulges of four spiral galaxies. Both the central values and radial profiles of the line strength of some of the most common Lick indices are measured along the major- and minor- axis of the bulge-dominated region of the sample galaxies. The corresponding age, metallicity, and {\\alpha}/Fe ratio are derived by using the simple stellar population synthesis model predictions. The central values and the gradients of the stellar population properties of ESO-LV1890070, ESO-LV4460170, and ESO-LV 5140100 are consistent with previous findings for bulges of spiral galaxies. On the contrary, the bulge of ESO-LV 4500200 shows peculiar chemical properties possibly due to the presence of a central kinematically-decoupled component. The negative metallicity gradient found in our bulges samp...

  3. Galaxy And Mass Assembly (GAMA): Stellar mass growth of spiral galaxies in the cosmic web

    CERN Document Server

    Alpaslan, Mehmet; Marcum, Pamela M; Popescu, Cristina; Tuffs, Richard; Bland-Hawthorn, Joss; Brough, Sarah; Brown, Michael J I; Davies, Luke J M; Driver, Simon P; Holwerda, Benne W; Kelvin, Lee S; Lara-López, Maritza A; López-Sánchez, Ángel R; Loveday, Jon; Moffett, Amanda; Taylor, Edward N; Owers, Matt; Robotham, Aaron S G

    2016-01-01

    We look for correlated changes in stellar mass and star formation rate along filaments in the cosmic web by examining the stellar masses and UV-derived star formation rates (SFR) of 1,799 ungrouped and unpaired spiral galaxies that reside in filaments. We devise multiple distance metrics to characterise the complex geometry of filaments, and find that galaxies closer to the cylindrical centre of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. In addition, these peripheral spiral galaxies have higher specific star formation rates (SSFR) at a given mass. Complementing our sample of filament spiral galaxies with spiral galaxies in tendrils and voids, we find that the average SFR of these objects in different large scale environments are similar to each other with the primary discriminant in SFR being stellar mass, in line with previous works. However, the distributions of SFRs are found to vary with large-scale environment. Our results thus su...

  4. The Red and Featureless Outer Disks of Nearby Spiral Galaxies

    Science.gov (United States)

    Watkins, Aaron E.; Mihos, J. Christopher; Harding, Paul

    2016-07-01

    We present results from deep, wide-field surface photometry of three nearby (D = 4-7 Mpc) spiral galaxies: M94 (NGC 4736), M64 (NGC 4826), and M106 (NGC 4258). Our imaging reaches a limiting surface brightness of {μ }B ˜ 28-30 mag arcsec-2 and probes colors down to {μ }B ˜ 27.5 mag arcsec-2. We compare our broadband optical data to available ultraviolet and high column density H i data to better constrain the star-forming history and stellar populations of the outermost parts of each galaxy’s disk. Each galaxy has a well-defined radius beyond which little star formation occurs and the disk light appears both azimuthally smooth and red in color, suggestive of old, well-mixed stellar populations. Given the lack of ongoing star formation or blue stellar populations in these galaxies’ outer disks, the most likely mechanisms for their formation are dynamical processes such as disk heating or radial migration, rather than inside-out growth of the disks. This is also implied by the similarity in outer disk properties despite each galaxy showing distinct levels of environmental influence, from a purely isolated galaxy (M94) to one experiencing weak tidal perturbations from its satellite galaxies (M106) to a galaxy recovering from a recent merger (M64), suggesting that a variety of evolutionary histories can yield similar outer disk structure. While this suggests a common secular mechanism for outer disk formation, the large extent of these smooth, red stellar populations—which reach several disk scale lengths beyond the galaxies’ spiral structure—may challenge models of radial migration given the lack of any nonaxisymmetric forcing at such large radii.

  5. Energetic constraints to chemo-photometric evolution of spiral galaxies

    Science.gov (United States)

    Buzzoni, Alberto

    2011-08-01

    galaxies; (iii) although lower-mass galaxies tend more likely to take the look of later-type spirals, it is mass, not morphology, that drives galaxy chemical properties. Facing the relatively flat trend of ? versus galaxy type, the increasingly poorer gas metallicity, as traced by the [O/H] abundance of H II regions along the Sa → Im Hubble sequence, seems to be mainly the result of the softening process, that dilute enriched stellar mass within a larger fraction of residual gas. The problem of the residual lifetime for spiral galaxies as active star-forming systems has been investigated. If returned mass is left as the main (or unique) gas supplier to the ISM, as implied by the Roberts time-scale, then star formation might continue only at a maximum birthrate bmax≪f/(1 -f) ≲ 0.45, for a Salpeter IMF. As a result, only massive (Mgal≳ 1011 M⊙) Sa/Sb spirals may have some chance to survive ˜30 per cent or more beyond a Hubble time. Things may be worse, on the contrary, for dwarf systems, that seem currently on the verge of ceasing their star formation activity unless to drastically reduce their apparent birthrate below the bmax threshold.

  6. Kinematic and Structural Evolution of Field and Cluster Spiral Galaxies

    CERN Document Server

    Ziegler, Bodo L; Da Rocha, Cristiano; Böhm, Asmus; Peletier, Reynier F; Verdugo, Miguel

    2009-01-01

    To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster (z = 0.3 & 0.5) fields to study the environmental influence. Their stellar masses derived from multiband VLT/FORS photometry are distributed around but mostly below the characteristic Schechter-fit mass. From HST/ACS images we determine morphologies and structural parameters like disk length, position angle and ellipticity. Combining the spectra of three slit positions per galaxy using the MXU mode of VLT/FORS2 we construct the two-dimensional velocity field from gas emission lines for 16 cluster members and 33 field galaxies. The kinematic position angle and flatness are derived by a Fourier expansion of elliptical velocity profiles. To trace possible interaction processes, we define three irregularity indicators based on an identical analysis of local galaxies from the SINGS project. Our distant sample display...

  7. Chemical abundances from planetary nebulae in local spiral galaxies

    CERN Document Server

    Richer, M G

    2015-01-01

    While the chemical abudances observed in bright planetary nebulae in local spiral galaxies are less varied than their counterparts in dwarfs, they provide new insight. Their helium abundances are typically enriched by less than 50\\% compared to the primordial abundance. Nitrogen abundances always show some level of secondary enrichment, but the absolute enrichment is not extreme. In particular, type I PNe are rare among the bright PNe in local spirals. The oxygen and neon abundances are very well correlated and follow the relation between these abundances observed in star-forming galaxies, implying that either the progenitor stars of these PNe modify neither abundance substantially or that they modify both to maintain the ratio (not predicted by theory). According to theory, these results imply that the progenitor stars of bright PNe in local spirals have masses of about $2\\,\\mathrm M_{\\odot}$ or less. If so, the progenitors of these PNe have substantial lifetimes that allow us to use them to study the recent...

  8. Dynamical effect of gas on spiral pattern speed in galaxies

    CERN Document Server

    Ghosh, Soumavo

    2016-01-01

    In the density wave theory of spiral structure, the grand-design two-armed spiral pattern is taken to rotate rigidly in a galactic disc with a constant, definite pattern speed. The observational measurement of the pattern speed of the spiral arms, though difficult, has been achieved in a few galaxies such as NGC 6946, NGC 2997, and M 51 which we consider here. We examine whether the theoretical dispersion relation permits a real solution for wavenumber corresponding to a stable wave, for the observed rotation curve and the pattern speed values. We find that the disc when treated to consist of stars alone, as is usually done in literature, does not generally support a stable density wave for the observed pattern speed. Instead the inclusion of the low velocity dispersion component, namely, gas, is essential to obtain a stable density wave. Further, we obtain a theoretical range of allowed pattern speeds that correspond to a stable density wave at a certain radius, and check that for the three galaxies consider...

  9. Formation of Nuclear Spirals in Barred Galaxies

    CERN Document Server

    Ann, H B; Thakur, Parijat

    2004-01-01

    We have performed smoothed particle hydrodynamics (SPH) simulations for the response of the gaseous disk to the imposed moderately strong non-axisymmetric potentials. The model galaxies are composed of the three stellar components (disk, bulge and bar) and two dark ones (supermassive black hole and halo) whose gravitational potentials are assumed to be invariant in time in the frame corotating with the bar. We found that the torques alone generated by the moderately strong bar that gives the maximum of tangential-to-radial force ratio as $(F_{Tan}/F_{Rad})_{max}= 0.3$ are not sufficient to drive the gas particles close to the center due to the barrier imposed by the inner Lindblad resonances (ILRs). In order to transport the gas particles towards the nucleus ($r<100$ pc), a central supermassive black hole (SMBH) and high sound speed of the gas are required to be present. The former is required to remove the inner inner Lindblad resonance (IILR) that prevents gas inflow close to the nucleus, while the latte...

  10. Stellar diffusion in barred spiral galaxies

    CERN Document Server

    Brunetti, Maura; Pfenniger, Daniel

    2011-01-01

    We characterize empirically the radial diffusion of stars in the plane of a typical barred disk galaxy by calculating the local spatial diffusion coefficient and diffusion time-scale for bulge-disk-halo N-body self-consistent systems which initially differ in the Safronov-Toomre-Q_T parameter. We find different diffusion scenarios that depend on the bar strength and on the degree of instability of the disk. Marginally stable disks, with Q_T \\sim 1, have two families of bar orbits with different values of angular momentum and energy, which determine a large diffusion in the corotation region. In hot disks, Q_T> 1, stellar diffusion is reduced with respect to the case of marginally stable disks. In cold models, we find that spatial diffusion is not constant in time and strongly depends on the activity of the bar, which can move stars all over the disk recurrently. We conclude that to realistically study the impact of radial migration on the chemical evolution modeling of the Milky Way the role of the bar has to...

  11. Gas velocity patterns in simulated galaxies: Observational diagnostics of spiral structure theories

    CERN Document Server

    Baba, Junichi; Miyamoto, Yusuke; Egusa, Fumi; Kuno, Nario

    2016-01-01

    There are two theories of stellar spiral arms in isolated disc galaxies that model stellar spiral arms with different longevities: quasi-stationary density wave theory, which characterises spirals as rigidly rotating, long-lived patterns (i.e. steady spirals), and dynamic spiral theory, which characterises spirals as differentially rotating, transient, recurrent patterns (i.e. dynamic spirals). In order to discriminate between these two spiral models observationally, we investigated the differences between the gas velocity patterns predicted by these two spiral models in hydrodynamic simulations. We found that the azimuthal phases of the velocity patterns relative to the gas density peaks (i.e. gaseous arms) differ between the two models, as do the gas flows; nevertheless, the velocity patterns themselves are similar for both models. Such similarity suggests that the mere existence of streaming motions does not conclusively confirm the steady spiral model. However, we found that the steady spiral model shows ...

  12. MAGNETIC FIELDS IN A SAMPLE OF NEARBY SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Van Eck, C. L. [Department of Astrophysics, Faculty of Science, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen (Netherlands); Brown, J. C. [Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4 (Canada); Shukurov, A.; Fletcher, A., E-mail: c.vaneck@astro.ru.nl, E-mail: jocat@ucalgary.ca, E-mail: anvar.shukurov@ncl.ac.uk, E-mail: andrew.fletcher@ncl.ac.uk [School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom)

    2015-01-20

    Both observations and modeling of magnetic fields in the diffuse interstellar gas of spiral galaxies are well developed, but the theory has been confronted with observations for only a handful of individual galaxies. There is now sufficient data to consider the statistical properties of galactic magnetic fields. We have collected data from the literature on the magnetic fields and interstellar media of 20 spiral galaxies, and tested for various physically motivated correlations between magnetic field and interstellar medium parameters. Clear correlations emerge between the total magnetic field strength and molecular gas density as well as the star formation rate. The magnetic pitch angle exhibits correlations with the total gas density, the star formation rate, and the strength of the axisymmetric component of the mean magnetic field. The total and mean magnetic field strengths exhibit a noticeable degree of correlation, suggesting a universal behavior of the degree of order in galactic magnetic fields. We also compare the predictions of galactic dynamo theory to observed magnetic field parameters and identify directions in which theory and observations might be usefully developed.

  13. In-spiraling Clumps in Blue Compact Dwarf Galaxies

    CERN Document Server

    Elmegreen, Bruce G; Hunter, Deidre

    2012-01-01

    Giant star-formation clumps in dwarf irregular galaxies can have masses exceeding a few percent of the galaxy mass enclosed inside their orbital radii. They can produce sufficient torques on dark matter halo particles, halo stars, and the surrounding disk to lose their angular momentum and spiral into the central region in 1 Gyr. Pairs of giant clumps with similarly large relative masses can interact and exchange angular momentum to the same degree. The result of this angular momentum loss is a growing central concentration of old stars, gas, and star formation that can produce a long-lived starburst in the inner region, identified with the BCD phase. This central concentration is proposed to be analogous to the bulge in a young spiral galaxy. Observations of star complexes in five local BCDs confirm the relatively large clump masses that are expected for this process. The observed clumps also seem to contain old field stars, even after background light subtraction, in which case the clumps may be long-lived....

  14. Rotation curves of 967 spiral galaxies implications for dark matter

    CERN Document Server

    Persic, M; Stel, F; Persic, Massimo; Salucci, Paolo; Stel, Fulvio

    1995-01-01

    We present the rotation curves of 967 spiral galaxies, obtained by deprojecting and folding the raw data published by Mathewson et al. (1992). Of these, 80 meet objective excellence criteria and are suitable for individual detailed mass modelling, while 820 are suitable for statistical studies. A preliminary analysis of theire properties confirms that rotation curves are a universal function of luminosity and that the dark matter fraction in spirals increase with decreasing luminosity. Quantitative considerations on the virial radius of dark halos allow us to make hypotheses about their structure and nature. The deprojected folded curves, the smoothed curves, and various related quantities are available via anonymous ftp at ftp://galileo.sissa.it/users/ftp/pub/psrot

  15. Gas Density and the Volume Schmidt Law for Spiral Galaxies

    CERN Document Server

    Abramova, O V

    2007-01-01

    The thickness of the equilibrium isothermal gaseous layers and their volume densities \\rho_{gas}(R) in the disc midplane are calculated for 7 spiral galaxies (including our Galaxy) in the frame of self-consistent axisymmetric model. Local velocity dispersions of stellar discs were assumed to be close to marginal values necessary for the discs to be in a stable equilibrium state. Under this condition the stellar discs of at least 5 of 7 galaxies reveal a flaring. Their volume densities decrease with R faster than \\rho_{gas}, and, as a result, the gas dominates by the density at the disc periphery. Comparison of the azimuthally averaged star formation rate SFR with the gas density shows that there is no universal Schmidt law SFR \\rho_{gas}^n, common to all galaxies. Nevertheless, SFR in different galaxies reveals better correlation with the volume gas density than with the column one. Parameter n in the Schmidt law SFR \\rho_{gas}^n, formally calculated by the least square method, lies within 0.8-2.4 range and i...

  16. Magnetic fields and star formation in spiral galaxies

    CERN Document Server

    Krause, Marita

    2008-01-01

    The main observational results from radio continuum and polarization observations about the magnetic field strength and large-scale pattern for face-on and edge-on spiral galaxies are summarized and compared within our sample of galaxies of different morphological types, inclinations, and star formation rates (SFR). We found that galaxies with low SFR have higher thermal fractions/smaller synchrotron fractions than those with normal or high SFR. Adopting an equipartition model, we conclude that the nonthermal radio emission and the \\emph{total magnetic field} strength grow nonlinearly with SFR, while the regular magnetic field strength does not seem to depend on SFR. We also studied the magnetic field structure and disk thicknesses in highly inclined (edge-on) galaxies. We found in four galaxies that - despite their different radio appearance - the vertical scale heights for both, the thin and thick disk/halo, are about equal (0.3/1.8 kpc at 4.75 GHz), independently of their different SFR. This implies that a...

  17. Fundamental mass-spin-morphology relation of spiral galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Obreschkow, D. [International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Glazebrook, K. [ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) (Australia)

    2014-03-20

    This work presents high-precision measurements of the specific baryon angular momentum j {sub b} contained in stars, atomic gas, and molecular gas, out to ≳ 10 scale radii, in 16 nearby spiral galaxies of the THINGS sample. The accuracy of these measurements improves on existing studies by an order of magnitude, leading to the discovery of a strong correlation between the baryon mass M {sub b}, j {sub b}, and the bulge mass fraction β, fitted by β=−(0.34±0.03) lg (j{sub b}M{sub b}{sup −1}/[10{sup −7} kpc km s{sup −1} M{sub ⊙}{sup −1}])−(0.04±0.01) on the full sample range of 0 ≤ β ≲ 0.3 and 10{sup 9} M {sub ☉} < M {sub b} < 10{sup 11} M {sub ☉}. The corresponding relation for the stellar quantities M {sub *} and j {sub *} is identical within the uncertainties. These M-j-β relations likely originate from the proportionality between jM {sup –1} and the surface density of the disk that dictates its stability against (pseudo-)bulge formation. Using a cold dark matter model, we can approximately explain classical scaling relations, such as the fundamental plane of spiral galaxies, the Tully-Fisher relation, and the mass-size relation, in terms of the M-j(-β) relation. These results advocate the use of mass and angular momentum as the most fundamental quantities of spiral galaxies.

  18. Chandra ACIS Observations of the Nearby Spiral Galaxy NGC 300

    Science.gov (United States)

    Bobar, Dale; Turner, Kevin; Schlegel, Eric M.

    2017-01-01

    The ACIS detector (Advanced CCD Imaging Spectrometer) onboard the Chandra X-ray Observatory has imaged the nearby spiral NGC 300 over three epochs for a total exposure of 1.885x102 ksec. We describe each observation as well as the merged data set. Each exposure contains 132 individual sources. We focus on the time variability and luminosity distributions of the sources. Initial results show no diffuse emissions in the galaxy. Finally, we compare the merged data set and the detected sources with other wavebands.

  19. Central Mass Concentration and Bar Dissolution in Nearby Spiral Galaxies

    CERN Document Server

    Das, M; Vogel, S N; Regan, M W; Sheth, K; Harris, A I; Jefferys, W H; Das, Mousumi; Teuben, Peter J.; Vogel, Stuart N.; Regan, Michael W.; Sheth, Kartik; Harris, Andrew I.; Jefferys, William H.

    2003-01-01

    We use data from the BIMA Survey of Nearby Galaxies (SONG) to investigate the relationship between ellipticity and central mass concentration in barred spirals. Existing simulations predict that bar ellipticity decreases as inflowing mass driven by the bar accumulates in the central regions, ultimately destroying the bar. Using the ratio of the bulge mass to the mass within the bar radius as an estimate of the central mass concentration, we obtain dynamical mass estimates from SONG CO 1-0 rotation curve data. We find an inverse correlation between bar ellipticity and central mass concentration, consistent with simulations of bar dissolution.

  20. Particle Paths of Lagrangian Velocity Distribution Simulating the Spiral Arms of Galaxy M51

    Institute of Scientific and Technical Information of China (English)

    Tzu-Fang Chen; Georgios H. Vatistas; Sui Lin

    2008-01-01

    Galaxies are huge families of stars held together by their own gravities. The system M51 is a spiral galaxy. It possesses billions of stars. The range of the spiral arms extends hundred thousand light years. The present study is in an attempt in using the particle paths of the Lagrangian flow field to simulate the spiral arms of Galaxy M51.The Lagrangian flow field is introduced. The initial locations of fluid particles in the space between two concentric cylinders are first specified. Then a linear velocity distribution of the fluid particles is used with different angle rotations of the particles to obtain the particle paths in the Lagrangian diagram. For simulating the spiral arms of Galaxy M51, the Lagrangian M51 diagram is developed. The particle paths of the Lagrangian M51 diagram agree quite well with the spiral arms of Galaxy M51.

  1. Does the Milky Way Obey Spiral Galaxy Scaling Relations?

    CERN Document Server

    Licquia, Timothy C; Bershady, Matthew A

    2016-01-01

    It is crucial to understand how the Milky Way, the galaxy we can study in the most intimate detail, fits in amongst other galaxies. Key examples include the Tully-Fisher relation (TFR) --- i.e., the tight correlation between luminosity ($L$) and rotational velocity ($V_\\textrm{rot}$) --- and the 3-dimensional luminosity-velocity-radius ($LVR$) scaling relation. Several past studies have characterized the MW as a 1--1.5$\\sigma$ outlier to the TFR. This study reexamines such comparisons using new estimates of MW properties that are robust to many of the systematic uncertainties that have been a problem in the past and are based on assumptions consistent with those used for other spiral galaxies. Comparing to scaling relations derived from modern extragalactic data, we find that our Galaxy's properties are in excellent agreement with TFRs defined using any SDSS-filter absolute magnitude, stellar mass, or baryonic mass as the $L$ proxy. We next utilize disk scale length ($R_\\textrm{d}$) measurements to extend thi...

  2. The Red and Featureless Outer Disks of Nearby Spiral Galaxies

    CERN Document Server

    Watkins, Aaron E; Harding, Paul

    2016-01-01

    We present results from deep, wide-field surface photometry of three nearby (D=4--7 Mpc) spiral galaxies: M94 (NGC 4736), M64 (NGC 4826), and M106 (NGC 4258). Our imaging reaches limiting surface brightnesses of $\\mu_{B} \\sim$ 28 -- 30 mag arcsec$^{-2}$ and probes colors down to $\\mu_{B} \\sim$ 27.5 mag arcsec$^{-2}$. We compare our broadband optical data to available ultraviolet and high column-density HI data to better constrain the star forming history and stellar populations of the outermost parts of each galaxy's disk. Each galaxy has a well-defined radius beyond which little star formation occurs and the disk light appears both azimuthally smooth and red in color, suggestive of old, well-mixed stellar populations. Given the lack of ongoing star formation or blue stellar populations in these galaxies' outer disks, the most likely mechanisms for their formation are dynamical processes such as disk heating or radial migration, rather than inside-out growth of the disks. This is also implied by the similarit...

  3. Fundamental Mass-Spin-Morphology Relation of Spiral Galaxies

    CERN Document Server

    Obreschkow, Danail

    2013-01-01

    This work present high-precision measurements of the specific baryon angular momentum jb, contained in stars, atomic gas, and molecular gas, out to ~10 scale radii, in 16 nearby spiral galaxies of the THINGS sample. The accuracy of these measurements improves on existing studies by more than an order of magnitude, leading to the discovery of a strong correlation between the baryon mass Mb, jb, and the bulge mass fraction B/T, fitted by B/T=-(0.34+-0.03)*log(jb/Mb/[1e-7 kpc km/s/Msun])-(0.04+-0.01) on the full sample range of B/T=0.00-0.32 and Mb/Msun=1e9-1e11. The corresponding relation for the stellar quantities Ms and js is identical within the uncertainties. These M-j-B/T relations likely originate from the proportionality between j/M and the surface density of the disk that dictates its stability against (pseudo-)bulge formation. Using a CDM model, we can approximately explain classical scaling relations, such as the fundamental plane of spiral galaxies, the Tully-Fisher relation, and the mass-size relati...

  4. Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 1097

    CERN Document Server

    Lin, Lien-Hsuan; Hsieh, Pei-Ying; Taam, Ronald E; Yang, Chao-Chin; Yen, David C C

    2013-01-01

    NGC 1097 is a nearby barred spiral galaxy believed to be interacting with the elliptical galaxy NGC 1097A located to its northwest. It hosts a Seyfert 1 nucleus surrounded by a circumnuclear starburst ring. Two straight dust lanes connected to the ring extend almost continuously out to the bar. The other ends of the dust lanes attach to two main spiral arms. To provide a physical understanding of its structural and kinematical properties, two-dimensional hydrodynamical simulations have been carried out. Numerical calculations reveal that many features of the gas morphology and kinematics can be reproduced provided that the gas flow is governed by a gravitational potential associated with a slowly rotating strong bar. By including the self-gravity of the gas disk in our calculation, we have found the starburst ring to be gravitationally unstable which is consistent with the observation in \\citet{hsieh11}. Our simulations show that the gas inflow rate is 0.17 M$_\\sun$ yr$^{-1}$ into the region within the starbu...

  5. Spectroscopy of Outlying H II Regions in Spiral Galaxies Abundances and Radial Gradients

    CERN Document Server

    Van Zee, L; Haynes, M P; O'Donoghue, A A; Balonek, T J

    1998-01-01

    We present the results of low dispersion optical spectroscopy of 186 H II regions spanning a range of radius in 13 spiral galaxies. Abundances for several elements (oxygen, nitrogen, neon, sulfur, and argon) were determined for 185 of the H II regions. As expected, low metallicities were found for the outlying H II regions of these spiral galaxies. Radial abundance gradients were derived for the 11 primary galaxies; similar to results for other spiral galaxies, the derived abundance gradients are typically -0.04 to -0.07 dex/kpc.

  6. Effects of Spiral Arms on Star Formation in Nuclear Rings of Barred-spiral Galaxies

    CERN Document Server

    Seo, Woo-Young

    2014-01-01

    We use hydrodynamic simulations to study the effect of spiral arms on the star formation rate (SFR) occurring in nuclear rings of barred-spiral galaxies. We find that spiral arms can be an efficient means of gas transport from the outskirts to the central parts, provided that the arms are rotating slower than the bar. While the ring star formation in models with no-arm or corotating arms is active only during about the bar growth phase, arm-driven gas accretion makes the ring star formation both enhanced and prolonged significantly in models with slow-rotating arms. The arm-enhanced SFR is larger by a factor of ~ 3-20 than in the no-arm model, with larger values corresponding to stronger and slower arms. Arm-induced mass inflows also make dust lanes stronger. Nuclear rings in slow-arm models are ~ 45% larger than in the no-arm counterparts. Star clusters that form in a nuclear ring exhibit an age gradient in the azimuthal direction only when the SFR is small, whereas no noticeable age gradient is found in the...

  7. Starbursts in Barred Spiral Galaxies; 2, Molecular and Optical Study of Three Wolf-Rayet Galaxies

    CERN Document Server

    Contini, T; Considère, S; Davoust, E

    1997-01-01

    We have searched for dense molecular gas in three barred spiral galaxies with young starbursts, NGC 3049, 5430 and 6764, which are known Wolf-Rayet galaxies. We detected HCN in the latter two, and CS was marginally detected in NGC 6764. The dense molecular gas contents of the three galaxies are compared to those of other galaxies and to other indicators of star formation. The HCN luminosities (relative to the CO and far infrared ones) in these galaxies with very young starbursts are consistent with those observed in galaxies with older starbursts and in normal galaxies, and so are our upper limits to the CS intensities (relative to CO). The starburst ages evaluated from our spectrophotometric observations are in the range 3.4 to 6.0 Myr. A circum-nuclear ring is apparent on our images of NGC 5430, the galaxy with the oldest central starburst; this galaxy also has the widest molecular lines. The central star formation rates derived from the Halpha luminosity are consistent with those expected from the global F...

  8. The Dragonfly nearby Galaxies Survey. I. Substantial Variation in the Diffuse Stellar Halos around Spiral Galaxies

    Science.gov (United States)

    Merritt, Allison; van Dokkum, Pieter; Abraham, Roberto; Zhang, Jielai

    2016-10-01

    Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep ({μ }g\\gt 31 mag arcsec‑2) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. Our sample includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of 16-19 degrees and distances between 7-18 Mpc. We construct stellar mass surface density profiles from the observed g-band surface brightness in combination with the g ‑ r color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk+bulge fit) beyond 5 half-mass radii. We find a mean halo fraction of 0.009 ± 0.005 and a large rms scatter of {1.01}-0.26+0.9 dex. The peak-to-peak scatter of the halo fraction is a factor of \\gt 100—while some galaxies feature strongly structured halos resembling that of M31, three of the eight have halos that are completely undetected in our data. We conclude that spiral galaxies as a class exhibit a rich variety in stellar halo properties, implying that their assembly histories have been highly non-uniform. We find no convincing evidence for an environmental or stellar mass dependence of the halo fraction in the sample.

  9. Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias

    Science.gov (United States)

    Hart, Ross E.; Bamford, Steven P.; Willett, Kyle W.; Masters, Karen L.; Cardamone, Carolin; Lintott, Chris J.; Mackay, Robert J.; Nichol, Robert C.; Rosslowe, Christopher K.; Simmons, Brooke D.; Smethurst, Rebecca J.

    2016-10-01

    The majority of galaxies in the local Universe exhibit spiral structure with a variety of forms. Many galaxies possess two prominent spiral arms, some have more, while others display a many-armed flocculent appearance. Spiral arms are associated with enhanced gas content and star formation in the discs of low-redshift galaxies, so are important in the understanding of star formation in the local universe. As both the visual appearance of spiral structure, and the mechanisms responsible for it vary from galaxy to galaxy, a reliable method for defining spiral samples with different visual morphologies is required. In this paper, we develop a new debiasing method to reliably correct for redshift-dependent bias in Galaxy Zoo 2, and release the new set of debiased classifications. Using these, a luminosity-limited sample of ˜18 000 Sloan Digital Sky Survey spiral galaxies is defined, which are then further sub-categorized by spiral arm number. In order to explore how different spiral galaxies form, the demographics of spiral galaxies with different spiral arm numbers are compared. It is found that whilst all spiral galaxies occupy similar ranges of stellar mass and environment, many-armed galaxies display much bluer colours than their two-armed counterparts. We conclude that two-armed structure is ubiquitous in star-forming discs, whereas many-armed spiral structure appears to be a short-lived phase, associated with more recent, stochastic star-formation activity.

  10. The Local Galaxy Density and the Arm Class of Spiral Galaxies

    CERN Document Server

    Giuricin, G; Mardirossian, F; Mezzetti, M

    1993-01-01

    We have examined the effect of the environmental density on the arm classification of an extensive sample of spiral galaxies included in the Nearby Galaxy Catalog (Tully, 1988a). We have also explored the dependence of the arm class of a galaxy on other factors, such as its blue absolute magnitude and its disk-to-total mass ratio, inferred in the literature either from the gradient of a good galaxy rotation curve or from a photometric mass decomposition method. We have found that the arm class is strongly related to the absolute magnitude in the mid-type spirals (in the sense that grand design galaxies are, on average, more luminous than flocculent objects), whilst this relation is considerably weaker in the early and late types. In general the influence of the local density on the arm structure appears to be much weaker than that of the absolute magnitude. The local density acts essentially in strengthening the arm class--absolute magnitude relation for the mid types, whereas no environmental density effects...

  11. ON THE STAR FORMATION LAW FOR SPIRAL AND IRREGULAR GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Elmegreen, Bruce G., E-mail: bge@us.ibm.com [IBM Research Division, T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States)

    2015-12-01

    A dynamical model for star formation on a galactic scale is proposed in which the interstellar medium is constantly condensing to star-forming clouds on the dynamical time of the average midplane density, and the clouds are constantly being disrupted on the dynamical timescale appropriate for their higher density. In this model, the areal star formation rate scales with the 1.5 power of the total gas column density throughout the main regions of spiral galaxies, and with a steeper power, 2, in the far outer regions and in dwarf irregular galaxies because of the flaring disks. At the same time, there is a molecular star formation law that is linear in the main and outer parts of disks and in dIrrs because the duration of individual structures in the molecular phase is also the dynamical timescale, canceling the additional 0.5 power of surface density. The total gas consumption time scales directly with the midplane dynamical time, quenching star formation in the inner regions if there is no accretion, and sustaining star formation for ∼100 Gyr or more in the outer regions with no qualitative change in gas stability or molecular cloud properties. The ULIRG track follows from high densities in galaxy collisions.

  12. Kiloparsec-scale molecular gas excitation in spiral galaxies

    Science.gov (United States)

    Wall, W. F.; Jaffe, D. T.; Bash, F. N.; Israel, F. P.; Maloney, P. R.; Baas, F.

    1993-09-01

    We combine beam-matched (C-13)O, (C-12)O J = 3 - 2 and J = 2 - 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of IR-bright external galaxies: NGC 253, IC 342, M83, Maffei 2, and NGC 6946. We find that the central 170 to 530 pc diameter regions have typical molecular gas densities ranging from approximately less than 10,000/cu cm (in M83) to approximately greater than 100,000/cu cm (in NGC 253) and that, outside of these regions, the densities are likely to be approximately less than 10,000/cu cm. The molecular clouds outside the inner 170-530 pc are at least as warm as the molecular clouds in our Galaxy. Column densities derived from integrated (C-13)O line strengths and H-alpha surface brightnesses suggest that the star formation rate is enhanced in the central 170-530 pc diameters by an order of magnitude over that inferred for the outer star-forming disks in spiral galaxies.

  13. 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.

  14. Disk Thicknesses and Some Parameters of 108 Non-Edge-On Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We present disk thicknesses, some other parameters and their statistics of 108 non-edge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of matter density in three-dimensional spiral galaxies.From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point (the forbidden region with radius r0 to the galactic center) of the spiral arm, and finally the thickness.

  15. Vertical Scale Parameter Estimates for 48 Non-edge-on Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    Jun Ma

    2003-01-01

    In the first paper of this series, we directly studied the mathematical forms, symmetry of spiral structure, and the projection of galactic discs on the images, and measured the pitch angles of the spiral arms and inclination angles of the galactic discs for 60 spiral galaxies. In this second paper, we estimate the vertical scale parameters of 48 non-edge-on spiral galaxies based on the method proposed by Peng et al. and on the results given in Paper I. As we know, for edge-on disc galaxies we can obtain the vertical scale parameter from the photometry, once a mathematical form is specified for the vertical light distribution. For non-edgeon galaxies, some other methods have to be used. The statistical result was that the vertical scale parameter is comparable for edge-on and non-edge-on galaxies,although it is obtained from two very different methods.

  16. Spiral galaxies : the light and color distributions in the optical and near-infrared

    NARCIS (Netherlands)

    de Jong, Roelof Sybe

    1995-01-01

    This thesis deals with surface photometry of face-on spiral galaxies in a statistical way, using both single passband as well as color information of a large sample of galaxies. In this chapter I first discuss galaxy formation and evolution models and the role that photometry plays in testing these

  17. Effects of interaction on the properties of spiral galaxies. II. Isolated galaxies: The zero point

    Science.gov (United States)

    Márquez, I.; Moles, M.

    1999-04-01

    We analyse the properties of a sample of 22 bright isolated spiral galaxies on the basis of Johnson B,V,I images and optical rotation curves. The fraction of early morphological types in our sample of isolated galaxies (or in other samples of non-interacting spiral galaxies) appears to be smaller than in samples including interacting systems. The overall morphological aspect is regular and symmetric, but all the galaxies present non-axisymmetric components in the form of bars or rings. We find that the color indices become bluer towards the outer parts and that their central values are well correlated with the total colors. The properties of the bulges span a larger range than those of the disks, that thus are more alike between them. None of the galaxies shows a truncated, type II disk profile. It is found that the relation between surface brightness and size for the bulges, the Kormendy relation, is tighter when only isolated galaxies are considered. We find a similar relation for the disk parameters with an unprecedented low scatter. A Principal Component Analysis of the measured parameters shows that 2 eigenvectors suffice to explain more than 95 % of the total variance. These are, as found for other samples including spiral galaxies in different environmental situations, a scale parameter given by the mass or, equivalently, the luminosity or the size; and a form parameter given by the bulge to disk luminosity ratio, B/D, or, equivalently, by the gradient of the solid-body rotation region of the rotation curve, the G-parameter. We report here a tight correlation between G and B/D for our sample of isolated spirals that could be used as a new distance indicator. Based on data obtained at the 1.5m telescope of the Estacion de Observacion de Calar Alto, Instituto Geografico Nacional, which is jointly operated by the Instituto Geografico Nacional and the Consejo Superior de Investigaciones Cientificas through the Instituto de Astrofisica de Andalucia

  18. The Dragonfly Nearby Galaxies Survey. I. Substantial variation in the diffuse stellar halos around spiral galaxies

    CERN Document Server

    Merritt, Allison; Abraham, Roberto; Zhang, Jielai

    2016-01-01

    Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep ($\\mu_{g} > 31$ mag arcsec$^{-2}$) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. Our sample includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of $16-90$ degrees and distances between $7-18$ Mpc. We construct stellar mass surface density profiles from the observed $g$-band surface brightness in combination with the $g-r$ color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk$+$bulge fit) beyond $5$ half-mass radii. We find a mean halo fraction of $0.009 \\pm 0.005$ and a large RMS scatter of $1.01^{+0.9}_{-0.26}$ dex. The...

  19. STAR FORMATION IN THE OUTER DISK OF SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Kate L.; Van Zee, Liese [Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States); Cote, Stephanie [Canadian Gemini Office, Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria (Canada); Schade, David, E-mail: barneskl@astro.indiana.edu, E-mail: vanzee@astro.indiana.edu, E-mail: Stephanie.Cote@nrc-cnrc.gc.ca, E-mail: David.Schade@nrc-cnrc.gc.ca [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria (Canada)

    2012-09-20

    We combine new deep and wide field of view H{alpha} imaging of a sample of eight nearby (d Almost-Equal-To 17 Mpc) spiral galaxies with new and archival H I and CO imaging to study the star formation and the star formation regulation in the outer disk. We find that, in agreement with previous studies, star formation in the outer disk has low covering fractions, and star formation is typically organized into spiral arms. The star formation in the outer disk is at extremely low levels, with typical star formation rate surface densities of {approx}10{sup -5} to 10{sup -6} M{sub Sun} yr{sup -1} kpc{sup -2}. We find that the ratio of the radial extent of detected H II regions to the radius of the H I disk is typically {approx}>85%. This implies that in order to further our understanding of the implications of extended star formation, we must further our understanding of the formation of extended H I disks. We measure the gravitational stability of the gas disk, and find that the outer gaseous disk is typically a factor of {approx}2 times more stable than the inner star-forming disk. We measure the surface density of outer disk H I arms, and find that the disk is closer to gravitational instability along these arms. Therefore, it seems that spiral arms are a necessary, but not sufficient, requirement for star formation in the outer disk. We use an estimation of the flaring of the outer gas disk to illustrate the effect of flaring on the Schmidt power-law index; we find that including flaring increases the agreement between the power-law indices of the inner and outer disks.

  20. UIT Ultraviolet Surface Photometry of the Spiral Galaxy M74

    Science.gov (United States)

    Cornett, R. H.; Greason, M. R.; Offenberg, J. D.; Bohlin, R. C.; Cheng, K. P.; O'Connell, R. W.; Roberts, M. R.; Smith, A. M.; Smith, E. P.; Angione, R. J.; Talbert, F. D.; Stecher, T. P.

    1993-05-01

    UV photometry from Ultraviolet Imaging Telescope (UIT) images at 1520 Angstroms (magnitudes mbone) and 2490 Angstroms (maone) of the spiral galaxy M74 (NGC628) is compared with ha, R, V, and B surface photometry and models. M74's surface brightness profiles have central peaks with exponential falloffs; the profiles' exponential scale lengths increase with decreasing continuum wavelength. The slope of the continuum-subtracted ha profile is between those of FUV and NUV profiles, consistent with related origins of ha and UV emission in extreme Population I material. M74's color profiles have small gradients, all becoming bluer with increasing radius. The UIT color (mbone-maone) averages near 0.0, the color of an A0 star, over the central 20 arcsec radius, and slopes from ~ -0.2 to ~ -0.4 from 20 to 200 arcsec. Spiral arms dominate surface photometry colors; interarm regions are slightly redder. In the UV, M74's nuclear region resembles disk/spiral arm material in color and morphology, unlike M81. (mbone-maone) colors and models of M74's central region clearly demonstrate that there are no O or B stars in the central 10 arcsec. M74's (mbone-maone) profile is similar to M33's but is ~ 0.5 mag redder. M74 is ~ 0.4 mag bluer than M81 in its outer disk. We investigate explanations for both the color profiles and the differences among the galaxies. M74's maone-V and mbone-V color profiles cannot be explained by a disk of uniform color behind a screen of dust with a known reddening function, distributed like the neutral gas with a fixed gas-to-dust ratio. Known abundance variations could produce the observed color gradient in M74; however, evolutionary cluster models show that sensible time parameters, including star formation start time and exponential decay rate, also produce the observed colors of M74, M33, and M81.

  1. On the Star Formation Law for Spiral and Irregular Galaxies

    CERN Document Server

    Elmegreen, Bruce G

    2015-01-01

    A dynamical model for star formation on a galactic scale is proposed in which the interstellar medium is constantly condensing to star-forming clouds on the dynamical time of the average midplane density, and the clouds are constantly being disrupted on the dynamical time scale appropriate for their higher density. In this model, the areal star formation rate scales with the 1.5 power of the total gas column density throughout the main regions of spiral galaxies, and with a steeper power, 2, in the far outer regions and in dwarf irregular galaxies because of the flaring disks. At the same time, there is a molecular star formation law that is linear in the main and outer parts of disks and in dIrrs because the duration of individual structures in the molecular phase is also the dynamical time scale, canceling the additional 0.5 power of surface density. The total gas consumption time scales directly with the midplane dynamical time, quenching star formation in the inner regions if there is no accretion, and su...

  2. Spiral- and bar-driven peculiar velocities in Milky Way-sized galaxy simulations

    Science.gov (United States)

    Grand, Robert J. J.; Bovy, Jo; Kawata, Daisuke; Hunt, Jason A. S.; Famaey, Benoit; Siebert, Arnaud; Monari, Giacomo; Cropper, Mark

    2015-10-01

    We investigate the kinematic signatures induced by spiral and bar structure in a set of simulations of Milky Way-sized spiral disc galaxies. The set includes test particle simulations that follow a quasi-stationary density wave-like scenario with rigidly rotating spiral arms, and N-body simulations that host a bar and transient, corotating spiral arms. From a location similar to that of the Sun, we calculate the radial, tangential and line-of-sight peculiar velocity fields of a patch of the disc and quantify the fluctuations by computing the power spectrum from a two-dimensional Fourier transform. We find that the peculiar velocity power spectrum of the simulation with a bar and transient, corotating spiral arms fits very well to that of APOGEE red clump star data, while the quasi-stationary density wave spiral model without a bar does not. We determine that the power spectrum is sensitive to the number of spiral arms, spiral arm pitch angle and position with respect to the spiral arm. However, it is necessary to go beyond the line-of-sight velocity field in order to distinguish fully between the various spiral models with this method. We compute the power spectrum for different regions of the spiral discs, and discuss the application of this analysis technique to external galaxies.

  3. Stellar Orbital Studies in Normal Spiral Galaxies II: Restrictions to Structural and Dynamical parameters on Spiral Arms

    CERN Document Server

    Pérez-Villegas, Angeles; Moreno, Edmundo

    2015-01-01

    Making use of a set of detailed potential models for normal spiral galaxies, we analyze the disk stellar orbital dynamics as the structural and dynamical parameters of the spiral arms (mass, pattern speed and pitch angle) are gradually modified. With this comprehensive study of ordered and chaotic behavior, we constructed an assemblage of orbitally supported galactic models and plausible parameters for orbitally self-consistent spiral arms models. We find that, to maintain orbital support for the spiral arms, the spiral arm mass, M$_{sp}$, must decrease with the increase of the pitch angle, $i$; if $i$ is smaller than $\\sim10\\deg$, M$_{sp}$ can be as large as $\\sim7\\%$, $\\sim6\\%$, $\\sim5\\%$ of the disk mass, for Sa, Sb, and Sc galaxies, respectively. If $i$ increases up to $\\sim25\\deg$, the maximum M$_{sp}$ is $\\sim1\\%$ of the disk mass independently in this case of morphological type. For values larger than these limits, spiral arms would likely act as transient features. Regarding the limits posed by extrem...

  4. Gas and stellar spiral arms and their offsets in the grand-design spiral galaxy M51

    Science.gov (United States)

    Egusa, Fumi; Mentuch Cooper, Erin; Koda, Jin; Baba, Junichi

    2017-02-01

    Theoretical studies on the response of interstellar gas to a gravitational potential disc with a quasi-stationary spiral arm pattern suggest that the gas experiences a sudden compression due to standing shock waves at spiral arms. This mechanism, called a galactic shock wave, predicts that gas spiral arms move from downstream to upstream of stellar arms with increasing radius inside a corotation radius. In order to investigate if this mechanism is at work in the grand-design spiral galaxy M51, we have measured azimuthal offsets between the peaks of stellar mass and gas mass distributions in its two spiral arms. The stellar mass distribution is created by the spatially resolved spectral energy distribution fitting to optical and near-infrared images, while the gas mass distribution is obtained by high-resolution CO and H I data. For the inner region (r ≤ 150 arcsec), we find that one arm is consistent with the galactic shock while the other is not. For the outer region, results are less certain due to the narrower range of offset values, the weakness of stellar arms, and the smaller number of successful offset measurements. The results suggest that the nature of two inner spiral arms is different, which is likely due to an interaction with the companion galaxy.

  5. Supermassive black holes in the Sbc spiral galaxies NGC 3310, NGC 4303 and NGC 4258

    CERN Document Server

    Pastorini, G; Capetti, A; Axon, D J; Alonso-Herrero, A; Atkinson, J; Batcheldor, D; Carollo, C M; Collett, J; Dressel, L; Hughes, M A; Macchetto, D; Maciejewski, W; Sparks, W; van der Marel, R; Pastorini, Guia; Marconi, Alessandro; Capetti, Alessandro; Axon, David J.; Alonso-Herrero, Almudena; Atkinson, John; Batcheldor, Dan; Collett, James; Dressel, Linda; Hughes, Mark A.; Macchetto, Duccio; Maciejewski, Witold; Sparks, William; Marel, Roeland van der

    2007-01-01

    We present new Space Telescope Imaging Spectrograph (STIS) observations of three spiral galaxies, NGC 4303, NGC 3310 and NGC 4258. The bright optical emission lines H$\\alpha$ $\\lambda$ $6564 \\AA$, [NII] $\\lambda

  6. Gravitational torques in spiral galaxies gas accretion as a driving mechanism of galactic evolution

    CERN Document Server

    Block, D L; Combes, F; Puerari, I; Buta, R J; Block, David L.; Bournaud, Frederic; Combes, Francoise; Puerari, Ivanio; Buta, Ron

    2002-01-01

    The distribution of gravitational torques and bar strengths in the local Universe is derived from a detailed study of 163 galaxies observed in the near-infrared. The results are compared with numerical models for spiral galaxy evolution. It is found that the observed distribution of torques can be accounted for only with external accretion of gas onto spiral disks. Accretion is responsible for bar renewal - after the dissolution of primordial bars - as well as the maintenance of spiral structures. Models of isolated, non-accreting galaxies are ruled out. Moderate accretion rates do not explain the observational results: it is shown that galactic disks should double their mass in less than the Hubble time. The best fit is obtained if spiral galaxies are open systems, still forming today by continuous gas accretion, doubling their mass every 10 billion years.

  7. The opacity of spiral galaxy disks. III. Automating the synthetic field method

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; Allen, RJ; van der Kruit, PC

    2005-01-01

    Dust extinction in spiral disks can be estimated from the counts of background field galaxies, provided the deleterious effects of confusion introduced by structure in the image of the foreground spiral disk can be calibrated. Gonzalez et al. developed a method for this calibration, the Synthetic Fi

  8. The Opacity of Spiral Galaxy Disks III : Automating the "Synthetic Field Method"

    NARCIS (Netherlands)

    Holwerda, B. W.; González, R. A.; Allen, R. J.; Kruit, P. C. van der

    2004-01-01

    Abstract: The dust extinction in spiral disks can be estimated from the counts of background field galaxies, provided the deleterious effects of confusion introduced by structure in the image of the foreground spiral disk can be calibrated. Gonzalez et al. (1998) developed a method for this calibrat

  9. An atlas of mid-infrared dust emission in spiral galaxies

    CERN Document Server

    Roussel, H; Bosma, A; Sauvage, M; Bonoli, C; Gallais, P; Hawarden, T G; Lequeux, J; Madden, S; Mazzei, P

    2001-01-01

    We present maps of dust emission at 7 microns and 15 microns/7 microns intensity ratios of selected regions in 43 spiral galaxies observed with ISOCAM. This atlas is a complement to studies based on these observations, dealing with star formation in centers of barred galaxies and in spiral disks. It is accompanied by a detailed description of data reduction and an inventory of generic morphological properties in groups defined according to bar strength and HI gas content.

  10. SpArcFiRe: Scalable Automated Detection of Spiral Galaxy Arm Segments

    Science.gov (United States)

    Davis, Darren R.; Hayes, Wayne B.

    2014-08-01

    Given an approximately centered image of a spiral galaxy, we describe an entirely automated method that finds, centers, and sizes the galaxy (possibly masking nearby stars and other objects if necessary in order to isolate the galaxy itself) and then automatically extracts structural information about the spiral arms. For each arm segment found, we list the pixels in that segment, allowing image analysis on a per-arm-segment basis. We also perform a least-squares fit of a logarithmic spiral arc to the pixels in that segment, giving per-arc parameters, such as the pitch angle, arm segment length, location, etc. The algorithm takes about one minute per galaxies, and can easily be scaled using parallelism. We have run it on all ~644,000 Sloan objects that are larger than 40 pixels across and classified as "galaxies." We find a very good correlation between our quantitative description of a spiral structure and the qualitative description provided by Galaxy Zoo humans. Our objective, quantitative measures of structure demonstrate the difficulty in defining exactly what constitutes a spiral "arm," leading us to prefer the term "arm segment." We find that pitch angle often varies significantly segment-to-segment in a single spiral galaxy, making it difficult to define the pitch angle for a single galaxy. We demonstrate how our new database of arm segments can be queried to find galaxies satisfying specific quantitative visual criteria. For example, even though our code does not explicitly find rings, a good surrogate is to look for galaxies having one long, low-pitch-angle arm—which is how our code views ring galaxies. SpArcFiRe is available at http://sparcfire.ics.uci.edu.

  11. Aperture corrections for disk galaxy properties derived from the CALIFA survey. Balmer emission lines in spiral galaxies

    CERN Document Server

    Iglesias-Páramo, J; Galbany, L; Sánchez, S F; Rosales-Ortega, F F; Mast, D; García-Benito, R; Husemann, B; Aguerri, J A L; Alves, J; Bekeraité, S; Bland-Hawthorn, J; Catalán-Torrecilla, C; de Amorim, A L; de Lorenzo-Cáceres, A; Ellis, S; Falcón-Barroso, J; Flores, H; Florido, E; Gallazzi, A; Gomes, J M; Delgado, R M González; Haines, T; Hernández-Fernández, J D; Kehrig, C; López-Sánchez, A R; Lyubenova, M; Marino, R A; Mollá, M; Monreal-Ibero, A; Mourão, A; Papaderos, P; Sánchez-Blázquez, P; Spekkens, K; Stanishev, V; van de Ven, G; Walcher, C J; Wisotzki, L; Zibetti, S; Ziegler, B

    2013-01-01

    This work investigates the effect of the aperture size on derived galaxy properties for which we have spatially-resolved optical spectra. We focus on some indicators of star formation activity and dust attenuation for spiral galaxies that have been widely used in previous work on galaxy evolution. We have used 104 spiral galaxies from the CALIFA survey for which 2D spectroscopy with complete spatial coverage is available. From the 3D cubes we have derived growth curves of the most conspicuous Balmer emission lines (Halpha, Hbeta) for circular apertures of different radii centered at the galaxy's nucleus after removing the underlying stellar continuum. We find that the Halpha flux (f(Halpha)) growth curve follows a well defined sequence with aperture radius showing low dispersion around the median value. From this analysis, we derive aperture corrections for galaxies in different magnitude and redshift intervals. Once stellar absorption is properly accounted for, the f(Halpha)/f(Hbeta) ratio growth curve shows...

  12. A Comparative Study of Knots of Star Formation in Interacting vs. Spiral Galaxies

    CERN Document Server

    Smith, Beverly J; Struck, Curtis; Olmsted, Susan; Jones, Keith

    2016-01-01

    Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published H-alpha images, we have compared the star formation rates of ~700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high star formation rates than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The star formation rates of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest star formation rates, the apparent dust a...

  13. The Evolution of Interacting Spiral Galaxy NGC 5194

    CERN Document Server

    Kang, Xiaoyu; Zhang, Fenghui; Cheng, Liantao; Wang, Lang

    2015-01-01

    NGC 5194 (M51a) is a grand-design spiral galaxy and undergoing interactions with its companion. Here we focus on investigating main properties of its star-formation history (SFH) by constructing a simple evolution model, which assumes that the disc builds up gradually by cold gas infall and the gas infall rate can be parameterizedly described by a Gaussian form. By comparing model predictions with the observed data, we discuss the probable range for free parameter in the model and then know more about the main properties of the evolution and SFH of M51a. We find that the model predictions are very sensitive to the free parameter and the model adopting a constant infall-peak time $t_{\\rm p}\\,=\\,7.0{\\rm Gyr}$ can reproduce most of the observed constraints of M51a. Although our model does not assume the gas infall time-scale of the inner disc is shorter than that of the outer disc, our model predictions still show that the disc of M51a forms inside-out. We find that the mean stellar age of M51a is younger than t...

  14. A spiral galaxy's mass distribution uncovered through lensing and dynamics

    CERN Document Server

    Trick, Wilma H; Dutton, Aaron A

    2016-01-01

    We investigate the matter distribution of a spiral galaxy with a counter-rotating stellar core, SDSS J1331+3628 (J1331), independently with gravitational lensing and stellar dynamical modelling. By fitting a gravitational potential model to a quadruplet of lensing images around J1331's bulge, we tightly constrain the mass inside the Einstein radius R_ein = (0.91 +/- 0.02)'' (~= 1.83 +/- 0.04 kpc) to within 4%: M_ein = (7.8 +/- 0.3) x 10^10 M_Sun. We model observed long-slit major axis stellar kinematics in J1331's central regions by finding Multi-Gaussian Expansion (MGE) models for the stellar and dark matter distribution that solve the axisymmetric Jeans equations. The lens and dynamical model are independently derived, but in very good agreement with each other around ~R_ein. We find that J1331's center requires a steep total mass-to-light ratio gradient. A dynamical model including an NFW halo (with virial velocity v_200 ~= 240 +/- 40 km/s and concentration c_200 ~= 8 +/- 2) and moderate tangential velocit...

  15. The transformation of Spirals into S0 galaxies in the cluster environment

    CERN Document Server

    D'Onofrio, Mauro; Buson, Lucio

    2015-01-01

    We discuss the observational evidences of the morphological transformation of Spirals into S0 galaxies in the cluster environment exploiting two big databases of galaxy clusters: WINGS (0.04 < z < 0.07) and EDisCS (0.4 < z < 0.8). The most important results are: 1) the average number of S0 galaxies in clusters is almost a factor of $\\sim 3 - 4$ larger today than at redshift $z \\sim 1$; 2) the fraction of S0's to Spirals increases on average by a factor $\\sim$ 2 every Gyr; 3) the average rate of transformation for Spirals (not considering the infall of new galaxies from the cosmic web) is: $\\sim$ 5 Sp into S0's per Gyr and $\\sim$ 2 Sp into E's per Gyr; 4) there are evidences that the interstellar gas of Spirals is stripped by an hot intergalactic medium; 5) there are also indirect hints that major/minor merging events have played a role in the transformation of Spiral galaxies. In particular, we show that: 1) the ratio between the number of S0's and Spirals (NS0/NSp) in the WINGS clusters is correl...

  16. Spiral density wave triggering of star formation in SA and SAB galaxies

    CERN Document Server

    Martínez-García, Eric E; Bruzual-A, Gustavo

    2008-01-01

    Azimuthal color (age) gradients across spiral arms are one of the main predictions of density wave theory; gradients are the result of star formation triggering by the spiral waves. In a sample of 13 spiral galaxies of types A and AB, we find that 10 of them present regions that match the theoretical predictions. By comparing the observed gradients with stellar population synthesis models, the pattern speed and the location of major resonances have been determined. The resonance positions inferred from this analysis indicate that 9 of the objects have spiral arms that extend to the outer Lindblad resonance (OLR); for one of the galaxies, the spiral arms reach the corotation radius. The effects of dust, and of stellar densities, velocities, and metallicities on the color gradients are also discussed.

  17. Determining Star Formation Timescale and Pattern Speed in Nearby Spiral Galaxies

    CERN Document Server

    Egusa, Fumi; Sofue, Yoshiaki; Nakanishi, Hiroyuki; Komugi, Shinya

    2009-01-01

    We present a revised method for simultaneous determination of the pattern speed and star formation timescale of spiral galaxies, its application, and results for CO and Ha images of nearby spiral galaxies. Out of 13 galaxies, we were able to derive the 2 parameters for 5 galaxies. We categorize them as "C" galaxies, and find (1) The corotation radius is close to the edge of the CO data, and is about half of the optical radius for 3 galaxies. (2) The star formation timescale is roughly consistent with the free-fall time of typical molecular clouds, which indicates that the gravitational instability is the dominant mechanism triggering star formation in spiral arms. (3) The timescale is found to be almost independent of surface density of molecular gas, metallicity, or spiral arm strengths. The number of "C" galaxies and the quality of CO data, however, are not enough to confirm these relationships. We also find that 2 other galaxies show no offsets between CO and Ha, although their arms are clearly traced, and...

  18. Synthetic Observations of the HI Line in SPH-Simulated Spiral Galaxies

    NARCIS (Netherlands)

    Douglas, Kevin A.; Acreman, David; Dobbs, Clare; Brunt, Chris

    2009-01-01

    Using the radiative transfer code Torus, we produce spectral-line cubes of the predicted HI profile from global SPH simulations of spiral galaxies. Torus grids the SPH galaxy using Adaptive Mesh Refinement, then applies a ray-tracing method to infer the HI profile along the line(s) of sight. The gri

  19. The opacity of spiral galaxy disks V. Dust opacity, HI distributions and sub-mm emission

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; Allen, RJ; van der Kruit, PC

    2005-01-01

    The opacity of spiral galaxy disks, from counts of distant galaxies, is compared to HI column densities. The opacity measurements are calibrated using the "Synthetic Field Method" from Gonzalez et al. (1998, ApJ, 506, 152), Holwerda et al. (2005a, AJ, 129, 1381). When compared for individual disks,

  20. The Chemical Anatomy of Nuclei of Nearby Barred Spiral Galaxies

    Science.gov (United States)

    Meier, D. S.; Turner, J. L.

    2004-12-01

    We present images of the millimeter lines of eight molecules---C2H, C34S, N2H+, CH3OH, HNCO, HNC, HC3N, and SO---in the nuclei of the nearby barred spiral galaxies, IC 342 and Maffei 2, made with the OVRO and BIMA arrays. These maps are compared to obtain a picture of changes in chemistry on sizescales of individual giant molecular clouds (GMCs) within a nucleus and between nuclei of similar morphological type. Emission from all species except SO are detected in both galaxies. Marked differences in morphology between the observed species are seen in both galaxies. A principal component analysis (PCA) is performed to quantify differences among the images. In IC 342, the PCA reveals that while all molecules are zeroth order correlated, that is, trace dense GMCs, there are three distinct groups of molecules distinguished by the location of their emission within the nucleus. N2H+ and HNC are widespread and bright, tracing all of the GMCs. C2H and C34S, tracers of photo-dissociation region chemistry, originate exclusively from the central ˜ 5'' ring illuminated by the 60 Myr, massive central cluster. CH3OH (and HNCO), a typical tracer of grain processing, correlates well with the expected locations of bar-induced orbital shocks. In Maffei 2, the PCA demonstrates that its chemistry is quite similar to IC 342, with the molecules tending to couple together in the same groups and with the same structural components of the nucleus. C2H dominates from the central starburst region, but is significantly more extended than IC 342 because its star formation is more extended. The correlation between HNCO and CH3OH in Maffei 2 is even strongly than in IC 342, being entirely dominated by the bar ends and orbit intersections. This provides strong evidence that HNCO is formed by the same processes as CH3OH. Funding for this research is provided by the Laboratory for Astronomical Imaging at the University of Illinois through the NSF grant AST-0228953, and by NSF grants AST-0071276 and

  1. Supernovae and their host galaxies - IV. The distribution of supernovae relative to spiral arms

    CERN Document Server

    Aramyan, L S; Petrosian, A R; de Lapparent, V; Bertin, E; Mamon, G A; Kunth, D; Nazaryan, T A; Adibekyan, V; Turatto, M

    2016-01-01

    Using a sample of 215 supernovae (SNe), we analyze their positions relative to the spiral arms of their host galaxies, distinguishing grand-design (GD) spirals from non-GD (NGD) galaxies. We find that: (1) in GD galaxies, an offset exists between the positions of Ia and core-collapse (CC) SNe relative to the peaks of arms, while in NGD galaxies the positions show no such shifts; (2) in GD galaxies, the positions of CC SNe relative to the peaks of arms are correlated with the radial distance from the galaxy nucleus. Inside (outside) the corotation radius, CC SNe are found closer to the inner (outer) edge. No such correlation is observed for SNe in NGD galaxies nor for SNe Ia in either galaxy class; (3) in GD galaxies, SNe Ibc occur closer to the leading edges of the arms than do SNe II, while in NGD galaxies they are more concentrated towards the peaks of arms. In both samples of hosts, the distributions of SNe Ia relative to the arms have broader wings. These observations suggest that shocks in spiral arms of...

  2. Stellar Orbital Studies in Normal Spiral Galaxies I: Restrictions to the Pitch Angle

    CERN Document Server

    Pérez-Villegas, A; Moreno, E

    2013-01-01

    We built a family of non-axisymmetric potential models for normal non-barred or weakly-barred spiral galaxies as defined in the simplest classification of galaxies: the Hubble sequence. For this purpose a three-dimensional self-gravitating model for spiral arms PERLAS is superimposed to the galactic axisymmetric potentials. We analyze the stellar dynamics varying only the pitch angle of the spiral arms, from 4$\\deg$ to 40$\\deg$, for an Sa galaxy, from 8$\\deg$ to 45$\\deg$, for an Sb galaxy, and from 10$\\deg$ to 60$\\deg$, for an Sc galaxy. Self-consistency is indirectly tested through periodic orbital analysis, and through density response studies for each morphological type. Based on ordered behavior, periodic orbits studies show that for pitch angles up to approximately $15\\deg$, $18\\deg$, and $20\\deg$ for Sa, Sb and Sc galaxies, respectively, the density response supports the spiral arms potential, a requisite for the existence of a long-lasting large-scale spiral structure. Beyond those limits, the density ...

  3. A New Method to Determine the Thickness of Spiral Galaxies: Apply to M31

    Institute of Scientific and Technical Information of China (English)

    LI Meng; LUO Xin-Lian; PENG Qiu-He; ZOU Zhi-Gang

    2000-01-01

    A new method is presented to determine the thickness of spiral galaxies. Based on the rigorous solution of the Poisson equation for logarithmic density disturbance in three-dimensional spiral galaxies, we have derived an accurate dispersion relation for the stellar and gaseous disk with a finite thickness. From this relation, a new method is put forward here for determining the thickness of galaxies. We apply this way to M31 and get the thickness of about 0.7kpc, which is in good agreement with the previous results.

  4. Analysis of the spiral structure in a simulated galaxy

    CERN Document Server

    Mata-Chávez, Dolores; Puerari, Ivânio

    2014-01-01

    We analyze the spiral structure that results in a numerical simulation of a galactic disk with stellar and gaseous components evolving in a potential that includes an axisymmetric halo and bulge. We perform a second simulation without the gas component to observe how it affects the spiral structure in the disk. To quantify this, we use a Fourier analysis and obtain values for the pitch angle and the velocity of the self-excited spiral pattern of the disk. The results show a tighter spiral in the simulation with gaseous component. The spiral structure is consistent with a superposition of waves, each with a constant pattern velocity in given radial ranges.

  5. Galactic Scale Flows and the Triggering of Star Formation in Spiral Galaxies

    Science.gov (United States)

    Ramón-Fox, F. G.; Bonnell, I. A.

    2016-06-01

    Galactic scale gas flows feed the growth of molecular clouds where stars form in high-density cores. Large scale flows also play a role in injecting the energy that drives the internal dynamics of these clouds, which affects their overall stability and star formation activity. The triggering of star formation involves a connection between large and small-scale dynamical processes in galaxies, which can be explored using high-resolution hydrodynamical simulations. We present results of current work in high-resolution N-body and Smoothed Particle Hydrodynamics simulations of a model spiral galaxy with a realistic spiral arm morphology. These simulations allow to study gas flows in a self-consistent galaxy and their role on molecular cloud formation and growth. They also provide a ground for studying molecular cloud properties in different environments of a galaxy, the effects of spiral arms on large scale flows and for understanding global star formation relations.

  6. The JCMT Nearby Galaxies Legacy Survey I. Star Forming Molecular Gas in Virgo Cluster Spiral Galaxies

    CERN Document Server

    Wilson, C D; Israel, F P; Serjeant, S; Bendo, G; Brinks, E; Clements, D; Courteau, S; Irwin, J; Knapen, J H; Leech, J; Matthews, H E; Muehle, S; Mortier, A M J; Petitpas, G; Sinukoff, E; Spekkens, K; Tan, B K; Tilanus, R P J; Usero, A; Van der Werf, P P; Wiegert, T; Zhu, M

    2008-01-01

    We present large-area maps of the CO J=3-2 emission obtained at the James Clerk Maxwell Telescope for four spiral galaxies in the Virgo Cluster. We combine these data with published CO J=1-0, 24 micron, and Halpha images to measure the CO line ratios, molecular gas masses, and instantaneous gas depletion times. For three galaxies in our sample (NGC 4254, NGC4321, and NGC 4569), we obtain molecular gas masses of 7E8-3E9 Msun and disk-averaged instantaneous gas depletion times of 1.1-1.7 Gyr. We argue that the CO J=3-2 line is a better tracer of the dense star forming molecular gas than the CO J=1-0 line, as it shows a better correlation with the star formation rate surface density both within and between galaxies. NGC 4254 appears to have a larger star formation efficiency(smaller gas depletion time), perhaps because it is on its first passage through the Virgo Cluster. NGC 4569 shows a large-scale gradient in the gas properties traced by the CO J=3-2/J=1-0 line ratio, which suggests that its interaction with ...

  7. Gas and stellar spiral arms and their offsets in the grand-design spiral galaxy M51

    CERN Document Server

    Egusa, Fumi; Koda, Jin; Baba, Junichi

    2016-01-01

    Theoretical studies on the response of interstellar gas to a gravitational potential disc with a quasi-stationary spiral arm pattern suggest that the gas experiences a sudden compression due to standing shock waves at spiral arms. This mechanism, called a galactic shock wave, predicts that gas spiral arms move from downstream to upstream of stellar arms with increasing radius inside a corotation radius. In order to investigate if this mechanism is at work in the grand-design spiral galaxy M51, we have measured azimuthal offsets between the peaks of stellar mass and gas mass distributions in its two spiral arms. The stellar mass distribution is created by the spatially resolved spectral energy distribution fitting to optical and near infrared images, while the gas mass distribution is obtained by high-resolution CO and HI data. For the inner region (r < 150"), we find that one arm is consistent with the galactic shock while the other is not. For the outer region, results are less certain due to the narrower...

  8. Effect of dark matter halo on global spiral modes in galaxies

    Science.gov (United States)

    Ghosh, Soumavo; Saini, Tarun Deep; Jog, Chanda J.

    2016-02-01

    Low surface brightness (LSB) galaxies form a major class of galaxies, and are characterized by low disc surface density and low star formation rate. These are known to be dominated by dark matter halo from the innermost regions. Here, we study the role of the dark matter halo on the grand-design, m = 2, spiral modes in a galactic disc by carrying out a global mode analysis in the WKB approximation. The Bohr-Sommerfeld quantization rule is used to determine how many discrete global spiral modes are permitted. First, a typical superthin, LSB galaxy UGC 7321 is studied by taking only the galactic disc, modelled as a fluid; and then the disc embedded in a dark matter halo. We find that both cases permit the existence of global spiral modes. This is in contrast to earlier results where the inclusion of dark matter halo was shown to nearly fully suppress local, swing-amplified spiral features. Although technically global modes are permitted in the fluid model as shown here, we argue that due to lack of tidal interactions, these are not triggered in LSB galaxies. For comparison, we carried out a similar analysis for the Galaxy, for which the dark matter halo does not dominate in the inner regions. We show that here too the dark matter halo has little effect, hence the disc embedded in a halo is also able to support global modes. The derived pattern speed of the global mode agrees fairly well with the observed value for the Galaxy.

  9. Spiral structure in nearby galaxies I. Sample, data analysis, and overview of results

    CERN Document Server

    Kendall, S; Clarke, C

    2011-01-01

    This paper, the first of two, introduces an observational study of spiral structure in galaxies chosen from the SINGS survey. Near infrared (NIR) and optical data are used to produce mass surface density maps, and from these the morphology of the disc is examined. The aim of this work is to characterise the prevalence of spiral structure in this sample and, in the cases where a clear spiral pattern is found, include the findings in a comparative study (reported in paper II). A two-armed (`grand design') spiral pattern is found in approximately half the galaxies studied, including all those that are designated as grand design in the optical, but also including some, but not all, optically flocculent galaxies. It is found that the level of non-axisymmetric structure in the galaxies' mass distributions is only modestly higher in those galaxies that are classified as `grand design' compared with those that are not, implying that non-grand design galaxies possess significant power in higher order modes. There is n...

  10. On galaxy spiral arms' nature as revealed by rotation frequencies

    NARCIS (Netherlands)

    Roca-Fabrega, Santi; Valenzuela, Octavio; Figueras, Francesca; Romero-Gomez, Merce; Velazquez, Hector; Antoja Castelltort, Teresa; Pichardo, Barbara

    2013-01-01

    High-resolution N-body simulations using different codes and initial condition techniques reveal two different behaviours for the rotation frequency of transient spiral arms like structures. Whereas unbarred discs present spiral arms nearly corotating with disc particles, strong barred models (bulge

  11. A Chandra Observation of the Face-on Spiral Galaxy NGC 3938

    Science.gov (United States)

    Buhidar, Kelsey; Schlegel, Eric M.

    2017-01-01

    The ACIS detector (Advanced CCD Imaging Spectrometer) onboard the Chandra X-ray Observatory has imaged the face-on spiral NGC 3938 for 50 ksec. We will detect ~50 sources within the D25 radius. We will describe the luminosity distribution in comparison with distributions from other nearby spiral galaxies. We do not detect any diffuse emission. We will compare the X-ray data to observations at other wavebands.

  12. AXIAL RATIO OF EDGE-ON SPIRAL GALAXIES AS A TEST FOR BRIGHT RADIO HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; Jones, E.; Dunlap, H. [Physics Department, University of Richmond 28 Westhampton Way, Richmond, VA 23173 (United States); Kogut, A., E-mail: jsingal@richmond.edu [Code 665, NASA Goddard Space Flight Center Greenbelt, MD 20771 (United States)

    2015-01-20

    We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan and Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo. (letters)

  13. A Search for double-lobed radio emission from Galactic Stars and Spiral Galaxies

    CERN Document Server

    Martínez, Abiel Felipe Ortiz

    2016-01-01

    We present a systematic search for two types of very unusual astronomical objects: Galactic stars and spiral galaxies with double radio lobes, i.e. radio emission on opposite sides of the optical object, suggesting the ejection of jets from them. We designed an algorithm to search for pairs of radio sources straddling objects from two unprecedented samples of 878,031 Galactic stars from the Sloan Digital Sky Survey and 675,874 spiral galaxy candidates drawn from the recent literature. We found three new examples of double-lobed radio stars, while for the spiral galaxies we only rediscovered one known such double source, confirming that the latter objects are extremely rare.

  14. Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias

    CERN Document Server

    Hart, Ross E; Willett, Kyle W; Masters, Karen L; Cardamone, Carolin; Lintott, Chris J; Mackay, Robert J; Nichol, Robert C; Rosslowe, Christopher K; Simmons, Brooke D; Smethurst, Rebecca J

    2016-01-01

    The majority of galaxies in the local Universe exhibit spiral structure with a variety of forms. Many galaxies possess two prominent spiral arms, some have more, while others display a many-armed flocculent appearance. Spiral arms are associated with enhanced gas content and star-formation in the disks of low-redshift galaxies, so are important in the understanding of star-formation in the local universe. As both the visual appearance of spiral structure, and the mechanisms responsible for it vary from galaxy to galaxy, a reliable method for defining spiral samples with different visual morphologies is required. In this paper, we develop a new debiasing method to reliably correct for redshift-dependent bias in Galaxy Zoo 2, and release the new set of debiased classifications. Using these, a luminosity-limited sample of ~18,000 Sloan Digital Sky Survey spiral galaxies is defined, which are then further sub-categorised by spiral arm number. In order to explore how different spiral galaxies form, the demographic...

  15. Formation of S0 galaxies through mergers. Explaining angular momentum and concentration change from spirals to S0s

    NARCIS (Netherlands)

    Querejeta, M.; Eliche-Moral, M. C.; Tapia, T.; Borlaff, A.; van de Ven, G.; Lyubenova, M.; Martig, M.; Falcón-Barroso, J.; Méndez-Abreu, J.

    2015-01-01

    The CALIFA team has recently found that the stellar angular momentum and concentration of late-type spiral galaxies are incompatible with those of lenticular galaxies (S0s), concluding that fading alone cannot satisfactorily explain the evolution from spirals into S0s. Here we explore whether major

  16. Spiral and bar driven peculiar velocities in Milky Way sized galaxy simulations

    CERN Document Server

    Grand, Robert J J; Kawata, Daisuke; Hunt, Jason A S; Famaey, Benoit; Siebert, Arnaud; Monari, Giacomo; Cropper, Mark

    2015-01-01

    We investigate the kinematic signatures induced by spiral and bar structure in a set of simulations of Milky Way-sized spiral disc galaxies. The set includes test particle simulations that follow a quasi-stationary density wave-like scenario with rigidly rotating spiral arms, and $N$-body simulations that host a bar and transient, co-rotating spiral arms. From a location similar to that of the Sun, we calculate the radial, tangential and line-of-sight peculiar velocity fields of a patch of the disc and quantify the fluctuations by computing the power spectrum from a two-dimensional Fourier transform. We find that the peculiar velocity power spectrum of the simulation with a bar and transient, co-rotating spiral arms fits very well to that of APOGEE red clump star data, while the quasi-stationary density wave spiral model without a bar does not. We determine that the power spectrum is sensitive to the number of spiral arms, spiral arm pitch angle and position with respect to the spiral arm. However, it is nece...

  17. Invariant manifolds and the response of spiral arms in barred galaxies

    CERN Document Server

    Tsoutsis, P; Efthymiopoulos, C; Contopoulos, George

    2008-01-01

    The unstable invariant manifolds of the short-period family of periodic orbits around the unstable Lagrangian points $L_1$ and $L_2$ of a barred galaxy define loci in the configuration space which take the form of a trailing spiral pattern. In the present paper we investigate this association in the case of the self-consistent models of Kaufmann & Contopoulos (1996) which provide an approximation of real barred-spiral galaxies. We also examine the relation of `response' models of barred-spiral galaxies with the theory of the invariant manifolds. Our main results are the following: The invariant manifolds yield the correct form of the imposed spiral pattern provided that their calculation is done with the spiral potential term turned on. We provide a theoretical model explaining the form of the invariant manifolds that supports the spiral structure. The azimuthal displacement of the Lagrangian points with respect to the bar's major axis is a crucial parameter in this modeling. When this is taken into accou...

  18. XCHANGES: XMM-Newton data on CHANG-ES spiral galaxies

    Science.gov (United States)

    Wezgowiec, M.; Dettmar, R.

    2014-07-01

    The CHANG-ES survey of galaxies provides a unique sample of edge-on spiral galaxies with deep radio observations, that allow detailed analysis of their magnetic fields. Since the co-existence of halo magnetic fields and hot gas is likely to greatly influence the dynamics of the galactic halo, we analyse diffuse X-ray emission for the sample galaxies. Here, we present preliminary results of the imaging of the soft X-ray emission (0.2-1 keV) from selected galaxies of the sample using archive data of the XMM-Newton X-ray telescope.

  19. A COMPARATIVE STUDY OF KNOTS OF STAR FORMATION IN INTERACTING VERSUS SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Beverly J.; Olmsted, Susan; Jones, Keith [Department of Physics and Astronomy, East Tennessee State University, Johnson City TN 37614 (United States); Zaragoza-Cardiel, Javier [Instituto de Astrofisica de Canarias, La Laguna, Tenerife (Spain); Struck, Curtis, E-mail: smithbj@etsu.edu [Department of Physics and Astronomy, Iowa State University, Ames IA 50011 (United States)

    2016-03-15

    Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published Hα images, we have compared the star formation rates (SFRs) of ∼700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high SFRs than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Space Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The SFRs of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest SFRs, the apparent dust attenuation is consistent with the Calzetti starburst dust attenuation law. This suggests that the high luminosity regions are dominated by a central group of young stars surrounded by a shell of clumpy interstellar gas. In contrast, the lower luminosity clumps are bright in the UV relative to Hα, suggesting either a high differential attenuation between the ionized gas and the stars, or a post-starburst population bright in the UV but faded in Hα. The fraction of the global light of the galaxies in the clumps is higher on average for the interacting galaxies than for the spirals. Thus either star formation in interacting galaxies is “clumpier” on average, or the star forming regions in interacting galaxies are more luminous, dustier, or younger on average.

  20. The transformation of Spirals into S0 galaxies in the cluster environment

    Directory of Open Access Journals (Sweden)

    Mauro eD'onofrio

    2015-08-01

    Full Text Available We discuss the observational evidences of the morphological transformation of Spirals into S0 galaxies in the cluster environment exploiting two big databases of galaxy clusters: WINGS (0.04galaxies in clusters is almost a factor of ∼ 3 − 4 larger today than at redshift z ∼ 1; 2 the fraction of S0’s to Spirals increases on average by a factor ∼ 2 every Gyr; 3 the average rate of transformation for Spirals (not considering the infall of new galaxies from the cosmic web is: ∼ 5 Sp→S0’s per Gyr and ∼ 2 Sp→E’s per Gyr; 4 there are evidences that the interstellar gas of Spirals is stripped by an hot intergalactic medium; 5 there are also indirect hints that major/minor merging events have played a role in the transformation of Spiral galaxies. In particular, we show that: 1 the ratio between the number of S0’s and Spirals (NS0/NSp in the WINGS clusters is correlated with their X-ray luminosity LX ; 2 that the brightest and massive S0’s are always close to the cluster center; 3 that the mean Se ́rsic index of S0’s is always larger than that of Spirals (and lower than E’s for galaxy stellar masses above 10^9.5M⊙; 4 that the number of E’s in clusters cannot be constant; 5 that the largest difference between the mean mass of S0’s and E’s with respect to Spirals is observed in clusters with low velocity dispersion.Finally, by comparing the properties of the various morphological types for galaxies in clusters and in the field, we find that the most significant effect of the environment is the stripping of the outer galaxy regions, resulting in a systematic difference in effective radius and Se ́rsic index.

  1. The opacity of spiral galaxy disks. IV. Radial extinction profiles from counts of distant galaxies seen through foreground disks

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; Allen, RJ; van der Kruit, PC

    2005-01-01

    Dust extinction can be determined from the number of distant field galaxies seen through a spiral disk. To calibrate this number for the crowding and confusion introduced by the foreground image, Gonzalez et al. and Holwerda et al. developed the Synthetic Field Method (SFM), which analyzes synthetic

  2. On the nature and correction of the spurious S-wise spiral galaxy winding bias in Galaxy Zoo 1

    Science.gov (United States)

    Hayes, Wayne B.; Davis, Darren; Silva, Pedro

    2017-04-01

    The Galaxy Zoo 1 catalogue displays a bias towards the S-wise winding direction in spiral galaxies, which has yet to be explained. The lack of an explanation confounds our attempts to verify the Cosmological Principle, and has spurred some debate as to whether a bias exists in the real Universe. The bias manifests not only in the obvious case of trying to decide if the universe as a whole has a winding bias, but also in the more insidious case of selecting which Galaxies to include in a winding direction survey. While the former bias has been accounted for in a previous image-mirroring study, the latter has not. Furthermore, the bias has never been corrected in the GZ1 catalogue, as only a small sample of the GZ1 catalogue was reexamined during the mirror study. We show that the existing bias is a human selection effect rather than a human chirality bias. In effect, the excess S-wise votes are spuriously 'stolen' from the elliptical and edge-on-disc categories, not the Z-wise category. Thus, when selecting a set of spiral galaxies by imposing a threshold T so that max (PS, PZ) > T or PS + PZ > T, we spuriously select more S-wise than Z-wise galaxies. We show that when a provably unbiased machine selects which galaxies are spirals independent of their chirality, the S-wise surplus vanishes, even if humans still determine the chirality. Thus, when viewed across the entire GZ1 sample (and by implication, the Sloan catalogue), the winding direction of arms in spiral galaxies as viewed from Earth is consistent with the flip of a fair coin.

  3. The Black Hole Mass - Pitch Angle Relation of Type I AGN In Spiral Galaxies

    Science.gov (United States)

    Schilling, Amanda; Jones, Logan; Hughes, John A.; Barrows, R. Scott; Kennefick, Julia D.

    2017-01-01

    A relationship between the mass of supermassive black holes, M, at the center of galaxies and the pitch angle, P, a measure of tightness of spiral arms, was recently reported by Berrier, et al. (2013 ApJ 769, 132) for late type galaxies. The relationship, established for a local sample, shows that spiral galaxies with tighter pitch angles host higher mass black holes. In this work, we explore the M-P relation for a sample of 50 low to moderate redshift (0.04spiral galaxies that host Type 1 Active Galactic Nuclei, AGN. These objects were selected from the SDSS quasar catalog and various studies involving HST imaging. Broad Hβ, Hα, and MgII and narrow [OIII]λ5007 emission lines were used with established mass scaling relations to estimate black-hole mass. Pitch angles were measured using a 2DFFT technique (Davis, et al., 2012 ApJS 199, 33). We find that the M-P relation for the higher redshift, AGN sample differs from that of the local sample and discuss the possibility of AGN feedback by looking at a proposed Fundamental Plane for late-type galaxies - a correlation between bulge mass, disk mass, and spiral-arm pitch angle (Davis, et al. 2015, ApJ 802, L13).

  4. 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

  5. SPIN ALIGNMENTS OF SPIRAL GALAXIES WITHIN THE LARGE-SCALE STRUCTURE FROM SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Youcai; Yang, Xiaohu; Luo, Wentao [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China); Wang, Huiyuan [Key Laboratory for Research in Galaxies and Cosmology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Lei [Purple Mountain Observatory, The Partner Group of MPI für Astronomie, 2 West Beijing Road, Nanjing 210008 (China); Mo, H. J. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Van den Bosch, Frank C., E-mail: yczhang@shao.ac.cn, E-mail: xyang@sjtu.edu.cn [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

    2015-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 and Galaxy Zoo 2, we investigate the alignment of spin axes of spiral galaxies with their surrounding large-scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes only have weak tendencies to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a cluster environment where all three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and the local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  6. Unequal-mass galaxy merger remnants: spiral-like morphology but elliptical-like kinematics

    CERN Document Server

    Bournaud, F; Jog, C J

    2004-01-01

    It is generally believed that major galaxy mergers with mass ratios in the range 1:1-3:1 result in remnants that have properties similar to elliptical galaxies, and minor mergers below 10:1 result in disturbed spiral galaxies. The intermediate range of mass ratios 4:1-10:1 has not been studied so far. Using N-body simulations, we show that such mergers can result in very peculiar systems, that have the morphology of a disk galaxy with an exponential profile, but whose kinematics is closer to that of elliptical systems. These objects are similar to those recently observed by Jog & Chitre (2002). We present two cases with mass ratios 4.5:1 and 7:1, and show that the merging causes major heating and results in the appearance of elliptical-type kinematics, while surprisingly the initial spiral-like mass profile is conserved.

  7. The 2X-HI disks of spiral galaxies

    CERN Document Server

    Koribalski, B S

    2016-01-01

    The outskirts of galaxies - especially the very extended HI disks of galaxies - are strongly affected by their local environment. I highlight the giant 2X-HI disks of nearby galaxies (M 83, NGC 3621, and NGC 1512), studied as part of the Local Volume HI Survey (LVHIS), their kinematics and relation to XUV disks, signatures of tidal interactions and accretion events, the MHI - DHI relation as well as the formation of tidal dwarf galaxies. - Using multi-wavelength data, I create 3D visualisations of the gas and stars in galaxies, with the shape of their warped disks obtained through kinematic modelling of their HI velocity fields.

  8. Sustaining star formation rates in spiral galaxies - Supernova-driven turbulent accretion disk models applied to THINGS galaxies

    CERN Document Server

    Vollmer, B

    2010-01-01

    Gas disks of spiral galaxies can be described as clumpy accretion disks without a coupling of viscosity to the actual thermal state of the gas. The model description of a turbulent disk consisting of emerging and spreading clumps (Vollmer & Beckert 2003) contains free parameters, which can be constrained by observations of molecular gas, atomic gas and the star formation rate for individual galaxies. Radial profiles of 18 nearby spiral galaxies from THINGS, HERACLES, SINGS, and GALEX data are used to compare the observed star formation efficiency, molecular fraction, and velocity dispersion to the model. The observed radially decreasing velocity dispersion can be reproduced by the model. In the framework of this model the decrease in the inner disk is due to the stellar mass distribution which dominates the gravitational potential. Introducing a radial break in the star formation efficiency into the model improves the fits significantly. This change in star formation regime is realized by replacing the fr...

  9. A neutral hydrogen study of the barred spiral galaxy NGC 3319

    Science.gov (United States)

    Moore, E. M.; Gottesman, S. T.

    1998-03-01

    Neutral hydrogen line observations of the late-type barred spiral galaxy NGC 3319 are presented. The distribution and kinematics of the galaxy are studied using the Very Large Array, with spatial resolutions between 11 and 50 arcsec and a channel separation of 10.33 km/s. As is typical for late-type galaxies, NGC 3319 is rich in H I, with a gaseous bar and spiral features. Several large, low-density regions are present, and the H I spiral structure is distorted, especially in the south. The gas distribution is asymmetric and extends significantly further to the southeast due to a long, off-center tail. Noncircular motions caused by the bar, spiral structure, and low-density regions are present in the radial velocity field, complicating the rotation curve analysis. These nonaxisymmetric structures cause the values of the position angle and inclination derived from the velocity field to vary across the disk. In addition, beyond a radius of 180 arcsec, the velocity field is severely perturbed on the approaching (southern) side of the galaxy, and the disk becomes nonplanar. However, the galaxy does not show the typical 'integral sign' shape of a warped system. We detect a small system approximately 11 arcmin south of the center of NGC 3319. It is seen in eight velocity channels and is coincident with a small, resolved object in the Palomar Sky Survey. A tidal interaction between this object and NGC 3319 is the most likely cause of the distorted spiral structure, the H I tail, and the velocity perturbations found in the southern half of the galaxy. Infalling tidal debris from such an event may account for the large, low-density regions found in the disk, several of which show kinematic evidence that suggest they are expanding superstructures.

  10. The Luminous Convolution Model as an alternative to dark matter in spiral galaxies

    CERN Document Server

    Cisneros, S; Formaggio, J A; Ott, R A; Chester, D; Battaglia, D J; Ashley, A; Robinson, R; Rodriguez, A

    2014-01-01

    The Luminous Convolution Model (LCM) demonstrates that it is possible to predict the rotation curves of spiral galaxies directly from estimates of the luminous matter. We consider two frame-dependent effects on the light observed from other galaxies: relative velocity and relative curvature. With one free parameter, we predict the rotation curves of twenty-three (23) galaxies represented in forty-two (42) data sets. Relative curvature effects rely upon knowledge of both the gravitational potential from luminous mass of the emitting galaxy and the receiving galaxy, and so each emitter galaxy is compared to four (4) different Milky Way luminous mass models. On average in this sample, the LCM is more successful than either dark matter or modified gravity models in fitting the observed rotation curve data. Implications of LCM constraints on populations synthesis modeling are discussed in this paper. This paper substantially expands the results in arXiv:1309.7370.

  11. Disc colours in field and cluster spiral galaxies at 0.5 < z < 0.8

    CERN Document Server

    Cantale, Nicolas; Courbin, Frederic; Rudnick, Gregory; Zaritsky, Dennis; Meylan, Georges; Desai, Vandana; De Lucia, Gabriella; Aragon-Salamanca, Alfonso; Poggianti, Bianca M; Finn, Rose; Simard, Luc

    2016-01-01

    We present a detailed study of the colours in late-type galaxy discs for ten of the EDisCS galaxy clusters with 0.5 < z < 0.8. Our cluster sample contains 172 spiral galaxies, and our control sample is composed of 96 field disc galaxies. We deconvolve their ground-based V and I images obtained with FORS2 at the VLT with initial spatial resolutions between 0.4 and 0.8 arcsec to achieve a final resolution of 0.1 arcsec with 0.05 arcsec pixels, which is close to the resolution of the ACS at the HST. After removing the central region of each galaxy to avoid pollution by the bulges, we measured the V-I colours of the discs. We find that 50% of cluster spiral galaxies have disc V-I colours redder by more than 1 sigma of the mean colours of their field counterparts. This is well above the 16% expected for a normal distribution centred on the field disc properties. The prominence of galaxies with red discs depends neither on the mass of their parent cluster nor on the distance of the galaxies to the cluster cor...

  12. Energetic constraints to chemo-photometric evolution of spiral galaxies

    CERN Document Server

    Buzzoni, Alberto

    2011-01-01

    The problem of chemo-photometric evolution of late-type galaxies is dealt with relying on prime physical arguments of energetic self-consistency between chemical enhancement of galaxy mass, through nuclear processing inside stars, and luminosity evolution of the system. Chemical enhancement is assessed in terms of the so-called "yield metallicity", that is the metal abundance of processed mass inside stars, as constrained by the galaxy photometric history.

  13. HI study of the warped spiral galaxy NGC5055 : a disk/dark matter halo offset?

    NARCIS (Netherlands)

    Battaglia, G; Fraternali, F; Oosterloo, T; Sancisi, R

    2006-01-01

    We present a study of the Hi distribution and dynamics of the nearby spiral galaxy NGC 5055 based on observations with the Westerbork Synthesis Radio Telescope. The gaseous disk of NGC5055 extends out to about 40 kpc, equal to 3.5 R-25, and shows a pronounced warp that starts at the end of the brigh

  14. HI study of the warped spiral galaxy NGC5055 : a disk/dark matter halo offset?

    NARCIS (Netherlands)

    Battaglia, G.; Fraternali, F.; Oosterloo, T.; Sancisi, R.

    2005-01-01

    Abstract: We present a study of the HI distribution and the dynamics of the nearby spiral galaxy NGC5055 based on observations with the Westerbork Synthesis Radio Telescope. The gaseous disk of NGC5055 extends out to about 40 kpc, equal to 3.5 R_25 and shows a pronounced warp, starting at the end of

  15. The DiskMass Survey. VII. The distribution of luminous and dark matter in spiral galaxies

    NARCIS (Netherlands)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Andersen, David R.; Swaters, Rob A.

    2013-01-01

    We present dynamically-determined rotation-curve mass decompositions of 30 spiral galaxies, which were carried out to test the maximum-disk hypothesis and to quantify properties of their dark-matter halos. We used measured vertical velocity dispersions of the disk stars to calculate dynamical mass s

  16. Absorption-line strengths of 18 late-type spiral galaxies observed with SAURON

    NARCIS (Netherlands)

    Ganda, Katia; Peletier, Reynier F.; McDermid, Richard M.; Falcon-Barroso, Jesus; de Zeeuw, P. T.; Bacon, Roland; Cappellari, Michele; Davies, Roger L.; Emsellem, Eric; Krajnovic, Davor; Kuntschner, Harald; Sarzi, Marc; van de Ven, Glenn

    2007-01-01

    We present absorption line strength maps for a sample of 18 Sb-Sd galaxies observed using the integral-field spectrograph SAURON operating at the William Herschel Telescope on La Palma, as part of a project devoted to the investigation of the kinematics and stellar populations of late-type spirals,

  17. Optical observations of Dwingeloo 1, a nearby barred spiral galaxy behind the Milky Way

    NARCIS (Netherlands)

    Loan, AJ; Maddox, SJ; Lahav, O; Balcells, M; KraanKorteweg, RC; Assendorp, R; Almoznino, E; Brosch, N; Goldberg, E; Ofek, EO

    1996-01-01

    We present new optical observations of the nearby barred spiral galaxy Dwingeloo 1 (Dw1) obtained with the Isaac Newton, William Herschel and Wise telescopes. Dw1 lies at Galactic coordinates (l=138.degrees 52, b=-0.degrees 11) and it is heavily obscured by dust and gas in the Milky Way. We infer th

  18. The opacity of spiral galaxy disks. VIII. Structure of the cold ISM

    NARCIS (Netherlands)

    Holwerda, B. W.; Draine, B.; Gordon, K. D.; Gonzalez, R. A.; Calzetti, D.; Thornley, M.; Buckalew, B.; Allen, Ronald J.; van der Kruit, P. C.

    2007-01-01

    The quantity of dust in a spiral disk can be estimated using the dust's typical emission or the extinction of a known source. In this paper we compare two techniques, one based on emission and one on absorption, applied to sections of 14 disk galaxies. The two measurements reflect, respectively, the

  19. The opacity of spiral galaxy disks VI. Extinction, stellar light and color

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; van der Kruit, PC; Allen, RJ

    2005-01-01

    In this paper we explore the relation between dust extinction and stellar light distribution in disks of spiral galaxies. Extinction influences our dynamical and photometric perception of disks, since it can distort our measurement of the contribution of the stellar component. To characterize the to

  20. Comparison between Disk-like Objects Formed in Hierarchical Hydrodynamical Simulations and Observations of Spiral Galaxies

    CERN Document Server

    Saiz, A; Tissera, P B; Courteau, S

    2001-01-01

    We analyze the structural and dynamical properties of disk-like objects formed in fully consistent cosmological simulations which include inefficient star formation. Comparison with data of similar observable properties of spiral galaxies gives satisfactory agreement, in contrast with previous findings using other codes. This suggests that the stellar formation implementation used has allowed the formation of disks as well as guaranteed their stability.

  1. Formation of S0 galaxies through mergers: Explaining angular momentum and concentration change from spirals to S0s

    CERN Document Server

    Querejeta, Miguel; Tapia, Trinidad; Borlaff, Alejandro; van de Ven, Glenn; Lyubenova, Mariya; Martig, Marie; Falcón-Barroso, Jesús; Méndez-Abreu, Jairo

    2015-01-01

    The CALIFA team has recently found that the stellar angular momentum and concentration of late-type spiral galaxies are incompatible with those of lenticular galaxies (S0s), concluding that fading alone cannot satisfactorily explain the evolution from spirals into S0s. Here we explore whether major mergers can provide an alternative way to transform spirals into S0s by analysing the spiral-spiral major mergers from the GalMer database that lead to realistic, relaxed S0-like galaxies. We find that the change in stellar angular momentum and concentration can explain the differences in the $\\lambda_\\mathrm{Re}$--$R_{90}/R_{50}$ plane found by the CALIFA team. Major mergers thus offer a feasible explanation for the transformation of spirals into S0s.

  2. A close nuclear black-hole pair in the spiral galaxy NGC 3393.

    Science.gov (United States)

    Fabbiano, G; Wang, Junfeng; Elvis, M; Risaliti, G

    2011-08-31

    The current picture of galaxy evolution advocates co-evolution of galaxies and their nuclear massive black holes, through accretion and galactic merging. Pairs of quasars, each with a massive black hole at the centre of its galaxy, have separations of 6,000 to 300,000 light years (refs 2 and 3; 1 parsec = 3.26 light years) and exemplify the first stages of this gravitational interaction. The final stages of the black-hole merging process, through binary black holes and final collapse into a single black hole with gravitational wave emission, are consistent with the sub-light-year separation inferred from the optical spectra and light-variability of two such quasars. The double active nuclei of a few nearby galaxies with disrupted morphology and intense star formation (such as NGC 6240 with a separation of about 2,600 light years and Mrk 463 with a separation of about 13,000 light years between the nuclei) demonstrate the importance of major mergers of equal-mass spiral galaxies in this evolution; such mergers lead to an elliptical galaxy, as in the case of the double-radio-nucleus elliptical galaxy 0402+379 (with a separation of about 24 light years between the nuclei). Minor mergers of a spiral galaxy with a smaller companion should be a more common occurrence, evolving into spiral galaxies with active massive black-hole pairs, but have hitherto not been seen. Here we report the presence of two active massive black holes, separated by about 490 light years, in the Seyfert galaxy NGC 3393 (50 Mpc, about 160 million light years). The regular spiral morphology and predominantly old circum-nuclear stellar population of this galaxy, and the closeness of the black holes embedded in the bulge, provide a hitherto missing observational point to the study of galaxy/black hole evolution. Comparison of our observations with current theoretical models of mergers suggests that they are the result of minor merger evolution.

  3. Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disk morphology

    CERN Document Server

    Willett, Kyle W; Simmons, Brooke D; Masters, Karen L; Skibba, Ramin A; Kaviraj, Sugata; Melvin, Thomas; Wong, O Ivy; Nichol, Robert C; Cheung, Edmond; Lintott, Chris J; Fortson, Lucy

    2015-01-01

    We measure the stellar mass-star formation rate relation in star-forming disk galaxies at z1. Of the galaxies lying significantly above the M-SFR relation in the local Universe, more than 50% are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.

  4. The role of interactions in triggering bars, spiral arms and AGN in disk galaxies

    Science.gov (United States)

    Nair, Preethi; Ellison, Sara L.; Patton, David R.

    2016-01-01

    The role of secular structures like bars, rings and spiral arms in triggering star formation and AGN activity in disk galaxies are not well understood. In addition, the mechanisms which create and destroy these structures are not well characterized. Mergers are considered to be one of the main mechanisms which can trigger bars in massive disk galaxies. Using a sample of ~8000 close pair galaxies at 0.02 MaNGA will help to place stronger constraints on the role of these structures in triggering star formation and AGN.

  5. Long-Lived Spiral Structure for Galaxies with Intermediate Size Bulges

    CERN Document Server

    Saha, Kanak

    2016-01-01

    Spiral structure in disk galaxies is modeled with nine collisionless N-body simulations including live disks, halos, and bulges with a range of masses. Two of these simulations make long-lasting and strong two-arm spiral wave modes that last for $\\sim5$ Gyr with constant pattern speed. These two had a light stellar disk and the largest values of the Toomre $Q$ parameter in the inner region at the time the spirals formed, suggesting the presence of a Q-barrier to wave propagation resulting from the bulge. The relative bulge mass in these cases is about 10\\%. Models with weak two-arm spirals had pattern speeds that followed the radial dependence of the Inner Lindblad Resonance.

  6. The JCMT Nearby Galaxies Legacy Survey II: Warm Molecular Gas and Star Formation in Three Field Spiral Galaxies

    CERN Document Server

    Warren, B E; Israel, F P; Serjeant, S; Bendo, G J; Brinks, E; Clements, D L; Irwin, J A; Knapen, J H; Leech, J; Matthews, H E; Mühle, S; Mortimer, A M J; Petitpas, G; Sinukoff, E; Spekkens, K; Tan, B K; Tilanus, R P J; Usero, A; van der Werf, P P; Vlahakis, C; Wiegert, T; Zhu, M

    2010-01-01

    We present the results of large-area CO J=3-2 emission mapping of three nearby field galaxies, NGC 628, NGC 3521, and NGC 3627, completed at the James Clerk Maxwell Telescope as part of the Nearby Galaxies Legacy Survey. These galaxies all have moderate to strong CO J=3-2 detections over large areas of the fields observed by the survey, showing resolved structure and dynamics in their warm/dense molecular gas disks. All three galaxies were part of the Spitzer Infrared Nearby Galaxies Survey sample, and as such have excellent published multi-wavelength ancillary data. These data sets allow us to examine the star formation properties, gas content, and dynamics of these galaxies on sub-kiloparsec scales. We find that the global gas depletion times for dense/warm molecular gas in these galaxies is consistent with other results for nearby spiral galaxies, indicating this may be independent of galaxy properties such as structures, gas compositions, and environments. Similar to the results from the THINGS HI survey,...

  7. Megamaser Disks Reveal a Broad Distribution of Black Hole Mass in Spiral Galaxies

    Science.gov (United States)

    Greene, J. E.; Seth, A.; Kim, M.; Läsker, R.; Goulding, A.; Gao, F.; Braatz, J. A.; Henkel, C.; Condon, J.; Lo, K. Y.; Zhao, W.

    2016-08-01

    We use new precision measurements of black hole (BH) masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive BH mass. The megamaser-derived BH masses span 106-108 {M}⊙ , while all the galaxy properties that we examine (including total stellar mass, central mass density, and central velocity dispersion) lie within a narrower range. Thus, no galaxy property correlates tightly with {M}{BH} in ˜L* spiral galaxies as traced by megamaser disks. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed {σ }* the mean megamaser {M}{BH} are offset by -0.6 ± 0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not appear to show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to an inability to resolve their spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.

  8. Megamaser Disks Reveal a Broad Distribution of Black Hole Mass in Spiral Galaxies

    CERN Document Server

    Greene, Jenny E; Kim, Minjin; Laesker, Ronald; Goulding, Andy D; Gao, Feng; Braatz, James A; Henkel, Christian; Condon, James; Lo, Fred K Y; Zhao, Wei

    2016-01-01

    We use new precision measurements of black hole masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive black hole (BH) mass. The megamaser-derived BH masses span 10^6-10^8 M_sun, while all the galaxy properties that we examine (including stellar mass, central mass density, central velocity dispersion) lie within a narrow range. Thus, no galaxy property correlates tightly with M_BH in ~L* spiral galaxies. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed sigma* the mean megamaser M_BH are offset by -0.6+/-0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to inability to resolve the spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.

  9. A catalog of warps in spiral and lenticular galaxies in the Southern hemisphere

    CERN Document Server

    Sánchez-Saavedra, M L; Guijarro, A; López-Corredoira, M; Castro-Rodriguez, N

    2003-01-01

    A catalog of optical warps of galaxies is presented. This can be considered complementary to that reported by Sanchez-Saavedra et al., with 42 galaxies in the northern hemisphere, and to that by Reshetnikov & Combes, with 60 optical warps. The limits of the present catalog are: logr25 > 0.60, B_{t} < 14.5, delta(2000) < 0, -2.5 < t < 7. Therefore, lenticular galaxies have also been considered. This catalog lists 150 warped galaxies out of a sample of 276 edge-on galaxies and covers the whole southern hemisphere, except the Avoidance Zone. It is therefore very suitable for statistical studies of warps. It also provides a source guide for detailed particular observations. We confirm the large frequency of warped spirals: nearly all galaxies are warped. The frequency and warp angle do not present important differences for the different types of spirals. However, no lenticular warped galaxy has been found within the specified limits. This finding constitutes an important restriction for theoretica...

  10. The environmental dependence of the structure of outer galactic discs in STAGES spiral galaxies

    CERN Document Server

    Maltby, David T; Aragón-Salamanca, Alfonso; Wolf, Christian; Bell, Eric F; Jogee, Shardha; Haeussler, Boris; Barazza, Fabio D; Boehm, Asmus; Jahnke, Knud

    2011-01-01

    We present an analysis of V-band radial surface brightness profiles for spiral galaxies from the field and cluster environments using Hubble Space Telescope/Advanced Camera for Surveys imaging and data from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). We use a large sample of ~330 face-on to intermediately inclined spiral galaxies and assess the effect of the galaxy environment on the azimuthally averaged radial surface brightness mu profiles for each galaxy in the outer stellar disc (24 < mu < 26.5 mag per sq arcsec). For galaxies with a purely exponential outer disc (~50 per cent), we determine the significance of an environmental dependence on the outer disc scalelength h_out. For galaxies with a broken exponential in their outer disc, either down-bending (truncation, ~10 per cent) or up-bending (anti-truncation, ~40 per cent), we measure the strength T (outer-to-inner scalelength ratio, log_10(h_out/h_in) of the mu breaks and determine the significance of an environmental dependence ...

  11. Outer Spiral Disks as Clues to Galaxy Formation and Evolution

    CERN Document Server

    Vlajić, Marija

    2010-01-01

    Recent studies of outer spiral disks have given rise to an abundance of new results. We discuss the observational and theoretical advances that have spurred the interest in disk outskirts, as well as where we currently stand in terms of our understanding of outer disk structure, ages and metallicities.

  12. Departures From Axisymmetric Morphology and Dynamics in Spiral Galaxies

    CERN Document Server

    Kornreich, D A; Lovelace, R V E; Van Zee, L; Kornreich, David A.; Haynes, Martha P.; Zee, Liese van

    2000-01-01

    New HI synthesis data have been obtained for six face-on galaxies with the Very Large Array. These data and reanalyses of three additional data sets make up a sample of nine face-on galaxies analyzed for deviations from axisymmetry in morphology and dynamics. This sample represents a subsample of galaxies already analyzed for morphological symmetry properties in the R-band. Four quantitative measures of dynamical nonaxisymmetry are compared to one another and to the quantitative measures of morphological asymmetry in HI and R-band to investigate the relationships between nonaxisymmetric morphology and dynamics. We find no significant relationship between asymmetric morphology and most of the dynamical measures in our sample. A possible relationship is found, however, between morphology and dynamical position angle differences between approaching and receding sides of the galaxy.

  13. The Chemical Evolution Carousel of Spiral Galaxies: Azimuthal Variations of Oxygen Abundance in NGC1365

    Science.gov (United States)

    Ho, I.-Ting; Seibert, Mark; Meidt, Sharon E.; Kudritzki, Rolf-Peter; Kobayashi, Chiaki; Groves, Brent A.; Kewley, Lisa J.; Madore, Barry F.; Rich, Jeffrey A.; Schinnerer, Eva; D’Agostino, Joshua; Poetrodjojo, Henry

    2017-09-01

    The spatial distribution of oxygen in the interstellar medium of galaxies is the key to understanding how efficiently metals that are synthesized in massive stars can be redistributed across a galaxy. We present here a case study in the nearby spiral galaxy NGC 1365 using 3D optical data obtained in the TYPHOON Program. We find systematic azimuthal variations of the H ii region oxygen abundance imprinted on a negative radial gradient. The 0.2 dex azimuthal variations occur over a wide radial range of 0.3–0.7 R 25 and peak at the two spiral arms in NGC 1365. We show that the azimuthal variations can be explained by two physical processes: gas undergoes localized, sub-kiloparsec-scale self-enrichment when orbiting in the inter-arm region, and experiences efficient, kiloparsec-scale mixing-induced dilution when spiral density waves pass through. We construct a simple chemical evolution model to quantitatively test this picture and find that our toy model can reproduce the observations. This result suggests that the observed abundance variations in NGC 1365 are a snapshot of the dynamical local enrichment of oxygen modulated by spiral-driven, periodic mixing and dilution.

  14. Dependence of Spiral Galaxy Distribution on Viewing Angle in RC3

    Institute of Scientific and Technical Information of China (English)

    MA Jun; SONG Guo-Xuan; SHU Cheng-Gang

    2000-01-01

    The normalized inclination distributions are presented for the spiral galaxies in RC3. The results show that,except for the bin of 81°-90°, in which the apparent minor isophotal diameters that are used to obtain the inclinations are affected by the central bulges, the distributions for Sa, Sab, Scd and Sd are well consistent with the Monte-Carlo simulation of random inclinations within 3-σ, and Sb and Sbc almost, but Sc is different. One reason for the difference between the real distribution and the Monte-Carlo simulation of Sc may be that some quite inclined spirals, the arms of which are inherently loosely wound on the galactic plane and should be classified to Sc galaxies, have been incorrectly classified to the earlier ones, because the tightness of spiral arms which is one of the criteria of the Hubble classification in RC3 is different between on the galactic plane and on the tangent plane of the celestial sphere. Our result also implies that there might exist biases in the luminosity functions of individual Hubble types if spiral galaxies are only classified visually.

  15. Effect of dark matter halo on global spiral modes in galaxies

    CERN Document Server

    Ghosh, Soumavo; Jog, Chanda J

    2015-01-01

    Low surface brightness (LSB) galaxies form a major class of galaxies, and are characterized by low disc surface density and low star formation rate. These are known to be dominated by dark matter halo from the innermost regions. Here we study the role of dark matter halo on the grand-design, $m=2$, spiral modes in a galactic disc by carrying out a global mode analysis in the WKB approximation. The Bohr-Sommerfeld quantization rule is used to determine how many discrete global spiral modes are permitted. First a typical superthin LSB galaxy, UGC 7321 is studied by taking only the galactic disc, modelled as fluid; and then the disc embedded in a dark matter halo. We find that both cases permit the existence of global spiral modes. This is in contrast to earlier results where the inclusion of dark matter halo was shown to nearly fully suppress local, swing-amplified spiral features. Although technically global modes are permitted in the fluid model as shown here, we argue that due to lack of tidal interactions, ...

  16. PITCH ANGLE RESTRICTIONS IN LATE-TYPE SPIRAL GALAXIES BASED ON CHAOTIC AND ORDERED ORBITAL BEHAVIOR

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Villegas, A.; Pichardo, B.; Moreno, E.; Peimbert, A. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, A.P. 70-264, 04510 Mexico D.F. (Mexico); Velazquez, H. M., E-mail: barbara@astroscu.unam.mx [Observatorio Astronomico Nacional, Universidad Nacional Autonoma de Mexico, Apdo. Postal 877, 22800 Ensenada (Mexico)

    2012-01-20

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a three-dimensional self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, ranging from 10 Degree-Sign to 60 Degree-Sign . Indirectly testing orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately {approx}20 Degree-Sign , the response closely supports the potential readily permitting the presence of long-lasting spiral structures. The density response tends to 'avoid' larger pitch angles in the potential by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than {approx}20 Degree-Sign would not be long-lasting structures but would rather be transient. On the other hand, from an extensive orbital study in phase space, we also find that for late-type galaxies with pitch angles larger than {approx}50 Degree-Sign , chaos becomes pervasive, destroying the ordered phase space surrounding the main stable periodic orbits and even destroying them. This result is in good agreement with observations of late-type galaxies, where the maximum observed pitch angle is {approx}50 Degree-Sign .

  17. Gas Clouds in Whirlpool Galaxy Yield Important Clues Supporting Theory on Spiral Arms

    Science.gov (United States)

    2004-06-01

    Astronomers studying gas clouds in the famous Whirlpool Galaxy have found important clues supporting a theory that seeks to explain how the spectacular spiral arms of galaxies can persist for billions of years. The astronomers applied techniques used to study similar gas clouds in our own Milky Way to those in the spiral arms of a neighbor galaxy for the first time, and their results bolster a theory first proposed in 1964. M51 The spiral galaxy M51: Left, as seen with the Hubble Space Telescope; Right, radio image showing location of Carbon Monoxide gas. CREDIT: STScI, OVRO, IRAM (Click on image for larger version) Image Files Optical and Radio (CO) Views (above image) HST Optical Image with CO Contours Overlaid Radio/Optical Composite Image of M51 VLA/Effelsberg Radio Image of M51, With Panel Showing Magnetic Field Lines The Whirlpool Galaxy, about 31 million light-years distant, is a beautiful spiral in the constellation Canes Venatici. Also known as M51, it is seen nearly face-on from Earth and is familiar to amateur astronomers and has been featured in countless posters, books and magazine articles. "This galaxy made a great target for our study of spiral arms and how star formation works along them," said Eva Schinnerer, of the National Radio Astronomy Observatory in Socorro, NM. "It was ideal for us because it's one of the closest face-on spirals in the sky," she added. Schinnerer worked with Axel Weiss of the Institute for Millimeter Radio Astronomy (IRAM) in Spain, Susanne Aalto of the Onsala Space Observatory in Sweden, and Nick Scoville of Caltech. The astronomers presented their findings to the American Astronomical Society's meeting in Denver, Colorado. The scientists analyzed radio emission from Carbon Monoxide (CO) molecules in giant gas clouds along M51's spiral arms. Using telescopes at Caltech's Owens Valley Radio Observatory and the 30-meter radio telescope of IRAM, they were able to determine the temperatures and amounts of turbulence within the

  18. The flaring HI disk of the nearby spiral galaxy NGC 2683

    OpenAIRE

    Vollmer, B.; Nehlig, F.; Ibata, R.

    2015-01-01

    New deep VLA D array HI observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model HI data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80 degrees; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution ...

  19. Reviewing the observational evidence against long-lived spiral arms in galaxies

    CERN Document Server

    Martinez-Garcia, Eric E

    2013-01-01

    We review Foyle et al. (2011) previous results, by applying a Fourier intensity phases method to a nine object sample of galaxies. It was found that two of the objects (NGC 628 and NGC 5194), with strong two-arm patterns, present positive evidence for long-lived spirals. Only one of the objects (NGC 3627) shows the contrary evidence. As determined by an analysis of resolved mass maps, the rest of the objects can not be included in the analysis because they belong to flocculent and multi-arm type of spiral arms, which are not described by density wave theory.

  20. Supernovae and their host galaxies - II. The relative frequencies of supernovae types in spirals

    CERN Document Server

    Hakobyan, A A; Adibekyan, V Zh; Petrosian, A R; Aramyan, L S; Kunth, D; Mamon, G A; de Lapparent, V; Bertin, E; Gomes, J M; Turatto, M

    2014-01-01

    (Abridged) In this second paper of a series, we present an analysis of the relative frequencies of different supernova (SN) types in spirals with various morphologies and in barred or unbarred galaxies. We use a well-defined and homogeneous sample of host galaxies from the Sloan Digital Sky Survey (SDSS) in different stages of galaxy-galaxy interaction. We propose that the underlying mechanisms shaping the number ratios of SNe types can be interpreted within the framework of interaction-induced star formation, in addition to the known relations between morphologies and stellar populations. We find a strong trend in behaviour of the NIa/NCC ratio depending on host morphology, such that early spirals include more type Ia SNe, reflecting the change of the specific star formation rate (SFR). The NIbc/NII ratio is higher in a broad bin of early-type hosts. The NIa/NCC ratio is nearly constant when changing from normal, perturbed to interacting galaxies, then declines in merging galaxies, whereas it jumps to the hi...

  1. Detection of a Hot Gaseous Halo Around the Giant Spiral Galaxy NGC 1961

    CERN Document Server

    Anderson, Michael E

    2011-01-01

    Hot gaseous halos are predicted around all large galaxies and are critically important for our understanding of galaxy formation, but they have never been detected at distances beyond a few kpc around a spiral galaxy. We used the Chandra ACIS-I instrument to search for diffuse X-ray emission around an ideal candidate galaxy: the isolated giant spiral NGC 1961. We observed four quadrants around the galaxy for 30 ks each, carefully subtracting background and point source emission, and found diffuse emission that appears to extend to 40-50 kpc. We fit $\\beta$-models to the emission, and estimate a hot halo mass within 50 kpc of $5\\times10^9 M_{\\odot}$. When this profile is extrapolated to 500 kpc (the approximate virial radius), the implied hot halo mass is $1-3\\times10^{11} M_{\\odot}$. These mass estimates assume a gas metallicity of $Z = 0.5 Z_{\\odot}$. This galaxy's hot halo is a large reservoir of gas, but falls significantly below observational upper limits set by pervious searches, and suggests that NGC 19...

  2. 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.

  3. X-ray emission from spiral galaxies with normal and low-activity nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Giuricin, G. (Trieste Univ. (Italy). Dip. di Astronomia); Bertotti, G. (Centre for Advanced Research in Space Optics, Trieste (Italy)); Mardirossian, F.; Mezzetti, M. (Trieste Univ. (Italy). Dip. di Astronomia Centro Interuniversitario Regionale per l' Astrofisica e la Cosmologia (CIRAC), Trieste (Italy))

    1991-05-15

    A statistical analysis of the soft X-ray emission from spiral galaxies with normal and low-luminosity active nuclei (LINERs and Seyfert 2) - derived from published observations obtained with the Einstein Observatory - has revealed a number of previously unrecognised characteristics of the X-ray emission. Seyfert 2 galaxies (the least powerful X-ray sources of the Seyfert class) turn out to be, on average, stronger X-ray emitters (per unit light) than non-Seyfert galaxies, whereas galaxies with LINER nuclei and H II-region-like nuclei exhibit X-ray emissions of comparable strength. We have verified that the X-ray luminosity (per unit light) is linked to the total H {alpha} emission-line strength. Remarkably, more enhanced X-ray emission (per unit light) has been found in Arp atlas galaxies, in galaxies included in the Atlas and Catalogue of Interacting Galaxies of Vorontsov-Vel'yaminov, and in interacting galaxies compared to normal galaxies. (Author).

  4. Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disc morphology

    Science.gov (United States)

    Willett, Kyle W.; Schawinski, Kevin; Simmons, Brooke D.; Masters, Karen L.; Skibba, Ramin A.; Kaviraj, Sugata; Melvin, Thomas; Wong, O. Ivy; Nichol, Robert C.; Cheung, Edmond; Lintott, Chris J.; Fortson, Lucy

    2015-05-01

    We measure the stellar mass-star formation rate (SFR) relation in star-forming disc galaxies at z ≤ 0.085, using Galaxy Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral arms, their relative pitch angle, and the presence of a galactic bar in the disc, and show that both the slope and dispersion of the M⋆-SFR relation is constant when varying all the above parameters. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by ˜0.3 dex; this is significantly smaller than the increase seen in merging systems at z > 1. Of the galaxies lying significantly above the M⋆-SFR relation in the local Universe, more than 50 per cent are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.

  5. Mega parsec relativistic jets launched from an accreting supermassive blackhole in an extreme spiral galaxy

    CERN Document Server

    Bagchi, Joydeep; Vikram, Vinu; Hota, Ananda; G., Biju K; Sirothia, S K; Srianand, Raghunathan; Gopal-Krishna,; Jacob, Joe

    2014-01-01

    Radio galaxy phenomenon is directly connected to mass accreting, spinning supermassive black holes found in the active galactic nuclei (AGN). It is still unclear how the collimated jets of relativistic plasma on hundreds to thousands of kpc scale form, and why nearly always they are launched from the nuclei of bulge dominated elliptical galaxies and not flat spirals. Here we present the discovery of giant radio source J2345-0449 (z=0.0755), a clear and extremely rare counter example where relativistic jets are ejected from a luminous and massive spiral galaxy on scale of ~1.6 Mpc, the largest known so far. Extreme physical properties observed for this bulgeless spiral host, such as its high optical and infra-red luminosity, large dynamical mass, rapid disk rotation, and episodic jet activity are possibly the results of its unusual formation history, which has also assembled, via gas accretion from a disk, its central black hole of mass >2 x 10^8 M_sun. The very high mid-IR luminosity of the galaxy suggests th...

  6. The discovery of seven extremely low surface brightness galaxies in the field of the nearby spiral galaxy M101

    CERN Document Server

    Merritt, Allison; Abraham, Roberto

    2014-01-01

    Dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, which makes it difficult to identify and study them outside of the Local Group. We used a low surface brightness-optimized telescope, the Dragonfly Telephoto Array, to search for dwarf galaxies in the field of the massive spiral galaxy M101. We identify seven large, low surface brightness objects in this field, with effective radii of \\(10 - 30\\) arcseconds and central surface brightnesses of \\(\\mu_{g} \\sim 25.5 - 27.5\\) mag arcsec\\(^{-2}\\). Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Assuming the galaxies are dwarf satellites of M101, their absolute magnitudes are in the range \\(-11.6 \\lesssim M_{V} \\lesssim -9.3\\) and their effective radii are \\(350\\) pc \\(-\\) \\(1.3\\) kpc. Their radial surface brightness profiles ar...

  7. Model of Outgrowths in the Spiral Galaxies NGC 4921 and NGC 7049 and the Origin of Spiral Arms

    CERN Document Server

    Carlqvist, Per

    2012-01-01

    NGC 4921 and 7049 are two spiral galaxies presenting narrow, distinct dust features. A detailed study of the morphology of those features has been carried out using Hubble Space Telescope archival images. NGC 4921 shows a few but well-defined dust arms midway to its centre while NGC 7049 displays many more dusty features, mainly collected within a ring-shaped formation. Numerous dark and filamentary structures, called outgrowths, are found to protrude from the dusty arms in both galaxies. The outgrowths point both outwards and inwards in the galaxies. Mostly they are found to be V-shaped or Y-shaped with the branches connected to dark arm filaments. Often the stem of the Y appears to consist of intertwined filaments. Remarkably, the outgrowths show considerable similarities to elephant trunks in H II regions. A model of the outgrowths, based on magnetized filaments, is proposed. The model provides explanations of both the shapes and orientations of the outgrowths. Most important, it can also give an account f...

  8. Stellar Populations in the Barred Spiral Galaxy NGC 4900

    CERN Document Server

    Cantin, Simon; Mollá, Mercedes; Pellerin, Anne

    2010-01-01

    We present OASIS observations obtained at the Canada-France-Hawaii Telescope for the SB(rs)c galaxy NGC 4900. About 800 spectra in the wavelength range 4700-5500 AA and 6270- 7000 AA have been collected with a spatial resolution of ~50 pc. This galaxy is part of a sample to study the stellar populations and their history in the central region of galaxies. In this paper, we present our iterative technique developed to describe consistently the different stellar com- ponents seen through emission and absorption lines. In NGC 4900 we find many young bursts of star formation distributed along the galaxy large scale bar on each side of the nucleus. They represent nearly 40 per cent of the actual stellar mass in the field of view. The age for these bursts ranges from 5.5 to 8 Myr with a metallicity near and above 2 Zsun . The extinction map gives E(B-V) values from 0.19+/-0.01 near the youngest bursts to 0.62+/-0.06 in a dusty internal bar perpendicular to the large scale bar. The Mg 2 and Fe I absorption lines ind...

  9. A spectroscopic method for determining the luminosities of spiral galaxies and estimating their stellar population

    Science.gov (United States)

    Cowley, A. P.; Crampton, D.; McClure, R. D.

    1982-12-01

    Spectra of the nuclei of 44 normal spiral galaxies have been obtained using the McGraw-Hill Observatory intensified Reticon scanner. A composite spectral index, Σ, has been formed which measures the strengths of Ca II, Hδ , CH, and Mg, all of which correlate with absolute magnitude of the nuclear bulge. It is found that this index can predict the magnitudes of normal galaxies with a dispersion of 0.5 mag. This index is used to show that many galaxies within 6° of the Virgo cluster center, normally assumed to be members, may not be at the mean cluster distance. Using the same instrument, we also obtained fluxed spectra of halo globular clusters and solar neighborhood stars of both Population I and II. These data were used to construct simple population models for the nuclei of late-type spiral galaxies. It was found that, except in the case of the ˜2" semistellar nucleus in M33, the line strengths of Sc galaxy nuclei fit well models constructed from globular cluster observations but could not be reproduced using only a Population I stellar mix. The reverse was true, on the other hand, for the semistellar nucleus of M33, where a good fit is obtained by using young star light plus a smaller contribution from an old metalpoor population. We interpret this to indicate that the predominant light from the amorphous nuclear bulges of late-type spiral nuclei is old, but some of these galaxies may have had recent bursts of star formation that affect the spectral characteristics of a central component of the nucleus.

  10. Megaparsec relativistic jets launched from an accreting supermassive black hole in an extreme spiral galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Bagchi, Joydeep; Vivek, M.; Srianand, Raghunathan; Gopal-Krishna [The Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune University Campus, Post Bag 4, Pune 411007 (India); Vikram, Vinu [Department of Physics and Astronomy, University of Pennsylvania, PA 19104 (United States); Hota, Ananda [UM-DAE Centre for Excellence in Basic Sciences, Vidyanagari, Mumbai 400098 (India); Biju, K. G. [Department of Physics, W.M.O. Arts and Science College, Post Office Muttil, North Kalpetta, Wayanad (India); Sirothia, S. K. [National Centre for Radio Astrophysics (NCRA), TIFR, Pune University Campus, Post Bag 3, Ganeshkhind, Pune 411 007 (India); Jacob, Joe, E-mail: joydeep@iucaa.ernet.in [Department of Physics, Newman College, Thodupuzha 685 585 (India)

    2014-06-20

    The radio galaxy phenomenon is directly connected to mass-accreting, spinning supermassive black holes found in the active galactic nuclei. It is still unclear how the collimated jets of relativistic plasma on hundreds to thousands of kiloparsec scales form and why they are nearly always launched from the nuclei of bulge-dominated elliptical galaxies and not flat spirals. Here we present the discovery of the giant radio source J2345–0449 (z = 0.0755), a clear and extremely rare counterexample where relativistic jets are ejected from a luminous and massive spiral galaxy on a scale of ∼1.6 Mpc, the largest known so far. Extreme physical properties observed for this bulgeless spiral host, such as its high optical and infrared luminosity, large dynamical mass, rapid disk rotation, and episodic jet activity, are possibly the results of its unusual formation history, which has also assembled, via gas accretion from a disk, its central black hole of mass >2 × 10{sup 8} M {sub ☉}. The very high mid-IR luminosity of the galaxy suggests that it is actively forming stars and still building a massive disk. We argue that the launch of these powerful jets is facilitated by an advection-dominated, magnetized accretion flow at a low Eddington rate onto this unusually massive (for a bulgeless disk galaxy) and possibly fast spinning central black hole. Therefore, J2345–0449 is an extremely rare, unusual galactic system whose properties challenge the standard paradigms for black hole growth and the formation of relativistic jets in disk galaxies. Thus, it provides fundamental insight into accretion disk-relativistic jet coupling processes.

  11. Luminous X-ray sources in spiral and star-forming galaxies.

    Science.gov (United States)

    Ward, Martin

    2002-09-15

    For studies of discrete X-ray source populations in nearby galaxies, high spatial resolution is a key to making progress. Now, for the first time, using the Chandra X-ray observatory, we are able to study these source populations in detail for galaxies beyond M31 and our local group galaxies. Analysis of accretion-driven and supernova-related discrete sources provides a new perspective on the evolution of galactic stellar populations, as well as giving insights into the physical mechanisms operating in individual cases. A particularly intriguing area, which we are only just beginning to address, is the nature of the most X-ray-luminous sources that are being discovered in many spiral and star-forming galaxies.

  12. Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model

    CERN Document Server

    Michtchenko, Tatiana A; Barros, Douglas A; Lépine, Jacques R D

    2016-01-01

    Context: Resonances in the stellar orbital motion under perturbations from spiral arms structure play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (for nearly circular orbits), but is not suitable in general. Aims: To expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped profiles, without any restriction on the stellar orbital configurations, and expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions. Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes are constructed numerically, in order to characterize the phase-space structure and identify the precise location of the resonances. The study is complemented by the construction of dynamical power spectra, which provide the identif...

  13. MOND rotation curves for spiral galaxies with Cepheid-based distances

    CERN Document Server

    Bottema, R; Rothberg, B; Sanders, R H; Bottema, Roelof; Pestana, Jose L.G.; Rothberg, Barry; Sanders, Robert H.

    2002-01-01

    Rotation curves for four spiral galaxies with recently determined Cepheid-based distances are reconsidered in terms of modified Newtonian dynamics (MOND). For two of the objects, NGC 2403 and NGC 7331, the rotation curves predicted by MOND are compatible with the observed curves when these galaxies are taken to be at the Cepheid distance. For NGC 3198, the largest distance for which reasonable agreement is obtained is 10% smaller than the Cepheid-based distance; i.e., MOND clearly prefers a smaller distance. This conclusion is unaltered when new near-infrared photometry of NGC 3198 is taken as the tracer of the stellar mass distribution. For the large Sc spiral, NGC 2841, MOND requires a distance which is at least 20% larger than the Cepheid-based distance. However, the discrepancy of the Tully-Fisher and SNIa distances with the Cepheid determination casts some doubt upon the Cepheid method in this case.

  14. A Pilot Survey of Stellar Tidal Streams in Nearby Spiral Galaxies

    Science.gov (United States)

    Martínez-Delgado, David; Gabany, R. Jay; Peñarrubia, Jorge; Rix, Hans-Walter; Majewski, Steven R.; Trujillo, Ignacio; Pohlen, Michael

    Within the hierarchical framework for galaxy formation, merging and tidal interactions are expected to shape large galaxies to this day. While major mergers are quite rare at present, minor mergers and satellite disruptions-which result in stellar streams-should be common, and are indeed seen in both the Milky Way and the Andromeda Galaxy. As a pilot study, we have carried out ultra-deep, wide-field imaging of some spiral galaxies in the Local Volume, which has revealed external views of such stellar tidal streams at unprecedented detail, with data taken at small robotic telescopes (0.1-0.5m) that provide exquisite surface brightness sensitivity. The goal of this project is to undertake the first systematic and comprehensive imaging survey of stellar tidal streams, from a sample of˜50 nearby Milky Way-like spiral galaxies within 15Mpc, that features a surface brightness sensitivity of˜30mag/arcsec2. The survey will result in estimates of the incidence, size/geometry and stellar luminosity/mass distribution of such streams. This will not only put our Milky Way and M31 in context but, for the first time, also provide an extensive statistical basis for comparison with state-of-the-art, self-consistent cosmological simulations of this phenomenon.

  15. Radio spectral index images of the spiral galaxies NGC 0628, NGC 3627, and NGC 7331

    CERN Document Server

    Paladino, R; Orrù, E

    2009-01-01

    In order to understand the cosmic ray propagation mechanism in galaxies, and its correlation with the sites of star formation, we compare the spatially resolved radio spectral index of three spiral galaxies with their IR distribution. We present new low-frequency radio continuum observations of the galaxies NGC 0628, NGC 3627, and NGC 7331, taken at 327 MHz with the Very Large Array. We complemented our data set with sensitive archival observations at 1.4 GHz and we studied the variations of the radio spectral index within the disks of these spiral galaxies. We also compared the spectral index distribution and the IR distribution, using 70 $\\mu$m Spitzer observations. We found that in these galaxies the non-thermal spectral index is anticorrelated with the radio brightness. Bright regions, like the bar in NGC 3627 or the circumnuclear region in NGC 7331, are characterized by a flatter spectrum with respect to the underlying disk. Therefore, a systematic steepening of the spectral index with the increasing dis...

  16. The influence of the cluster environment on the star formation efficiency of 12 Virgo spiral galaxies

    CERN Document Server

    Vollmer, B; Braine, J; Chung, A; Kenney, J D P

    2012-01-01

    The influence of the environment on gas surface density and star formation efficiency of cluster spiral galaxies is investigated. We extend previous work on radial profiles by a pixel-to pixel analysis looking for asymmetries due to environmental interactions. The star formation rate is derived from GALEX UV and Spitzer total infrared data. As in field galaxies, the star formation rate for most Virgo galaxies is approximately proportional to the molecular gas mass. Except for NGC 4438, the cluster environment does not affect the star formation efficiency with respect to the molecular gas. Gas truncation is not associated with major changes in the total gas surface density distribution of the inner disk of Virgo spiral galaxies. In three galaxies, possible increases in the molecular fraction and the star formation efficiency with respect to the total gas, of factors of 1.5 to 2, are observed on the windward side of the galactic disk. A significant increase of the star formation efficiency with respect to the m...

  17. Large and small-scale structures and the dust energy balance problem in spiral galaxies

    CERN Document Server

    Saftly, W; De Geyter, G; Camps, P; Renaud, F; Guedes, J; De Looze, I

    2015-01-01

    The interstellar dust content in galaxies can be traced in extinction at optical wavelengths, or in emission in the far-infrared. Several studies have found that radiative transfer models that successfully explain the optical extinction in edge-on spiral galaxies generally underestimate the observed FIR/submm fluxes by a factor of about three. In order to investigate this so-called dust energy balance problem, we use two Milky Way-like galaxies produced by high-resolution hydrodynamical simulations. We create mock optical edge-on views of these simulated galaxies (using the radiative transfer code SKIRT), and we then fit the parameters of a basic spiral galaxy model to these images (using the fitting code FitSKIRT). The basic model includes smooth axisymmetric distributions along a S\\'ersic bulge and exponential disc for the stars, and a second exponential disc for the dust. We find that the dust mass recovered by the fitted models is about three times smaller than the known dust mass of the hydrodynamical in...

  18. Spiral-like Light Profiles but Elliptical-like Kinematics in Mergers of Galaxies

    CERN Document Server

    Jog, C J; Jog, Chanda J.; Chitre, Aparna

    2002-01-01

    It is commonly accepted that a merger of two spiral galaxies results in a remnant with an elliptical-like surface-brightness profile. Surprisingly, our recent study (Chitre & Jog 2002) of the 2MASS data for twenty-seven advanced mergers of galaxies has shown that half of these have a light distribution that decreases exponentially with radius. Such a distribution normally characterizes a rotationally supported disk in a spiral galaxy. Here we show from kinematic data for two of these mergers, Arp 224 and Arp 214, that the main support against gravitational collapse comes from pressure due to random motion of stars as seen in an elliptical galaxy rather than from rotation. The origin of the unusual combination of properties seen here is a puzzle. The standard theoretical N-body models in the literature cannot account for these systems. Further observational and dynamical studies of this new class of merger remnants are needed, and would be important for understanding merger dynamics and galaxy evolution.

  19. The central region of spiral galaxies as seen by Herschel. M81, M99 and M100

    CERN Document Server

    Sauvage, M; Bendo, G J; Boselli, A; Pohlen, M; Wilson, C D; Auld, R; Baes, M; Barlow, M J; Bock, J J; Bradford, M; Buat, V; Castro-Rodriguez, N; Chanial, P; Charlot, S; Ciesla, L; Clements, D L; Cooray, A; Cormier, D; Cortese, L; Davies, J I; Dwek, E; Eales, S A; Elbaz, D; Galametz, M; Galliano, F; Gear, W K; Glenn, J; Gomez, H L; Griffin, M; Hony, S; Isaak, K G; Levenson, L R; Lu, N; Madden, S C; O'Halloran, B; Okumura, K; Oliver, S; Page, M J; Panuzzo, P; Papageorgiou, A; Parkin, T J; Perez-Fournon, I; Rangwala, N; Rigby, E E; Roussel, H; Rykala, A; Schulz, B; Schirm, M R P; Smith, M W L; Spinoglio, L; Stevens, J A; Srinivasan, S; Symeonidis, M; Trichas, M; Vaccari, M; Vigroux, L; Wozniak, H; Wright, G S; Zeilinger, W W

    2010-01-01

    With appropriate spatial resolution, images of spiral galaxies in thermal infrared (~10 micron and beyond) often reveal a bright central component, distinct from the stellar bulge, superimposed on a disk with prominent spiral arms. ISO and Spitzer studies have shown that much of the scatter in the mid-infrared colors of spiral galaxies is related to changes in the relative importance of these two components, rather than to other modifications, such as the morphological type or star formation rate, that affect the properties of the galaxy as a whole. With the Herschel imaging capability from 70 to 500 micron, we revisit this two-component approach at longer wavelengths, to see if it still provides a working description of the brightness distribution of galaxies, and to determine its implications on the interpretation of global far-infrared properties of galaxies.

  20. The relation between magnetic and material arms in models for spiral galaxies

    CERN Document Server

    Moss, D; Sokoloff, D; Stepanov, R; Krause, M; Arshakian, T G

    2013-01-01

    Context. Observations of polarized radio emission show that large-scale (regular) magnetic fields in spiral galaxies are not axisymmetric, but generally stronger in interarm regions. In some nearby galaxies such as NGC 6946 they are organized in narrow magnetic arms situated between the material spiral arms. Aims. The phenomenon of magnetic arms and their relation to the optical spiral arms (the material arms) call for an explanation in the framework of galactic dynamo theory. Several possibilities have been suggested but are not completely satisfactory; here we attempt a consistent investigation. Methods. We use a 2D mean-field dynamo model in the no-z approximation and add injections of small-scale magnetic field, taken to result from supernova explosions, to represent the effects of dynamo action on smaller scales. This injection of small scale field is situated along the spiral arms, where star-formation mostly occurs. Results. A straightforward explanation of magnetic arms as a result of modulation of th...

  1. H{\\alpha} Kinematics of S4G spiral galaxies I. NGC 864

    CERN Document Server

    Erroz-Ferrer, Santiago; Font, Joan; Beckman, John E; Falcón-Barroso, Jesús; Sánchez-Gallego, José Ramón; Athanassoula, E; Bosma, Albert; Gadotti, Dimitri A; Muñoz-Mateos, Juan Carlos; Sheth, Kartik; Buta, Ronald J; Comerón, Sébastien; de Paz, Armando Gil; Hinz, Joannah L; Ho, Luis C; Kim, Taehyun; Laine, Jarkko; Laurikainen, Eija; Madore, Barry F; Menéndez-Delmestre, Karín; Mizusawa, Trisha; Regan, Michael W; Salo, Heikki; Seibert, Mark

    2012-01-01

    We present a study of the kinematics of the isolated spiral galaxy NGC 864, using H{\\alpha} Fabry-Perot data obtained with the GH{\\alpha}FaS instrument at the William Herschel Telescope in La Palma, complemented with images at 3.6 {\\mu}m, in the R band and in H{\\alpha} filter, and integral field spectroscopic data. The resulting data cubes and velocity maps allow the study of the kinematics of the galaxy, including in-depth investigations of the rotation curve, velocity moment maps, velocity residual maps, gradient maps and position-velocity diagrams. We find asymmetries in the velocity field in the bar zone, caused by non-circular motions, probably in response to the potential of the bar. We also find a flat-profile bar, in agreement with the strong bar, with the grand design spiral pattern, and with the gap between the ends of the bar and the start of the spiral arms. We quantify the rate of massive star formation, which is concentrated in the two spiral arms.

  2. Pitch Angle Restrictions in Late Type Spiral Galaxies Based on Chaotic and Ordered Orbital Behavior

    CERN Document Server

    Perez-Villegas, Angeles; Moreno, Edmundo; Peimbert, Antonio; Velazquez, Hector M

    2011-01-01

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a 3-D self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, going from 10$\\deg$ to 60$\\deg$. Testing undirectly orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately $\\sim 20\\deg$, the response supports closely the potential permitting readily the presence of long lasting spiral structures. The density response tends to "avoid" larger pitch angles in the potential, by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than $\\sim 20\\deg$, would not be long-lasting structures but rather transient. On the other hand, from an extensive orbital study in phase space, we also find that for late type galaxies with pitch angles larger than $\\sim 50\\deg$, chaos becomes pervasive destroying the ordered phase space surrounding the main sta...

  3. Structure and mass distribution of spiral galaxies at intermediate redshifts

    CERN Document Server

    Tamm, A; Tamm, Antti; Tenjes, Peeter

    2003-01-01

    Using the HST archive WFPC2 observations and rotation curves measeured by Vogt et al. (1996), we constructed self-consistent light and mass distribution models for three disk galaxies at redshifts z = 0.15, 0.90 and 0.99. The models consist of three components: the bulge, the disk and the dark matter. Spatial density distribution parameters for the components were calculated. After applying k-corrections, mass-to-light ratios for galactic disks within the maximum disk assumption are M/L_B = 4.4, 1.2 and 1.2, respectively. Corresponding central densities of dark matter halos within a truncated isothermal model are 0.0092, 0.028 and 0.015 in units M_sol/pc^3. The light distribution of galaxies in outer parts is steeper than a simple exponential disk.

  4. The JCMT Nearby Galaxies Legacy Survey X. Environmental Effects on the Molecular Gas and Star Formation Properties of Spiral Galaxies

    CERN Document Server

    Mok, Angus; Golding, J; Warren, B E; Israel, F P; Serjeant, S; Knapen, J H; Sanchez-Gallego, J R; Barmby, P; Bendo, G J; Rosolowsky, E; van der Werf, P

    2015-01-01

    We present a study of the molecular gas properties in a sample of 98 HI - flux selected spiral galaxies within $\\sim25$ Mpc, using the CO $J=3-2$ line observed with the James Clerk Maxwell Telescope. We use the technique of survival analysis to incorporate galaxies with CO upper limits into our results. Comparing the group and Virgo samples, we find a larger mean H$_{2}$ mass in the Virgo galaxies, despite their lower mean HI mass. This leads to a significantly higher H$_{2}$ to HI ratio for Virgo galaxies. Combining our data with complementary H$\\alpha$ star formation rate measurements, Virgo galaxies have longer molecular gas depletion times compared to group galaxies, due to their higher H$_{2}$ masses and lower star formation rates. We suggest that the longer depletion times may be a result of heating processes in the cluster environment or differences in the turbulent pressure. From the full sample, we find that the molecular gas depletion time has a positive correlation with the stellar mass, indicative...

  5. The flaring HI disk of the nearby spiral galaxy NGC 2683

    CERN Document Server

    Vollmer, B; Ibata, R

    2015-01-01

    New deep VLA D array HI observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model HI data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80 degrees; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution of the gas disk; (iii) a slight warp in inclination; (iv) an exponential flare; and (v) a low surface-density gas ring. The slope of NGC 2683's flare is comparable, but somewhat steeper than those of other spiral galaxies. NGC 2683's maximum height of the flare is also comparable to those of other galaxies. On the other hand, a saturation of the flare is only observed in NGC 2683. Based on the comparison between the high resolution model and observations, we exclude the existence of an extended atomic gas halo around the ...

  6. A Massive Spiral Galaxy in the Zone of Avoidance

    CERN Document Server

    Donley, J L; Koribalski, B S; Kraan-Korteweg, R C; Schröder, A; Staveley-Smith, L

    2006-01-01

    We report the discovery of a very HI-massive disk galaxy, HIZOA J0836-43, at a velocity of v_hel = 10689 km/s, corresponding to a distance of 148 Mpc (assuming H_0=75 km/s/Mpc). It was found during the course of a systematic HI survey of the southern Zone of Avoidance (|b| < 5 deg) with the multibeam system at the 64m Parkes radio telescope. Follow-up observations with the Australia Telescope Compact Array (ATCA) reveal an extended HI disk. We derive an HI mass of 7.5 x 10^10 Msun. Using the HI radius, we estimate a total dynamical mass of 1.4 x 10^12 Msun, similar to the most massive known disk galaxies such as Malin 1. HIZOA J0836-43 lies deep in the Zone of Avoidance (l, b = 262.48 deg, -1.64 deg) where the optical extinction is very high, A_B = 9.8. However, in the near-infrared wavebands, where the extinction is considerably lower, HIZOA J0836-43 is clearly detected by both DENIS and 2MASS. Deep AAT near-infrared (Ks and H-band) images show that HIZOA J0836-43 is an inclined disk galaxy with a promine...

  7. The effects of bar-spiral coupling on stellar kinematics in the Galaxy

    CERN Document Server

    Monari, Giacomo; Siebert, Arnaud; Grand, Robert J J; Kawata, Daisuke; Boily, Christian

    2016-01-01

    We investigate models of the Milky Way disc taking into account simultaneously the bar and a two-armed quasi-static spiral pattern. Away from major resonance overlaps, the mean stellar radial motions in the plane are essentially a linear superposition of the isolated effects of the bar and spirals. Thus, provided the bar is strong enough, even in the presence of spiral arms, these mean radial motions are predominantly affected by the Galactic bar for large scale velocity fluctuations. This is evident when comparing the peculiar line-of-sight velocity power spectrum of our coupled models with bar-only models. However, we show how forthcoming spectroscopic surveys could disentangle bar-only non-axisymmetric models of the Galaxy from models in which spiral arms have a significant amplitude. We also point out that overlaps of low-order resonances are sufficient to enhance stellar churning within the disc, even when the spirals amplitude is kept constant. Nevertheless, for churning to be truly non-local, stronger ...

  8. A Numerical Simulation of Star Formation in Nuclear Rings of Barred-Spiral Galaxies

    Science.gov (United States)

    Seo, Woo-Young; Kim, W.

    2014-01-01

    We use grid-based hydrodynamic simulations to study star formation history in nuclear rings of barred-spiral galaxies. We assume infinitesimally thin, isothermal, and unmagnetized gaseous disk. To investigate effects of spiral arm potential, we calculate both models with and without spiral. We find that star formation rate (SFR) in a nuclear ring is determined by the mass inflow rate to the ring rather than the total gas mass in the ring. In case of models without spiral arms, the SFR shows a strong primary burst at early time, and declines to small values after after that. The primary burst is caused by the rapid gas infall to the ring due to the bar growth. On the other hand, models with spiral arms show multiple star bursts at late time caused by additional gas inflow from outside bar region. When the SFR is low, ages of young star clusters exhibit a bipolar azimuthal gradient along the ring since star formation occurs near the contact points between dust lanes and the nuclear ring. When the SFR is large, there are no age gradient of star clusters since star formation sites are widely distributed throughout the whole ring region.

  9. A new model for the gravitational potential perturbations in disks of spiral galaxies. An application to our Galaxy

    CERN Document Server

    Junqueira, T C; Braga, C A S; Barros, D A

    2012-01-01

    We propose a new, more realistic, description of the perturbed gravitational potential of spiral galaxies, with spiral arms having Gaussian-shaped groove profiles. We investigate the stable stellar orbits in galactic disks, using the new perturbed potential. The influence of the bulge mass on the stellar orbits in the inner regions of a disk is also investigated. The new description offers the advantage of easy control of the parameters of the Gaussian profile of its potential. We find a range of values for the perturbation amplitude from 400 to 800 km^2 s^{-2} kpc^{-1} which implies a maximum ratio of the tangential force to the axisymmetric force between 3% and 6%, approximately. Good self-consistency of arm shapes is obtained between the Inner Lindblad resonance (ILR) and the 4:1 resonance. Near the 4:1 resonance the response density starts to deviate from the imposed logarithmic spiral form. This creates bifurcations that appear as short arms. Therefore the deviation from a perfect logarithmic spiral in g...

  10. GHASP : An Halpha kinematic survey of spiral and irregular galaxies - VI. New Halpha data cubes for 108 galaxies

    CERN Document Server

    Epinat, B; Marcelin, M; Balkowski, C; Daigle, O; Hernández, O; Chemin, L; Carignan, C; Gach, J L; Balard, P

    2008-01-01

    We present the Fabry-Perot observations obtained for a new set of 108 galaxies that completes the GHASP survey (Gassendi HAlpha survey of SPirals). The GHASP survey consists of 3D Ha data cubes for 203 spiral and irregular galaxies, covering a large range in morphological types and absolute magnitudes, for kinematics analysis. The GHASP sample is by now the largest sample of Fabry-Perot data ever published. We have derived Ha data cubes from which are computed Ha maps, radial velocity fields as well as residual velocity fields, position-velocity diagrams, rotation curves and the kinematical parameters for almost all galaxies. Original improvements in the determination of the kinematical parameters, rotation curves and their uncertainties have been implemented in the reduction procedure. This new method is based on the whole 2D velocity field and on the power spectrum of the residual velocity fieldrather than the classical method using successive crowns in the velocity field. Among the results, we point out th...

  11. An extended star cluster at the outer edge of the spiral galaxy M33

    CERN Document Server

    Stonkute, Rima; Arimoto, Nobuo; Hasegawa, Takashi; Narbutis, Donatas; Tamura, Naoyuki; Jablonka, Pascale; Ohta, Kouji; Yamada, Yoshihiko

    2008-01-01

    We report a discovery of an extended globular-like star cluster, M33-EC1, at the outer edge of the spiral galaxy M33. The distance to the cluster is 890 kpc, and it lies at a 12.5 kpc projected distance from the center of M33. Old age (>~7 Gyr) and low metallicity ([M/H] <~ -1.4) are estimated on the basis of isochrone fits. Color-magnitude diagrams of stars, located in the cluster's area, photometric and structural parameters of the cluster are presented. Cluster's luminosity (M_V = -6.6) and half-light radius (r_h = 20.3 pc) are comparable to those of the extended globular clusters, discovered in more luminous Local Group galaxies, the Milky Way and M31. Extended globular clusters are suspected to be remnants of accreted dwarf galaxies, and the finding of such a cluster in the late-type dwarf spiral galaxy M33 would imply a complex merging history in the past.

  12. Spin alignments of spiral galaxies within the large-scale structure from SDSS DR7

    CERN Document Server

    Zhang, Youcai; Wang, Huiyuan; Wang, Lei; Luo, Wentao; Mo, H J; Bosch, Frank C van den

    2014-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and Galaxy Zoo 2 (GZ2), we investigate the alignment of spin axes of spiral galaxies with their surrounding large scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes of only have weak tendency to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a \\cluster environment where all the three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  13. Bar Diagnostics in Edge-On Spiral Galaxies; 1, The Periodic Orbits Approach

    CERN Document Server

    Bureau, M

    1999-01-01

    We develop diagnostics to detect the presence and orientation of a bar in an edge-on disk, using its kinematical signature in the position-velocity diagram (PVD) of a spiral galaxy observed edge-on. Using a well-studied barred spiral galaxy mass model, we briefly review the orbital properties of two-dimensional non-axisymmetric disks and identify the main families of periodic orbits. We use those families as building blocks to model real galaxies and calculate the PVDs obtained for various realistic combinations of periodic orbit families and for a number of viewing angles with respect to the bar. We show that the global structure of the PVD is a reliable bar diagnostic in edge-on disks. Specifically, the presence of a gap between the signatures of the families of periodic orbits in the PVD follows directly from the non-homogeneous distribution of the orbits in a barred galaxy. Similarly, material in the two so-called forbidden quadrants of the PVD results from the elongated shape of the orbits. We show how t...

  14. Large-Scale Asymmetry of Rotation Curves in Lopsided Spiral Galaxies

    CERN Document Server

    Jog, C J

    2002-01-01

    Many spiral galaxies show a large-scale asymmetry with a cos\\phi dependence in their rotation curves as well as in their morphology, such as M101 and NGC 628. We show that both these features can be explained by the response of a galactic disk to an imposed lopsided halo potential. A perturbation potential of 5 % is deduced for the morphologically lopsided galaxies in the Rix & Zaritsky (1995) sample. This is shown to result in a difference of 10 % or about 20-30 kms^{-1} in the rotation velocity on the two sides of the major axis. Interestingly, the observed isophotal asymmetry in a typical spiral galaxy is not much smaller and it results in a velocity asymmetry of 7 % or about 14-21 kms^{-1} . Hence, we predict that most galaxies show a fairly significant rotational asymmetry. The rotation velocity is shown to be maximum along the elongated isophote - in agreement with the observations along the SW in M101, while it is minimum along the opposite direction. This result leads to the distinctive asymmetric...

  15. A Turbulent Origin for Flocculent Spiral Structure in Galaxies

    CERN Document Server

    Elmegreen, B G; Leitner, S N; Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Leitner, Samuel N.

    2003-01-01

    The flocculent structure of star formation in 7 galaxies has a Fourier transform power spectrum for azimuthal intensity scans with a power law slope that increases systematically from -1 at large scales to -1.7 at small scales. This is the same pattern as in the power spectra for azimuthal scans of HI emission in the Large Magellanic Clouds and for flocculent dust clouds in galactic nuclei. The steep part also corresponds to the slope of -3 for two-dimensional power spectra that have been observed in atomic and molecular gas surveys of the Milky Way and the Large and Small Magellanic Clouds. The same power law structure for star formation arises in both flocculent and grand design galaxies, which implies that the star formation process is the same in each. Fractal Brownian motion models that include discrete stars and an underlying continuum of starlight match the observations if all of the emission is organized into a global fractal pattern with an intrinsic 1D power spectrum having a slope between 1.3 and 1...

  16. A new method to estimate local pitch angles in spiral galaxies: Application to spiral arms and feathers in M81 and M51

    CERN Document Server

    Puerari, Ivânio; Block, David L

    2014-01-01

    We examine $8\\mu$m IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of $(\\ln R, \\theta)$ space and logarithmic spirals with various pitch angles. The diameter of the windows is varied to study different scales. The result is a best-fit pitch angle to the spiral structure as a function of position and scale, or a distribution function of pitch angles as a function of scale for a given galactic region or area. We apply the method to determine the distribution of pitch angles in the arm and interarm regions of these two galaxies. In the arms, the method reproduces the known pitch angles for the main spirals on a large scale, but also shows higher pitch angles on smaller scales resulting from ...

  17. Gas accretion on spiral galaxies bar formation and renewal

    CERN Document Server

    Bournaud, F

    2002-01-01

    The effects of gas accretion on spiral disk dynamics and stability are studied through N-body simulations, including star formation and gas/stars mass exchange. The detailed processes of bar formation, bar destruction and bar re-formation are followed, while in the same time the disk to bulge ratio is varying. The accreted gas might be first prevented to flow inwards to the center by the bar gravity torques, which maintains it to the outer Lindblad resonance. While the first bar is weakening, the accreted gas replenishes the disk, increasing the disk-to-bulge ratio, and the disk self-gravity. A second bar is then unstable, with a higher pattern speed, due both to the increased mass, and shorter bar length. Three or four bar episodes have been followed over a Hubble time. Their strength is decreasing with time, while their pattern speed is increasing. Detailed balance of the angular momentum transfer and evolution can account for these processes. The gas recycled through star formation, and rejected through st...

  18. On the origin of the luminosity-metalicity relation for late-type galaxies Spirals to irregulars transition

    CERN Document Server

    Pilyugin, L S

    2000-01-01

    We consider the roles of two widely invoked mechanisms for the metallicity-luminosity correlation among late-type galaxies: higher astration level and decreasing efficiency of heavy-element loss with increasing luminosity. We find that both mechanisms contribute about equally to the range in oxygen abundance between low (logL_B = 8) and high (logL_B = 10.5) luminosity galaxies. We also consider the transition from spirals to irregulars, finding that both the oxygen abundance deficiency (indicating the degree of mass exchange between a galaxy and its environment) and the gas fraction vary smoothly along the sequence. Thus we find no "irregular versus spiral dichotomy".

  19. The JCMT Nearby Galaxies Legacy Survey IV. Velocity Dispersions in the Molecular Interstellar Medium in Spiral Galaxies

    CERN Document Server

    Wilson, C D; Irwin, J; Knapen, J H; Israel, F P; Serjeant, S; Attewell, D; Bendo, G J; Brinks, E; Butner, H M; Clements, D L; Leech, J; Matthews, H E; Muehle, S; Mortier, A M J; Parkin, T J; Petitpas, G; Tan, B K; Tilanus, R P J; Usero, A; Vaccari, M; van der Werf, P; Wiegert, T; Zhu, M

    2010-01-01

    An analysis of large-area CO J=3-2 maps from the James Clerk Maxwell Telescope for 12 nearby spiral galaxies reveals low velocity dispersions in the molecular component of the interstellar medium. The three lowest luminosity galaxies show a relatively flat velocity dispersion as a function of radius while the remaining nine galaxies show a central peak with a radial fall-off within 0.2-0.4 r(25). Correcting for the average contribution due to the internal velocitydispersions of a population of giant molecular clouds, the average cloud-cloud velocity dispersion across the galactic disks is 6.1 +/- 1.0 km/s (standard deviation 2.9 km/s), in reasonable agreement with previous measurements for the Galaxy andM33. The cloud-cloud velocity dispersion derived from the CO data is on average two times smaller than the HI velocity dispersion measured in the same galaxies. The low cloud-cloudvelocity dispersion implies that the molecular gas is the critical component determining the stability of the galactic disk against...

  20. Untangling the magnetic fields in spiral galaxy NGC 6946 with wide-band polarimetry

    Science.gov (United States)

    Williams, Anna; Heald, George; Wilcots, Eric M.; Gould Zweibel, Ellen

    2017-01-01

    We present 13 cm polarization observations of nearby spiral galaxy NGC 6946. These data provide a new perspective into the magnetic field structure of this galaxy. Previous observations show strong depolarization between 6 cm and 22 cm, and we show that the morphology of the 13 cm polarization bridges this gap. We combine all available high resolution polarization observations to fit models of the line of sight magnetic field structure across the disk. We find simple screens of Faraday rotation, differential Faraday rotation, and internal Faraday dispersion are insufficient to explain the observed depolarization, and present the results of the best fit models. We discuss how future broadband observations and improved models will help reconstruct the full 3D model of the magnetic field structure in the disks and haloes of galaxies.

  1. A new method to estimate local pitch angles in spiral galaxies: Application to spiral arms and feathers in M81 and M51

    Energy Technology Data Exchange (ETDEWEB)

    Puerari, Ivânio [Instituto Nacional de Astrofísica, Optica y Electrónica, Calle Luis Enrique Erro 1, 72840 Santa María Tonantzintla, Puebla (Mexico); Elmegreen, Bruce G. [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States); Block, David L., E-mail: puerari@inaoep.mx [School of Computational and Applied Mathematics, University of Witwatersrand, Private Bag 3, WITS 2050 (South Africa)

    2014-12-01

    We examine 8 μm IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of (lnR,θ) space and logarithmic spirals with various pitch angles. The diameter of the windows is varied to study different scales. The result is a best-fit pitch angle to the spiral structure as a function of position and scale, or a distribution function of pitch angles as a function of scale for a given galactic region or area. We apply the method to determine the distribution of pitch angles in the arm and interarm regions of these two galaxies. In the arms, the method reproduces the known pitch angles for the main spirals on a large scale, but also shows higher pitch angles on smaller scales resulting from dust feathers. For the interarms, there is a broad distribution of pitch angles representing the continuation and evolution of the spiral arm feathers as the flow moves into the interarm regions. Our method shows a multiplicity of spiral structures on different scales, as expected from gas flow processes in a gravitating, turbulent and shearing interstellar medium. We also present results for M81 using classical 1D and 2D Fourier transforms, together with a new correlation method, which shows good agreement with conventional 2D Fourier transforms.

  2. Star Formation Histories Across the Interacting Galaxy NGC 6872, the Largest-Known Spiral

    CERN Document Server

    Eufrasio, Rafael T; Arendt, Richard G; de Mello, Duilia F; Gadotti, Dimitri; Urrutia-Viscarra, Fernanda; de Oliveira, Claudia Mendes; Benford, Dominic

    2014-01-01

    NGC 6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drive the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution (SED) of 17, 10 kpc diameter, regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, ...

  3. The Red Spiral Galaxy UGC11680: Clues for the Inside-Out Quenching.

    Science.gov (United States)

    Bárcenas, J.; Sanchez, S. F.

    2016-06-01

    Broadly, galaxies can be divided in two groups, thanks to the Color-Magnitude Diagram: the lively star formation ones, ``The blue Cloud'' and galaxies which halted their star formation, ``The Red Sequence''. It is a currently accepted that the galaxies start their lifespan as a blue objects, turning red when they stop to assembly more mass and thus more stars. Nevertheless, This change need to be quick (˜ 1 Gyr), due to the dearth of galaxies between this two populations (the so called ``green valley'').Previous works have found two distinct stellar mass assembly modes, they are termed as ``the inside-out'' and ``the outside-in'' growth scenarios in the literature. In the ``inside-out'' scenario, mass assembly is finished in the galactic central region. In some cases, the inflow gas can fuel the central SuperMassive BlackHole. The subsequent AGN feedback will then shut-off the central star formation. One possible case of this scenario is the galaxy UGC11680, an unusual face-on red spiral galaxy with an AGN type 2, at the red sequence belonging to the CALIFA survey. We used the so called fossil method to study its star formation history and try to understand what happened to its stellar populations.

  4. Globular Clusters and Spur Clusters in NGC 4921, the Brightest Spiral Galaxy in the Coma Cluster

    CERN Document Server

    Lee, Myung Gyoon

    2016-01-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in Coma. Also we find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3x10^5 M_odot. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions (LF) of the blue (metal-poor) GCs (0.70<(V-I)<1.05) in the halo are estimated to be V(max) =27.11+-0.09 mag and I(max)=26.21+-0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max)=26.25+-0.03 mag. Adopting M_I (max) = -8.56+-0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies, 91+-4 Mpc. Combining this and the Coma radial velocity, we derive a value of the Hubble constant, ...

  5. The angular momentum of cosmological coronae and the inside-out growth of spiral galaxies

    Science.gov (United States)

    Pezzulli, Gabriele; Fraternali, Filippo; Binney, James

    2017-01-01

    Massive and diffuse haloes of hot gas (coronae) are important intermediaries between cosmology and galaxy evolution, storing mass and angular momentum acquired from the cosmic web until eventual accretion onto star forming discs. We introduce a method to reconstruct the rotation of a galactic corona, based on its angular momentum distribution (AMD). This allows us to investigate in what conditions the angular momentum acquired from tidal torques can be transferred to star forming discs and explain observed galaxy-scale processes, such as inside-out growth and the build-up of abundance gradients. We find that a simple model of an isothermal corona with a temperature slightly smaller than virial and a cosmologically motivated AMD is in good agreement with galaxy evolution requirements, supporting hot-mode accretion as a viable driver for the evolution of spiral galaxies in a cosmological context. We predict moderately sub-centrifugal rotation close to the disc and slow rotation close to the virial radius. Motivated by the observation that the Milky Way has a relatively hot corona (T ≃ 2 × 106 K), we also explore models with a temperature larger than virial. To be able to drive inside-out growth, these models must be significantly affected by feedback, either mechanical (ejection of low angular momentum material) or thermal (heating of the central regions). However, the agreement with galaxy evolution constraints becomes, in these cases, only marginal, suggesting that our first and simpler model may apply to a larger fraction of galaxy evolution history.

  6. 13CO/C18O Gradients across the Disks of Nearby Spiral Galaxies

    Science.gov (United States)

    Jiménez-Donaire, María J.; Cormier, Diane; Bigiel, Frank; Leroy, Adam K.; Gallagher, Molly; Krumholz, Mark R.; Usero, Antonio; Hughes, Annie; Kramer, Carsten; Meier, David; Murphy, Eric; Pety, Jérôme; Schinnerer, Eva; Schruba, Andreas; Schuster, Karl; Sliwa, Kazimierz; Tomicic, Neven

    2017-02-01

    We use the IRAM Large Program EMPIRE and new high-resolution ALMA data to measure 13CO(1-0)/C18O(1-0) intensity ratios across nine nearby spiral galaxies. These isotopologues of 12CO are typically optically thin across most of the area in galaxy disks, and this ratio allows us to gauge their relative abundance due to chemistry or stellar nucleosynthesis effects. Resolved 13CO/C18O gradients across normal galaxies have been rare due to the faintness of these lines. We find a mean 13CO/C18O ratio of 6.0 ± 0.9 for the central regions of our galaxies. This agrees well with results in the Milky Way, but differs from results for starburst galaxies (3.4 ± 0.9) and ultraluminous infrared galaxies (1.1 ± 0.4). In our sample, the 13CO/C18O ratio consistently increases with increasing galactocentric radius and decreases with increasing star formation rate surface density. These trends could be explained if the isotopic abundances are altered by fractionation; the sense of the trends also agrees with those expected for carbon and oxygen isotopic abundance variations due to selective enrichment by massive stars.

  7. On the influence of ram-pressure stripping on the star formation of simulated spiral galaxies

    CERN Document Server

    Kronberger, T; Ferrari, C; Unterguggenberger, S; Schindler, S

    2008-01-01

    We investigate the influence of ram-pressure stripping on the star formation and the mass distribution in simulated spiral galaxies. Special emphasis is put on the question where the newly formed stars are located. The stripping radius from the simulation is compared to analytical estimates. Disc galaxies are modelled in combined N-body/hydrodynamic simulations (GADGET-2) with prescriptions for cooling, star formation, stellar feedback, and galactic winds. These model galaxies move through a constant density and temperature gas, which has parameters comparable to the intra-cluster medium (ICM) in the outskirts of a galaxy cluster (T=3 keV ~3.6x10^7 K and rho=10^-28 g/cm^3). With this numerical setup we analyse the influence of ram-pressure stripping on the star formation rate of the model galaxy. We find that the star formation rate is significantly enhanced by the ram-pressure effect (up to a factor of 3). Stars form in the compressed central region of the galaxy as well as in the stripped gas behind the gal...

  8. STAR Formation Histories Across the Interacting Galaxy NGC 6872, the Largest-Known Spiral

    Science.gov (United States)

    Eufrasio, Rafael T.; Dwek, E.; Arendt, RIchard G.; deMello, Duilia F.; Gadotti, DImitri A.; Urrutia-Viscarra, Fernanda; deOliveira, CLaudia Mendes; Benford, Dominic J.

    2014-01-01

    NGC6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drives the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution of seventeen 10 kpc diameter regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, and no evidence for a recent increase in the current star formation rate due to the interaction. The nucleus itself shows no significant current star formation activity. The extent of the Condor also provides an opportunity to test the applicability of a single standard prescription for conversion of the FUV + IR (22 micrometer) intensities to a star formation rate for all regions. We find that the conversion factor differs from region to region, arising from regional differences in the stellar populations.

  9. The effects of bar-spiral coupling on stellar kinematics in the Galaxy

    Science.gov (United States)

    Monari, Giacomo; Famaey, Benoit; Siebert, Arnaud; Grand, Robert J. J.; Kawata, Daisuke; Boily, Christian

    2016-10-01

    We investigate models of the Milky Way disc taking into account simultaneously the bar and a two-armed quasi-static spiral pattern. Away from major resonance overlaps, the mean stellar radial motions in the plane are essentially a linear superposition of the isolated effects of the bar and spirals. Thus, provided the bar is strong enough, even in the presence of spiral arms, these mean radial motions are predominantly affected by the Galactic bar for large-scale velocity fluctuations. This is evident when comparing the peculiar line-of-sight velocity power spectrum of our coupled models with bar-only models. However, we show how forthcoming spectroscopic surveys could disentangle bar-only non-axisymmetric models of the Galaxy from models in which spiral arms have a significant amplitude. We also point out that overlaps of low-order resonances are sufficient to enhance stellar churning within the disc, even when the spirals amplitude is kept constant. Nevertheless, for churning to be truly non-local, stronger or (more likely) transient amplitudes would be needed: otherwise the disc is actually mostly unaffected by churning in the present models. Finally, regarding vertical breathing modes, the combined effect of the bar and spirals on vertical motions is a clear non-linear superposition of the isolated effects of both components, significantly superseding the linear superposition of modes produced by each perturber separately, thereby providing an additional effect to consider when analysing the observed breathing mode of the Galactic disc in the extended solar neighbourhood.

  10. Star formation in grand-design, spiral galaxies. Young, massive clusters in the near-infrared

    Science.gov (United States)

    Grosbøl, P.; Dottori, H.

    2012-06-01

    Aims: Spiral structure is a prominent feature in many disk galaxies and is often outlined by bright, young objects. We study the distribution of young stellar clusters in grand-design spiral galaxies and thereby determine whether strong spiral perturbations can influence star formation. Methods: Deep, near-infrared JHK-maps were observed for ten nearby, grand-design, spiral galaxies using HAWK-I at the Very Large Telescope. Complete, magnitude-limited candidate lists of star-forming complexes were obtained by searching within the K-band maps. The properties of the complexes were derived from (H - K) - (J - H) diagrams including the identification of the youngest complexes (i.e. ≲7 Myr) and the estimation of their extinction. Results: Young stellar clusters with ages ≲7 Myr have significant internal extinction in the range of AV = 3-7m, while older ones typically have AV pattern, the star formation rate in the arms is higher by a factor of 2-5 than in the inter-arm regions. The CLF in the arms is also shifted towards brighter MK by at least 0.4m. We also detect clusters with colors compatible with Large Magellanic Cloud intermediate age clusters and Milky Way globular clusters. The (J - K) - MK diagram of several galaxies shows, for the brightest clusters, a clear separation between young clusters that are highly attenuated by dust and older ones with low extinction. Conclusions: The gap in the (J - K) - MK diagrams implies that there has been a rapid expulsion of dust at an age around 7 Myr, possibly triggered by supernovae. Strong spiral perturbations concentrate the formation of clusters in the arm regions and shifts their CLF towards brighter magnitudes. Based on observations collected at the European Southern Observatory, Chile; program: ESO 82.B-0331.Appendices A-C are available in electronic form at http://www.aanda.orgThe photometric data are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http

  11. Properties of the giant HII regions and bar in the nearby spiral galaxy NGC5430

    CERN Document Server

    Brière, É; Spekkens, K

    2012-01-01

    In order to better understand the impact of the bar on the evolution of spiral galaxies, we measure the properties of giant HII regions and the bar in the SB(s)b galaxy NGC5430. We use two complementary data sets, both obtained at the Observatoire du Mont-M\\'egantic: a hyperspectral data cube from the imaging Fourier transform spectrograph SpIOMM, and high-resolution spectra across the bar from a long-slit spectrograph. We flux-calibrate SpIOMM spectra for the first time, and produce H{\\alpha} and [NII]{\\lambda}6584\\r{A} intensity maps from which we identify 51 giant HII regions in the spiral arms and bar. We evaluate the type of activity, the oxygen abundance and the age of the young populations contained in these giant HII regions and in the bar. Thus, we confirm that NGC5430 does not harbour a strong AGN, and that its Wolf-Rayet knot shows a pure HII region nature. We find no variation in abundance or age between the bar and spiral arms, nor as a function of galactocentric radius. These results are consist...

  12. Destruction of star clusters due to the radial migration in spiral galaxies

    CERN Document Server

    Fujii, M S

    2012-01-01

    Most stars in galactic disks are believed to be born as a member of star clusters or associations. Star clusters formed in disks are disrupted due to the tidal stripping and the evolution of star clusters themselves, and as a results new stars are supplied to the galactic disks. We performed $N$-body simulations of star clusters in galactic disks, in which both star clusters and galactic disks are modeled as $N$-body ("live") systems, and as a consequence the disks form transient and recurrent spiral arms. In such non-steady spiral arms, star clusters migrate radially due to the interaction with spiral arms. We found that the migration timescale is a few hundreds Myr and that the angular momentum changes of star clusters are at most $\\sim 50$% in 1 Gyr. Radial migration of star clusters to the inner region of galaxies results in a fast disruption of the star clusters because of a stronger tidal field in the inner region of the galaxy. This effect is not negligible for the disruption timescale of star clusters...

  13. Strong Evidence for the Density-wave Theory of Spiral Structure in Disk Galaxies

    CERN Document Server

    Pour-Imani, Hamed; Kennefick, Julia; Davis, Benjamin L; Shields, Douglas W; Abdeen, Mohamed Shameer

    2016-01-01

    The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxy's image. The reason is that stars are born in the density wave but move out of it as they age. They move ahead of the density wave inside the co-rotation radius, and fall behind outside of it, resulting in a tighter pitch angle at wavelengths that image stars (optical and near-infrared) than those that are associated with star formation (far-infrared and ultraviolet). In this study we combined large sample size with wide range of wavelengths, from the ultraviolet to the infrared to investigate this issue. For each galaxy we used an optical wavelength image (B-band: 445 nm) and images from the Spitzer Space Telescope at two infrared wavelengths (infrared: 3.6 and 8.0 {\\mu}m) and we measured the pitch angle with the 2DFFT and Spirality codes. We find that the B-band and 3.6 {\\mu}m images have smaller pitch angles than the infrared 8.0 {\\mu}m image...

  14. Rings and spirals in barred galaxies. III. Further comparisons and links to observations

    CERN Document Server

    Athanassoula, E; Bosma, A; Masdemont, J J

    2010-01-01

    In a series of papers, we propose a theory to explain the formation and properties of rings and spirals in barred galaxies. The building blocks of these structures are orbits guided by the manifolds emanating from the unstable Lagrangian points located near the ends of the bar. In this paper, the last of the series, we present more comparisons of our theoretical results to observations and also give new predictions for further comparisons. Our theory provides the right building blocks for the rectangular-like bar outline and for ansae. We consider how our results can be used to give estimates for the pattern speed values, as well as their effect on abundance gradients in barred galaxies. We present the kinematics along the manifold loci, to allow comparisons with the observed kinematics along the ring and spiral loci. We consider gaseous arms and their relations to stellar ones. We discuss several theoretical aspects and stress that the orbits that constitute the building blocks of the spirals and rings are c...

  15. Catalog of observed tangents to the spiral arms in the Milky Way galaxy

    CERN Document Server

    Vallee, Jacques P

    2014-01-01

    From the sun's location in the Galactic disk, one can use different arm tracers (CO, HII, thermal or ionized or relativistic electrons, masers, cold or hot dust, etc) to locate a tangent to each spiral arm in the disk of the Milky Way galaxy. We present a Master catalog of the astronomically observed tangents to the Galaxy's spiral arms, using different arm tracers from the literature. Some arm tracers can have slightly divergent results from several papers, so a mean is taken - see Appendix for CO, HII, and masers. The Master catalog of means currently consists of 63 mean tracer entries, spread over many arms (Carina, Crux-Centaurus, Norma, Perseus origin, near 3-kpc, Scutum, Sagittarius), stemming from 107 original arm tracer entries. Additionally, we updated and revised a previous a previous statistical analysis of the angular offset and linear separation from the mid-arm, for each different mean arm tracer. Given enough arm tracers, and summing and averaging over all spiral arms, one could determine if ar...

  16. Simulations of the grand design galaxy M51: a case study for analysing tidally induced spiral structure

    Science.gov (United States)

    Dobbs, C. L.; Theis, C.; Pringle, J. E.; Bate, M. R.

    2010-04-01

    We present hydrodynamical models of the grand design spiral M51 (NGC 5194), and its interaction with its companion NGC 5195. Despite the simplicity of our models, our simulations capture the present-day spiral structure of M51 remarkably well, and even reproduce details such as a kink along one spiral arm, and spiral arm bifurcations. We investigate the offset between the stellar and gaseous spiral arms, and find at most times (including the present day) there is no offset between the stars and gas within our error bars. We also compare our simulations with recent observational analysis of M51. We compute the pattern speed versus radius, and similar to observations, find no single global pattern speed. We also show that the spiral arms cannot be fitted well by logarithmic spirals. We interpret these findings as evidence that M51 does not exhibit a quasi-steady density wave, as would be predicted by density wave theory. The internal structure of M51 derives from the complicated and dynamical interaction with its companion, resulting in spiral arms showing considerable structure in the form of short-lived kinks and bifurcations. Rather than trying to model such galaxies in terms of global spiral modes with fixed pattern speeds, it is more realistic to start from a picture in which the spiral arms, while not being simple material arms, are the result of tidally induced kinematic density `waves' or density patterns, which wind up slowly over time.

  17. The Spiral Host Galaxy of the Double Radio Source 0313-192

    CERN Document Server

    Keel, W C; Owen, F N; Ledlow, M J; Keel, William C.; III, Raymond E. White; Owen, Frazer N.; Ledlow, Michael J.

    2006-01-01

    We present new Hubble, Gemini-S, and Chandra observations of the radio galaxy 0313-192, which hosts a 350-kpc double source and jets, even though previous data have suggested that it is a spiral galaxy. We measure the bulge scale and luminosity, radial and vertical profiles of disk starlight, and consider the distributions of H II regions and absorbing dust. In each case, the HST data confirm its classification as an edge-on spiral galaxy, the only such system known to produce such an extended radio source of this kind. The Gemini near-IR images and Chandra spectral fit reveal a strongly obscured central AGN, seen through the entire ISM path length of the disk and showing X-ray evidence of additional absorption from warm or dense material close to the central object. We consider several possible mechanisms for producing such a rare combination of AGN and host properties, some combination of which may be at work. These include an unusually luminous bulge (suggesting a black hole of mass 0.5-0.9 billion solar m...

  18. Investigating the nuclear activity of barred spiral galaxies: the case of NGC 1672

    CERN Document Server

    Jenkins, L P; Colbert, E J M; Koribalski, B; Kuntz, K D; Levan, A J; Ojha, R; Roberts, T P; Ward, M J; Zezas, A

    2011-01-01

    We have performed an X-ray study of the nearby barred spiral galaxy NGC1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST), infrared imaging from the Spitzer Space Telescope, and ATCA ground-based radio data. We detect 28 X-ray sources within the D25 area of the galaxy, many of which correlate spatially with star-formation in the bar and spiral arms, while two are identified as background galaxies in the HST images. Nine of the X-ray sources are ULXs, with the three brightest (LX > 5E39 erg/s) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC1672 possesses a hard (Gamma~1.5) nuclear X-ray source with a 2-10 keV luminosity of 4E38 erg/s. This is surrounded by an X-ray bright circumnuclear star-forming ring, comprised of point sources an...

  19. H{\\alpha} to FUV ratios in resolved star forming region populations of nearby spiral galaxies

    CERN Document Server

    Hermanowicz, Maciej T; Eldridge, John J

    2013-01-01

    We present a new study of H{\\alpha}/FUV flux ratios of star forming regions within a sample of nearby spiral galaxies. We search for evidence of the existence of a cluster mass dependent truncation in the underlying stellar initial mass function (IMF). We use an automated approach to identification of extended objects based on the SExtractor algorithm to catalogue resolved Hii regions within a set of nearby spiral galaxies. Corrections due to dust attenuation effects are applied to avoid artificially boosted H{\\alpha}/FUV values. We use the BPASS stellar population synthesis code of Eldridge & Stanway (2009) to create a benchmark population of star forming regions to act as a reference for our observations. Based on those models, we identify a zone of parameter space populated by regions that cannot be obtained with a cluster mass dependent truncation in the stellar IMF imposed. We find that the investigated galaxies display small subpopulations of star forming regions falling within our zone of interest,...

  20. THE INFLUENCE OF RED SPIRAL GALAXIES ON THE SHAPE OF THE LOCAL K-BAND LUMINOSITY FUNCTION

    Energy Technology Data Exchange (ETDEWEB)

    Bonne, Nicolas J.; Brown, Michael J. I.; Jones, Heath; Pimbblet, Kevin A., E-mail: nicolas.bonne@monash.edu [School of Physics, Monash University, P.O. Box 27, Clayton, Victoria 3800 (Australia)

    2015-02-01

    We have determined K-band luminosity functions for 13,325 local universe galaxies as a function of morphology and color (for K {sub tot} ≤ 10.75). Our sample is drawn from the Two Micron All Sky Survey Extended Source Catalog, with all sample galaxies having measured morphologies and distances (including 4219 archival redshift-independent distances). The luminosity function for our total sample is in good agreement with previous works, but is relatively smooth at faint magnitudes (due to bulk flow distance corrections). We investigated the differences due to morphological and color selection using 5417 sample galaxies with NASA Sloan Atlas optical colors and find that red spirals comprise 20%-50% of all spirals with –25 ≤ M{sub K}  < –20. Fainter than M{sub K} = –24, red spirals are as common as early types, explaining the different faint end slopes (α = –0.87 and –1.00 for red and early-types, respectively). While we find red spirals comprise more than 50% of all M{sub K}  < –25 spiral galaxies, they do not dominate the bright end of the overall red galaxy luminosity function, which is dominated by early-type galaxies. The brightest red spirals have ongoing star formation and those without are frequently misclassified as early-types. The faintest ones have an appearance and Sérsic indices consistent with faded disks, rather than true bulge-dominated galaxies.

  1. Halpha Kinematics of S4G Spiral Galaxies - III. Inner rotation curves

    CERN Document Server

    Erroz-Ferrer, Santiago; Leaman, Ryan; Dıaz-Garcia, Simon; Salo, Heikki; Laurikainen, Eija; Querejeta, Miguel; Muñoz-Mateos, Juan Carlos; Athanassoula, E; Bosma, Albert; Comeron, Sebastien; Elmegreen, Bruce G; Martınez-Valpuesta, Inma

    2016-01-01

    We present a detailed study of the shape of the innermost part of the rotation curves of a sample of 29 nearby spiral galaxies, based on high angular and spectral resolution kinematic Halpha Fabry-Perot observations. In particular, we quantify the steepness of the rotation curve by measuring its slope dRvc(0). We explore the relationship between the inner slope and several galaxy parameters, such as stellar mass, maximum rotational velocity, central surface brightness ({\\mu}0), bar strength and bulge-to-total ratio. Even with our limited dynamical range, we find a trend for low-mass galaxies to exhibit shallower rotation curve inner slopes than high-mass galaxies, whereas steep inner slopes are found exclusively in high-mass galaxies. This trend may arise from the relationship between the total stellar mass and the mass of the bulge, which are correlated among them. We find a correlation between the inner slope of the rotation curve and the morphological T-type, complementary to the scaling relation between d...

  2. TWO-DIMENSIONAL KINEMATICS OF THE EDGE-ON SPIRAL GALAXY ESO 379-006

    Energy Technology Data Exchange (ETDEWEB)

    Rosado, M.; Gabbasov, R. F.; Repetto, P.; Martos, M. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-264, CP 04510 Mexico, D. F. (Mexico); Fuentes-Carrera, I. [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional, U. P. Adolfo Lopez Mateos, Zacatenco, 07730 Mexico, D. F. (Mexico); Amram, P.; Hernandez, O. [Laboratoire d' Astrophysique de Marseille, Aix-Marseille University (France); CNRS, 38 rue Frederic Joliot-Curie, 13338 Marseille Cedex 13 (France)

    2013-05-15

    We present a kinematical study of the nearly edge-on galaxy ESO 379-006 that shows the existence of extraplanar ionized gas. With Fabry-Perot spectroscopy at H{alpha}, we study the kinematics of ESO 379-006 using velocity maps and position-velocity diagrams parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the disk and discuss the role of projection effects due to the fact of viewing this galaxy nearly edge-on. The twisting of the isovelocities in the radial velocity field of the disk of ESO 379-006 as well as the kinematical asymmetries found in some position-velocity diagrams parallel to the minor axis of the galaxy suggest the existence of deviations to circular motions in the disk that can be modeled and explained with the inclusion of a radial inflow probably generated by a bar or by spiral arms. We succeeded in detecting extraplanar diffuse ionized gas in this galaxy. At the same time, from the analysis of position-velocity diagrams, we found some evidence that the extraplanar gas could lag in rotation velocity with respect to the midplane rotation.

  3. 2D kinematics of the edge-on spiral galaxy ESO 379-G006

    CERN Document Server

    Rosado, M; Repetto, P; Fuentes-Carrera, I; Amram, P; Martos, M; Hernandez, O

    2013-01-01

    We present a kinematical study of the nearly edge-on galaxy ESO 379-G006 that shows the existence of extraplanar ionized gas. With Fabry-Perot spectroscopy at H-alpha, we study the kinematics of ESO 379-G006 using velocity maps and position-velocity diagrams parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the disk and discuss the role of projection effects due to the fact of viewing this galaxy nearly edge-on. The twisting of the isovelocities in the radial velocity field of the disk of ESO 379-G006 as well as the kinematic asymmetries found in some position-velocity diagrams parallel to the minor axis of the galaxy suggest the existence of deviations to circular motions in the disk that can be modeled and explained with the inclusion of a radial inflow probably generated by a bar or by spiral arms. We succeeded in detecting extraplanar Diffuse Ionized Gas in this galaxy. At the same time, from the analysis of position-velocity diagrams, we found some evidence that th...

  4. The effects of ram-pressure stripping on the internal kinematics of simulated spiral galaxies

    CERN Document Server

    Kronberger, T; Unterguggenberger, S; Schindler, S; Ziegler, B L

    2008-01-01

    We investigate the influence of ram-pressure stripping on the internal gas kinematics of simulated spiral galaxies. Additional emphasis is put on the question of how the resulting distortions of the gaseous disc are visible in the rotation curve and/or the full 2D velocity field of galaxies at different redshifts. A Milky-Way type disc galaxy is modelled in combined N-body/hydrodynamic simulations with prescriptions for cooling, star formation, stellar feedback, and galactic winds. This model galaxy moves through a constant density and temperature gas, which has parameters similar to the intra-cluster medium (ICM). Rotation curves (RCs) and 2D velocity fields of the gas are extracted from these simulations in a way that follows the procedure applied to observations of distant, small, and faint galaxies as closely as possible. We find that the appearance of distortions of the gaseous disc due to ram-pressure stripping depends on the direction of the acting ram pressure. In the case of face-on ram pressure, the...

  5. SDSS-IV MaNGA: Variation of the Stellar Initial Mass Function in Spiral and Early-type Galaxies

    Science.gov (United States)

    Li, Hongyu; Ge, Junqiang; Mao, Shude; Cappellari, Michele; Long, R. J.; Li, Ran; Emsellem, Eric; Dutton, Aaron A.; Li, Cheng; Bundy, Kevin; Thomas, Daniel; Drory, Niv; Lopes, Alexandre Roman

    2017-04-01

    We perform Jeans anisotropic modeling (JAM) on elliptical and spiral galaxies from the MaNGA DR13 sample. By comparing the stellar mass-to-light ratios estimated from stellar population synthesis and from JAM, we find a systematic variation of the initial mass function (IMF) similar to that in the earlier {{ATLAS}}3{{D}} results. Early-type galaxies (elliptical and lenticular) with lower velocity dispersions within one effective radius are consistent with a Chabrier-like IMF, while galaxies with higher velocity dispersions are consistent with a more bottom-heavy IMF such as the Salpeter IMF. Spiral galaxies have similar systematic IMF variations, but with slightly different slopes and larger scatters, due to the uncertainties caused by the higher gas fractions and extinctions for these galaxies. Furthermore, we examine the effects of stellar mass-to-light ratio gradients on our JAM modeling, and we find that the trends become stronger after considering the gradients.

  6. Interplay of CR-driven galactic wind, magnetic field, and galactic dynamo in spiral galaxies

    CERN Document Server

    Krause, Marita

    2009-01-01

    From our radio observations of the magnetic field strength and large-scale pattern of spiral galaxies of different Hubble types and star formation rates (SFR) we conclude that - though a high SFR in the disk increases the total magnetic field strength in the disk and the halo - the SFR does not change the global field configuration nor influence the global scale heights of the radio emission. The similar scale heights indicate that the total magnetic field regulates the galactic wind velocities. The galactic wind itself may be essential for an effective dynamo action.

  7. UBVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group

    Institute of Scientific and Technical Information of China (English)

    Sang Chul Kim; Hwankyung Sung; Hong Soo Park; Eon-Chang Sung

    2004-01-01

    We present UB Visurface photometry over a 20.5'× 20.5' area of the latetype spiral galaxy NGC 300.We have derived isophotal maps,surface brightness profiles,ellipticity profiles,position angle profiles,and color profiles.By merging ourI-band measurements with those of Boker et al.Based on Hubble Space Telescope observations,we have obtained combinedI-band surface brightness profiles for the region 0.02″< r < 500″ and have decomposed the profiles into three components:a nucleus,a bulge,and an exponential disk.

  8. Spectroscopy of H II Regions in the Late-Type Spiral Galaxy NGC 6946

    CERN Document Server

    Gusev, Alexander S; Dodonov, Sergey N; 10.1134/S1990341313010045

    2013-01-01

    We present the results of spectroscopy of 39 H II regions in the spiral galaxy NGC 6946. The spectral observations were carried out at the 6-m BTA telescope of the SAO RAS with the SCORPIO focal reducer in the multi-slit mode with the dispersion of 2.1A/px and spectral resolution of 10A. The absorption estimates for 39 H II regions were obtained. Using the "strong line" method (NS-calibration) we determined the electron temperature, and the abundances of oxygen and nitrogen for 30 H II regions. The radial gradients of O/H and N/H were constructed.

  9. CATALOG OF OBSERVED TANGENTS TO THE SPIRAL ARMS IN THE MILKY WAY GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Vallée, Jacques P., E-mail: jacques.vallee@nrc-cnrc.gc.ca [Herzberg Astrophysics, National Research Council Canada, National Science Infrastructure portfolio, 5071 West Saanich Road, Victoria, BC, V9E 2E7 (Canada)

    2014-11-01

    From the Sun's location in the Galactic disk, one can use different arm tracers (CO, H I, thermal or ionized or relativistic electrons, masers, cold and hot dust, etc.) to locate a tangent to each spiral arm in the disk of the Milky Way. We present a master catalog of the astronomically observed tangents to the Galaxy's spiral arms, using different arm tracers from the literature. Some arm tracers can have slightly divergent results from several papers, so a mean value is taken—see the Appendix for CO, H II, and masers. The catalog of means currently consists of 63 mean tracer entries, spread over many arms (Carina, Crux-Centaurus, Norma, Perseus origin, near 3 kpc, Scutum, Sagittarius), stemming from 107 original arm tracer entries. Additionally, we updated and revised a previous statistical analysis of the angular offset and linear separation from the mid-arm for each different mean arm tracer. Given enough arm tracers, and summing and averaging over all four spiral arms, one could determine if arm tracers have separate and parallel lanes in the Milky Way. This statistical analysis allows a cross-cut of a Galactic spiral arm to be made, confirming a recent discovery of a linear separation between arm tracers. Here, from the mid-arm's CO to the inner edge's hot dust, the arm halfwidth is about 340 pc; doubling would yield a full arm width of 680 pc. We briefly compare these observations with the predictions of many spiral arm theories, notably the density wave theory.

  10. Hα kinematics of S4G spiral galaxies - III. Inner rotation curves

    Science.gov (United States)

    Erroz-Ferrer, Santiago; Knapen, Johan H.; Leaman, Ryan; Díaz-García, Simón; Salo, Heikki; Laurikainen, Eija; Querejeta, Miguel; Muñoz-Mateos, Juan Carlos; Athanassoula, E.; Bosma, Albert; Comerón, Sebastien; Elmegreen, Bruce G.; Martínez-Valpuesta, Inma

    2016-05-01

    We present a detailed study of the shape of the innermost part of the rotation curves of a sample of 29 nearby spiral galaxies, based on high angular and spectral resolution kinematic Hα Fabry-Perot observations. In particular, we quantify the steepness of the rotation curve by measuring its slope dRvc(0). We explore the relationship between the inner slope and several galaxy parameters, such as stellar mass, maximum rotational velocity, central surface brightness (μ0), bar strength and bulge-to-total ratio. Even with our limited dynamical range, we find a trend for low-mass galaxies to exhibit shallower rotation curve inner slopes than high-mass galaxies, whereas steep inner slopes are found exclusively in high-mass galaxies. This trend may arise from the relationship between the total stellar mass and the mass of the bulge, which are correlated among them. We find a correlation between the inner slope of the rotation curve and the morphological T-type, complementary to the scaling relation between dRvc(0) and μ0 previously reported in the literature. Although we find that the inner slope increases with the Fourier amplitude A2 and decreases with the bar torque Qb, this may arise from the presence of the bulge implicit in both A2 and Qb. As previously noted in the literature, the more compact the mass in the central parts of a galaxy (more concretely, the presence of a bulge), the steeper the inner slopes. We conclude that the baryonic matter dominates the dynamics in the central parts of our sample galaxies.

  11. Carbon abundances and radial gradients in NGC300 and other nearby spiral galaxies

    CERN Document Server

    Cipriano, L Toribio San; Esteban, C

    2014-01-01

    We present preliminary results of deep echelle spectrophotometry of a sample of HII regions along the disk of the Scd galaxy NGC300 obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT) with the aim of detect and measure very faint OII and CII permitted lines. We focus this study on the C and O abundances obtained from faint optical recombination lines (ORLs) instead of the most commonly used collisionally excited lines (CELs). We have derived the ionic abundances of C++ from the CII 4267 angstrom RL and O++ from the multiplet 1 of OII around 4649 angstrom in several objects. Finally, we have computed the radial gradients of C/H, O/H and C/O ratios in NGC300 from RLs, which has allowed the comparison with similar data obtained by our group in other nearby spiral galaxies.

  12. STAR FORMATION IN THE OUTER DISKS OF SPIRAL GALAXIES: ULTRAVIOLET AND H{alpha} PHOTOMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Kate L.; Van Zee, Liese [Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States); Skillman, Evan D., E-mail: barneskl@astro.indiana.edu, E-mail: vanzee@astro.indiana.edu, E-mail: skillman@astro.umn.edu [Department of Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)

    2011-12-20

    We present an analysis of ultradeep UV and H{alpha} imaging of five nearby spiral galaxies to study the recent star formation in the outer disk. Using azimuthally averaged ellipse photometry as well as aperture photometry of individual young stellar complexes, we measure how star formation rates (SFRs) and UV and H{alpha} colors vary with radius. We detect azimuthally averaged UV flux to {approx}1.2-1.4 R{sub 25} in most galaxies; at the edge of the detected UV disk, the surface brightnesses are 28-29 mag arcsec{sup -2}, corresponding to SFR surface densities of {approx}3 Multiplication-Sign 10{sup -4} M{sub Sun} yr{sup -1} kpc{sup -2}. Additionally, we detect between 120 and 410 young stellar complexes per galaxy, with a significant number of detections out to {approx}1.5 R{sub 25}. We measure radial FUV-NUV profiles, and find that the dispersion in the UV colors of individual young stellar complexes increases with radius. We investigate how radial variations in the frequency of star formation episodes can create color gradients and increasing dispersion in the UV colors of star-forming regions, like those observed in our study. Specifically, we use recently published, high spatial and temporal resolution measurements of {Sigma}{sub SFR} throughout the disk of M33 to estimate the frequency of star formation episodes throughout the disk of a typical spiral galaxy. We use stellar synthesis models of these star formation histories (SFHs) to measure the variations in UV colors and find that we can replicate large dispersions in UV colors based on episodic SFHs.

  13. Ram-Pressure Stripping of Gas from Companions and Accretion onto a Spiral Galaxy A Gaseous Merger

    CERN Document Server

    Sofue, Y

    1993-01-01

    We simulated the behavior of interstellar gas clouds in a companion galaxy during a gas-dynamical interaction with the halo and disk of a spiral galaxy. By ram pressure, the gas clouds are stripped from the companion, and accreted to ward the disk of the spiral galaxy. If the companion's orbit is retrograde with respect to the rotation of the spiral galaxy, infalling clouds hit the nuclear region. Angular momentum transfer causes disruption of the inner gaseous disk, and makes a void of interstellar gas in the bulge. If the companion's orbit is either prograde or polar, infalling clouds are accreted by the outer disk, and form a rotating gas ring. We show that the ram-pressure stripping-and-accretion is one way from the companion to a gas-rich larger galaxy, which causes disposal of interstellar gas from the companion and effectively changes its galaxy type into earlier (redder). The ram-pressure process is significant durig merger of galaxies, in which interstellar gas is stripped and accreted prior to the s...

  14. Massive Star Formation Rates and Radial Distributions from Halpha Imaging of 84 Virgo Cluster and Isolated Spiral Galaxies

    CERN Document Server

    Koopmann, R A; Koopmann, Rebecca A.; Kenney, Jeffrey D. P.

    2002-01-01

    The massive star formation properties of 55 Virgo Cluster and 29 isolated S0-Scd spiral galaxies are compared via analyses of R and Halpha surface photometry and integrated fluxes as functions of Hubble type and central R light concentration. The total massive star formation rates in Virgo Cluster spirals have been reduced by factors up to 2.5 in the median compared to isolated spirals. The inner disk star formation rates of most Virgo Cluster spirals are similar or enhanced by factors up to 2.5 in the median, while outer disk star formation rates are reduced by factors up to 7.1 in the median. Thus the reduction in total star formation of Virgo Cluster spirals is caused primarily by truncation of the star-forming disks. The star formation morphologies of Virgo Cluster spirals compared to isolated spirals can be divided into four categories: normal (27%), anemic (6%), enhanced (15%), and truncated (52%). Several galaxies with truncated star-forming disks have anemic inner disks, but the majority have normal-e...

  15. On the nature and correction of the spurious S-wise spiral galaxy winding bias in Galaxy Zoo 1

    CERN Document Server

    Hayes, Wayne; Silva, Pedro

    2016-01-01

    The Galaxy Zoo 1 catalog displays a bias towards the S-wise winding direction in spiral galaxies which has yet to be explained. The lack of an explanation confounds our attempts to verify the Cosmological Principle, and has spurred some debate as to whether a bias exists in the real universe. The bias manifests not only in the obvious case of trying to decide if the universe as a whole has a winding bias, but also in the more insidious case of selecting which galaxies to include in a winding direction survey. While the former bias has been accounted for in a previous image-mirroring study, the latter has not. Furthermore, the bias has never been {\\em corrected} in the GZ1 catalog, as only a small sample of the GZ1 catalog was re-examined during the mirror study. We show that the existing bias is a human {\\em selection} effect rather than a human chirality bias. In effect, the excess S-wise votes are spuriously "stolen" from the elliptical and edge-on-disk categories, not the Z-wise category. Thus, when select...

  16. Quantifying the Faint Structure of Galaxies: The Late-type Spiral NGC 2403

    CERN Document Server

    Barker, Mike K; Irwin, Mike J; Arimoto, Nobuo; Jablonka, Pascale

    2011-01-01

    Ground-based surveys have mapped the stellar outskirts of Local Group galaxies in unprecedented detail, but extending this work to other galaxies is necessary to overcome stochastic variations in evolutionary history and provide more stringent constraints on cosmological galaxy formation models. As part of our continuing program of ultra-deep imagery of galaxies beyond the Local Group, we present a wide-field analysis of the isolated late-type spiral NGC2403 using data obtained with Suprime-Cam on Subaru. The survey reaches a maximum projected radius of 30 kpc or deprojected radius of R_dp~60 kpc. The colour-magnitude diagram reaches 1.5 mag below the tip of the metal-poor red giant branch (RGB) at a completeness rate > 50% for R_dp >12 kpc. Using the combination of diffuse light photometry and resolved star counts, we are able to trace the radial surface brightness (SB) profile over a much larger range of radii and surface brightness than is possible with either technique alone. The exponential disc as trace...

  17. Multi-dimensional analysis of the chemical and physical properties of spiral galaxies

    CERN Document Server

    Rosales-Ortega, F F

    2010-01-01

    In this thesis, wide-field 2D spectroscopy is employed in order to characterise the nebular properties of late-type field galaxies. The observations performed for this dissertation represent the first endeavour to obtain full 2D coverage of the disks of a sample of nearby spiral galaxies, by the application of the Integral Field Spectroscopy (IFS) technique, under the PPAK IFS Nearby Galaxies Survey: PINGS. A self-consistent methodology is defined in terms of observation, data reduction and analysis techniques for this and upcoming IFS surveys, as well as providing a whole new set of IFS visualization and analysis software made available for the public domain (PINGSoft). The scientific analysis comprises the study of the integrated properties of the ionized gas and a detailed 2D study from the emission line spectra of four selected galaxies. Evidence is found suggesting that measurements of emission lines of classical HII regions are not only aperture, but spatial dependent, and therefore, the derived physica...

  18. The nature of the UV halo around the spiral galaxy NGC 3628

    CERN Document Server

    Baes, Maarten

    2016-01-01

    Thanks to deep UV observations with GALEX and Swift, diffuse UV haloes have recently been discovered around galaxies. Based on UV-optical colours, it has been advocated that the UV haloes around spiral galaxies are due to UV radiation emitted from the disc and scattered off dust grains at high latitudes. Detailed UV radiative transfer models that take into account scattering and absorption can explain the morphology of the UV haloes, and they require the presence of an additional thick dust disc next the to traditional thin disc for half of the galaxies in their sample. We test whether such an additional thick dust disc agrees with the observed infrared emission in NGC 3628, an edge-on galaxy with a clear signature of a thick dust disc. We extend the far-ultraviolet radiative transfer models to full-scale panchromatic models. Our model, which contains no fine-tuning, can almost perfectly reproduce the observed spectral energy distribution from UV to mm wavelengths. These results corroborate the interpretation...

  19. Composite Bulges: The Coexistence of Classical Bulges and Disky Pseudobulges in S0 and Spiral Galaxies

    CERN Document Server

    Erwin, Peter; Fabricius, Maximilian; Thomas, Jens; Nowak, Nina; Rusli, Stephanie; Bender, Ralf; Beltran, Juan Carlos Vega; Beckman, John E

    2014-01-01

    We study nine S0-Sb galaxies with (photometric) bulges consisting of two distinct components. The outer component is a flattened, kinematically cool, disklike structure: a "disky pseudobulge". Embedded inside is a rounder, kinematically hot spheroid: a "classical bulge". This indicates that pseudobulges and classical bulges are not mutually exclusive: some galaxies have both. The disky pseudobulges almost always have an exponential disk (scale lengths = 125-870 pc, mean $\\sim 440$ pc) with disk-related subcomponents: nuclear rings, bars, and/or spiral arms. They constitute 11-59% of the galaxy stellar mass (mean PB/T = 0.33), with stellar masses $\\sim 7 \\times 10^{9}$-$9 \\times 10^{10} M_{\\odot}$. Classical-bulge components have Sersic indices of 0.9-2.2, effective radii of 25-430 pc and stellar masses of $5 \\times 10^{8}$-$3 \\times 10^{10} M_{\\odot}$ (usually < 10% of the galaxy's stellar mass; mean B/T = 0.06). The classical bulges show rotation, but are kinematically hotter than the disky pseudobulges. ...

  20. The DiskMass Survey. X. Radio synthesis imaging of spiral galaxies

    CERN Document Server

    Martinsson, Thomas P K; Bershady, Matthew A; Westfall, Kyle B; Andersen, David R; Swaters, Rob A

    2016-01-01

    We present results from 21 cm radio synthesis imaging of 28 spiral galaxies from the DiskMass Survey obtained with the VLA, WSRT, and GMRT facilities. We detail the observations and data reduction procedures and present a brief analysis of the radio data. We construct 21 cm continuum images, global HI emission-line profiles, column-density maps, velocity fields, and position-velocity diagrams. From these we determine star formation rates (SFRs), HI line widths, total HI masses, rotation curves, and azimuthally-averaged radial HI column-density profiles. All galaxies have an HI disk that extends beyond the readily observable stellar disk, with an average ratio and scatter of R_{HI}/R_{25}=1.35+/-0.22, and a majority of the galaxies appear to have a warped HI disk. A tight correlation exists between total HI mass and HI diameter, with the largest disks having a slightly lower average column density. Galaxies with relatively large HI disks tend to exhibit an enhanced stellar velocity dispersion at larger radii, ...

  1. Effect of the disc on the rotation curves of spiral galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Salucci, Paolo; Frenk, C.S.

    1989-03-01

    We discuss the role of the galactic disc in the interpretation of the circular velocities of spiral galaxies at large galactocentric radii. The fractional amount of mass in the disc can be shown to be an increasing function of the luminosity. As a result, the shape of the rotation curve near the edge of the optical disc is expected to vary systematically with luminosity. Using a simple disc/halo model we find that in bright, disc-dominated galaxies the rotation curve should drop by a few tens of km s/sup -1/ immediately outside the disc, even in the presence of an extended dark halo. Only in faint, halo-dominated galaxies, do we expect the rotation curve to remain flat or even to rise beyond the optical radius. We find evidence for this behaviour in several published rotation curves. In the case of the Milky Way we show that if the disc dominates the gravitational potential in the inner regions, then the low mass estimated from the dynamics of the outer satellites is consistent with a dark halo that extends beyond the region sampled. This and other available data are well fit by a model in which the luminous component of the Galaxy contributes /similar to/ 70 per cent of the mass at 12 kpc from the centre and the mass at large radii increases in proportion to the radius.

  2. An Atlas of Hubble Space Telescope Spectra and Images of Nearby Spiral Galaxies

    Science.gov (United States)

    Hughes, M. A.; Alonso-Herrero, A.; Axon, D.; Scarlata, C.; Atkinson, J.; Batcheldor, D.; Binney, J.; Capetti, A.; Carollo, C. M.; Dressel, L.; Gerssen, J.; Macchetto, D.; Maciejewski, W.; Marconi, A.; Merrifield, M.; Ruiz, M.; Sparks, W.; Stiavelli, M.; Tsvetanov, Z.; van der Marel, R.

    2003-08-01

    We have observed 54 nearby spiral galaxies with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope to obtain optical long-slit spectra of nuclear gas disks and STIS optical (~R band) images of the central 5''×5'' of the galaxies. These spectra are being used to determine the velocity field of nuclear disks and hence to detect the presence of central massive black holes. Here we present the spectra for the successful observations. Dust obscuration can be significant at optical wavelengths, and so we also combine the STIS images with archival Near-Infrared Camera and Multi-Object Spectrometer H-band images to produce color maps to investigate the morphology of gas and dust in the central regions. We find a great variety in the different morphologies, from smooth distributions to well-defined nuclear spirals and dust lanes. Based on observations 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 NAS5-26555.

  3. 2MTF III. HI 21cm observations of 1194 spiral galaxies with the Green Bank Telescope

    CERN Document Server

    Masters, Karen L; Hong, Tao; Jarrett, T H; Koribalski, Baerbel S; Macri, Lucas; Springob, Christopher M; Staveley-Smith, Lister

    2014-01-01

    We present HI 21cm observations of 1194 galaxies out to a redshift of 10,000 km/s selected as inclined spirals (i>60deg) from the 2MASS Redshift Survey. These observations were carried out at the National Radio Astronomy Observatory Robert C. Byrd Green Bank Telescope (GBT). This observing program is part of the 2MASS Tully-Fisher (2MTF) survey. This project will combine HI widths from these GBT observations with those from further dedicated observing at the Parkes Telescope, from the ALFALFA survey at Arecibo, and S/N>10 and spectral resolution, v_res < 10km/s published widths from a variety of telescopes. We will use these HI widths along with 2MASS photometry to estimate Tully-Fisher distances to nearby spirals and investigate the peculiar velocity field of the local Universe. In this paper we report on detections of neutral hydrogen in emission in 727 galaxies, and measure good signal-to-noise and symmetric HI global profiles suitable for use in the Tully-Fisher relation in 484.

  4. Modelling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies

    CERN Document Server

    Bournaud, F; Weiss, A; Renaud, F; Mastropietro, C; Teyssier, R

    2014-01-01

    We model the intensity of emission lines from the CO molecule, based on hydrodynamic simulations of spirals, mergers, and high-redshift galaxies with very high resolutions (3pc and 10^3 Msun) and detailed models for the phase-space structure of the interstellar gas including shock heating, stellar feedback processes and galactic winds. The simulations are analyzed with a Large Velocity Gradient (LVG) model to compute the local emission in various molecular lines in each resolution element, radiation transfer and opacity effects, and the intensity emerging from galaxies, to generate synthetic spectra for various transitions of the CO molecule. This model reproduces the known properties of CO spectra and CO-to-H2 conversion factors in nearby spirals and starbursting major mergers. The high excitation of CO lines in mergers is dominated by an excess of high-density gas, and the high turbulent velocities and compression that create this dense gas excess result in broad linewidths and low CO intensity-to-H2 mass r...

  5. Radial metallicity gradients in spiral galaxies from H II regions and planetary nebulae: probing galactic chemical evolution

    Science.gov (United States)

    Stanghellini, Letizia

    2015-08-01

    Radial metallicity gradients, typically observed in spiral galaxies, are excellent constraints for chemical evolution models. The contemporary studies of the two stellar populations, whose progenitors have formed at different times, yield to the chemical and time constraining of the models. In this context, planetary nebula and HII region analysis proved to be ideal two-epochs test populations. We present an assortment of galaxies whose oxygen abundances have been determined both with weak- and strong-line methods, and whose radial metallicity gradients and their evolution in time have disclosed very interesting correlations with the galaxy characteristics. New results from our Gemini/GMOS observations, and a review of the best literature data, set the stage for a better understanding of spiral galaxy evolution.

  6. The Spiral Arm Segments of the Galaxy within 3 kpc from the Sun: A Statistical Approach

    Science.gov (United States)

    Griv, Evgeny; Jiang, Ing-Guey; Hou, Li-Gang

    2017-08-01

    As can be reasonably expected, upcoming large-scale APOGEE, GAIA, GALAH, LAMOST, and WEAVE stellar spectroscopic surveys will yield rather noisy Galactic distributions of stars. In view of the possibility of employing these surveys, our aim is to present a statistical method to extract information about the spiral structure of the Galaxy from currently available data, and to demonstrate the effectiveness of this method. The model differs from previous works studying how objects are distributed in space in its calculation of the statistical significance of the hypothesis that some of the objects are actually concentrated in a spiral. A statistical analysis of the distribution of cold dust clumps within molecular clouds, H ii regions, Cepheid stars, and open clusters in the nearby Galactic disk within 3 kpc from the Sun is carried out. As an application of the method, we obtain distances between the Sun and the centers of the neighboring Sagittarius arm segment, the Orion arm segment in which the Sun is located, and the Perseus arm segment. Pitch angles of the logarithmic spiral segments and their widths are also estimated. The hypothesis that the collected objects accidentally form spirals is refuted with almost 100% statistical confidence. We show that these four independent distributions of young objects lead to essentially the same results. We also demonstrate that our newly deduced values of the mean distances and pitch angles for the segments are not too far from those found recently by Reid et al. using VLBI-based trigonometric parallaxes of massive star-forming regions.

  7. Differences between CO- and calcium triplet-derived velocity dispersions in spiral galaxies: evidence for central star formation?

    CERN Document Server

    Riffel, Rogemar A; Mason, Rachel; Rodriguez-Ardila, Alberto; Martins, Lucimara; Riffel, Rogerio; Diaz, Ruben; Colina, Luis; Alonso-Herrero, Almudena; Flohic, Helene; Martin, Omaira Gonzalez; Lira, Paulina; McDermid, Richard; Almeida, Cristina Ramos; Schiavon, Ricardo; Thanjavur, Karun; Dutra, Daniel Ruschel; Winge, Claudia; Perlman, Eric

    2014-01-01

    We examine the stellar velocity dispersions (sigma) of a sample of 48 galaxies, 35 of which are spirals, from the Palomar nearby galaxy survey. It is known that for ultra-luminous infrared galaxies (ULIRGs) and merger remnants thesigma derived from the near-infrared CO band-heads is smaller than that measured from optical lines, while no discrepancy between these measurements is found for early-type galaxies. No such studies are available for spiral galaxies - the subject of this paper. We used cross-dispersed spectroscopic data obtained with the Gemini Near-Infrared Spectrograph (GNIRS), with spectral coverage from 0.85 to 2.5um, to obtain sigma measurements from the 2.29 $\\mu$m CO band-heads (sigma_{CO}), and the 0.85 um calcium triplet (sigma_{CaT}). For the spiral galaxies in the sample, we found that sigma_{CO} is smaller than sigma_{CaT}, with a mean fractional difference of 14.3%. The best fit to the data is given by sigma_{opt} = (46.0+/-18.1) + (0.85+/-0.12)sigma_{CO}. This "sigma discrepancy" may be...

  8. GALEX Observations of "Passive Spirals" in the Cluster Cl 0024+17: Clues to the Formation of S0 Galaxies

    CERN Document Server

    Moran, S M; Treu, T; Salim, S; Rich, R M; Smith, G P; Kneib, J P; Moran, Sean M.; Ellis, Richard S.; Treu, Tommaso; Salim, Samir; Smith, Graham P.; Kneib, Jean-Paul

    2006-01-01

    We present new results from deep GALEX UV imaging of the cluster Cl 0024+17 at z~0.4. Rest-frame far UV emission is detected from a large fraction of so-called ``passive spiral galaxies'' -a significant population which exhibits spiral morphology with little or no spectroscopic evidence for ongoing star formation. This population is thought to represent infalling galaxies whose star formation has been somehow truncated by environmental processes, possibly in morphological transition to S0 galaxies. Compared to normal cluster spirals, we find that passive spirals are redder in FUV-optical color, while exhibiting much stronger UV emission than cluster E/S0s - as expected for recently-truncated star formation. By modeling the different temporal sensitivities of UV and spectroscopic data to recent activity, we show that star formation in passive spirals decayed on timescales of less than 1 Gyr, consistent with `gas starvation' - a process where the cluster environment prevents cold gas from accreting onto the spi...

  9. The detection of spiral arm modulation in the stellar disk of an optically flocculent and an optically grand design galaxy

    CERN Document Server

    Puerari, I; Elmegreen, B G; Frogel, J A; Eskridge, P B; Puerari, Ivanio; Block, David L.; Elmegreen, Bruce G.; Frogel, Jay A.; Eskridge, Paul B.

    2000-01-01

    Two dimensional Fourier spectra of near-infrared images of galaxies provide a powerful diagnostic tool for the detection of spiral arm modulation in stellar disks. Spiral arm modulation may be understood in terms of interference patterns of outgoing and incoming density wave packets or modes. The brightness along a spiral arm will be increased where two wave crests meet and constructively interfere, but will be decreased where a wave crest and a wave trough destructively interfere. Spiral arm modulation has hitherto only been detected in grand design spirals (such as Messier 81). Spiral arm amplitude variations have the potential to become a powerful constraint for the study of galactic dynamics. We illustrate our method in two galaxies: NGC 4062 and NGC 5248. In both cases, we have detected trailing and leading m=2 waves with similar pitch angles. This suggests that the amplification mechanism is the WASER type II. In this mechanism, the bulge region reflects (rather than refracts) incoming waves with no cha...

  10. Late-type galaxies observed with SAURON : two-dimensional stellar and emission-line kinematics of 18 spirals

    NARCIS (Netherlands)

    Ganda, K; Falcon-Barroso, J; Peletier, RF; Cappellari, M; Emsellem, E; McDermid, RM; de Zeeuw, PT; Carollo, CM; Andersen, DR; Swaters, RA

    2006-01-01

    We present the stellar and gas kinematics of a sample of 18 nearby late-type spiral galaxies (Hubble types ranging from Sb to Sd), observed with the integral-field spectrograph SAURON at the 4.2-m William Herschel Telescope. SAURON covers the spectral range 4800-5380 angstrom, allowing us to measure

  11. The opacity of Spiral Disks IV : Radial Extinction Profiles from Counts of Distant Galaxies seen through Foreground Disks

    NARCIS (Netherlands)

    Holwerda, B. W.; González, R. A.; Allen, R. J.; Kruit, P.C. van der

    2004-01-01

    Dust extinction can be determined from the number of distant field galaxies seen through a spiral disk. To calibrate this number for the crowding and confusion introduced by the foreground image, Gonzalez et al. (1998) and Holwerda et al. (2005a) developed the ``Synthetic Field Method'' (SFM), which

  12. The DiskMass Survey. VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy

    NARCIS (Netherlands)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Schechtman-Rook, Andrew; Andersen, David R.; Swaters, Rob A.

    2013-01-01

    We present ionized-gas ([Oiii]λ5007 Å) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths (hR). These data have been derived from PPak integral-field-unit spectroscopy from 4980-5370 Å observed at a mea

  13. The DiskMass Survey : VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy

    NARCIS (Netherlands)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Schechtman-Rook, Andrew; Andersen, David R.; Swaters, Rob A.

    2013-01-01

    We present ionized-gas ([OIII]lambda 5007 angstrom) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths (h(R)). These data have been derived from PPak integral-field-unit spectroscopy from 4980-5370 angs

  14. Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model

    Science.gov (United States)

    Michtchenko, T. A.; Vieira, R. S. S.; Barros, D. A.; Lépine, J. R. D.

    2017-01-01

    Context. Resonances in the stellar orbital motion under perturbations from the spiral arm structure can play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (in the context of nearly circular orbits), but is not suitable in general. Aims: We expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped groove profiles without any restriction on the stellar orbital configurations, and we expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions. Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes of initial conditions are constructed numerically in order to characterize the phase-space structure and identify the precise location of the co-rotation and Lindblad resonances. The study is complemented by the construction of dynamical power spectra, which provide the identification of fundamental oscillatory patterns in the stellar motion. Results: Our approach allows a precise description of the resonance chains in the whole phase space, giving a broader view of the dynamics of the system when compared to the classical epicyclic approach. We generalize the concept of Lindblad resonances and extend it to cases of resonant orbits with large radial excursions, even for objects in retrograde motion. The analysis of the solar neighbourhood shows that, depending on the current azimuthal phase of the Sun with respect to the spiral arms, a star with solar kinematic parameters (SSP) may evolve in dynamically distinct regions, either inside the stable co-rotation resonance or in a chaotic zone. Conclusions: Our approach contributes to quantifying the domains of resonant orbits and the degree of chaos in the whole Galactic phase-space structure. It may serve as a

  15. Internal kinematics of spiral galaxies in distant clusters III. Velocity fields from FORS2/MXU spectroscopy

    CERN Document Server

    Kutdemir, E; Peletier, R F; Da Rocha, C; Kronberger, T; Kapferer, W; Schindler, S; Böhm, A; Jäger, K; Kuntschner, Harald; Verdugo, M

    2008-01-01

    (Abridged) We study the impact of cluster environment on the evolution of spiral galaxies by examining their structure and kinematics. Rather than two-dimensional rotation curves, we observe complete velocity fields by placing three adjacent and parallel FORS2 MXU slits on each object, yielding several emission and absorption lines. The gas velocity fields are reconstructed and decomposed into circular rotation and irregular motions using kinemetry. To quantify irregularities in the gas kinematics, we define three parameters: sigma_{PA} (standard deviation of the kinematic position angle), Delta phi (the average misalignment between kinematic and photometric position angles) and k_{3,5} (squared sum of the higher order Fourier terms). Using local, undistorted galaxies from SINGS, these can be used to establish the regularity of the gas velocity fields. Here we present the analysis of 22 distant galaxies in the MS0451.6-0305 field with 11 members at z=0.54. In this sample we find both field (4 out of 8) and cl...

  16. Study of the stellar population properties in the discs of ten spiral galaxies

    CERN Document Server

    Morelli, L; Pizzella, A; Bontà, E Dalla; Coccato, L; Méndez-Abreu, J

    2015-01-01

    We investigated the properties of the stellar populations in the discs of a sample of ten spiral galaxies. Our analysis focused on the galaxy region where the disc contributes more than 95 per cent of total surface brightness in order to minimise the contamination of the bulge and bar. The luminosity-weighted age and metallicity were obtained by fitting the galaxy spectra with a linear combination of stellar population synthesis models, while the total overabundance of {\\alpha}-elements over iron was derived by measuring the line-strength indices. Most of the sample discs display a bimodal age distribution and they are characterised by a total [{\\alpha}/Fe] enhancement ranging from solar and supersolar. We interpreted the age bimodality as due to the simultaneous presence of both a young (Age$\\,\\leq\\,4$ Gyr) and an old (Age$\\,>\\,$4 Gyr) stellar population. The old stellar component usually dominates the disc surface brightness and its light contribution is almost constant within the observed radial range. For...

  17. Milgrom Relation Models for Spiral Galaxies from Two-Dimensional Velocity Maps

    CERN Document Server

    Barnes, E I; Sellwood, J A; Barnes, Eric I.; Kosowsky, Arthur; Sellwood, Jerry A.

    2007-01-01

    Using two-dimensional velocity maps and I-band photometry, we have created mass models of 40 spiral galaxies using the Milgrom relation (the basis of modified Newtonian dynamics, or MOND) to complement previous work. A Bayesian technique is employed to compare several different dark matter halo models to Milgrom and Newtonian models. Pseudo-isothermal dark matter halos provide the best statistical fits to the data in a majority of cases, while the Milgrom relation generally provides good fits as well. We also find that Milgrom models give mass-to-light ratios that roughly correlate with galaxy color, as predicted by stellar population models. A subsample of galaxies in the Hydra cluster follow a tight relation between mass-to-light and color, but one that is significantly different from relations found in previous studies. Ruling out the Milgrom relation with rotational kinematics is difficult due to systematic uncertainties in the observations as well as underlying model assumptions. We discuss in detail two...

  18. The \\HI column density power spectrum of six nearby spiral galaxies

    CERN Document Server

    Dutta, Prasun

    2013-01-01

    We propose a method to determine the power spectrum of \\HI column density fluctuations using radio-interferometric observations of 21-cm emission from the ISM of galaxies. We have used this to estimate the power spectra of six nearly face on nearby spiral galaxies. Earlier work has shown that these power spectra are well fitted by power laws with slopes around -1.6 across length-scales $\\sim 1 \\, {\\rm kpc}$ to $\\sim 10 \\, {\\rm kpc}$, the amplitude however was undetermined. In the present work we have determined the amplitude of the \\HI column density power spectrum. We find that the \\HI column density $N_{\\rm HI}$ expressed in units of $10^{20} \\, {\\rm cm}^{-2}$ has mean square fluctuations in the range $\\sim 0.03$ to $\\sim 20$. The amplitude of the power spectrum is found to be tightly correlated with the \\HI mass fraction of the galaxies. The physical process responsible for these scale-invariant fluctuations is, however, at present not known.

  19. Determination of resonance locations in barred spiral galaxies using multiband photometry

    CERN Document Server

    Sierra, Amber D; Treuthardt, Patrick; Puerari, Ivanio

    2015-01-01

    In this paper, we apply a method identified by Puerari & Dottori (1997) to find the corotation radii (CR) in spiral galaxies. We apply our method to 57 galaxies, 17 of which have already have their CR locations determined using other methods. The method we adopted entails taking Fourier transforms along radial cuts in the u, g, r, i, and z wavebands and comparing the phase angles as a function of radius between them. The radius at which the phase angles cross indicates the location of the corotation radius. We then calculated the relative bar pattern speed, $\\mathcal{R}$, and classified the bar as "fast", where $\\mathcal{R} < 1.4$, slow, where $\\mathcal{R} \\geq 1.4$, or intermediate, where the errors on $\\mathcal{R}$ are consistent with the bar being "slow" or "fast". For the 17 galaxies that had their CR locations previously measured, we found that our results were consistent with the values of $\\mathcal{R}$ obtained by the computer simulations of Rautiainen, Salo & Laurikainen (2008). For the lar...

  20. On the effective oxygen yield in the disks of spiral galaxies

    CERN Document Server

    Zasov, A; Abramova, O

    2015-01-01

    The factors influencing chemical evolution of galaxies are poorly understood. Both gas inflow and gas outflow reduce a gas-phase abundance of heavy elements (metallicity) whereas the ongoing star formation continuously increases it. To exclude the stellar nucleosynthesis from consideration, we analyze for the sample of 14 spiral galaxies the radial distribution of the effective yield of oxygen $y_{eff}$, which would be identical to the true stellar yield (per stellar generation) $y_o$ if the evolution followed the closed box model. As the initial data for gas-phase abundance we used the O/H radial profiles from Moustakas, Kennicutt, Tremonti et al. (2010), based on two different calibrations (Pilyugin & Thuan 2005 (PT2005) and Kobulnicky & Kewley 2004 (KK2004) methods). In most of galaxies with the PT2005 calibration, which we consider as a preferred one, the yield $y_{eff}$ in the main disk ($R \\ge 0.2~R_{25}$, where $R_{25}$ is the optical radius) increases with radius, remaining lower than the empi...

  1. Galaxy Secular Mass Flow Rate Determination Using the Potential-Density Phase Shift Approach: Application to Six Nearby Spiral Galaxies

    CERN Document Server

    Zhang, Xiaolei

    2016-01-01

    Using the potential-density phase shift approach developed by the present authors in earlier publications, we estimate the magnitude of radial mass accretion/excretion rates across the disks of six nearby spiral galaxies having a range of Hubble types. Our goal is to examine these rates in the context of bulge building and secular morphological evolution along the Hubble sequence. Stellar surface density maps of the sample galaxies are derived from SINGS 3.6um and SDSS i-band images. Corresponding molecular and atomic gas surface densities are derived from published CO(1-0) and HI interferometric observations of the BIMA SONG, THINGS, and VIVA surveys. The mass flow rate calculations utilize a volume-type torque integral to calculate the angular momentum exchange rate between the basic state disk matter and density wave modes. The potential-density phase shift approach yields angular momentum transport rates several times higher than those estimated using the Lynden-Bell and Kalnajs (1972) approach. The curre...

  2. GLOBULAR CLUSTERS AND SPUR CLUSTERS IN NGC 4921, THE BRIGHTEST SPIRAL GALAXY IN THE COMA CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Myung Gyoon; Jang, In Sung, E-mail: mglee@astro.snu.ac.kr, E-mail: isjang@astro.snu.ac.kr [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-742 (Korea, Republic of)

    2016-03-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 10{sup 5} M{sub ⊙}. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 < (V − I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting M{sub I} (max) = −8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H{sub 0} = 77.9 ± 3.6 km s{sup −1} Mpc{sup −1}. We estimate the GC specific frequency of NGC 4921 to be S{sub N} = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.

  3. Grand Design and Flocculent Spirals in the Spitzer Survey of Stellar Structure in Galaxies (S4G)

    CERN Document Server

    Elmegreen, Debra Meloy

    2011-01-01

    Spiral arm properties of 46 galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G) were measured at 3.6mu, where extinction is small and the old stars dominate. The sample includes flocculent, multiple arm, and grand design types with a wide range of Hubble and bar types. We find that most optically flocculent galaxies are also flocculent in the mid-IR because of star formation uncorrelated with stellar density waves, whereas multiple arm and grand design galaxies have underlying stellar waves. Arm-interarm contrasts increase from flocculent to multiple arm to grand design galaxies and with later Hubble types. Structure can be traced further out in the disk than in previous surveys. Some spirals peak at mid-radius while others continuously rise or fall, depending on Hubble and bar type. We find evidence for regular and symmetric modulations of the arm strength in NGC 4321. Bars tend to be long, high amplitude, and flat-profiled in early type spirals, with arm contrasts that decrease with radius...

  4. Neutrino Flux from Cosmic Ray Accelerators in the Cygnus Spiral Arm of the Galaxy

    CERN Document Server

    Anchordoqui, Luis A; Montaruli, T; O'Murchadha, A; Anchordoqui, Luis; Halzen, Francis; Montaruli, Teresa; Murchadha, Aongus O'

    2006-01-01

    Intriguing evidence has been accumulating for the production of cosmic rays in the Cygnus region of the Galactic plane. We here show that the IceCube experiment can produce incontrovertible evidence for cosmic ray acceleration by observing neutrinos from the decay of charged pions accompanying the TeV photon flux observed in the HEGRA, Whipple, Tibet and Milagro experiments. Our assumption is that the TeV photons observed are the decay products of neutral pions produced by cosmic ray accelerators in the nearby spiral arm of the Galaxy. Because of the proximity of the sources, IceCube will obtain evidence at the 5sigma level in 10 years of observation.

  5. New insights into the X-ray properties of the nearby barred spiral galaxy NGC 1672

    CERN Document Server

    Jenkins, L P; Colbert, E J M; Levan, A J; Roberts, T P; Ward, M J; Zezas, A

    2008-01-01

    We present some preliminary results from new Chandra and XMM-Newton X-ray observations of the nearby barred spiral galaxy NGC1672. It shows dramatic nuclear and extra-nuclear star formation activity, including starburst regions located near each end of its strong bar, both of which host ultraluminous X-ray sources (ULXs). With the new high-spatial-resolution Chandra imaging, we show for the first time that NGC1672 possesses a faint ($L(X)~10^39 erg/s), hard central X-ray source surrounded by an X-ray bright circumnuclear starburst ring that dominates the X-ray emission in the region. The central source may represent low-level AGN activity, or alternatively the emission from X-ray binaries associated with star-formation in the nucleus.

  6. Extinction law variations and dust excitation in the spiral galaxy NGC 300

    CERN Document Server

    Roussel, H; Seibert, M; Helou, G; Madore, B F; Martin, C

    2005-01-01

    We investigate the origin of the strong radial gradient in the ultraviolet-to-infrared ratio in the spiral galaxy NGC 300, and emphasize the importance of local variations in the interstellar medium geometry, concluding that they cannot be neglected with respect to metallicity effects. This analysis is based upon a combination of maps from GALEX and Spitzer, and from the ground (UBVRI, Halpha and Hbeta). We select ionizing stellar clusters associated with HII regions of widely varying morphologies, and derive their fundamental parameters from population synthesis fitting of their spectral energy distributions, measured to eliminate local backgrounds accurately. From these fits, we conclude that the stellar extinction law is highly variable in the line of sight of young clusters of similar ages. In the particular model geometry that we consider most appropriate to the sampled regions, we checked that our findings are not significantly altered by the correct treatment of radiative transfer effects. The variatio...

  7. Corrugated velocity patterns in the spiral galaxies: NGC 278, NGC 1058, NGC 2500 \\& UGC 3574

    CERN Document Server

    Sánchez-Gil, M Carmen; Pérez, Enrique

    2015-01-01

    We address the study of the \\Ha\\ vertical velocity field in a sample of four nearly face-on galaxies using long slit spectroscopy taken with the ISIS spectrograph attached to the WHT at the Roque de los Muchachos Observatory (Spain). The spatial structure of the velocity vertical component shows a radial corrugated pattern with spatial scales higher or within the order of { one} kiloparsec. The gas is mainly ionized by high-energy photons: only in some locations of NGC~278 and NGC~1058 is there some evidence of ionization by low-velocity shocks, which, in the case of NGC~278, could be due to minor mergers. The behaviour of the gas in the neighbourhood of the spiral arms fits, in the majority of the observed cases, with that predicted by the so-called hydraulic bore mechanism, where a thick magnetized disk encounters a spiral density perturbation. The results obtained show that it is { difficult to explain the \\Ha\\ large scale velocity field without the presence of a magnetized, thick galactic disk}. Larger sa...

  8. Spiral-like star-forming patterns in CALIFA early-type galaxies

    CERN Document Server

    Gomes, J M; Vílchez, J M; Kehrig, C; Iglesias-Páramo, J; Breda, I; Lehnert, M D; Sánchez, S F; Ziegler, B; Reis, S N dos; Bland-Hawthorn, J; Galbany, L; Bomans, D J; Rosales-Ortega, F F; Walcher, C J; García-Benito, R; Márquez, I; del Olmo, A; Mollá, M; Marino, R A; Catalán-Torrecilla, C; Delgado, R M González; López-Sánchez, Á R

    2015-01-01

    Based on a combined analysis of SDSS imaging and CALIFA integral field spectroscopy data, we report on the detection of faint (24 < {\\mu}$_r$ mag/arcsec$^2$ < 26) star-forming spiral-arm-like features in the periphery of three nearby early-type galaxies (ETGs). These features are of considerable interest because they document the still ongoing inside-out growth of some local ETGs and may add valuable observational insight into the origin and evolution of spiral structure in triaxial stellar systems. A characteristic property of the nebular component in the studied ETGs, classified i+, is a two-radial-zone structure, with the inner zone that displays faint (EW(H\\alpha)$\\simeq$1{\\AA}) low-ionization nuclear emission-line region (LINER) properties, and the outer one (3{\\AA}

  9. Revealing a spiral-shaped molecular cloud in our galaxy: Cloud fragmentation under rotation and gravity

    Science.gov (United States)

    Li, Guang-Xing; Wyrowski, Friedrich; Menten, Karl

    2017-02-01

    The dynamical processes that control star formation in molecular clouds are not well understood, and in particular, it is unclear if rotation plays a major role in cloud evolution. We investigate the importance of rotation in cloud evolution by studying the kinematic structure of a spiral-shaped Galactic molecular cloud G052.24+00.74. The cloud belongs to a large filament, and is stretching over 100 pc above the Galactic disk midplane. The spiral-shaped morphology of the cloud suggests that the cloud is rotating. We have analysed the kinematic structure of the cloud, and study the fragmentation and star formation. We find that the cloud exhibits a regular velocity pattern along west-east direction - a velocity shift of 10km s-1 at a scale of 30 pc. The kinematic structure of the cloud can be reasonably explained by a model that assumes rotational support. Similarly to our Galaxy, the cloud rotates with a prograde motion. We use the formalism of Toomre (1964) to study the cloud's stability, and find that it is unstable and should fragment. The separation of clumps can be consistently reproduced assuming gravitational instability, suggesting that fragmentation is determined by the interplay between rotation and gravity. Star formation occurs in massive, gravitational bound clumps. Our analysis provides a first example in which the fragmentation of a cloud is regulated by the interplay between rotation and gravity.

  10. Revealing a spiral-shaped molecular cloud in our galaxy - Cloud fragmentation under rotation and gravity

    CERN Document Server

    Li, Guang-Xing; Menten, Karl

    2016-01-01

    The dynamical processes that control star formation in molecular clouds are not well understood, and in particular, it is unclear if rotation plays a major role in cloud evolution. We investigate the importance of rotation in cloud evolution by studying the kinematic structure of a spiral-shaped Galactic molecular cloud G052.24+00.74. The cloud belongs to a large filament, and is stretching over ~ 100 pc above the Galactic disk midplane. The spiral-shaped morphology of the cloud suggests that the cloud is rotating. We have analysed the kinematic structure of the cloud, and study the fragmentation and star formation. We find that the cloud exhibits a regular velocity pattern along west-east direction - a velocity shift of ~ 10 km/s at a scale of ~ 30 pc. The kinematic structure of the cloud can be reasonably explained by a model that assumes rotational support. Similarly to our Galaxy, the cloud rotates with a prograde motion. We use the formalism of Toomre (1964) to study the cloud's stability, and find that ...

  11. Radial distribution of gas and dust in the two spiral galaxies M99 and M100

    CERN Document Server

    Pohlen, M; Smith, M W L; Eales, S A; Boselli, A; Bendo, G J; Gomez, H L; Papageorgiou, A; Auld, R; Baes, M; Bock, J J; Bradford, M; Buat, V; Castro-Rodriguez, N; Chanial, P; Charlot, S; Ciesla, L; Clements, D L; Cooray, A; Cormier, D; Dwek, E; Eales, S A; Elbaz, D; Galametz, M; Galliano, F; Gear, W K; Glenn, J; Griffin, M; Hony, S; Isaak, K G; Levenson, L R; Lu, N; Madden, S; O'Halloran, B; Okumura, K; Oliver, S; Page, M J; Panuzzo, P; Parkin, T J; Perez-Fournon, I; Rangwala, N; Rigby, E E; Roussel, H; Rykala, A; Sacchi, N; Sauvage, M; Schulz, B; Schirm, M R P; Smith, M W L; Spinoglio, L; Stevens, J A; Srinivasan, S; Symeonidis, M; Trichas, M; Vaccari, M; Vigroux, L; Wilson, C D; Wozniak, H; Wright, G S; Zeiliner, W W

    2010-01-01

    By combining Herschel-SPIRE data with archival Spitzer, HI, and CO maps, we investigate the spatial distribution of gas and dust in the two famous grand-design spirals M99 and M100 in the Virgo cluster. Thanks to the unique resolution and sensitivity of the Herschel-SPIRE photometer, we are for the first time able to measure the distribution and extent of cool, submillimetre (submm)-emitting dust inside and beyond the optical radius. We compare this with the radial variation in both the gas mass and the metallicity. Although we adopt a model-independent, phenomenological approach, our analysis provides important insights. We find the dust extending to at least the optical radius of the galaxy and showing breaks in its radial profiles at similar positions as the stellar distribution. The colour indices f350/f500 and f250/f350 decrease radially consistent with the temperature decreasing with radius. We also find evidence of an increasing gas to dust ratio with radius in the outer regions of both galaxies.

  12. Building Late-Type Spiral Galaxies by In-Situ and Ex-Situ Star Formation

    CERN Document Server

    Pillepich, Annalisa; Mayer, Lucio

    2014-01-01

    We analyze the formation and evolution of the stellar components in "Eris", a 120 pc-resolution cosmological hydrodynamic simulation of a late-type spiral galaxy. The simulation includes the effects of a uniform UV background, a delayed-radiative-cooling scheme for supernova feedback, and a star formation recipe based on a high gas density threshold. It allows a detailed study of the relative contributions of "in-situ" (within the main host) and "ex-situ" (within satellite galaxies) star formation to each major Galactic component in a close Milky Way analog. We investigate these two star-formation channels as a function of galactocentric distance, along different lines of sight above and along the disk plane, and as a function of cosmic time. We find that: 1) approximately 70 percent of today's stars formed in-situ; 2) more than two thirds of the ex-situ stars formed within satellites after infall; 3) the majority of ex-situ stars are found today in the disk and in the bulge; 4) the stellar halo is dominated ...

  13. Shape of the oxygen abundance profiles in CALIFA face-on spiral galaxies

    CERN Document Server

    Sánchez-Menguiano, L; Pérez, I; García-Benito, R; Husemann, B; Mast, D; Mendoza, A; Ruiz-Lara, T; Ascasibar, Y; Bland-Hawthorn, J; Cavichia, O; Díaz, A I; Florido, E; Galbany, L; Delgado, R M Gónzalez; Kehrig, C; Marino, R A; Márquez, I; Masegosa, J; Méndez-Abreu, J; Mollá, M; del Olmo, A; Pérez, E; Sánchez-Blázquez, P; Stanishev, V; Walcher, C J; López-Sánchez, Á R

    2016-01-01

    We measured the gas abundance profiles in a sample of 122 face-on spiral galaxies observed by the CALIFA survey and included all spaxels whose line emission was consistent with star formation. This type of analysis allowed us to improve the statistics with respect to previous studies, and to properly estimate the oxygen distribution across the entire disc to a distance of up to 3-4 disc effective radii (r$_e$). We confirm the results obtained from classical HII region analysis. In addition to the general negative gradient, an outer flattening can be observed in the oxygen abundance radial profile. An inner drop is also found in some cases. There is a common abundance gradient between 0.5 and 2.0 r$_e$ of $\\alpha_{O/H} = -\\,0.075\\,\\rm{dex}/r_e$ with a scatter of $\\sigma = 0.016\\,\\rm{dex}/r_e$ when normalising the distances to the disc effective radius. By performing a set of Kolmogorov-Smirnov tests, we determined that this slope is independent of other galaxy properties, such as morphology, absolute magnitude...

  14. The inner mass distribution of late-type spiral galaxies from SAURON stellar kinematic maps

    Science.gov (United States)

    Kalinova, Veselina; van de Ven, Glenn; Lyubenova, Mariya; Falcón-Barroso, Jesús; Colombo, Dario; Rosolowsky, Erik

    2017-01-01

    We infer the central mass distributions within 0.4-1.2 disc scalelengths of 18 late-type spiral galaxies using two different dynamical modelling approaches - the asymmetric drift correction (ADC) and axisymmetric Jeans anisotropic multi-Gaussian expansion (JAM) model. ADC adopts a thin-disc assumption, whereas JAM does a full line-of-sight velocity integration. We use stellar kinematics maps obtained with the integral-field spectrograph {SAURON} to derive the corresponding circular velocity curves from the two models. To find their best-fitting values, we apply the Markov Chain Monte Carlo (MCMC) method. ADC and JAM modelling approaches are consistent within 5 per cent uncertainty when the ordered motions are significant comparable to the random motions, i.e. overline{v_{φ }}/σ _R is locally greater than 1.5. Below this value, the ratio vc, JAM/vc, ADC gradually increases with decreasing overline{v_{φ }}/σ _R, reaching vc,JAM ≈ 2 × vc, ADC. Such conditions indicate that the stellar masses of the galaxies in our sample are not confined to their disc planes and likely have a non-negligible contribution from their bulges and thick discs.

  15. Gas and Stellar Kinematics in the Giant Spiral Galaxy NGC 1961

    Science.gov (United States)

    Sacash, Brian; Pinkney, Jason

    2009-04-01

    Long-slit spectroscopy and CCD imaging from the Hubble Space Telescope and the MDM Observatory is presented for the massive spiral galaxy NGC 1961. We aimed to measure the mass of the central supermassive black hole (SMBH). We have developed our own software for spectral extraction and for the fitting of absorption and emission lines. The program subtracts the absorption-line (stellar) component from the emission-line spectra to improve the fidelity of our emission line measurements. We present our line centroids (velocities), widths (velocity dispersions), and strengths for the most prominent emission lines (Hα, [NII], and [SII]). The rotation curve from the ground-based data is in good agreement with previous work by Rubin (1979); its asymmetric appearance suggests a tidal interaction or merger. We use the rotation curve and surface photometry to estimate the enclosed mass profile of the galaxy. The emission lines near the nucleus broaden indicating more intrinsic dispersion than expected for a cold, gas disk. We estimate the BH mass using simple gas disk models. However, the high dispersion and the asymmetry in its inner rotation curve suggest that this approach is unreliable.

  16. The bolometric and UV attenuation in normal spiral galaxies of the Herschel Reference Survey

    CERN Document Server

    Viaene, S; Bendo, G; Boquien, M; Boselli, A; Ciesla, L; Cortese, L; De Looze, I; Eales, S; Fritz, J; Karczewski, O Ł; Madden, S; Smith, M W L; Spinoglio, L

    2016-01-01

    The dust in nearby galaxies absorbs a fraction of the UV-optical-near-infrared radiation produced by stars. This energy is consequently re-emitted in the infrared. We investigate the fraction of the stellar radiation absorbed by spiral galaxies from the HRS by modelling their UV-to-submillimetre spectral energy distributions. Our models provide an attenuated and intrinsic SED from which we find that on average 32 % of all starlight is absorbed by dust. We define the UV heating fraction as the fraction of dust luminosity that comes from absorbed UV photons and find that this is 56 %, on average. This percentage varies with morphological type, with later types having significantly higher UV heating fractions. We find a strong correlation between the UV heating fraction and specific star formation rate and provide a power-law fit. Our models allow us to revisit the IRX-AFUV relations, and derive these quantities directly within a self-consistent framework. We calibrate this relation for different bins of NUV-r c...

  17. Spatial distribution of far infrared emission in spiral galaxies; 1, relation with radio continuum emission

    CERN Document Server

    Mayya, Y D

    1997-01-01

    We use high resolution IRAS and 20 cm radio continuum (RC) images of a sample of 22 spiral galaxies to study the correlation between the far infra-red (FIR) and RC emissions within the galactic disks. A combination of exponential and gaussian profiles rather than a single exponential profile is found to be a better representation of the observed intensity profiles in the two bands. The gaussian component, which we show is not due to the effects of limited beam-resolution, contains more than 60% of the total flux in majority of the galaxies. The dominance of the gaussian component suggests that the nuclear star forming regions and the bulge stars are more important contributors to the emission in the two bands, rather than the outer exponential stellar disks. The RC profile is flatter compared to the FIR profile, resulting in a decrease of their ratio, Q60, away from the center. However, the Q60 increases in the extreme outer parts, where the dispersion in the FIR and RC correlation is also higher than in the ...

  18. A spectral and photometric study of 102 star forming regions in seven spiral galaxies

    CERN Document Server

    Gusev, A S; Piskunov, A E; Kharchenko, N V; Bruevich, V V; Ezhkova, O V; Guslyakova, S A; Lang, V; Shimanovskaya, E V; Efremov, Yu N

    2016-01-01

    We present a study of complexes of young massive star clusters (YMCs), embedded in extragalactic giant HII regions, based on the coupling of spectroscopic with photometric and spectrophotometric observations of about 100 star forming regions in seven spiral galaxies (NGC 628, NGC 783, NGC 2336, NGC 6217, NGC 6946, NGC 7331, and NGC 7678). The complete observational database has been observed and accumulated within the framework of our comprehensive study of extragalactic star forming regions. The current paper presents the last part of either unpublished or refreshed photometric and spectrophotometric observations of the galaxies NGC 6217, NGC 6946, NGC 7331, and NGC 7678. We derive extinctions, chemical abundances, continuum and line emissions of ionised gas, ages and masses for cluster complexes. We find the young massive cluster complexes to have ages no greater than 10 Myr and masses between 10^4Msol and 10^7Msol, and the extinctions A(V) vary between ~ 0 and 3 mag, while the impact of the nebular emissio...

  19. Evidence for azimuthal variations of the oxygen-abundance gradient tracing the spiral structure of the galaxy HCG 91c

    Science.gov (United States)

    Vogt, F. P. A.; Pérez, E.; Dopita, M. A.; Verdes-Montenegro, L.; Borthakur, S.

    2017-05-01

    Context. The distribution of elements in galaxies forms an important diagnostic tool to characterize these systems' formation and evolution. This tool is, however, complex to use in practice, as galaxies are subject to a range of simultaneous physical processes active from pc to kpc scales. This renders observations of the full optical extent of galaxies down to sub-kpc scales essential. Aims: Using the WiFeS integral field spectrograph, we previously detected abrupt and localized variations in the gas-phase oxygen abundance of the spiral galaxy HCG 91c. Here, we follow-up on these observations to map HCG 91c's disk out to 2 Re at a resolution of 600 pc, and characterize the non-radial variations of the gas-phase oxygen abundance in the system. Methods: We obtained deep MUSE observations of the target under 0.6 arcsec seeing conditions. We perform both a spaxel-based and aperture-based analysis of the data to map the spatial variations of 12 +log (O/H) across the disk of the galaxy. Results: We confirm the presence of rapid variations of the oxygen abundance across the entire extent of the galaxy previously detected with WiFeS, for all azimuths and radii. The variations can be separated in two categories: a) localized and associated with individual H ii regions; and b) extended over kpc scales, and occurring at the boundaries of the spiral structures in the galaxy. Conclusions: Our MUSE observations suggest that the enrichment of the interstellar medium in HGC 91c has proceeded preferentially along spiral structures, and less efficiently across them. Our dataset highlights the importance of distinguishing individual star-forming regions down to scales of a few 100 pc when using integral field spectrographs to spatially resolve the distribution of oxygen abundances in a given system, and accurately characterize azimuthal variations and intrinsic scatter. The movie associated to Fig. 8 is available at http://www.aanda.org

  20. Caught in the act: Cluster `k+a' galaxies as a link between spirals and S0s

    CERN Document Server

    Del Pino, Bruno Rodriguez; Aragon-Salamanca, Alfonso; Milvang-Jensen, Bo; Merrifield, Michael R; Balcells, Marc

    2013-01-01

    We use integral field spectroscopy of 13 disk galaxies in the cluster AC114 at z ~ 0.31 in an attempt to disentangle the physical processes responsible for the transformation of spiral galaxies in clusters. Our sample is selected to display a dominant young stellar population, as indicated by strong Hdelta absorption lines in their integrated spectra. Most of our galaxies lack the [OII] emission line, and hence ongoing star formation. They therefore possess `k+a' spectra, indicative of a recent truncation of star formation, possibly preceded by a starburst. Disky `k+a' galaxies are a promising candidate for the intermediate stage of the transformation from star-forming spiral galaxies to passive S0s. Our observations allow us to study the spatial distributions and the kinematics of the different stellar populations within the galaxies. We used three different indicators to evaluate the presence of a young population: the equivalent width of Hdelta, the luminosity-weighted fraction of A stars, and the fraction...

  1. Bridging the Gap from Galactic to Extragalactic: Star Formation and Giant Molecular Clouds within the Nearby Spiral Galaxy NGC 300

    Science.gov (United States)

    Faesi, Christopher

    2017-01-01

    The questions surrounding the origins of stars are of key importance in astrophysics across a huge range in physical scales. However, until recently, investigations have been restricted to either detailed studies targeting a few nearby regions in the Milky Way, or kpc- or larger-scale studies of entire galaxies. Between these two scales lies a crucial gap in understanding. In this thesis work, I have taken steps in bridging this gap between Galactic and extragalactic star formation. I will present the results of a campaign of observations and modeling targeting the nearby spiral galaxy NGC 300. Using an extensive suite of multi-wavelength data I have characterized the star formation activity and molecular gas in a large sample of star-forming regions within this galaxy. Additionally, I have assembled an extensive (300 clouds) and high resolution (10 pc) catalog of Giant Molecular Clouds (GMCs) based on ALMA CO observations. This unprecedented look at the population of GMCs in a nearby spiral galaxy reveals an astonishing range of morphologies and properties in the Molecular Gas as well as providing a key testbed for comparison with GMCs in the Milky Way and other nearby galaxies. The GMCs in NGC 300 appear to have similar global properties and show scaling relations consistent with those seen in the Milky Way. Furthermore, the star formation rate appears to correlate with the mass of molecular gas with approximately 250 Gyr depletion time, extending the relation discovered in the Milky Way linearly to larger scales. These results suggest a level of universality in the star formation process within spiral galaxy disks like our own Milky Way.

  2. The Relation between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies: The Case Study of NGC 4258

    Science.gov (United States)

    González-Lópezlira, Rosa A.; Lomelí-Núñez, Luis; Álamo-Martínez, Karla; Órdenes-Briceño, Yasna; Loinard, Laurent; Georgiev, Iskren Y.; Muñoz, Roberto P.; Puzia, Thomas H.; Bruzual A., Gustavo; Gwyn, Stephen

    2017-02-01

    We aim to explore the relationship between globular cluster total number, {N}{GC}, and central black hole mass, M •, in spiral galaxies, and compare it with that recently reported for ellipticals. We present results for the Sbc galaxy NGC 4258, from Canada–France–Hawaii Telescope data. Thanks to water masers with Keplerian rotation in a circumnuclear disk, NGC 4258 has the most precisely measured extragalactic distance and supermassive black hole mass to date. The globular cluster (GC) candidate selection is based on the ({u}* -{i}\\prime ) versus ({i}\\prime -{K}s) diagram, which is a superb tool to distinguish GCs from foreground stars, background galaxies, and young stellar clusters, and hence can provide the best number counts of GCs from photometry alone, virtually free of contamination, even if the galaxy is not completely edge-on. The mean optical and optical-near-infrared colors of the clusters are consistent with those of the Milky Way and M 31, after extinction is taken into account. We directly identify 39 GC candidates; after completeness correction, GC luminosity function extrapolation, and correction for spatial coverage, we calculate a total {N}{GC}=144+/- {31}-36+38 (random and systematic uncertainties, respectively). We have thus increased to six the sample of spiral galaxies with measurements of both M • and {N}{GC}. NGC 4258 has a specific frequency {S}{{N}}=0.4+/- 0.1 (random uncertainty), and is consistent within 2σ with the {N}{GC} versus M • correlation followed by elliptical galaxies. The Milky Way continues to be the only spiral that deviates significantly from the relation.

  3. Large scale star formation in galaxies. II. The spirals NGC 3377A, NGC 3507 and NGC 4394

    CERN Document Server

    Vicari, A; Capuzzo-Dolcetta, R; Wyder, T K; Arrabito, G

    2001-01-01

    The identification of young star groupings (YSG) in the three spiral galaxies NGC 3377A, NGC 3507, NGC 4394 is obtained by mean of the statistical method described in Paper I. We find 83, 90, 185 YSGs, respectively. An identification map of YSGs, as well as their size distribution, their B-luminosity function, their surface luminosity density radial behaviour, are presented and comparatively discussed. These data, in addition to those in Paper I, constitute a first sample suitable for seeking correlations among properties of galaxies and their YSG, which we briefly discuss here.

  4. Nuclear spirals as feeding channels to the Supermassive Black Hole: the case of the galaxy NGC 6951

    CERN Document Server

    Storchi-Bergmann, Thaisa; Riffel, Rogemar A; Fathi, Kambiz; Axon, David J; Robinson, Andrew; Marconi, Alessandro; Ostlin, Goran

    2007-01-01

    We report the discovery of gas streaming motions along nuclear spiral arms towards the LINER nucleus of the galaxy NGC 6951. The observations, obtained using the GMOS integral field spectrograph on the Gemini North telescope, yielded maps of the flux distributions and gas kinematics in the Halpha, [NII]6584 and [SII]6717,31 emission lines of the inner 7x5 arcsec^2 of the galaxy. This region includes a circumnuclear star-forming ring with radius 500pc, a nuclear spiral inside the ring and the LINER nucleus. The kinematics of the ionized gas is dominated by rotation, but subtraction of a kinematic model of a rotating exponential disk reveals deviations from circular rotation within the nuclear ring which can be attributed to (1) streaming motions along the nuclear spiral arms and (2) a bipolar outflow which seems to be associated to a nuclear jet. On the basis of the observed streaming velocities and geometry of the spiral arms we estimate a mass inflow rate of ionized gas of 3x10^(-4) Msun/yr, which is of the ...

  5. BUILDING LATE-TYPE SPIRAL GALAXIES BY IN-SITU AND EX-SITU STAR FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Pillepich, Annalisa [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Madau, Piero [Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High St., Santa Cruz, CA 95064 (United States); Mayer, Lucio [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, CH-9057 Zurich (Switzerland)

    2015-02-01

    We analyze the formation and evolution of the stellar components in ''Eris'', a 120 pc resolution cosmological hydrodynamic simulation of a late-type spiral galaxy. The simulation includes the effects of a uniform UV background, a delayed-radiative-cooling scheme for supernova feedback, and a star formation recipe based on a high gas density threshold. It allows a detailed study of the relative contributions of ''in-situ'' (within the main host) and ''ex-situ'' (within satellite galaxies) star formation to each major Galactic component in a close Milky Way analog. We investigate these two star-formation channels as a function of galactocentric distance, along different lines of sight above and along the disk plane, and as a function of cosmic time. We find that: (1) approximately 70% of today's stars formed in-situ; (2) more than two thirds of the ex-situ stars formed within satellites after infall; (3) the majority of ex-situ stars are found today in the disk and in the bulge; (4) the stellar halo is dominated by ex-situ stars, whereas in-situ stars dominate the mass profile at distances ≲ 5 kpc from the center at high latitudes; and (5) approximately 25% of the inner, r ≲ 20 kpc, halo is composed of in-situ stars that have been displaced from their original birth sites during Eris' early assembly history.

  6. Multi-Wavelength Observations of the Supernova Remnant Populations in the Nearby Spiral Galaxies IC 342 and NGC 4258

    Science.gov (United States)

    Pannuti, Thomas; Chomiuk, L.; Grimes, C. K.; Staggs, W. D.; Tussey, J. M.; Laine, S.; Schlegel, E.

    2011-01-01

    Supernova remnants (SNRs) are intimately tied to many crucial processes associated with the interstellar medium of galaxies, such as the acceleration of cosmic-ray particles and the deposition of vast amounts of kinetic energy and chemically-enriched material. Well-known observational challenges in the study of SNRs located in the Milky Way Galaxy (for example, formidable extinction along Galactic lines of sight and considerable uncertainties in the distances to these sources) have motivated searches for SNRs in nearby galaxies at such characteristic wavelengths as X-ray, optical and radio. These searches have revealed a considerable number of SNRs and led to new insights into their properties, but the SNR populations in only a handful of nearby galaxies have been adequately surveyed at multiple wavelengths. To help remedy this situation, we are conducting a multi-wavelength study of the SNR population of selected nearby galaxies. To illustrate our work, we present the results of studies of the SNR population in two nearby spiral galaxies, IC 342 and NGC 4258. Our results draw upon the analysis of pointed archival radio and X-ray observations of these two galaxies. Initial results will be presented and discussed.

  7. Giant molecular clouds in the non-grand design spiral galaxy NGC 6946

    CERN Document Server

    Rebolledo, David; Leroy, Adam; Koda, Jin; Meyer, Jennifer Donovan

    2012-01-01

    We present high spatial resolution observations of Giant Molecular Clouds (GMCs) in the eastern part of the nearby spiral galaxy NGC 6946 obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We have observed 12CO(1-0), 12CO(2-1) and 13CO(1-0), achieving spatial resolutions of 5.4" x 5.0", 2.5" x 2.0" and 5.6" x 5.4" respectively over a region of 6 x 6 kpc. This region extends from 1.5 kpc to 8 kpc galactocentric radius, thus avoiding the intense star formation in the central kpc. We have recovered short-spacing u-v components by using single dish observations from the Nobeyama 45m and IRAM 30m telescopes. Using the automated CPROPS algorithm we identified 44 CO cloud complexes in the 12CO(1-0) map and 64 GMCs in the 12CO(2-1) maps. The sizes, line widths, and luminosities of the GMCs are similar to values found in other extragalactic studies. We have classified the clouds into on-arm and inter-arm clouds based on the stellar mass density traced by the 3.6 um map. On-arm clouds p...

  8. Ram-pressure stripped molecular gas in the Virgo spiral galaxy NGC 4522

    CERN Document Server

    Vollmer, B; Pappalardo, C; Hily-Blant, P

    2008-01-01

    IRAM 30m 12CO(1-0) and 12CO(2-1) HERA observations are presented for the ram-pressure stripped Virgo spiral galaxy NGC 4522. The CO emission is detected in the galactic disk and the extraplanar gas. The extraplanar CO emission follows the morphology of the atomic gas closely but is less extended. The CO maxima do not appear to correspond to regions where there is peak massive star formation as probed by Halpha emission. The presence of molecular gas is a necessary but not sufficient condition for star formation. Compared to the disk gas, the molecular fraction of the extraplanar gas is 30% lower and the star formation efficiency of the extraplanar gas is about 3 times lower. The comparison with an existing dynamical model extended by a recipe for distinguishing between atomic and molecular gas shows that a significant part of the gas is stripped in the form of overdense arm-like structures. It is argued that the molecular fraction depends on the square root of the total large-scale density. Based on the combi...

  9. Planetary Nebulae in Face-On Spiral Galaxies. I. Planetary Nebula Photometry and Distances

    CERN Document Server

    Herrmann, Kimberly A; Feldmeier, John J; Vinciguerra, Matt

    2008-01-01

    As the first step to determine disk mass-to-light ratios for normal spiral galaxies, we present the results of an imaging survey for planetary nebulae (PNe) in six nearby, face-on systems: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), NGC 5068, and NGC 6946. Using Blanco/Mosaic II and WIYN/OPTIC, we identify 165, 153, 241, 150, 19, and 71 PN candidates, respectively, and use the Planetary Nebula Luminosity Function (PNLF) to obtain distances. For M74 and NGC 5068, our distances of 8.6 +/- 0.3 Mpc and 5.4 +0.2/-0.4 Mpc are the first reliable estimates to these objects; for IC 342 (3.5 +/- 0.3 Mpc), M83 (4.8 +/- 0.1 Mpc), M94 (4.4 +0.1/-0.2 Mpc), and NGC 6946 (6.1 +/- 0.6 Mpc) our values agree well with those in the literature. In the larger systems, we find no evidence for any systematic change in the PNLF with galactic position, though we do see minor field-to-field variations in the luminosity function. In most cases, these changes do not affect the measurement of distance, but in one case the fluct...

  10. Circumnuclear star-forming regions in early type spiral galaxies: dynamical masses

    CERN Document Server

    Hagele, G F; Bosch, G L; Diaz, A I; Terlevich, E; Terlevich, R

    2012-01-01

    We present the measurements of gas and stellar velocity dispersions in 17 circumnuclear star-forming regions (CNSFRs) and the nuclei of three barred spiral galaxies: NGC2903, NGC3310 and NGC3351 from high dispersion spectra. The stellar dispersions have been obtained from the CaII triplet (CaT) lines at 8494, 8542, 8662A, while the gas velocity dispersions have been measured by Gaussian fits to the Hbeta and to the [OIII]5007A\\ lines. The CNSFRs, with sizes of about 100 to 150pc in diameter, are seen to be composed of several individual star clusters with sizes between 1.5 and 6.2pc on HST images. Using the stellar velocity dispersions, we have derived dynamical masses for the entire star-forming complexes and for the individual star clusters. Values of the stellar velocity dispersions are between 31 and 73 km/s. Dynamical masses for the whole CNSFRs are between 4.9x10^6 and 1.9x10^8 Mo and between 1.4x10^6 and 1.1x10^7 Mo for the individual star clusters. We have found indications for the presence of two dif...

  11. Herschel-SPIRE-Fourier Transform Spectroscopy of the nearby spiral galaxy IC342

    CERN Document Server

    Rigopoulou, D; Swinyard, B M; Virdee, J; Croxall, K V; Hopwood, R H B; Lim, T; Magdis, G E; Pearson, C P; Pellegrini, E; Polehampton, E; Smith, J-D

    2013-01-01

    We present observations of the nearby spiral galaxy IC342 with the Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer. The spectral range afforded by SPIRE, 196-671 microns, allows us to access a number of 12CO lines from J=4--3 to J=13--12 with the highest J transitions observed for the first time. In addition we present measurements of 13CO, [CI] and [NII]. We use a radiative transfer code coupled with Bayesian likelihood analysis to model and constrain the temperature, density and column density of the gas. We find two 12CO components, one at 35 K and one at 400 K with CO column densities of 6.3x10^{17} cm^{-2} and 0.4x10^{17} cm^{-2} and CO gas masses of 1.26x10^{7} Msolar and 0.15x10^{7} Msolar, for the cold and warm components, respectively. The inclusion of the high-J 12CO line observations, indicate the existence of a much warmer gas component (~400 K) confirming earlier findings from H_{2} rotational line analysis from ISO and Spitzer. The mass of the warm gas i...

  12. Kinematics and excitation of the nuclear spiral in the active galaxy Arp 102B

    CERN Document Server

    Couto, Guilherme S; Axon, David J; Robinson, Andrew; Kharb, Preeti; Riffel, Rogemar A

    2013-01-01

    We present a two-dimensional analysis of the gaseous excitation and kinematics of the inner 2.5 x 1.7 kpc^2 of the LINER/Seyfert 1 galaxy Arp 102B, from optical spectra obtained with the GMOS integral field spectrograph on the Gemini North telescope at a spatial resolution of 250 pc. Emission-line flux maps show the same two-armed nuclear spiral we have discovered in previous observations with the HST-ACS camera. One arm reaches 1 kpc to the east and the other 500 pc to the west, with a 8.4 GHz VLA bent radio jet correlating with the former. The gas density is highest (500 - 900 cm^(-3)) at the nucleus and in the northern border of the east arm, at a region where the radio jet seems to be deflected. Channel maps show blueshifts but also some redshifts at the eastern arm and jet location which can be interpreted as originated in the front and back walls of an outflow pushed by the radio jet, suggesting also that the outflow is launched close to the plane of the sky. We estimate a mass outflow rate along the ea...

  13. The inner mass distribution of late-type spiral galaxies from SAURON stellar kinematic maps

    CERN Document Server

    Kalinova, Veselina; Lyubenova, Mariya; Falcón-Barroso, Jesús; Colombo, Dario; Rosolowsky, Erik

    2016-01-01

    We infer the central mass distributions within 0.4-1.2 disc scale lengths of 18 late-type spiral galaxies using two different dynamical modelling approaches - the Asymmetric Drift Correction (ADC) and axisymmetric Jeans Anisotropic Multi-gaussian expansion (JAM) model. ADC adopts a thin disc assumption, whereas JAM does a full line-of-sight velocity integration. We use stellar kinematics maps obtained with the integral-field spectrograph SAURON to derive the corresponding circular velocity curves from the two models. To find their best-fit values, we apply Markov Chain Monte Carlo (MCMC) method. ADC and JAM modelling approaches are consistent within 5% uncertainty when the ordered motions are significant comparable to the random motions, i.e, $\\overline{v_{\\phi}}/\\sigma_R$ is locally greater than 1.5. Below this value, the ratio $v_\\mathrm{c,JAM}/v_\\mathrm{c,ADC}$ gradually increases with decreasing $\\overline{v_{\\phi}}/\\sigma_R$, reaching $v_\\mathrm{c,JAM}\\approx 2 \\times v_\\mathrm{c,ADC}$. Such conditions i...

  14. GMC Evolution in a Barred Spiral Galaxy with Star Formation and Thermal Feedback

    CERN Document Server

    Fujimoto, Yusuke; Tasker, Elizabeth J; Habe, Asao; Simpson, Christine M

    2016-01-01

    We explore the impact of star formation and thermal stellar feedback on the giant molecular cloud (GMC) population forming in a M83-type barred spiral galaxy. We compare three high-resolution simulations (1.5 pc cell size) with different star formation/feedback models: one with no star formation, one with star formation but no feedback, and one with star formation and thermal energy injection. We analyze the resulting population of clouds, finding that we can identify the same population of massive, virialized clouds and transient, low-surface density clouds found in our previous work (that did not include star formation or feedback). Star formation and feedback can affect the mix of clouds we identify. In particular, star formation alone simply converts dense cloud gas into stars with only a small change to the cloud populations, principally resulting in a slight decrease in the transient population. Feedback, however, has a stronger impact: while it is not generally sufficient to entirely destroy the clouds...

  15. High-resolution, 3D radiative transfer modeling : I. The grand-design spiral galaxy M51

    CERN Document Server

    De Looze, Ilse; Baes, Maarten; Bendo, George J; Cortese, Luca; Boquien, Médéric; Boselli, Alessandro; Camps, Peter; Cooray, Asantha; Cormier, Diane; Davies, Jon I; De Geyter, Gert; Hughes, Thomas M; Jones, Anthony P; Karczewski, Oskar L; Lebouteiller, Vianney; Lu, Nanyao; Madden, Suzanne C; Rémy-Ruyer, Aurélie; Spinoglio, Luigi; Smith, Matthew W L; Viaene, Sebastien; Wilson, Christine D

    2014-01-01

    Context: Dust reprocesses about half of the stellar radiation in galaxies. The thermal re-emission by dust of absorbed energy is considered driven merely by young stars and, consequently, often applied to trace the star formation rate in galaxies. Recent studies have argued that the old stellar population might anticipate a non-negligible fraction of the radiative dust heating. Aims: In this work, we aim to analyze the contribution of young (< 100 Myr) and old (~ 10 Gyr) stellar populations to radiative dust heating processes in the nearby grand-design spiral galaxy M51 using radiative transfer modeling. High-resolution 3D radiative transfer (RT) models are required to describe the complex morphologies of asymmetric spiral arms and clumpy star-forming regions and model the propagation of light through a dusty medium. Methods: In this paper, we present a new technique developed to model the radiative transfer effects in nearby face-on galaxies. We construct a high-resolution 3D radiative transfer model with...

  16. Two Populations of Old Star Clusters in the Spiral Galaxy M101 Based on HST/ACS Observations

    CERN Document Server

    Simanton, Lesley A; Whitmore, Bradley C

    2015-01-01

    We present a new photometric catalog of 326 candidate globular clusters (GCs) in the nearby spiral galaxy M101, selected from B, V, and I Hubble Space Telescope Advanced Camera for Surveys images. The luminosity function (LF) of these clusters has an unusually large number of faint sources compared with GCLFs in many other spiral galaxies. Accordingly, we separate and compare the properties of "bright" (M_V -6.5; one magnitude fainter than the expected GC peak) clusters within our sample. The LF of the bright clusters is well fit by a peaked distribution similar to those observed in the Milky Way (MW) and other galaxies. These bright clusters also have similar size (r_{eff}) and spatial distributions as MW GCs. The LF of the faint clusters, on the other hand, is well described by a power law, dN(L_V)/dL_V proportional to L_V^alpha with alpha = -2.6 plus or minus 0.3, similar to those observed for young and intermediate-age cluster systems in star forming galaxies. We find that the faint clusters have larger ...

  17. Spiral symmetry

    CERN Document Server

    Hargittai, Istvan

    1992-01-01

    From the tiny twisted biological molecules to the gargantuan curling arms of many galaxies, the physical world contains a startling repetition of spiral patterns. Today, researchers have a keen interest in identifying, measuring, and defining these patterns in scientific terms. Spirals play an important role in the growth processes of many biological forms and organisms. Also, through time, humans have imitated spiral motifs in their art forms, and invented new and unusual spirals which have no counterparts in the natural world. Therefore, one goal of this multiauthored book is to stress the c

  18. Accurate Distances to Important Spiral Galaxies: M63, M74, NGC 1291, NGC 4559, NGC 4625, and NGC 5398

    Science.gov (United States)

    McQuinn, Kristen. B. W.; Skillman, Evan D.; Dolphin, Andrew E.; Berg, Danielle; Kennicutt, Robert

    2017-08-01

    Accurate distances are fundamental for interpreting various measured properties of galaxies. Surprisingly, many of the best-studied spiral galaxies in the Local Volume have distance uncertainties that are much larger than can be achieved with modern observation techniques. Using Hubble Space Telescopeoptical imaging, we use the tip of the red giant branch method to measure the distances to six galaxies that are included in the Spitzer Infrared Nearby Galaxies Survey program and its offspring surveys. The sample includes M63, M74, NGC 1291, NGC 4559, NGC 4625, and NGC 5398. We compare our results with distances reported to these galaxies based on a variety of methods. Depending on the technique, there can be a wide range in published distances, particularly from the Tully-Fisher relation. In addition, differences between the planetary nebular luminosity function and surface brightness fluctuation techniques can vary between galaxies, suggesting inaccuracies that cannot be explained by systematics in the calibrations. Our distances improve upon previous results, as we use a well-calibrated, stable distance indicator, precision photometry in an optimally selected field of view, and a Bayesian maximum likelihood technique that reduces measurement uncertainties. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  19. The spatially resolved Kennicutt-Schmidt relation in the H I-dominated regions of spiral and dwarf irregular galaxies

    Science.gov (United States)

    Roychowdhury, Sambit; Huang, Mei-Ling; Kauffmann, Guinevere; Wang, Jing; Chengalur, Jayaram N.

    2015-06-01

    We study the Kennicutt-Schmidt relation between average star formation rate (SFR) and average cold gas surface density in the H I-dominated ISM of nearby spiral and dwarf irregular galaxies. We divide galaxies into grid cells varying from sub-kpc to tens of kpc in size. Grid-cell measurements of low SFRs using Hα emission can be biased and scatter may be introduced because of non-uniform sampling of the IMF or because of stochastically varying star formation. In order to alleviate these issues, we use far-ultraviolet emission to trace SFR, and we sum up the fluxes from different bins with the same gas surface density to calculate the average ΣSFR at a given value of Σgas. We study the resulting Kennicutt-Schmidt relation in 400 pc, 1 kpc and 10 kpc scale grids in nearby massive spirals and in 400 pc scale grids in nearby faint dwarf irregulars. We find a relation with a power-law slope of 1.5 in the H I-dominated regions for both kinds of galaxies. The relation is offset towards longer gas consumption time-scales compared to the molecular-hydrogen-dominated centres of spirals, but the offset is an order of magnitude less than that quoted by earlier studies. Our results lead to the surprising conclusion that conversion of gas to stars is independent of metallicity in the H I-dominated regions of star-forming galaxies. Our observed relations are better fit by a model of star formation based on thermal and hydrostatic equilibrium in the ISM, in which stellar heating and supernova feedback set the thermal and turbulent pressure.

  20. The spiral structure of the Galaxy revealed by CS sources and evidence for the 4:1 resonance

    CERN Document Server

    Lepine, J R D; Abraham, Zulema; Junqueira, T C; Mishurov, Yu N

    2010-01-01

    We present a map of the spiral structure of the Galaxy, as traced by molecular CS emission associated with IRAS sources which are believed to be compact HII regions. The CS line velocities are used to determine the kinematic distances of the sources, in order to investigate their distribution in the galactic plane. This allows us to use 870 objects to trace the arms, a number larger than that of previous studies based on classical HII regions. The distance ambiguity of the kinematic distances, when it exists, is solved by different procedures, including the latitude distribution and an analysis of the longitude-velocity diagram. The well defined spiral arms are seen to be confined inside the co-rotation radius, as is often the case in spiral galaxies. We identify a square-shaped sub-structure in the CS map with that predicted by stellar orbits at the 4:1 resonance (4 epicycle oscillations in one turn around the galactic center). The sub-structure is found at the expected radius, based on the known pattern rot...

  1. Non-Parametric Cell-Based Photometric Proxies for Galaxy Morphology: Methodology and Application to the Morphologically-Defined Star Formation -- Stellar Mass Relation of Spiral Galaxies in the Local Universe

    CERN Document Server

    Grootes, M W; Popescu, C C; Robotham, A S G; Seibert, M; Kelvin, L S

    2013-01-01

    (Abridged) We present a non-parametric cell-based method of selecting highly pure and largely complete samples of spiral galaxies using photometric and structural parameters as provided by standard photometric pipelines and simple shape fitting algorithms, demonstrably superior to commonly used proxies. Furthermore, we find structural parameters derived using passbands longwards of the $g$ band and linked to older stellar populations, especially the stellar mass surface density $\\mu_*$ and the $r$ band effective radius $r_e$, to perform at least equally well as parameters more traditionally linked to the identification of spirals by means of their young stellar populations. In particular the distinct bimodality in the parameter $\\mu_*$, consistent with expectations of different evolutionary paths for spirals and ellipticals, represents an often overlooked yet powerful parameter in differentiating between spiral and non-spiral/elliptical galaxies. We investigate the intrinsic specific star-formation rate - ste...

  2. Populations of High-Luminosity Density-Bounded HII Regions in Spiral Galaxies? Evidence and Implications

    Science.gov (United States)

    Beckman, J. E.; Rozas, M.; Zurita, A.; Watson, R. A.; Knapen, J. H.

    2000-01-01

    In this paper we present evidence that the H II regions of high luminosity in disk galaxies may be density bounded, so that a significant fraction of the ionizing photons emitted by their exciting OB stars escape from the regions. The key piece of evidence is the presence, in the Ha luminosity functions (LFs) of the populations of H iI regions, of glitches, local sharp peaks at an apparently invariant luminosity, defined as the Stromgren luminosity Lstr), LH(sub alpha) = Lstr = 10(sup 38.6) (+/- 10(sup 0.1)) erg/ s (no other peaks are found in any of the LFs) accompanying a steepening of slope for LH(sub alpha) greater than Lstr This behavior is readily explicable via a physical model whose basic premises are: (a) the transition at LH(sub alpha) = Lstr marks a change from essentially ionization bounding at low luminosities to density bounding at higher values, (b) for this to occur the law relating stellar mass in massive star-forming clouds to the mass of the placental cloud must be such that the ionizing photon flux produced within the cloud is a function which rises more steeply than the mass of the cloud. Supporting evidence for the hypothesis of this transition is also presented: measurements of the central surface brightnesses of H II regions for LH(sub alpha) less than Lstr are proportional to L(sup 1/3, sub H(sub alpha)), expected for ionization bounding, but show a sharp trend to a steeper dependence for LH(sub alpha) greater than Lstr, and the observed relation between the internal turbulence velocity parameter, sigma, and the luminosity, L, at high luminosities, can be well explained if these regions are density bounded. If confirmed, the density-bounding hypothesis would have a number of interesting implications. It would imply that the density-bounded regions were the main sources of the photons which ionize the diffuse gas in disk galaxies. Our estimates, based on the hypothesis, indicate that these regions emit sufficient Lyman continuum not only to

  3. The fundamental manifold of spiral galaxies: ordered versus random motions and the morphology dependence of the Tully-Fisher relation

    Science.gov (United States)

    Tonini, C.; Jones, D. H.; Mould, J.; Webster, R. L.; Danilovich, T.; Ozbilgen, S.

    2014-03-01

    We investigate the morphology dependence of the Tully-Fisher (TF) relation, and the expansion of the relation into a three-dimensional manifold defined by luminosity, total circular velocity and a third dynamical parameter, to fully characterize spiral galaxies across all morphological types. We use a full semi-analytic hierarchical model (based on Croton et al.), built on cosmological simulations of structure formation, to model galaxy evolution and build the theoretical TF relation. With this tool, we analyse a unique data set of galaxies for which we cross-match luminosity with total circular velocity and central velocity dispersion. We provide a theoretical framework to calculate such measurable quantities from hierarchical semi-analytic models. We establish the morphology dependence of the TF relation in both model and data. We analyse the dynamical properties of the model galaxies and determine that the parameter σ/VC, i.e. the ratio between random and total motions defined by velocity dispersion and circular velocity, accurately characterizes the varying slope of the TF relation for different model galaxy types. We apply these dynamical cuts to the observed galaxies and find indeed that such selection produces a differential slope of the TF relation. The TF slope in different ranges of σ/VC is consistent with that for the traditional photometric classification in Sa, Sb and Sc. We conclude that σ/VC is a good parameter to classify galaxy type, and we argue that such classification based on dynamics more closely mirrors the physical properties of the observed galaxies, compared to visual (photometric) classification. We also argue that dynamical classification is useful for samples where eye inspection is not reliable or impractical. We conclude that σ/VC is a suitable parameter to characterize the hierarchical assembly history that determines the disc-to-bulge ratio, and to expand the TF relation into a three-dimensional manifold, defined by luminosity

  4. M/L, Hα Rotation Curves, and H I Gas Measurements for 329 Nearby Cluster and Field Spirals. III. Evolution in Fundamental Galaxy Parameters

    Science.gov (United States)

    Vogt, Nicole P.; Haynes, Martha P.; Giovanelli, Riccardo; Herter, Terry

    2004-06-01

    We have conducted a study of optical and H I properties of spiral galaxies (size, luminosity, Hα flux distribution, circular velocity, H I gas mass) to investigate causes (e.g., nature vs. nurture) for variation within the cluster environment. We find H I-deficient cluster galaxies to be offset in fundamental plane space, with disk scale lengths decreased by a factor of 25%. This may be a relic of early galaxy formation, caused by the disk coalescing out of a smaller, denser halo (e.g., higher concentration index) or by truncation of the hot gas envelope due to the enhanced local density of neighbors, although we cannot completely rule out the effect of the gas stripping process. The spatial extent of Hα flux and the B-band radius also decreases, but only in early-type spirals, suggesting that gas removal is less efficient within steeper potential wells (or that stripped late-type spirals are quickly rendered unrecognizable). We find no significant trend in stellar mass-to-light ratios or circular velocities with H I gas content, morphological type, or clustercentric radius, for star-forming spiral galaxies throughout the clusters. These data support the findings of a companion paper that gas stripping promotes a rapid truncation of star formation across the disk and could be interpreted as weak support for dark matter domination over baryons in the inner regions of spiral galaxies.

  5. The spatially resolved Kennicutt-Schmidt relation in the HI dominated regions of spiral and dwarf irregular galaxies

    CERN Document Server

    Roychowdhury, Sambit; Kauffmann, Guinevere; Wang, Jing; Chengalur, Jayaram N

    2015-01-01

    We study the Kennicutt-Schmidt relation between average star formation rate and average cold gas surface density in the Hi dominated ISM of nearby spiral and dwarf irregular galaxies. We divide the galaxies into grid cells varying from sub-kpc to tens of kpc in size. Grid-cell measurements of low SFRs using H-alpha emission can be biased and scatter may be introduced because of non-uniform sampling of the IMF or because of stochastically varying star formation. In order to alleviate these issues, we use far-ultraviolet emission to trace SFR, and we sum up the fluxes from different bins with the same gas surface density to calculate the average $\\Sigma_{SFR}$ at a given value of $\\Sigma_{gas}$. We study the resulting Kennicutt-Schmidt relation in 400 pc, 1 kpc and 10 kpc scale grids in nearby massive spirals and in 400 pc scale grids in nearby faint dwarf irregulars. We find a relation with a power law slope of 1.5 in the HI-dominated regions for both kinds of galaxies. The relation is offset towards longer ga...

  6. Star Formation On Sub-kpc Scale Triggered By Non-linear Processes In Nearby Spiral Galaxies

    CERN Document Server

    Momose, Rieko; Kennicutt, Robert C; Egusa, Fumi; Calzetti, Daniela; Liu, Guilin; Meyer, Jennifer Donovan; Okumura, Sachiko K; Scoville, Nick Z; Sawada, Tsuyoshi; Kuno, Nario

    2013-01-01

    We report a super-linear correlation for the star formation law based on new CO($J$=1-0) data from the CARMA and NOBEYAMA Nearby-galaxies (CANON) CO survey. The sample includes 10 nearby spiral galaxies, in which structures at sub-kpc scales are spatially resolved. Combined with the star formation rate surface density traced by H$\\alpha$ and 24 $\\mu$m images, CO($J$=1-0) data provide a super-linear slope of $N$ = 1.3. The slope becomes even steeper ($N$ = 1.8) when the diffuse stellar and dust background emission is subtracted from the H$\\alpha$ and 24 $\\mu$m images. In contrast to the recent results with CO($J$=2-1) that found a constant star formation efficiency (SFE) in many spiral galaxies, these results suggest that the SFE is not independent of environment, but increases with molecular gas surface density. We suggest that the excitation of CO($J$=2-1) is likely enhanced in the regions with higher star formation and does not linearly trace the molecular gas mass. In addition, the diffuse emission contami...

  7. Anti-truncated stellar light profiles in the outer regions of STAGES spiral galaxies: bulge or disc related?

    CERN Document Server

    Maltby, David T; Gray, Meghan E; Aragón-Salamanca, Alfonso; Wolf, Christian

    2011-01-01

    We present a comparison of azimuthally averaged radial surface brightness mu(r) profiles and analytical bulge-disc decompositions (de Vaucouleurs, r^(1/4) bulge plus exponential disc) for spiral galaxies using Hubble Space Telescope/Advanced Camera for Surveys V-band imaging from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). In the established classification scheme, antitruncated mu(r) profiles (Type III) have a broken exponential disc with a shallower region beyond the break radius r_brk. The excess light at large radii (r > r_brk) can either be caused by an outer exponential disc (Type III-d) or an extended spheroidal component (Type III-s). Using our comparisons, we determine the contribution of bulge light at r > r_brk for a large sample of 78 (barred/unbarred, Sa-Sd) spiral galaxies with outer disc antitruncations (mu_brk > 24 mag arcsec^-2). In the majority of cases (~85 per cent), evidence indicates that excess light at r > r_brk is related to an outer shallow disc (Type III-d). Here, th...

  8. A test of arm-induced star formation in spiral galaxies from near-IR and H$\\alpha$ imaging

    CERN Document Server

    Seigar, M S; Seigar, Marc S.; James, Phil A.

    2002-01-01

    We have imaged a sample of 20 spiral galaxies in H$\\alpha$ and in the near-infrared K band (2.2 um), in order to determine the location and strength of star formation in these objects with respect to perturbations in the old stellar population. We have found that star formation rates are significantly enhanced in the vicinity of K band arms. We have also found that this enhancement in star formation rate in arm regions correlates well with a quantity that measures the relative strengths of shocks in arms. Assuming that the K band light is dominated by emission from the old stellar population, this shows that density waves trigger star formation in the vicinity of spiral arms.

  9. The VIRUS-P Exploration of Nearby Spiral Galaxies (VENGA): Spatially Resolved Gas-Phase Metallicity Distributions in Barred and Unbarred Spirals

    CERN Document Server

    Kaplan, Kyle F; Kewley, Lisa; Blanc, Guillermo A; Weinzirl, Tim; Song, Mimi; Drory, Niv; Luo, Rongxin; Bosch, Remco C E van den

    2016-01-01

    We present a study of the excitation conditions and metallicity of ionized gas ($Z_{\\rm gas}$) in eight nearby barred and unbarred spiral galaxies from the VIRUS-P Exploration of Nearby Galaxies (VENGA) survey, which provides high spatial sampling and resolution (median $\\sim$ 387 pc), large coverage from the bulge to outer disc, broad wavelength range (3600-6800 \\AA{}), and medium spectral resolution ($\\sim$ 120 km s$^{-1}$ at 5000 \\AA{}). Our results are: (1) We present high resolution gas excitation maps to differentiate between regions with excitation typical of Seyfert, LINER, or recent star formation. We find LINER-type excitation at large distances (3-10 kpc) from the centre, and associate this excitation with diffuse ionized gas (DIG). (2) After excluding spaxels dominated by Seyfert, LINER, or DIG, we produce maps with the best spatial resolution and sampling to date of the ionization parameter $q$, star formation rate, and $Z_{\\rm gas}$ using common strong line diagnostics. We find that isolated bar...

  10. Time Variability and Luminosity of X-ray Sources of Face-on Spiral Galaxy NGC 1232

    Science.gov (United States)

    Cantua, Oscar; Rucas, Tyler; Singh, Pranjal; Schlegel, Eric M.

    2017-01-01

    The ACIS detector (Advanced CCD Imaging Spectrometer) onboard the Chandra X-ray Observatory has imaged the face-on spiral NGC 1232 over six epochs for a total exposure of ~250 ksec. We describe each observation as well as the merged data set. Each exposure contains ~50 individual sources. We focus on the time variability and luminosity distributions of the sources. We also describe our search for diffuse emission as well as our search for evidence for a reported collision with a dwarf galaxy. Finally, we compare the merged data set and the detected sources with other wavebands.

  11. Infrared Survey of Pulsating Giant Stars in the Spiral Galaxy M33: Dust Production, Star Formation History, and Galactic Structure

    CERN Document Server

    Javadi, Atefeh; Mirtorabi, Mohammad Taghi

    2011-01-01

    We introduce a near-IR monitoring campaign of the Local Group spiral galaxy M33, carried out with the UK IR Telescope (UKIRT). The pulsating giant stars are identified and their distributions are used to derive the star formation rate as a function of age. We here present the star formation history for the central square kiloparsec. These stars are also important dust factories; we measure their dust production rates from a combination of our data with Spitzer Space Telescope mid-IR photometry.

  12. Gas-phase Oxygen Abundances and Radial Metallicity Gradients in the Two nearby Spiral Galaxies NGC 7793 and NGC 4945

    Science.gov (United States)

    Stanghellini, Letizia; Magrini, Laura; Casasola, Viviana

    2015-10-01

    Gas-phase abundances in H ii regions of two spiral galaxies, NGC 7793 and NGC 4945, have been studied to determine their radial metallicity gradients. We used the strong-line method to derive oxygen abundances from spectra acquired with GMOS-S, the multi-object spectrograph on the 8 m Gemini South telescope. We found that NGC 7793 has a well-defined gas-phase radial oxygen gradient of -0.321 ± 0.112 dex {R}25-1 (or -0.054 ± 0.019 dex kpc-1) in the galactocentric range 0.17 < RG/R25 < 0.82, not dissimilar from gradients calculated with direct abundance methods in galaxies of similar mass and morphology. We also determined a shallow radial oxygen gradient in NGC 4945, -0.253 ± 0.149 dex {R}25-1 (or -0.019 ± 0.011 dex kpc-1) for 0.04 < RG/R25 < 0.51, where the larger relative uncertainty derives mostly from the larger inclination of this galaxy. NGC 7793 and NGC 4945 have been selected for this study because they are similar, in mass and morphology, to M33 and the Milky Way, respectively. Since at zeroth order we expect the radial metallicity gradients to depend on mass and galaxy type, we compared our galaxies in the framework of radial metallicity models best suited for M33 and the Galaxy. We found a good agreement between M33 and NGC 7793, pointing toward similar evolution for the two galaxies. We notice instead differences between NGC 4945 and the radial metallicity gradient model that best fits the Milky Way. We found that these differences are likely related to the presence of an active galactic nucleus combined with a bar in the central regions of NGC 4945, and to its interacting environment.

  13. Simulating Galaxies: Investigating Spiral Pitch Angle and the Efficiency of Radial Mixing

    Science.gov (United States)

    Lifset, Noah; Barbano, Luke; Daniel, Kathryne J.

    2017-01-01

    Radial mixing refers to the permanent rearrangement of orbital angular momenta in a galactic disk due to interactions with transient spiral arms. A star is subject to this dynamical process when it is temporarily in a trapped orbit between the spiral arms near the corotation radius. The purpose of this research was to numerically investigate how spiral shape affects the efficiency of radial mixing. This was done by designing an orbital integrator that numerically simulated the motion of test particles in a 2D disk potential that had a steady spiral pattern and was populated using a Monte Carlo simulation. Several realizations of N=10^4 orbits were simulated and analyzed using the open source, distributed computing service Open Science Grid (OSG). The results were in agreement with previous theoretical predictions, and preliminary analysis of the data indicates that the RMS change in orbital angular momentum for stars in trapped orbits depends on spiral arm pitch angle.

  14. Spirality: A Noval Way to Measure Spiral Arm Pitch Angle

    Science.gov (United States)

    Shields, Douglas; Arkansas Galaxy Evolution Survey

    2017-01-01

    We present the MATLAB code Spirality, a novel method for measuring spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Computation time is typically on the order of 2 minutes per galaxy, assuming 8 GB of working memory. We tested the code using 117 synthetic spiral images with known pitches, varying both the spiral properties and the input parameters. The code yielded correct results for all synthetic spirals with galaxy-like properties. We also compared the code’s results to two-dimensional Fast Fourier Transform (2DFFT) measurements for the sample of nearby galaxies defined by DMS PPak. Spirality’s error bars overlapped 2DFFT’s error bars for 26 of the 30 galaxies. The two methods’ agreement correlates strongly with galaxy radius in pixels and also with i-band magnitude, but not with redshift, a result that is consistent with at least some galaxies’ spiral structure being fully formed by z=1.2, beyond which there are few galaxies in our sample. We also analyze apparent spiral structure of three galaxies beyond z=2. The Spirality code package also includes GenSpiral, which produces FITS images of synthetic spirals, and SpiralArmCount, which uses a one-dimensional Fast Fourier Transform to count the spiral arms of a galaxy after its pitch is determined.

  15. Two Populations of Old Star Clusters in the Spiral Galaxy M101 Based on HST/ACS Observations

    Science.gov (United States)

    Simanton, Lesley A.; Chandar, Rupali; Whitmore, Bradley C.

    2015-06-01

    We present a new photometric catalog of 326 candidate globular clusters (GCs) in the nearby spiral galaxy M101, selected from B, V, and I Hubble Space Telescope Advanced Camera for Surveys images. The luminosity function (LF) of these clusters has an unusually large number of faint sources compared with GCLFs in many other spiral galaxies. Accordingly, we separate and compare the properties of “bright” ({{M}V}\\lt -6.5) versus “faint” ({{M}V}\\gt -6.5; one magnitude fainter than the expected GC peak) clusters within our sample. The LF of the bright clusters is well fit by a peaked distribution similar to those observed in the Milky Way (MW) and other galaxies. These bright clusters also have similar size (reff) and spatial distributions as MW GCs. The LF of the faint clusters, on the other hand, is well described by a power law, dN({{L}V})/d{{L}V}\\propto LVα with α =-2.6+/- 0.3, similar to those observed for young and intermediate-age cluster systems in star forming galaxies. We find that the faint clusters have larger typical reff than the bright clusters, and have a flatter surface density profile, being more evenly distributed, as we would expect for clusters associated with the disk. We use the shape of the LF and predictions for mass-loss driven by two-body relaxation to constrain the ages of the faint clusters. Our results are consistent with two populations of old star clusters in M101: a bright population of halo clusters and a fainter, possibly younger, population of old disk clusters.

  16. Dust energy balance study of two edge-on spiral galaxies in the Herschel-ATLAS survey

    CERN Document Server

    De Geyter, Gert; De Looze, Ilse; Bendo, George J; Bourne, Nathan; Camps, Peter; Cooray, Asantha; De Zotti, Gianfranco; Dunne, Loretta; Dye, Simon; Eales, Steve A; Fritz, Jacopo; Furlanetto, Cristina; Gentile, Gianfranco; Hughes, Thomas M; Ivison, Rob J; Maddox, Steve J; Michałowski, Michał J; Smith, Matthew W L; Valiante, Elisabetta; Viaene, Sébastien

    2015-01-01

    Interstellar dust in galaxies can be traced either through its extinction effects on the star light, or through its thermal emission at infrared wavelengths. Recent radiative transfer studies of several nearby edge-on galaxies have found an apparent inconsistency in the dust energy balance: the radiative transfer models that successfully explain the optical extinction underestimate the observed fluxes by an average factor of three. We investigate the dust energy balance for IC4225 and NGC5166, two edge-on spiral galaxies observed by the Herschel Space Observatory in the frame of the H-ATLAS survey. We start from models which were constrained from optical data and extend them to construct the entire spectral energy distribution of our galaxies. These predicted values are subsequently compared to the observed far-infrared fluxes. We find that including a young stellar population in the modelling is necessary as it plays a non-negligible part in the heating of the dust grains. While the modelling approach for bo...

  17. The impact of bars on the mid-infrared dust emission of spiral galaxies global and circumnuclear properties

    CERN Document Server

    Roussel, H; Vigroux, L; Bosma, A; Bonoli, C; Gallais, P; Hawarden, T G; Madden, S; Mazzei, P

    2001-01-01

    We study the mid-infrared properties of a sample of 69 nearby spiral galaxies, selected to avoid Seyfert activity contributing a significant fraction of the central energetics, or strong tidal interaction, and to have normal infrared luminosities. These observations were obtained with ISOCAM, which provides an angular resolution of the order of 10 arcsec (half-power diameter of the point spread function) and low-resolution spectro-imaging information. Between 5 and 18 microns, we mainly observe two dust phases, aromatic infrared bands and very small grains, both out of thermal equilibrium. On this sample, we show that the global F15/F7 colors of galaxies are very uniform, the only increase being found in early-type strongly barred galaxies, consistent with previous IRAS studies. The F15/F7 excesses are unambiguously due to galactic central regions where bar-induced starbursts occur. However, the existence of strongly barred early-type galaxies with normal circumnuclear colors indicates that the relationship b...

  18. Internal kinematics of spiral galaxies in distant clusters - III. Velocity fields from FORS2/MXU spectroscopy

    NARCIS (Netherlands)

    Kutdemir, E.; Ziegler, B. L.; Peletier, R. F.; Da Rocha, C.; Kronberger, T.; Kapferer, W.; Schindler, S.; Boehm, A.; Jaeger, K.; Kuntschner, H.; Verdugo, M.

    2008-01-01

    Context. We continue our investigation on how the cluster environment affects the evolution of galaxies. Aims. By examining both galaxy structure and internal kinematics of cluster galaxies at lookback times of similar to 5 Gyr we study the nature and impact of possible interactions at the peak epoc

  19. Internal kinematics of spiral galaxies in distant clusters - III. Velocity fields from FORS2/MXU spectroscopy

    NARCIS (Netherlands)

    Kutdemir, E.; Ziegler, B. L.; Peletier, R. F.; Da Rocha, C.; Kronberger, T.; Kapferer, W.; Schindler, S.; Boehm, A.; Jaeger, K.; Kuntschner, H.; Verdugo, M.

    2008-01-01

    Context. We continue our investigation on how the cluster environment affects the evolution of galaxies. Aims. By examining both galaxy structure and internal kinematics of cluster galaxies at lookback times of similar to 5 Gyr we study the nature and impact of possible interactions at the peak epoc

  20. Mortality and dust expulsion in early phases of stellar clusters. Evidence from NIR photometry of nearby, spiral galaxies

    CERN Document Server

    Grosboel, P

    2013-01-01

    It is often argued that young stellar clusters suffer a significant infant mortality that is partly related to the expulsion of dust and gas in their early phases caused by radiation pressure from hot stars and supernovae. Near-infrared (J-K)-Mk diagrams of young stellar clusters in nearby spiral galaxies show a bi-modal distribution that is consistent with a fast decline of their intrinsic extinction at an early epoch. The distinct features in the color-magnitude diagrams (CMD) and the fast change of colors for the youngest clusters allow us to place constraints on their early evolutionary phases, including the time scale for the decreasing extinction caused for instance by gas and dust expulsion. Monte Carlo simulations of cluster populations were performed using the power-law distribution function g(M, t) ~ M^a t^gam. Integrated colors were computed from Starburst99 models. The simulated near-infrared CMD were compared with those observed for six grand-design, spiral galaxies using statistical goodness-of-...

  1. The mass dependence of star formation histories in barred spiral galaxies

    Science.gov (United States)

    Carles, Christian; Martel, Hugo; Ellison, Sara L.; Kawata, Daisuke

    2016-11-01

    We performed a series of 29 gas dynamical simulations of disc galaxies, barred and unbarred, with various stellar masses, to study the impact of the bar on star formation history. Unbarred galaxies evolve very smoothly, with a star formation rate (SFR) that varies by at most a factor of 3 over a period of 2 Gyr. The evolution of barred galaxies is much more irregular, especially at high stellar masses. In these galaxies, the bar drives a substantial amount of gas towards the centre, resulting in a high SFR, and producing a starburst in the most massive galaxies. Most of the gas is converted into stars, and gas exhaustion leads to a rapid drop of star formation after the starburst. In massive barred galaxies (stellar mass M_{ast }>2{×} 10^{10} {M_{⊙}}) the large amount of gas funnelled towards the centre is completely consumed by the starburst, while in lower mass barred galaxies it is only partially consumed. Gas concentration is thus higher in lower mass barred galaxies than it is in higher mass ones. Even though unbarred galaxies funnelled less gas towards their centre, the lower SFR allows this gas to accumulate. At late times, the star formation efficiency is higher in barred galaxies than unbarred ones, enabling these galaxies to maintain a higher SFR with a smaller gas supply. Several properties, such as the global SFR, central SFR, or central gas concentration, vary monotonically with time for unbarred galaxies, but not for barred galaxies. Therefore one must be careful when comparing barred and unbarred galaxies that share one observational property, since these galaxies might be at very different stages of their respective evolution.

  2. Development of a hot intergalactic medium in spiral-rich galaxy groups: the example of HCG 16

    Science.gov (United States)

    Vrtilek, Jan M.; O'Sullivan, Ewan; David, Laurence P.; Giacintucci, Simona; Zezas, Andreas; Mamon, Gary; Ponman, Trevor J; Raychaudhury, Somak

    2014-08-01

    Galaxy groups provide the environment in which the majority of galaxies evolve, with low velocity dispersions and small galaxy separations that are conducive to tidal interactions and mergers between group members. X-ray observations reveal the frequent presence of hot gas in groups, with larger quantities linked to early-type galaxies, whereas cold gas is common in spiral-dominated groups. Clarification of the origin and role of the hot medium is central to the understanding of the evolution of the galaxy population and of all phases of the IGM.We here report on the nuclear activity, star formation and the high luminosity X-ray binary populations of the spiral-dominated, likely not yet virialized, group HCG 16, as well as on its intra-group medium, based principally on deep (150 ks) Chandra X-ray observations of the group, as well as new Giant Metrewave Radio Telescope (GMRT) 610 MHz radio data. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify what may be a previously unrecognized nuclear source in NGC 838; all are variable. NGC 838 and NGC 839 are both starburst-dominated systems, with galactic superwinds that show X-ray and radio evidence of IGM interaction, but only weak nuclear activity; NGC 848 is also dominated by emission from its starburst.We confirm the existence of a faint, extended low-temperature (0.3 keV) intra-group medium, a subject of some uncertainty in earlier studies. The diffuse emission is strongest in a ridge linking the four principal galaxies, and is at least partly coincident with a large-scale HI tidal filament, indicating that the IGM in the inner part of the group is highly multi-phase. We conclude that starburst winds and shock-heating of stripped HI may play an important role in the early stages of IGM formation, with galactic winds contributing 20-40% of the observed hot gas in the system.

  3. The Universal Rotation Curve of Spiral Galaxies: I. the Dark Matter Connection

    OpenAIRE

    Persic, M.; Salucci, P.; Stel, F.

    1995-01-01

    We use a homogeneous sample of about 1100 rotation curves (RCs) and relative surface photometry to investigate (out to 2 optical radii and over 6 mag) the main mass structure properties of spirals. We confirm the strong dependence on luminosity for both the profile and the amplitude of RCs. Spiral RCs show the striking feature that a single parameter, the luminosity, dictates the rotation velocity at any radius for all objects, so revealing the existence of a universal RC. At high luminosity,...

  4. Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?

    CERN Document Server

    de Souza, R S; Krone-Martins, A; Cameron, E; Coelho, P; Hattab, M W; de Val-Borro, M; Hilbe, J M; Elliott, J; Hagen, A

    2016-01-01

    We developed a hierarchical Bayesian model (HBM) to investigate how the presence of Seyfert activity relates to their environment, herein represented by the galaxy cluster mass, $M_{200}$, and the normalized cluster centric distance, $r/r_{200}$. We achieved this by constructing an unbiased sample of galaxies from the Sloan Digital Sky Survey, with morphological classifications provided by the Galaxy Zoo Project. A propensity score matching approach is introduced to control for the effects of confounding variables: stellar mass, galaxy colour, and star formation rate. The connection between Seyfert-activity and environmental properties in the de-biased sample is modelled within a HBM framework using the so-called logistic regression technique, suitable for the analysis of binary data (e.g., whether or not a galaxy hosts an AGN). Unlike standard ordinary least square fitting methods, our methodology naturally allows modelling the probability of Seyfert-AGN activity in galaxies on their natural scale, i.e. as a...

  5. Cold gas kinematics in an L(*) spiral Galaxy at z=0.437 : The nature of damped Lyman-alpha absorbers

    NARCIS (Netherlands)

    Briggs, FH; de Bruyn, AG; Vermeulen, RC

    2001-01-01

    Westerbork Radio Synthesis Telescope observations of the redshifted 21 cm line absorber against the z(em) = 0.871 double lobed quasar 3C 196 show that the intervening absorber is an L approximate toL(*) spiral galaxy (3C 196-G1) and that the absorbing layer of cold gas extends to radii of at least 3

  6. Possible Local Spiral Counterparts to Compact Blue Galaxies at Intermediate Redshift

    CERN Document Server

    Barton, E J; Barton, Elizabeth J.; Zee, Liese van

    2001-01-01

    We identify nearby disk galaxies with optical structural parameters similar to those of intermediate-redshift compact blue galaxies. By comparing HI and optical emission-line widths, we show that the optical widths substantially underestimate the true kinematic widths of the local galaxies. By analogy, optical emission-line widths may underrepresent the masses of intermediate-z compact objects. For the nearby galaxies, the compact blue morphology is the result of tidally-triggered central star formation: we argue that interactions and minor mergers may cause apparently compact morphology at higher redshift.

  7. Dark and luminous matter in the NGC 3992 group of galaxies, I. The large barred spiral NGC 3992

    CERN Document Server

    Bottema, R; Bottema, Roelof; Verheijen, Marc A.W.

    2002-01-01

    Detailed neutral hydrogen observations have been obtained of the large barred spiral galaxy NGC 3992 and its three small companion galaxies, UGC 6923, UGC 6940, and UGC 6969. For the main galaxy, the HI distribution is regular with a low level radial extension outside the stellar disc. However, at exactly the region of the bar, there is a pronounced central HI hole in the gas distribution. Likely gas has been transported inwards by the bar and because of the emptyness of the hole no large accretion events can have happened in recent galactic times. The gas kinematics is very regular and it is demonstrated that the influence of the bar potential on the velocity field is negligible. A precise and extended rotation curve has been derived showing some distinct features which can be explained by the non-exponential radial light distribution of NGC 3992. The decomposition of the rotation curve gives a slight preference for a sub maximal disc, though a range of disc contributions, up to a maximum disc situation fits...

  8. A Luminous X-ray Flare From The Nucleus of The Dormant Bulgeless Spiral Galaxy NGC 247

    CERN Document Server

    Feng, Hua; Kaaret, Philip; Tao, Lian; Yamaoka, Kazutaka; Zhang, Shuo; Grisé, Fabien

    2015-01-01

    NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity up to 2*10^39 erg/s in the 0.3-10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3-4 keV, no pulsations on timescales longer than 150 ms, and a flat power spectrum consistent with Poisson noise from 1 mHz to nearly 10 Hz. Follow-up observations with Swift detected a second flux peak followed by a luminosity drop by factor of almost 20. The spectral and temporal behaviors of the nuclear source are well consistent with the scenario that the flare was due to an outburst of a low-mass X-ray binary that contains a stellar-mass black hole emitting near its Eddington limit at the peak. However, it cannot be ruled out that the sudden brightening in the nucleus was due to a...

  9. The DiskMass Survey. VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy

    CERN Document Server

    Martinsson, Thomas P K; Westfall, Kyle B; Bershady, Matthew A; Schechtman-Rook, Andrew; Andersen, David R; Swaters, Rob A

    2013-01-01

    We present ionized-gas (OIII) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as much as three disk scale lengths (h_R). These data have been derived from PPak IFU spectroscopy (4980-5370A), observed at a mean resolution of R=7700 (sigma_inst=17km/s). These data are a fundamental product of our survey and will be used in companion papers to, e.g., derive the detailed (baryonic+dark) mass budget of each galaxy in our sample. Our presentation provides a comprehensive description of the observing strategy, data reduction, and analysis. Along with a clear presentation of the data, we demonstrate: (1) The OIII and stellar rotation curves exhibit a clear signature of asymmetric drift with a rotation difference that is 11% of the maximum rotation speed of the galaxy disk, comparable to measurements in the solar neighborhood in the Milky Way. (2) The e-folding length of the stellar velocity dispersion is two times h_R on average, as expected for a disk with a ...

  10. Revealing the nature of the ULX and X-ray population of the spiral galaxy NGC 4088

    CERN Document Server

    Mezcua, M; Gladstone, J C; Farrell, S A; Soria, R

    2014-01-01

    We present the first \\textit{Chandra} and \\textit{Swift} X-ray study of the spiral galaxy NGC\\,4088 and its ultraluminous X-ray source (ULX N4088--X1). We also report very long baseline interferometry (VLBI) observations at 1.6 and 5 GHz performed quasi-simultaneously with the \\textit{Swift} and \\textit{Chandra} observations, respectively. Fifteen X-ray sources are detected by \\textit{Chandra} within the D25 ellipse of NGC\\,4088, from which we derive the X-ray luminosity function (XLF) of this galaxy. We find the XLF is very similar to those of star-forming galaxies and estimate a star-formation rate of 4.5 $M_{\\odot}$ yr$^{-1}$. The \\textit{Chandra} detection of the ULX yields its most accurate X-ray position, which is spatially coincident with compact radio emission at 1.6 GHz. The ULX \\textit{Chandra} X-ray luminosity, $L_\\mathrm{0.2-10.0 keV} = 3.4\\ \\times$ 10$^{39}$ erg s$^{-1}$, indicates that N4088--X1 could be located at the high-luminosity end of the high-mass X-ray binary (HMXB) population of NGC\\,4...

  11. Gas-phase oxygen abundances and radial metallicity gradients in the two nearby spiral galaxies NGC7793 and NGC4945

    CERN Document Server

    Stanghellini, Letizia; Casasola, Viviana

    2015-01-01

    Gas-phase abundances in HII regions of two spiral galaxies, NGC7793 and NGC4945, have been studied to determine their radial metallicity gradients. We used the strong-line method to derive oxygen abundances from spectra acquired with GMOS-S, the multi-object spectrograph on the 8m- Gemini South telescope. We found that NGC7793 has a well-defined gas-phase radial oxygen gradient of -0.321 $\\pm$ 0.112 dex R$_{\\rm 25}^{-1}$ (or -0.054 $\\pm$ 0.019 dex kpc$^{-1}$) in the galactocentric range 0.17$<$R$_{\\rm G}$/R$_{\\rm 25}$ $<$ 0.82, not dissimilar from gradients calculated with direct abundance methods in galaxies of similar mass and morphology. We also determined a shallow radial oxygen gradient in NGC4945, -0.253 $\\pm$ 0.149 dex R$_{\\rm 25}^{-1}$ (or -0.019 $\\pm$ 0.011 dex kpc$^{-1}$) for 0.04$<$R$_{\\rm G}$/R$_{\\rm 25}$ $<$ 0.51, where the larger relative uncertainty derives mostly from the larger inclination of this galaxy. NGC7793 and NGC4945 have been selected for this study because they are simil...

  12. Integral-Field Stellar and Ionized Gas Kinematics of Peculiar Virgo Cluster Spiral Galaxies

    CERN Document Server

    Cortés, J R; Hardy, E

    2014-01-01

    We present the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies observed with the DensePak Integral Field Unit at the WIYN 3.5-meter telescope, to seek kinematic evidence that these galaxies have experienced gravitational interactions or gas stripping. 2-Dimensional maps of the stellar velocity $V$, and stellar velocity dispersion $\\sigma$ and the ionized gas velocity (H$\\beta$ and/or [\\ion{O}{3}]) are presented for galaxies in the sample. The stellar rotation curves and velocity dispersion profiles are determined for 13 galaxies, and the ionized gas rotation curves are determined for 6 galaxies. Misalignments between the optical and kinematical major axis are found in several galaxies. While in some cases this is due to a bar, in other cases it seems associated with a gravitational interaction or ongoing ram pressure stripping. Non-circular gas motions are found in nine galaxies, with various causes including bars, nuclear outflows, or gravitational disturbances. Several galaxi...

  13. The Mass Dependence of Star Formation Histories in Barred Spiral Galaxies

    CERN Document Server

    Carles, Christian; Ellison, Sara L; Kawata, Daisuke

    2016-01-01

    We performed a series of 29 gasdynamical simulations of disc galaxies, barred and unbarred, with various stellar masses, to study the impact of the bar on star formation history. Unbarred galaxies evolve very smoothly, with a star formation rate (SFR) that varies by at most a factor of three over a period of 2 Gyr. The evolution of barred galaxies is much more irregular, especially at high stellar masses. In these galaxies, the bar drives a substantial amount of gas toward the centre, resulting in a high SFR, and producing a starburst in the most massive galaxies. Most of the gas is converted into stars, and gas exhaustion leads to a rapid drop of star formation after the starburst. In massive barred galaxies (stellar mass M* > 2x10^10 Msun) the large amount of gas funnelled toward the centre is completely consumed by the starburst, while in lower-mass barred galaxies it is only partially consumed. Gas concentration is thus higher in lower-mass barred galaxies than it is in higher-mass ones. Even though unbar...

  14. Discovery of ultra-compact nuclear rings in three spiral galaxies

    CERN Document Server

    Comerón, S; Beckman, J E; Shlosman, I

    2007-01-01

    Ring-shaped morphologies of nuclear star-forming regions within the central 40-200 pc of disk galaxies have been barely resolved so far in three composite Sy2 nuclei, the Sy2 Circinus galaxy and in three non-AGN galaxies. Such morphologies resemble those of the standard 1 kpc-size nuclear rings that lie in the inner Lindblad resonance regions of disk galaxies and, if they have a similar origin, represent recent radial gas inflows tantalisingly close to the central supermassive black holes. We aim to identify the population of such ultra-compact nuclear rings (UCNRs) and study their properties in relation to those of the host galaxies. From archival Hubble Space Telescope UV and Halpha images and from dust structure maps of the circumnuclear regions in nearby galaxies, we analyse the morphology of the star formation and dust, specifically searching for ring structures on the smallest observable scales. In a sample of 38 galaxies studied, we have detected a total of four new UCNRs, 30-130 pc in radius, in three...

  15. Globular Cluster Systems of Spiral and S0 Galaxies: Results from WIYN Imaging of NGC1023, NGC1055, NGC7332 and NGC7339

    CERN Document Server

    Young, Michael D; Rhode, Katherine L

    2012-01-01

    We present results from a study of the globular cluster (GC) systems of four spiral and S0 galaxies imaged as part of an ongoing wide-field survey of the GC systems of giant galaxies. The target galaxies -- the SB0 galaxy NGC1023, the SBb galaxy NGC1055, and an isolated pair comprised of the Sbc galaxy NGC7339 and the S0 galaxy NGC7332 -- were observed in BVR filters with the WIYN 3.5-m telescope and Minimosaic camera. For two of the galaxies, we combined the WIYN imaging with previously-published data from the Hubble Space Telescope and the Keck Observatory to help characterize the GC distribution in the central few kiloparsecs. We determine the radial distribution (surface density of GCs versus projected radius) of each galaxy's GC system and use it to calculate the total number of GCs (N_GC). We find N_GC = 490+/-30, 210+/-40, 175+/-15, and 75+/-10 for NGC1023, NGC1055, NGC7332, and NGC7339, respectively. We also calculate the GC specific frequency (N_GC normalized by host galaxy luminosity or mass) and fi...

  16. Multiple minor mergers: formation of elliptical galaxies and constraints for the growth of spiral disks

    CERN Document Server

    Bournaud, Frederic; Combes, Francoise

    2007-01-01

    Multiple, sequential mergers are unavoidable in the hierarchical build-up picture of galaxies, in particular for the minor mergers that are frequent and highly likely to have occured several times for most present-day galaxies. However the effect of repeated minor mergers on galactic structure and evolution has not been studied systematically so far. In this paper, we present a numerical study of multiple, subsequent, minor galaxy mergers, with various mass ratios ranging from 4:1 to 50:1. The N-body simulations include gas dynamics and star formation. We study the morphological and kinematical properties of the remnants, and show that several so-called "minor" mergers can lead to the formation of elliptical-like galaxies, that have global morphological and kinematical properties similar to that observed in real elliptical galaxies. The properties of these systems are compared with that of elliptical galaxies produced by the standard scenario of one single major merger. We thus show that repeated minor merger...

  17. Molecular gas in spiral galaxies a new warm phase at large galactocentric distances?

    CERN Document Server

    Papadopoulos, P P; Viti, S

    2002-01-01

    There is now strong evidence suggesting that the 12CO J = 1-0 transition, widely used to trace H2 gas, significantly underestimates its mass in metal-poor regions. In spiral disks such regions are found in large galactocentric distances where we show that any unaccounted H2 gas phase is likely to be diffuse (~5-20 cm^-3) and warmer (T(kin) ~ 50-100 K) than the cool (T(kin) ~ 15-20 K) CO-luminous one. Moreover we find that a high value of the H2 formation rate on grains, suggested by recent observational work, can compensate for the reduction of the available grain surface in the metal-poor part of typical galactic disks and thus enhance this CO-poor H2 component which may be contributing significantly to the mass and pressure of spiral disks beyond their optical radius.

  18. DISTRIBUTION OF SPIRAL GALAXIES ON VIEWING ANGLES%旋涡星系随倾角的分布

    Institute of Scientific and Technical Information of China (English)

    马骏; 宋国玄; 束成钢

    2000-01-01

    This paper presents the normalized inclination distributions for the spiral galaxies in RC3.The results show that,except for the bin of 81°~90°,in which the apparent minor isophotal diameters that are used to obtain the inclinations,are affected by the central bulges,the distributions for Sa,Sab,Scd and Sd are well consistent with those from the Monte-Carlo simulation of random inclinations within 3σ,and Sb and Sbc almost,but Sc is different.One reason that the difference between the real distribution and the Monte-Carlo simulation distribution for Sc may be that,some quite inclined spirals,the arms of which are inherently loosely wound on the galactic plane and should be classified to Sc galaxies,have been incorrectly classified to the earlier ones,because the tightness of spiral arms,which is one of the criteria of the Hubble classification in RC3,is different between on the galactic plane and on the tangent plane of the celestial sphere.Our result also implies that there might exist biases in the luminosity functions of individual Hubble types if spiral galaxies are only classified visually.%研究了RC3星系表中旋涡星系随倾角的分布.结果表明:在0°~80°之间,Sa,Sab,Scd和Sd星系随倾角的实际分布与Monte-Carlo随机分布在3σ内吻合较好;对Sb和Sbc星系几乎吻合;但对Sc星系却相差甚远.由以上的结果分析可知:在RC3星系表中,一些较侧向的旋涡星系,等光视短轴的值受核球的影响较大;同时,Sc星系的实际分布与Monte-Carlo随机分布相差甚远的一个原因可能是由于Hubble分类本身引起的,因为Hubble分类是在星系图像上进行,而旋臂的缠卷松紧程度却受倾角的影响.这样,一些较侧向的Sc星系就会被错分类到早型星系中.结果还直接表明:如果星系分类只是在图像上进行,则各类星系的光度函数就会出现偏差.

  19. First results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low Mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    CERN Document Server

    Carlin, Jeffrey L; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F; Brodie, Jean P; Crnojević, Denija; Forbes, Duncan A; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H G; Romanowsky, Aaron J; Strader, Jay

    2016-01-01

    We report the discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep imaging with Subaru/Hyper Suprime-Cam. MADCASH J074238+652501-dw lies $\\sim$35 kpc in projection from NGC 2403, a dwarf spiral galaxy at $D$$\\approx$3.2 Mpc. This new dwarf has $M_{g} = -7.4\\pm0.4$ and a half-light radius of $168\\pm70$ pc, at the calculated distance of $3.39\\pm0.41$ Mpc. The color-magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low luminosity dwarfs in the Local Group. The lack of either detected HI gas ($M_{\\rm HI}/L_{V} < 0.69 M_\\odot/L_\\odot$, based on Green Bank Telescope observations) or $GALEX$ NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey, which is conducting a census of the stellar substructure and faint satellites in the halos...

  20. Long-slit spectral observations and stellar mass-to-light ratio of spiral galaxy UGC11919

    CERN Document Server

    Saburova, A; Uklein, R; Katkov, I

    2015-01-01

    We performed the long-slit observations of spiral galaxy UGC11919 with the Russian 6-m telescope to study its kinematics and stellar population. The previous studies gave basis to suspect that this galaxy possesses a peculiarly low mass-to-light ratio $M/L_B$ of stellar population which could indicate the presence of bottom-light stellar initial mass function (IMF). The ratio $M/L_B$ estimated for different evolutionary models of stellar population using both the broad-band magnitudes and the detailed spectral data confirms this peculiarity if the disc inclination angle $i>30^o$, as it was obtained earlier from the optical photometry, in a good agreement with the HI data cube modelling. However the re-processing of HI data cube we carried out showed that it is compatible with much lower value $i=13^o$ corresponding to the "normal" ratio $M/L_B$, which does not need any peculiar stellar IMF. Stellar velocity dispersion measured at one disc radial scalelength from the center also better agrees with the low disc...

  1. The star cluster - field star connection in nearby spiral galaxies I. Data analysis techniques and application to NGC 4395

    CERN Document Server

    Silva-Villa, E

    2010-01-01

    It is generally assumed that a large fraction of stars are initially born in clusters. However, a large fraction of these disrupt on short timescales and the stars end up belonging to the field. Understanding this process is of paramount importance if we wish to constrain the star formation histories of external galaxies using star clusters. We attempt to understand the relation between field stars and star clusters by simultaneously studying both in a number of nearby galaxies. As a pilot study, we present results for the late-type spiral NGC 4395 using HST/ACS and HST/WFPC2 images. Different detection criteria were used to distinguish point sources (star candidates) and extended objects (star cluster candidates). Using a synthetic CMD method, we estimated the star formation history. Using simple stellar population model fitting, we calculated the mass and age of the cluster candidates. The field star formation rate appears to have been roughly constant, or to have possibly increased by up to about a factor ...

  2. Detection of a ~20 kpc coherent magnetic field in the outskirt of merging spirals: the Antennae galaxies

    CERN Document Server

    Basu, Aritra; Kepley, Amanda A; Robishaw, Timothy; Zweibel, Ellen G; Gallagher, John S

    2016-01-01

    We present a study of the magnetic field properties of NGC 4038/9 (the `Antennae' galaxies), the closest example of a late stage merger of two spiral galaxies. Wideband polarimetric observations were performed using the Karl G. Jansky Very Large Array between 2 and 4 GHz. Rotation measure synthesis and Faraday depolarization analysis was performed to probe the magnetic field strength and structure at spatial resolution of $\\sim1$ kpc. Highly polarized emission from the southern tidal tail is detected with intrinsic fractional polarization close to the theoretical maximum ($0.62\\pm0.18$), estimated by fitting the Faraday depolarization with a volume that is both synchrotron emitting and Faraday rotating containing random magnetic fields. Magnetic fields are well aligned along the tidal tail and the Faraday depths shows large-scale smooth variations preserving its sign. This suggests the field in the plane of the sky to be regular up to $\\sim20$ kpc, which is the largest detected regular field structure on gala...

  3. Tidal Dwarf Galaxies, Accretion Tails, and `Beads on a String' in the `Spirals, Bridges, and Tails' Interacting Galaxy Survey

    CERN Document Server

    Smith, Beverly J; Struck, Curtis; Hancock, Mark; Hurlock, Sabrina

    2009-01-01

    We have used the GALEX ultraviolet telescope to study stellar populations and star formation morphology in a well-defined sample of more than three dozen nearby optically-selected pre-merger interacting galaxy pairs. We have combined the GALEX NUV and FUV images with broadband optical maps from the Sloan Digitized Sky Survey to investigate the ages and extinctions of the tidal features and the disks. We have identified a few new candidate tidal dwarf galaxies in this sample, as well as other interesting morphologies such as accretion tails, `beads on a string', and `hinge clumps'. In only a few cases are strong tidal features seen in HI maps but not in GALEX.

  4. CHANG-ES - VI. Probing Supernova energy deposition in spiral galaxies through multiwavelength relationships

    Science.gov (United States)

    Li, Jiang-Tao; Beck, Rainer; Dettmar, Ralf-Jürgen; Heald, George; Irwin, Judith; Johnson, Megan; Kepley, Amanda A.; Krause, Marita; Murphy, E. J.; Orlando, Elena; Rand, Richard J.; Strong, A. W.; Vargas, Carlos J.; Walterbos, Rene; Wang, Q. Daniel; Wiegert, Theresa

    2016-02-01

    How a galaxy regulates its supernovae (SNe) energy into different interstellar/circumgalactic medium components strongly affects galaxy evolution. Based on the JVLA D-configuration C- (6 GHz) and L-band (1.6 GHz) continuum observations, we perform statistical analysis comparing multiwavelength properties of the Continuum Haloes in Nearby Galaxies - an EVLA Survey galaxies. The high-quality JVLA data and edge-on orientation enable us for the first time to include the halo into the energy budget for a complete radio-flux-limited sample. We find tight correlations of Lradio with the mid-IR-based star formation rate (SFR). The normalization of our I1.6 GHz/W Hz-1-SFR relation is ˜2-3times of those obtained for face-on galaxies, probably a result of enhanced IR extinction at high inclination. We also find tight correlations between Lradio and the SNe energy injection rate dot{E}_SN(Ia+CC), indicating the energy loss via synchrotron radio continuum accounts for ˜1 of dot{E}_SN, comparable to the energy contained in cosmic ray electrons. The integrated C-to-L-band spectral index is α ˜ 0.5-1.1 for non-active galactic nucleus galaxies, indicating a dominance by the diffuse synchrotron component. The low-scatter Lradio-SFR/L_radio-dot{E}_{SN (Ia+CC)} relationships have superlinear logarithmic slopes at ˜2σ in L band (1.132 ± 0.067/1.175 ± 0.102) while consistent with linear in C band (1.057 ± 0.075/1.100 ± 0.123). The superlinearity could be naturally reproduced with non-calorimeter models for galaxy discs. Using Chandra halo X-ray measurements, we find sublinear LX-Lradio relations. These results indicate that the observed radio halo of a starburst galaxy is close to electron calorimeter, and a galaxy with higher SFR tends to distribute an increased fraction of SNe energy into radio emission (than X-ray).

  5. Enhanced dust heating in the bulges of early-type spiral galaxies

    CERN Document Server

    Engelbracht, C W; Skibba, R A; Hinz, J L; Calzetti, D; Gordon, K D; Roussel, H; Crocker, A F; Misselt, K A; Bolatto, A D; Kennicutt, R C; Appleton, P N; Armus, L; Beirão, P; Brandl, B R; Croxall, K V; Dale, D A; Draine, B T; Dumas, G; de Paz, A Gil; Groves, B; Hao, C -N; Johnson, B D; Koda, J; Krause, O; Leroy, A K; Meidt, S E; Murphy, E J; Rahman, N; Rix, H -W; Sandstrom, K M; Sauvage, M; Schinnerer, E; Smith, J -D T; Srinivasan, S; Vigroux, L; Walter, F; Warren, B E; Wilson, C D; Wolfire, M G; Zibetti, S

    2010-01-01

    Stellar density and bar strength should affect the temperatures of the cool (T ~ 20-30 K) dust component in the inner regions of galaxies, which implies that the ratio of temperatures in the circumnuclear regions to the disk should depend on Hubble type. We investigate the differences between cool dust temperatures in the central 3 kpc and disk of 13 nearby galaxies by fitting models to measurements between 70 and 500 microns. We attempt to quantify temperature trends in nearby disk galaxies, with archival data from Spitzer/MIPS and new observations with Herschel/SPIRE, which were acquired during the first phases of the Herschel observations for the KINGFISH (key insights in nearby galaxies: a far-infrared survey with Herschel) sample. We fit single-temperature modified blackbodies to far-infrared and submillimeter measurements of the central and disk regions of galaxies to determine the temperature of the component(s) emitting at those wavelengths. We present the ratio of central-region-to-disk-temperatures ...

  6. N-body simulations of collective effects in spiral and barred galaxies

    Science.gov (United States)

    Zhang, X.

    2016-10-01

    We present gravitational N-body simulations of the secular morphological evolution of disk galaxies induced by density wave modes. In particular, we address the demands collective effects place on the choice of simulation parameters, and show that the common practice of the use of a large gravity softening parameter was responsible for the failure of past simulations to correctly model the secular evolution process in galaxies, even for those simulations where the choice of basic state allows an unstable mode to emerge, a prerequisite for obtaining the coordinated radial mass flow pattern needed for secular evolution of galaxies along the Hubble sequence. We also demonstrate that the secular evolution rates measured in our improved simulations agree to an impressive degree with the corresponding rates predicted by the recently-advanced theories of dynamically-driven secular evolution of galaxies. The results of the current work, besides having direct implications on the cosmological evolution of galaxies, also shed light on the general question of how irreversibility emerges from a nominally reversible physical system.

  7. M/L, H-alpha Rotation Curves, and HI Measurements for 329 Nearby Cluster and Field Spirals: II. Evidence for Galaxy Infall

    CERN Document Server

    Vogt, N P; Giovanelli, R; Herter, T; Vogt, Nicole P.; Haynes, Martha P.; Giovanelli, Riccardo; Herter, Terry

    2004-01-01

    We have conducted a study of optical and HI properties of spiral galaxies (size, luminosity, H-alpha flux distribution, circular velocity, HI gas mass) to explore the role of gas stripping as a driver of morphological evolution in clusters. We find a strong correlation between the spiral and S0 fractions within clusters, and the spiral fraction scales tightly with cluster X-ray gas luminosity. We explore young star formation and identify spirals that are (1) asymmetric, with truncated H-alpha emission and HI gas reservoirs on the leading edge of the disk, on a first pass through the dense intracluster medium in the cores of rich clusters; (2) strongly HI deficient and stripped, with star formation confined to the inner 5 kpc/h and 3 disk scale lengths; (3) reddened, extremely HI deficient and quenched, where star formation has been halted across the entire disk. We propose that these spirals are in successive stages of morphological transformation, between infalling field spirals and cluster S0s, and that the...

  8. NEAR-INFRARED POLARIMETRY OF A NORMAL SPIRAL GALAXY VIEWED THROUGH THE TAURUS MOLECULAR CLOUD COMPLEX

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, Dan P.; Cashman, L. R.; Pavel, M. D., E-mail: clemens@bu.edu, E-mail: pavelmi@utexas.edu, E-mail: lcashman@bu.edu [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)

    2013-03-15

    Few normal galaxies have been probed using near-infrared polarimetry, even though it reveals magnetic fields in the cool interstellar medium better than either optical or radio polarimetry. Deep H-band (1.6 {mu}m) linear imaging polarimetry toward Taurus serendipitously included the galaxy 2MASX J04412715+2433110 with adequate sensitivity and resolution to map polarization across nearly its full extent. The observations revealed the galaxy to be a steeply inclined ({approx}75 Degree-Sign ) disk type with a diameter, encompassing 90% of the Petrosian flux, of 4.2 kpc at a distance of 53 Mpc. Because the sight line passes through the Taurus Molecular Cloud complex, the foreground polarization needed to be measured and removed. The foreground extinction A{sub V} of 2.00 {+-} 0.10 mag and reddening E(H - K) of 0.125 {+-} 0.009 mag were also assessed and removed, based on analysis of Two Micron All Sky Survey, UKIRT Infrared Deep Sky Survey, Spitzer, and Wide-field Infrared Survey Explorer photometry using the Near-Infrared Color Excess, NICE-Revisited, and Rayleigh-Jeans Color Excess methods. Corrected for the polarized foreground, the galaxy polarization values range from 0% to 3%. The polarizations are dominated by a disk-parallel magnetic field geometry, especially to the northeast, while either a vertical field or single scattering of bulge light produces disk-normal polarizations to the southwest. The multi-kiloparsec coherence of the magnetic field revealed by the infrared polarimetry is in close agreement with short-wavelength radio synchrotron observations of edge-on galaxies, indicating that both cool and warm interstellar media of disk galaxies may be threaded by common magnetic fields.

  9. In-N-Out: the gas cycle from dwarfs to spiral galaxies

    CERN Document Server

    Christensen, Charlotte R; Governato, Fabio; Pontzen, Andrew; Brooks, Alyson; Munshi, Ferah; Quinn, Thomas; Wadsley, James

    2015-01-01

    We examine the scalings of galactic outflows with halo mass across a suite of twenty high-resolution cosmological zoom galaxy simulations covering halo masses from 10^9.5 - 10^12 M_sun. These simulations self-consistently generate outflows from the available supernova energy in a manner that successfully reproduces key galaxy observables including the stellar mass-halo mass, Tully-Fisher, and mass-metallicity relations. We quantify the importance of ejective feedback to setting the stellar mass relative to the efficiency of gas accretion and star formation. Ejective feedback is increasingly important as galaxy mass decreases; we find an effective mass loading factor that scales as v_circ^(-2.2), with an amplitude and shape that is invariant with redshift. These scalings are consistent with analytic models for energy-driven wind, based solely on the halo potential. Recycling is common: about half the outflow mass across all galaxy masses is later re-accreted. The recycling timescale is typically about 1 Gyr, v...

  10. Near-Infrared Surface Photometry of Bulges and Disks of Spiral Galaxies : The Data

    NARCIS (Netherlands)

    Peletier, R. F.; Balcells, M.

    1997-01-01

    Abstract: We present optical and near-infrared (NIR) surface brightness and colour profiles,in bands ranging from U to K, for the disk and bulge components of a complete sample of 30 nearby S0 to Sbc galaxies with inclinations larger than 50 degrees. We describe in detail the observations and the de

  11. Near-infrared polarimetry of a normal spiral galaxy viewed through the Taurus Molecular Cloud Complex

    CERN Document Server

    Clemens, Dan P; Cashman, L R

    2013-01-01

    Few normal galaxies have been probed using near-infrared polarimetry, even though it reveals magnetic fields in the cool interstellar medium better than either optical or radio polarimetry. Deep H-band (1.6um) linear imaging polarimetry toward Taurus serendipitously included the galaxy 2MASX J04412715+2433110 with adequate sensitivity and resolution to map polarization across nearly its full extent. The observations revealed the galaxy to be a steeply inclined (~75 deg) disk type with a diameter, encompassing 90% of the Petrosian flux, of 4.2 kpc at a distance of 53 Mpc. Because the sight line passes through the Taurus Molecular Cloud complex, the foreground polarization needed to be measured and removed. The foreground extinction Av of 2.00+/-0.10 mag and reddening E(H-K) of 0.125 +/- 0.009 mag were also assessed and removed, based on analysis of 2MASS, UKIDSS, Spitzer, and WISE photometry using the NICE, NICER, and RJCE methods. Corrected for the polarized foreground, the galaxy polarization values range fr...

  12. CHANG-ES VI: Probing Supernova Energy Deposition in Spiral Galaxies Through Multi-Wavelength Relationships

    CERN Document Server

    Li, Jiang-Tao; Dettmar, Ralf-Jurgen; Heald, George; Irwin, Judith; Johnson, Megan; Kepley, Amanda A; Krause, Marita; Murphy, E J; Orlando, Elena; Rand, Richard J; Strong, A W; Vargas, Carlos J; Walterbos, Rene; Wang, Q Daniel; Wiegert, Theresa

    2015-01-01

    How a galaxy regulates its SNe energy into different interstellar/circumgalactic medium components strongly affects galaxy evolution. Based on the JVLA D-configuration C- (6 GHz) and L-band (1.6 GHz) continuum observations, we perform statistical analysis comparing multi-wavelength properties of the CHANG-ES galaxies. The high-quality JVLA data and edge-on orientation enable us for the first time to include the halo into the energy budget for a complete radio-flux-limited sample. We find tight correlations of $L_{\\rm radio}$ with the mid-IR-based SFR. The normalization of our $I_{\\rm 1.6GHz}/{\\rm W~Hz^{-1}}-{\\rm SFR}$ relation is $\\sim$2-3 times of those obtained for face-on galaxies, probably a result of enhanced IR extinction at high inclination. We also find tight correlations between $L_{\\rm radio}$ and the SNe energy injection rate $\\dot{E}_{\\rm SN(Ia+CC)}$, indicating the energy loss via synchrotron radio continuum accounts for $\\sim0.1\\%$ of $\\dot{E}_{\\rm SN}$, comparable to the energy contained in CR ...

  13. Signatures of Interstellar-Intracluster Medium Interactions Spiral Galaxy Rotation Curves in Abell 2029

    CERN Document Server

    Dale, D A; Dale, Daniel A.; Uson, Juan M.

    2000-01-01

    We investigate the rich cluster Abell 2029 (z~0.08) using optical imaging and long-slit spectral observations of 52 disk galaxies distributed throughout the cluster field. No strong emission-line galaxies are present within ~400 kpc of the cluster center, a region largely dominated by the similarly-shaped X-ray and low surface brightness optical envelopes centered on the giant cD galaxy. However, two-thirds of the galaxies observed outside the cluster core exhibit line emission. H-alpha rotation curves of 14 cluster members are used in conjunction with a deep I band image to study the environmental dependence of the Tully-Fisher relation. The Tully-Fisher zero-point of Abell 2029 matches that of clusters at lower redshifts, although we do observe a relatively larger scatter about the Tully-Fisher relation. We do not observe any systematic variation in the data with projected distance to the cluster center: we see no environmental dependence of Tully-Fisher residuals, R-I color, H-alpha equivalent width, and t...

  14. The RINGS Survey: High-Resolution H-alpha Velocity Fields of Nearby Spiral Galaxies with the SALT Fabry-Perot

    CERN Document Server

    Mitchell, Carl J; Williams, T B; Spekkens, Kristine; Lee-Waddell, K; de Naray, Rachel Kuzio

    2015-01-01

    We have obtained high-spatial-resolution spectrophotometric data on several nearby spiral galaxies with the Southern African Large Telescope (SALT) Fabry-P\\'erot interferometer on the Robert Stobie Spectrograph (RSS) as a part of the RSS Imaging spectroscopy Nearby Galaxy Survey (RINGS). We have successfully reduced two tracks of Fabry-P\\'erot data for the galaxy NGC 2280 to produce a velocity field of the H-alpha line of excited hydrogen. We have modeled these data with the DiskFit modeling software and found these models to be in excellent agreement both with previous measurements in the literature and with our lower-resolution HI velocity field of the same galaxy. Despite this good agreement, small regions exist where the difference between the H-alpha and HI velocities is larger than would be expected from typical dispersions. We investigate these regions of high velocity difference and offer possible explanations for their existence.

  15. A Revised Host Galaxy Association for GRB 020819B: A High-Redshift Dusty Starburst, Not a Low-Redshift Gas-Poor Spiral

    CERN Document Server

    Perley, Daniel A; Schady, Patricia; Michałowski, Michał J; Thöne, Christina C; Petry, Dirk; Graham, John F; Greiner, Jochen; Schulze, Steve; Kim, Sam

    2016-01-01

    The purported spiral host galaxy of GRB 020819B at z=0.41 has been seminal in establishing our view of the diversity of long-duration gamma-ray burst environments: optical spectroscopy of this host provided evidence that GRBs can form even at high metallicities, while millimetric observations suggested that GRBs may preferentially form in regions with minimal molecular gas. We report new observations from VLT (MUSE and X-shooter) which demonstrate that the purported host is an unrelated foreground galaxy. The probable radio afterglow is coincident with a compact, highly star-forming, dusty galaxy at z=1.9621. The revised redshift naturally explains the apparent nondetection of CO(3-2) line emission at the afterglow site from ALMA. There is no evidence that molecular gas properties in GRB host galaxies are unusual, and limited evidence that GRBs can form readily at super-Solar metallicity.

  16. The fate of spiral galaxies in clusters: the star formation history of the anemic Virgo cluster galaxy NGC 4569

    CERN Document Server

    Boselli, A; Cortese, L; De Paz, A G; Seibert, M; Madore, B F; Buat, V; Martin, D C

    2006-01-01

    We present a new method for studying the star formation history of late-type, cluster galaxies undergoing gas starvation or a ram-pressure stripping event by combining bidimensional multifrequency observations with multi-zones models of galactic chemical and spectrophotometricevolution. This method is applied to the Virgo cluster anemic galaxy NGC 4569. We extract radial profiles from recently obtained UV GALEX images at 1530 and 2310 A, from visible and near-IR narrow (Halpha) and broad band images at different wavelengths (u, B, g, V, r, i, z, J, H, K), from Spitzer IRAC and MIPS images and from atomic and molecular gas maps. The model in the absence of interaction (characterized by its rotation velocity and spin parameter) is constrained by the unperturbed H band light profile and by the Halpha rotation curve. We can reconstruct the observed total-gas radial-density profile and the light surface-brightness profiles at all wavelengths in a ram-pressure stripping scenario by making simple assumptions about t...

  17. Similarity between the Spiral Arms of Galaxy M51 Image and the Interface Curve of Yin-Yang Balance in the Ancient Tai-Chi Diagram

    Institute of Scientific and Technical Information of China (English)

    Sui Lin

    2009-01-01

    The particle paths of the Lagrangian flow field between two cylinders simulate well the spiral arms of Galaxy M51 image [1] and the interface curve of the Yin-Yang balance in the ancient Tai-Chi diagram [2]. The particle paths of the Lagrangian flow field involve four parameters. The normalization of the system of equations signifi-cantly simplifies the formulation of the flow process and reduces the original four parameters to only one pa-rameter. Furthermore it provides the similarity between the formulation of the spiral arms of Galaxy M51 and that of the interface curve of the Yin-Yang balance in the ancient Tal-Chi diagram.

  18. The universal rotation curve of spiral galaxies; 1, the dark matter connection

    CERN Document Server

    Persic, M; Stel, F

    1996-01-01

    We use a homogeneous sample of about 1100 rotation curves (RCs) and relative surface photometry to investigate (out to 2 optical radii and over 6 mag) the main mass structure properties of spirals. We definitely confirm the strong dependence on luminosity for both the profile and the amplitude of RCs. Spiral RCs show the striking feature that a single parameter, the luminosity, dictates the rotation velocity at any radius for all objects, so unveiling the existence of a Universal RC. At high luminosity, the profiles of RCs are mildly discrepant from the pure luminous matter (LM) predictions, so the amount of dark matter (DM) is modest albeit detectable. At low luminosities the failure of the LM prediction is most severe, and DM is the only relevant mass component. Some of the derived scaling properties between dark and luminous galaxian parameters are: (a) the DM/LM mass ratio at the optical radius scales as L^{-0.6}; (b) the halo core radius is always comparable with the optical radius, but shrinks for lower...

  19. CO Multi-line Imaging of Nearby Galaxies (COMING). I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903

    Science.gov (United States)

    Muraoka, Kazuyuki; Sorai, Kazuo; Kuno, Nario; Nakai, Naomasa; Nakanishi, Hiroyuki; Takeda, Miho; Yanagitani, Kazuki; Kaneko, Hiroyuki; Miyamoto, Yusuke; Kishida, Nozomi; Hatakeyama, Takuya; Umei, Michiko; Tanaka, Takahiro; Tomiyasu, Yuto; Saita, Chey; Ueno, Saeko; Matsumoto, Naoko; Salak, Dragan; Morokuma-Matsui, Kana

    2016-10-01

    We present simultaneous mappings of J = 1-0 emission of 12CO, 13CO, and C18O molecules toward the whole disk (8' × 5' or 20.8 kpc × 13.0 kpc) of the nearby barred spiral galaxy NGC 2903 with the Nobeyama Radio Observatory 45 m telescope at an effective angular resolution of 20″ (or 870 pc). We detected 12CO(J = 1-0) emission over the disk of NGC 2903. In addition, significant 13CO(J = 1-0) emission was found at the center and bar-ends, whereas we could not detect any significant C18O(J = 1-0) emission. In order to improve the signal-to-noise ratio of CO emission and to obtain accurate line ratios of 12CO(J = 2-1)/12CO(J = 1-0) (R2-1/1-0) and 13CO(J = 1-0)/12CO(J = 1-0) (R13/12), we performed the stacking analysis for our 12CO(J = 1-0), 13CO(J = 1-0), and archival 12CO(J = 2-1) spectra with velocity axis alignment in nine representative regions of NGC 2903. We successfully obtained the stacked spectra of the three CO lines, and could measure averaged R2-1/1-0 and R13/12 with high significance for all the regions. We found that both R2-1/1-0 and R13/12 differ according to the regions, which reflects the difference in the physical properties of molecular gas, i.e., density (n_H_2) and kinetic temperature (TK). We determined n_H_2 and TK using R2-1/1-0 and R13/12 based on the large velocity gradient approximation. The derived n_H_2 ranges from ˜1000 cm-3 (in the bar, bar-ends, and spiral arms) to 3700 cm-3 (at the center) and the derived TK ranges from 10 K (in the bar and spiral arms) to 30 K (at the center). We examined the dependence of star formation efficiencies (SFEs) on n_H_2 and TK, and found a positive correlation between SFE and n_H_2 with correlation coefficient for the least-squares power-law fit R2 of 0.50. This suggests that molecular gas density governs the spatial variations in SFEs.

  20. The Evolution of Stellar Populations in the Outer Disks of Spiral Galaxies

    CERN Document Server

    Alberts, Stacey; Dong, Hui; Johnson, L C; Dale, Daniel A; Bianchi, Luciana; Chandar, Rupali; Kennicutt, Robert C; Meurer, Gerhardt R; Regan, Michael; Thilker, David

    2011-01-01

    We investigate recent star formation in the extended ultraviolet (XUV) disks of five nearby galaxies (NGC 0628, NGC 2090, NGC 2841, NGC 3621, and NGC 5055) using a long wavelength baseline comprised of ultraviolet and mid-infrared imaging from the Galaxy Evolution Explorer and the Spitzer Infrared Array Camera. We identify 229 unresolved stellar complexes across targeted portions of their XUV disks and utilize spectral energy distribution fitting to measure their stellar ages and masses through comparison with Starburst99 population synthesis models of instantaneous burst populations. We find that the median age of outer disk associations in our sample is ~100 Myr with a large dispersion that spans the entire range of our models (1 Myr-1 Gyr). This relatively evolved state for most associations addresses the observed dearth of Halpha emission in some outer disks, as Halpha can only be observed in star forming regions younger than ~10 Myr. The large age dispersion is robust against variations in extinction (in...

  1. Towards a more realistic population of bright spiral galaxies in cosmological simulations

    Science.gov (United States)

    Aumer, Michael; White, Simon D. M.; Naab, Thorsten; Scannapieco, Cecilia

    2013-10-01

    We present an update to the multiphase smoothed particle hydrodynamics galaxy formation code by Scannapieco et al. We include a more elaborate treatment of the production of metals, cooling rates based on individual element abundances and a scheme for the turbulent diffusion of metals. Our supernova feedback model now transfers energy to the interstellar medium (ISM) in kinetic and thermal form, and we include a prescription for the effects of radiation pressure from massive young stars on the ISM. We calibrate our new code on the well-studied Aquarius haloes and then use it to simulate a sample of 16 galaxies with halo masses between 1 × 1011 and 3 × 1012 M⊙. In general, the stellar masses of the sample agree well with the stellar mass to halo mass relation inferred from abundance matching techniques for redshifts z = 0-4. There is however a tendency to overproduce stars at z > 4 and to underproduce them at z metallicities at z = 0-3. Remaining discrepancies can be connected to deviations from predictions for star formation histories from abundance matching. At z = 0, the model galaxies show realistic morphologies, stellar surface density profiles, circular velocity curves and stellar metallicities, but overly flat metallicity gradients. 15 out of 16 of our galaxies contain disc components with kinematic disc fraction ranging between 15 and 65 per cent. The disc fraction depends on the time of the last destructive merger or misaligned infall event. Considering the remaining shortcomings of our simulations we conclude that even higher kinematic disc fractions may be possible for Λ cold dark matter haloes with quiet merger histories, such as the Aquarius haloes.

  2. Extraplanar HII regions in the edge-on spiral galaxies NGC 3628 and NGC 4522

    Science.gov (United States)

    Stein, Y.; Bomans, D. J.; Ferguson, A. M. N.; Dettmar, R.-J.

    2017-08-01

    Context. Gas infall and outflow are critical for determining the star formation rate and chemical evolution of galaxies but direct measurements of gas flows are difficult to make. Young massive stars and Hii regions in the halos of galaxies are potential tracers for accretion and/or outflows of gas. Aims: Gas phase abundances of three Hii regions in the lower halos of the edge-on galaxies NGC 3628 and NGC 4522 are determined by analyzing optical long-slit spectra. The observed regions have projected distances to the midplane of their host from 1.4 to 3 kpc. Methods: With the measured flux densities of the optical nebular emission lines, we derived the oxygen abundance 12 + log(O/H) for the three extraplanar Hii regions. The analysis was based on one theoretical and two empirical strong-line calibration methods. Results: The resulting oxygen abundances of the extraplanar Hii regions are comparable to the disk Hii regions in one case and are a little lower in the other case. Since our results depend on the accuracy of the metallicity determinations, we critically discuss the difference of the calibration methods we applied and confirm previously noted offsets. From our measurements, we argue that these three extraplanar Hii regions were formed in the disk or at least from disk material. We discuss the processes that could transport disk material into the lower halo of these systems and conclude that gravitational interaction with a companion galaxy is most likely for NGC 3628 while ram pressure is favored in the case of NGC 4522. Based on observations gathered as part of observing program 64.N-0208(A), 3.6 m telescope with European Southern Observatory (ESO) Faint Object Spectrograph and Camera (EFOSC2) at ESO, La Silla observatory.

  3. M/L, H-alpha Rotation Curves, and HI Measurements for 329 Nearby Cluster and Field Spirals: III. Evolutionin Fundamental Galaxy Parameters

    CERN Document Server

    Vogt, N P; Giovanelli, R; Herter, T; Vogt, Nicole P.; Haynes, Martha P.; Giovanelli, Riccardo; Herter, Terry

    2004-01-01

    We have conducted a study of optical and HI properties of spiral galaxies (size, luminosity, H-alpha flux distribution, circular velocity, HI gas mass) to investigate causes (e.g., nature versus nurture) for variation within the cluster environment. We find HI deficient cluster galaxies to be offset in Fundamental Plane space, with disk scale lengths decreased by a factor of 25%. This may be a relic of early galaxy formation, caused by the disk coalescing out of a smaller, denser halo (e.g., higher concentration index) or by truncation of the hot gas envelope due to the enhanced local density of neighbors, though we cannot completely rule out the effect of the gas stripping process. The spatial extent of H-alpha flux and the B-band radius also decreases, but only in early type spirals, suggesting that gas removal is less efficient within steeper potential wells (or that stripped late type spirals are quickly rendered unrecognizable). We find no significant trend in stellar mass-to-light ratios or circular vel...

  4. Hierarchical Bayesian approach for estimating physical properties in spiral galaxies: Age Maps for M74

    CERN Document Server

    Gil, M Carmen Sánchez; Alfaro, Emilio J; Pérez, Enrique; Sarro, Luis M

    2015-01-01

    One of the fundamental goals of modern Astronomy is to estimate the physical parameters of galaxies from images in different spectral bands. We present a hierarchical Bayesian model for obtaining age maps from images in the \\Ha\\ line (taken with Taurus Tunable Filter (TTF)), ultraviolet band (far UV or FUV, from GALEX) and infrared bands (24, 70 and 160 microns ($\\mu$m), from Spitzer). As shown in S\\'anchez-Gil et al. (2011), we present the burst ages for young stellar populations in the nearby and nearly face on galaxy M74. As it is shown in the previous work, the \\Ha\\ to FUV flux ratio gives a good relative indicator of very recent star formation history (SFH). As a nascent star-forming region evolves, the \\Ha\\ line emission declines earlier than the UV continuum, leading to a decrease in the \\Ha\\/FUV ratio. Through a specific star-forming galaxy model (Starburst 99, SB99), we can obtain the corresponding theoretical ratio \\Ha\\ / FUV to compare with our observed flux ratios, and thus to estimate the ages of...

  5. Improving Stellar Velocity Dispersion Measurements in Barred Spiral Galaxies With Supermassive Black Holes

    Science.gov (United States)

    Dittenber, Benjamin; Valluri, Monica

    2017-01-01

    For the past decade researchers have focused on accurately measuring the masses of supermassive black holes in different types of galaxies. Relatively less effort has been devoted to possible systematic errors in the measurement of the central velocity dispersion of stars, sigma_*, with which the masses of supermassive black holes are known to be well correlated. In barred galaxies the measurement of sigma_* depends quite sensitively on the method used to calculate it and the kind of spectroscopic data (long-slit or IFU) and the orientation of the bar to the line-of-sight and inclination of the disk. We used simulations of barred disk galaxies with adiabatically grown SMBHs to generate mock kinematical data from which sigma_* is derived and compared with the true 3D velocity dispersion of stars in the simulations. By comparing simulations with real IFU data we aim to correct the measured sigma_* for aperture size /shape, disk inclination and bar position angle, to obtain the intrinsic central velocity dispersion of stars.

  6. From Star-Forming Spirals to Passive Spheroids: Integral Field Spectroscopy of E+A Galaxies

    CERN Document Server

    Swinbank, Mark; Bower, Richard; Zabludoff, Ann; Lucey, John; McGee, Sean; Miller, Chris; Nichol, Robert

    2011-01-01

    We present three dimensional spectroscopy of eleven E+A galaxies, selected for their strong H-delta absorption but weak (or non-existent) [OII]3727 and H-alpha emission. This selection suggests that a recent burst of star-formation was triggered but subsequently abruptly ended. We probe the spatial and spectral properties of both the young (~1Gyr) and old (few Gyr) stellar populations. Using the H-delta equivalent widths we estimate that the burst masses must have been at least 10% by mass (Mburst~10^10Mo), which is also consistent with the star-formation history inferred from the broad-band SEDs. On average the A-stars cover ~33% of the galaxy image, extending over 2-15kpc^2, indicating that the characteristic E+A signature is a property of the galaxy as a whole and not due to a heterogeneous mixture of populations. In approximately half of the sample, we find that the A-stars, nebular emission, and continuum emission are not co-located, suggesting that the newest stars are forming in a different place than ...

  7. The unorthodox evolution of major merger remnants into star-forming spiral galaxies

    CERN Document Server

    Sparre, Martin

    2016-01-01

    Galaxy mergers are believed to play a key role in transforming star-forming disk galaxies into quenched ellipticals. Most of our theoretical knowledge about such morphological transformations does, however, rely on idealised simulations where processes such as cooling of hot halo gas into the disk and gas accretion in the post-merger phase are not treated in a self-consistent cosmological fashion. In this paper we study the morphological evolution of the stellar components of four major mergers occurring at z=0.5 in cosmological hydrodynamical zoom-simulations. In all simulations the merger reduces the disk mass-fraction, but all galaxies simulated at our highest resolution regrow a significant disk by z=0 (with a disk fraction larger than 24%). For runs with our default physics model, which includes galactic winds from star formation and black hole feedback, none of the merger remnants are quenched, but in a set of simulations with stronger black hole feedback we find that major mergers can indeed quench gal...

  8. Spirality: A Novel Way to Measure Spiral Arm Pitch Angle

    CERN Document Server

    Shields, Douglas W; Pfountz, Casey; Davis, Benjamin L; Hartley, Matthew; Imani, Hamed Pour; Slade, Zac; Kennefick, Daniel; Kennefick, Julia

    2015-01-01

    We present the MATLAB code Spirality, a novel method for measuring spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Computation time is typically on the order of 2 minutes per galaxy, assuming at least 8 GB of working memory. We tested the code using 117 synthetic spiral images with known pitches, varying both the spiral properties and the input parameters. The code yielded correct results for all synthetic spirals with galaxy-like properties. We also compared the code's results to two-dimensional Fast Fourier Transform (2DFFT) measurements for the sample of nearby galaxies defined by DMS PPak. Spirality's error bars overlapped 2DFFT's error bars for 26 of the 30 galaxies. The two methods' agreement correlates strongly with galaxy radius in pixels and also with i-band magnitude, but not with redshift, a result that is consistent with at least some galaxies' spiral structure being fully formed by z=1.2, beyond which there are few galaxies in our sample. The Spirality code pa...

  9. First Results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low-mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    Science.gov (United States)

    Carlin, Jeffrey L.; Sand, David J.; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F.; Brodie, Jean P.; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H. G.; Romanowsky, Aaron J.; Strader, Jay

    2016-09-01

    We report the discovery of the faintest known dwarf galaxy satellite of a Large Magellanic Cloud (LMC) stellar-mass host beyond the Local Group (LG), based on deep imaging with Subaru/Hyper Suprime-Cam. Magellanic Analog Dwarf Companions And Stellar Halos (MADCASH) J074238+652501-dw lies ˜35 kpc in projection from NGC 2403, a dwarf spiral galaxy at D ≈ 3.2 Mpc. This new dwarf has {M}g=-7.4+/- 0.4 and a half-light radius of 168 ± 70 pc, at the calculated distance of 3.39 ± 0.41 Mpc. The color-magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low-luminosity dwarfs in the LG. The lack of either detected HI gas ({M}{HI}/{L}V\\lt 0.69 {M}⊙ /{L}⊙ , based on Green Bank Telescope observations) or GALEX NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH survey, which is conducting a census of the stellar substructure and faint satellites in the halos of Local Volume LMC analogs via resolved stellar populations. Models predict a total of ˜4-10 satellites at least as massive as MADCASH J074238+652501-dw around a host with the mass of NGC 2403, with 2-3 within our field of view, slightly more than the one such satellite observed in our footprint. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  10. Detection of a ˜20 kpc coherent magnetic field in the outskirt of merging spirals: the Antennae galaxies

    Science.gov (United States)

    Basu, Aritra; Mao, S. A.; Kepley, Amanda A.; Robishaw, Timothy; Zweibel, Ellen G.; Gallagher, John. S.

    2016-09-01

    We present a study of the magnetic field properties of NGC 4038/9 (the `Antennae' galaxies), the closest example of a late stage merger of two spiral galaxies. Wideband polarimetric observations were performed using the Karl G. Jansky Very Large Array between 2 and 4 GHz. Rotation measure synthesis and Faraday depolarization analysis was performed to probe the magnetic field strength and structure at spatial resolution of ˜1 kpc. Highly polarized emission from the southern tidal tail is detected with intrinsic fractional polarization close to the theoretical maximum (0.62 ± 0.18), estimated by fitting the Faraday depolarization with a volume that is both synchrotron emitting and Faraday rotating containing random magnetic fields. Magnetic fields are well aligned along the tidal tail and the Faraday depths shows large-scale smooth variations preserving its sign. This suggests the field in the plane of the sky to be regular up to ˜20 kpc, which is the largest detected regular field structure on galactic scales. The equipartition field strength of ˜8.5~μG of the regular field in the tidal tail is reached within a few 100 Myr, likely generated by stretching of the galactic disc field by a factor of 4-9 during the tidal interaction. The regular field strength is greater than the turbulent fields in the tidal tail. Our study comprehensively demonstrates, although the magnetic fields within the merging bodies are dominated by strong turbulent magnetic fields of ˜20~μG in strength, tidal interactions can produce large-scale regular field structure in the outskirts.

  11. Hierarchical Bayesian approach for estimating physical properties in spiral galaxies: Age Maps for M74

    Science.gov (United States)

    Sánchez Gil, M. Carmen; Berihuete, Angel; Alfaro, Emilio J.; Pérez, Enrique; Sarro, Luis M.

    2015-09-01

    One of the fundamental goals of modern Astronomy is to estimate the physical parameters of galaxies from images in different spectral bands. We present a hierarchical Bayesian model for obtaining age maps from images in the Ha line (taken with Taurus Tunable Filter (TTF)), ultraviolet band (far UV or FUV, from GALEX) and infrared bands (24, 70 and 160 microns (μm), from Spitzer). As shown in [1], we present the burst ages for young stellar populations in the nearby and nearly face on galaxy M74. As it is shown in the previous work, the Hα to FUV flux ratio gives a good relative indicator of very recent star formation history (SFH). As a nascent star-forming region evolves, the Ha line emission declines earlier than the UV continuum, leading to a decrease in the HαFUV ratio. Through a specific star-forming galaxy model (Starburst 99, SB99), we can obtain the corresponding theoretical ratio Hα / FUV to compare with our observed flux ratios, and thus to estimate the ages of the observed regions. Due to the nature of the problem, it is necessary to propose a model of high complexity to take into account the mean uncertainties, and the interrelationship between parameters when the Hα / FUV flux ratio mentioned above is obtained. To address the complexity of the model, we propose a Bayesian hierarchical model, where a joint probability distribution is defined to determine the parameters (age, metallicity, IMF), from the observed data, in this case the observed flux ratios Hα / FUV. The joint distribution of the parameters is described through an i.i.d. (independent and identically distributed random variables), generated through MCMC (Markov Chain Monte Carlo) techniques.

  12. THE LINK BETWEEN LIGHT AND MASS IN LATE-TYPE SPIRAL GALAXY DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Swaters, Robert A. [National Optical Astronomical Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Martinsson, Thomas P. K. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Westfall, Kyle B. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Andersen, David R. [NRC Herzberg Programs in Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7 (Canada); Verheijen, Marc A. W., E-mail: rob@swaters.net [University of Groningen, Kapteyn Astronomical Institute, Landleven 12, 9747-AD Groningen (Netherlands)

    2014-12-20

    We present the correlation between the extrapolated central disk surface brightness (μ) and extrapolated central surface mass density (Σ) for galaxies in the DiskMass sample. This μ-Σ relation has a small scatter of 30% at the high surface brightness (HSB) end. At the low surface brightness (LSB) end, galaxies fall above the μ-Σ relation, which we attribute to their higher dark matter content. After correcting for the dark matter as well as for the contribution of gas and the effects of radial gradients in the disk, the LSB end falls back on the linear μ-Σ relation. The resulting scatter around the corrected μ-Σ relation is 25% at the HSB end and about 50% at the LSB end. The intrinsic scatter in the μ-Σ relation is estimated to be 10%-20%. Thus, if μ {sub K,} {sub 0} is known, the stellar surface mass density is known to within 10%-20% (random error). Assuming disks have an exponential vertical distribution of mass, the average Υ{sub ∗}{sup K} is 0.24 M {sub ☉}/L {sub ☉}, with an intrinsic scatter around the mean of at most 0.05 M {sub ☉}/L {sub ☉}. This value for Υ{sub ∗}{sup K} is 20% smaller than we found in Martinsson et al., mainly due to the correction for dark matter applied here. This small scatter means that among the galaxies in our sample, variations in scale height, vertical density profile shape, and/or the ratio of vertical over radial velocity dispersion must be small.

  13. CO Multi-line Imaging of Nearby Galaxies (COMING): I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903

    CERN Document Server

    Muraoka, Kazuyuki; Kuno, Nario; Nakai, Naomasa; Nakanishi, Hiroyuki; Takeda, Miho; Yanagitani, Kazuki; Kaneko, Hiroyuki; Miyamoto, Yusuke; Kishida, Nozomi; Hatakeyama, Takuya; Umei, Michiko; Tanaka, Takahiro; Tomiyasu, Yuto; Saita, Chey; Ueno, Saeko; Matsumoto, Naoko; Salak, Dragan; Morokuma, Kana

    2016-01-01

    We present simultaneous mappings of J=1-0 emission of 12CO, 13CO, and C18O molecules toward the whole disk (8' x 5' or 20.8 kpc x 13.0 kpc) of the nearby barred spiral galaxy NGC 2903 with the Nobeyama Radio Observatory 45-m telescope at an effective angular resolution of 20" (or 870 pc). We detected 12CO(J=1-0) emission over the disk of NGC 2903. In addition, significant 13CO(J=1-0) emission was found at the center and bar-ends, whereas we could not detect any significant C18O(J=1-0) emission. In order to improve the signal-to-noise ratio of CO emission and to obtain accurate line ratios of 12CO(J=2-1)/12CO(J=1-0) ($R_{2-1/1-0}$) and 13CO(J=1-0)/12CO(J=1-0) ($R_{13/12}$), we performed the stacking analysis for our 12CO(J=1-0), 13CO(J=1-0), and archival 12CO(J=2-1) spectra with velocity-axis alignment in nine representative regions of NGC 2903. We successfully obtained the stacked spectra of the three CO lines, and could measure averaged $R_{2-1/1-0}$ and $R_{13/12}$ with high significance for all the regions...

  14. Imaging and spectroscopic observations of a strange elliptical bubble in the northern arm of the spiral galaxy NGC 6946

    CERN Document Server

    Efremov, Yuri N

    2016-01-01

    NGC 6946, known as the Fireworks galaxy because of its high supernova rate and high star formation, is embedded in a very extended HI halo. Its northern spiral arm is well detached from the galactic main body. We found that this arm contains a large (~300 pc in size) Red Ellipse, named according to a strong contamination of the H-alpha emission line on its optical images. The ellipse is accompanied by a short parallel arc and a few others still smaller and less regular; a bright star cluster is seen inside these features. The complicated combination of arcs seems to be unique, it is only a bit similar to some SNRs. However, the long-slit spectral data obtained with the Russian 6-m telescope did not confirm the origin of the nebula as a result of a single SN outburst. The emission-line spectrum corresponds to the photoionization by young hot stars with a small contribution of shock ionization. The most likely explanation of the Red Ellipse is a superbbuble created by a collective feedback of massive stars in t...

  15. Imaging and spectroscopic observations of a strange elliptical bubble in the northern arm of the spiral galaxy NGC 6946

    Science.gov (United States)

    Efremov, Yuri N.; Moiseev, Alexei V.

    2016-09-01

    NGC 6946, known as the Fireworks galaxy because of its high supernova rate and high star formation, is embedded in a very extended H I halo. Its northern spiral arm is well detached from the galactic main body. We found that this arm contains a large (˜300 pc in size) Red Ellipse, named according to a strong contamination of the Hα emission line on its optical images. The ellipse is accompanied by a short parallel arc and a few others still smaller and less regular; a bright star cluster is seen inside these features. The complicated combination of arcs seems to be unique; it is only a bit similar to some SNRs. However, the long-slit spectral data obtained with the Russian 6-m telescope did not confirm the origin of the nebula as a result of a single SN outburst. The emission-line spectrum corresponds to the photoionization by young hot stars with a small contribution of shock ionization. The most likely explanation of the Red Ellipse is a superbubble created by a collective feedback of massive stars in the star cluster located in the NE side of the Red Ellipse. However, the very regular elliptical shape of the nebulae seems strange.

  16. Near-infrared observations of galaxies in Pisces-Perseus; 1, H-band surface photometry of 174 spirals

    CERN Document Server

    Moriondo, G; Casertano, S; Chincarini, G L; Gavazzi, G; Giovanardi, C; Hunt, L K; Pierini, D; Sperandio, M; Trinchieri, G

    1999-01-01

    We present near-infrared, H-band (1.65 um), surface photometry of 174 spiral galaxies in the area of the Pisces-Perseus supercluster. The images, acquired with the ARNICA camera mounted on various telescopes, are used to derive radial profiles of surface brightness, ellipticities, and position angles, together with global parameters such as H-band magnitudes and diameters. The mean relation between H-band isophotal diameter D_{21.5} and the B-band D_{25} implies a B-H color of the outer disk bluer than 3.5; moreover, D_{21.5}/D_{25} depends on (global) color and absolute luminosity. The correlations among the various photometric parameters suggest a ratio between isophotal radius D_{21.5}/2 and disk scale length of about 3.5 and a mean disk central brightness of 17.5 H-mag arcsec^{-2}. We confirm the trend of the concentration index C_{31} with absolute luminosity and, to a lesser degree, with morphological type. We also assess the influence of non-axisymmetric structures on the radial profiles and on the der...

  17. Integral Field Spectroscopy and multi-wavelength imaging of the nearby spiral galaxy NGC5668: an unusual flattening in metallicity gradient

    CERN Document Server

    Marino, Raffaella Anna; Castillo-Morales, Africa; Muñoz-Mateos, Juan Carlos; Sánchez, Sebastián F; Pérez-González, Pablo G; Gallego, Jesús; Zamorano, Jaime; Alonso-Herrero, Almudena; Boissier, Samuel

    2012-01-01

    We present the analysis of the full bi-dimensional optical spectral cube of the nearby spiral galaxy NGC 5668, observed with the PPAK IFU at the Calar Alto observatory 3.5m telescope. We make use of broad-band imaging to provide further constraints on the evolutionary history of the galaxy. This dataset will allow us to improve our understanding of the mechanisms that drive the evolution of disks. We investigated the properties of 62 H II regions and concentric rings in NGC 5668 and derived maps in ionized-gas attenuation and chemical (oxygen) abundances. We find that, while inwards of r\\,$\\sim\\,36",\\sim$\\,4.4kpc\\,$\\sim$\\,0.36\\,$(\\frac {D_{25}}{2})$ the derived O/H ratio follows the radial gradient typical of spiral galaxies, the abundance gradient beyond r$\\sim36"$ flattens out. The analysis of the multi-wavelength surface brightness profiles of NGC 5668 is performed by fitting these profiles with those predicted by chemo-spectrophotometric evolutionary models of galaxy disks. From this, we infer a spin and ...

  18. Towards a more realistic population of bright spiral galaxies in cosmological simulations

    CERN Document Server

    Aumer, Michael; Naab, Thorsten; Scannapieco, Cecilia

    2013-01-01

    We present an update to the multiphase SPH galaxy formation code by Scannapieco et al. We include a more elaborate treatment of the production of metals, cooling rates based on individual element abundances, and a scheme for the turbulent diffusion of metals. Our SN feedback model now transfers energy to the ISM in kinetic and thermal form, and we include a prescription for the effects of radiation pressure from massive young stars on the ISM. We calibrate our new code on the well studied Aquarius haloes and then use it to simulate a sample of 16 galaxies with halo masses between 1x10^11 and 3x10^12 M_sun. In general, the stellar masses of the sample agree well with the stellar mass to halo mass relation inferred from abundance matching techniques for redshifts z=0-4. There is however a tendency to overproduce stars at z>4 and to underproduce them at z<0.5 in the least massive haloes. Overly high SFRs at z<1 for the most massive haloes are likely connected to the lack of AGN feedback in our model. The s...

  19. A Turbulent Origin for Flocculent Spiral Structure in Galaxies: II. Observations and Models of M33

    CERN Document Server

    Elmegreen, B G; Elmegreen, D M; Cuillandre, J C; Elmegreen, Bruce G.; Leitner, Samuel N.; Elmegreen, Debra Meloy; Cuillandre, Jean-Charles

    2003-01-01

    Fourier transform power spectra of azimuthal scans of the optical structure of M33 are evaluated for B, V, and R passbands and fit to fractal models of continuum emission with superposed star formation. Power spectra are also determined for Halpha. The best models have intrinsic power spectra with 1D slopes of around -0.7pm0.7, significantly shallower than the Kolmogorov spectrum (slope =-1.7) but steeper than pure noise (slope=0). A fit to the power spectrum of the flocculent galaxy NGC 5055 gives a steeper slope of around -1.5pm0.2, which could be from turbulence. Both cases model the optical light as a superposition of continuous and point-like stellar sources that follow an underlying fractal pattern. Foreground bright stars are clipped in the images, but they are so prominent in M33 that even their residual affects the power spectrum, making it shallower than what is intrinsic to the galaxy. A model consisting of random foreground stars added to the best model of NGC 5055 fits the observed power spectrum...

  20. The Link Between Light and Mass in Late-type Spiral Galaxy Disks

    CERN Document Server

    Swaters, Robert A; Martinsson, Thomas P K; Westfall, Kyle B; Andersen, David R; Verheijen, Marc A W

    2014-01-01

    We present the correlation between the extrapolated central disk surface brightness (mu) and extrapolated central surface mass density (Sigma) for galaxies in the DiskMass sample. This mu-Sigma-relation has a small scatter of 30% at the high-surface-brightness (HSB) end. At the low surface brightness (LSB) end, galaxies fall above the mu-Sigma-relation, which we attribute to their higher dark matter content. After correcting for the dark matter, as well as for the contribution of gas and the effects of radial gradients in the disk, the LSB end falls back on the linear mu-Sigma-relation. The resulting scatter about the corrected mu-Sigma-relation is 25% at the HSB end, and about 50% at the LSB end. The intrinsic scatter in the mu-Sigma-relation is estimated to be 10% to 20%. Thus, if the surface brightness is known, the stellar surface mass density is known to within 10-20% (random error). Assuming disks have an exponential vertical distribution of mass, the average (M_L)_K is 0.24 Msun/Lsun, with an intrinsic...

  1. Sub-arcsecond radio continuum mapping in and around the spiral galaxy NGC3351 using MERLIN

    CERN Document Server

    Hagele, Guillermo F; Richards, Anita M S; Cardaci, Monica V; Vasquez, Javier; Diaz, Angeles I; Gonzalez, Daniel Rosa; Terlevich, Roberto; Terlevich, Elena

    2010-01-01

    We report sub-arcsecond scale radio continuum observations of a field of 35 by 22 arcmin centred in NGC3351 obtained with the Multi-Element Radio Linked Interferometer Network (MERLIN). We found 23 radio sources in this field, 6 of which are projected within the D$_{25}$ isophote of the galaxy, and 3 are located inside the central 100 arcsec in radius. Two of these three are significantly extended, while the third one is relatively compact. This one is the only source with a previously detected counterpart at other wavelengths and could constitute the radio counterpart of a young supernova remnant. The other two are probably related to jets from a background AGN. We are not able to detect individual supernovae or SNRs in the central region ($r<600$ pc) of the galaxy. This could imply that the ionising populations of the circumnuclear star-forming regions (CNSFRs) are too young (less than a few Myr) to host supernovae. Also the diffusion length of the relativistic electrons in the ISM associated with the SN...

  2. W. W. Morgan and the Discovery of the Spiral Arm Structure of our Galaxy

    CERN Document Server

    Sheehan, William

    2011-01-01

    William Wilson Morgan was one of the great astronomers of the twentieth century. He considered himself a morphologist, and was preoccupied throughout his career with matters of classification. Though his early life was difficult, and his pursuit of astronomy as a career was opposed by his father, he took a position at Yerkes Observatory in 1926 and remained there for the rest of his working life. Thematically, his work was also a unified whole. Beginning with spectroscopic studies under Otto Struve at Yerkes Observatory, by the late 1930s he concentrated particularly on the young O and B stars. His work on stellar classification led to the Morgan-Keenan- Kellman [MKK] system of classification of stars, and later - as he grappled with the question of the intrinsic color and brightness of stars at great distances - to the Johnson-Morgan UBV system for measuring stellar colors. Eventually these concerns with classification and method led to his greatest single achievement - the recognition of the nearby spiral a...

  3. Bar Diagnostics in Edge-On Spiral Galaxies. III. N-Body Simulations of Disks

    CERN Document Server

    Bureau, M

    2004-01-01

    Present in over 45% of local spirals, boxy and peanut-shaped bulges are generally interpreted as edge-on bars and may represent a key phase in the evolution of bulges. Aiming to test such claims, the kinematic properties of self-consistent 3D N-body simulations of bar-unstable disks are studied. Using Gauss-Hermite polynomials to describe the stellar kinematics, a number of characteristic bar signatures are identified in edge-on disks: 1) a major-axis light profile with a quasi-exponential central peak and a plateau at moderate radii (Freeman Type II profile); 2) a ``double-hump'' rotation curve; 3) a sometime flat central velocity dispersion peak with a plateau at moderate radii and occasional local central minimum and secondary peak; 4) an h3-V correlation over the projected bar length. All those kinematic features are spatially correlated and can easily be understood from the orbital structure of barred disks. They thus provide a reliable and easy-to-use tool to identify edge-on bars. Interestingly, they a...

  4. PTF10fqs: A Luminous Red Nova in the Spiral Galaxy Messier 99

    CERN Document Server

    Kasliwal, Mansi M; Quimby, Robert M; Ofek, Eran O; Nugent, Peter; Jacobsen, Janet; Gal-Yam, Avishay; Green, Yoav; Arcavi, Iair; Yaron, Ofer; Howell, Jacob L; Fox, Derek B; Cenko, S Bradley; Kleiser, Io; Bloom, Joshua S; Miller, Adam; Poznanski, Dovi; Li, Weidong; Filippenko, Alexei V; Starr, Dan; Law, Nicholas M; Helou, George; Frail, Dale A; Neill, James D; Forster, Karl; Martin, D Christopher; Tendulkar, Shriharsh P; Gehrels, Neil; Kennea, Jamie; Sullivan, Mark; Dekany, Richard; Rahmer, Gustavo; Hale, David; Smith, Roger; Zolkower, Jeff; Velur, Viswa; Walters, Richard; Henning, John; Bui, Kahnh; McKenna, Dan; Blake, Cullen

    2010-01-01

    The Palomar Transient Factory (PTF) is systematically charting the optical transient and variable sky. A primary science driver of PTF is building a complete inventory of transients in the local Universe (distance less than 200 Mpc). Here, we report the discovery of PTF10fqs, a transient in the luminosity "gap" between novae and supernovae. Located in the spiral arm of Messier 99, PTF10fqs is red, slowly evolving and has a spectrum dominated by intermediate width Halpha and Calcium lines. The explosion signature is similar to M85OT2006-1, SN2008S and NGC300-OT. The origin of these events is shrouded in mystery, controversy (and in some cases, in dust). PTF10fqs shows some evidence of a broad feature (around 8600A) that may suggest very large velocities in this explosion (~10000 km/s). Ongoing surveys can be expected to find a few such events per year. Sensitive spectroscopy and statistics (disk versus bulge) will eventually make it possible for astronomers to unravel the nature of these mysterious explosions.

  5. Bar-driven evolution and quenching of spiral galaxies in cosmological simulations

    Science.gov (United States)

    Spinoso, Daniele; Bonoli, Silvia; Dotti, Massimo; Mayer, Lucio; Madau, Piero; Bellovary, Jillian

    2017-03-01

    We analyse the outputs of the cosmological 'zoom-in' hydrodynamical simulation ErisBH to study a strong stellar bar which naturally emerges in the late evolution of the simulated Milky Way-type galaxy. We focus on the analysis of the formation and evolution of the bar and on its effects on the galactic structure, the gas distribution and the star formation. A large central region in the ErisBH disc becomes bar unstable after z ∼ 1.4, but a clear bar starts to grow significantly only after z ≃ 0.4, possibly triggered by the interaction with a massive satellite. At z ≃ 0.1, the bar stabilizes and reaches its maximum radial extent of l ≈ 2.2 kpc. As the bar grows, it becomes prone to buckling instability. The actual buckling event, observable at z ≃ 0.1, results in the formation of a boxy-peanut bulge clearly discernible at z = 0. During its early growth, the bar exerts a strong torque on the gas and drives gas inflows that enhance the nuclear star formation on sub-kpc scales. Later on, as the bar reaches its maximum length and strength, the gas within its extent is nearly all consumed into stars, leaving behind a gas-depleted region in the central ∼2 kpc. Observations would more likely identify a prominent, large-scale bar at the stage when the galactic central region has already been gas depleted, giving a hint at the fact that bar-driven quenching may play an important role in the evolution of disc-dominated galaxies.

  6. Highly Ionized Plasma in the Halo of a Luminous Spiral Galaxy Near z=0.225

    CERN Document Server

    Narayanan, Anand; Wakker, Bart P

    2010-01-01

    We present analyses of the physical conditions in the z=0.22496 and z=0.22638 multi-phase O VI absorption systems detected in the ultraviolet HST/STIS and FUSE spectra of the quasar H1821+643. Both absorbers are likely associated with the extended halo of a ~2L* Sbc-Sc galaxy situated at a projected distance of ~116 kpc from the sight line. The z=0.22496 absorber is detected in C II, C III, C IV, O III, O VI, Si II, Si III and H I at > 3 sigma significance. The low and intermediate ions in this absorber are consistent with an origin in photoionized gas with [Si/H] and [C/H] of -0.6 dex. In contrast, the broader O VI absorption is likely produced in collisionally ionized plasma under nonequilibrium conditions. The z=0.22638 system has broad-Lya (BLA) and C III absorption offset by v = -53 km/s from O VI. The H I and C III line widths for the BLA imply T = 1.1 x 10^5 K. For non-equilibrium cooling we obtain [C/H] of -1.5 dex and a total hydrogen column of N(H) = 3.2 x 10^{18} cm^-2 in the BLA. The O VI, offset ...

  7. Disk mass and disk heating in the spiral galaxy NGC 3223

    CERN Document Server

    Gentile, G; Baes, M; De Geyter, G; Koleva, M; Angus, G W; de Blok, W J G; Saftly, W; Viaene, S

    2015-01-01

    We present the stellar and gaseous kinematics of an Sb galaxy, NGC 3223, with the aim of determining the vertical and radial stellar velocity dispersion as a function of radius, which can help to constrain disk heating theories. Together with the observed NIR photometry, the vertical velocity dispersion is also used to determine the stellar mass-to-light (M/L) ratio, typically one of the largest uncertainties when deriving the dark matter distribution from the observed rotation curve. We find a vertical-to-radial velocity dispersion ratio of sigma_z/sigma_R=1.21+-0.14, significantly higher than expectations from known correlations, and a weakly-constrained Ks-band stellar M/L ratio in the range 0.5-1.7, at the high end of (but consistent with) the predictions of stellar population synthesis models. Such a weak constraint on the stellar M/L ratio, however, does not allow us to securely determine the dark matter density distribution. To achieve this, either a statistical approach or additional data (e.g. integr...

  8. Outside-in stellar formation in the spiral galaxy M33?

    CERN Document Server

    Robles-Valdez, F; Peimbert, M

    2012-01-01

    We present and discuss results from chemical evolution models for M33. For our models we adopt a galactic formation with an inside-out scenario. The models are built to reproduce three observational constraints of the M33 disk: the radial distributions of: the total baryonic mass, the gas mass, and the O/H abundance. From observations, we find that the total baryonic mass profile in M33 has a double exponential behavior, decreasing exponentially for r 6 kpc due to the increase of the gas mass surface density. To adopt a concordant set of stellar and H II regions O/H values, we had to correct the later for the effect of temperature variations and O dust depletion. Our best model shows a good agreement with the observed the radial distributions of: the SFR, the stellar mass, C/H, N/H, Ne/H, Mg/H, Si/H, P/H, S/H, Ar/H, Fe/H,and Z. According to our model, the star formation efficiency is constant in time and space for r 6 kpc. The reduction of the SFR efficiency occurs earlier at higher r. While the galaxy follo...

  9. Baryonic and dark matter distribution in cosmological simulations of spiral galaxies

    CERN Document Server

    Mollitor, Pol; Teyssier, Romain

    2014-01-01

    We study three high resolution cosmological hydrodynamical simulations of Milky Way-sized halos including a comparison with the corresponding DM-only counterparts performed with the adaptive mesh refinement code RAMSES. We analyse the stellar and the gas distribution and find one of our simulated galaxies with interesting Milky Way-like features with regard to several observational tests. Thanks to consistently tuned star formation rate and supernovae feedback, we manage to obtain an extended disk and a flat rotation curve with a circular velocity and a dark matter density in the solar neighbourhood in agreement with observations. With a careful look at the derivation of the stellar-to-halo mass ratio, we also obtain competitive values for this criterion. Concerning the dark matter distribution, we explicitly show the interaction with the baryons and show how the dark matter is first contracted by star formation and then cored by feedback processes. Analysing the clump spectrum, we find a shift in mass with r...

  10. The nearby spiral density-wave structure of the Galaxy: line-of-sight and longitudinal velocities of 223 Cepheids

    Science.gov (United States)

    Griv, Evgeny; Hou, Li-Gang; Jiang, Ing-Guey; Ngeow, Chow-Choong

    2017-02-01

    The data of 223 stars within 4 kpc from the Sun and 400 pc from the plane are collected from Melnik et al., who listed photometric distances and velocities of 674 long-period Cepheids in the disc of our Galaxy. Both line-of-sight and transverse along the Galactic longitude velocities of the selected stars are analysed on the assumption that the system is the subject to Lin-Shu-type moderately unstable, low-amplitude, tightly wound and rigidly rotating density waves. Minimization of the least-squares estimator S of measured and modelled velocities of stars was performed in the geometrical parameters of waves. The wave structures defined from the two independent samples of velocities are nearly similar. Different radial scales (wavelengths) of velocity inhomogeneity of about 1, 2 and 4 kpc, which do not depend on the number of spiral arms m, were found. But for now it is unclear if one can identify these scales as fully independent global modes of collective oscillations or they are Fourier harmonics of a single wave, or they just reveal the segments of large-scale Orion, Sagittarius and Perseus arms. The dominant mode is the one-armed wave for the main minimum of all S considered. However, because the S values for fits with m = 1-4 are almost equal the latter conclusion must be regarded as tentative until more extensive data are available. High-precision Gaia observations could reveal in the near future whether the wave-like velocity fluctuations near the Sun reported here do indeed exist.

  11. INTEGRAL FIELD SPECTROSCOPY AND MULTI-WAVELENGTH IMAGING OF THE NEARBY SPIRAL GALAXY NGC 5668 : AN UNUSUAL FLATTENING IN METALLICITY GRADIENT

    Energy Technology Data Exchange (ETDEWEB)

    Marino, R. A.; Gil de Paz, A.; Castillo-Morales, A.; Perez-Gonzalez, P. G.; Gallego, J.; Zamorano, J. [CEI Campus Moncloa, UCM-UPM, Departamento de Astrofisica y CC. de la Atmosfera, Facultad de CC. Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Munoz-Mateos, J. C. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Sanchez, S. F. [Centro Astronomico Hispano Aleman, Calar Alto (CSIC-MPG), C/Jesus Durban Remon 2-2, E-04004 Almeria (Spain); Alonso-Herrero, A. [Instituto de Fisica de Cantabria, CSIC-UC, Avenida de los Castros s/n, 39005 Santander (Spain); Boissier, S., E-mail: ramarino@fis.ucm.es [Laboratoire dAstrophysique de Marseille, OAMP, Universite Aix-Marseille and CNRS UMR 6110, 38 rue Frederic Joliot-Curie, 13388 Marseille cedex 13 (France)

    2012-07-20

    We present an analysis of the full bidimensional optical spectral cube of the nearby spiral galaxy NGC 5668, observed with the Pmas fiber PAcK Integral Field Unit (IFU) at the Calar Alto observatory 3.5 m telescope. We make use of broadband imaging to provide further constraints on the evolutionary history of the galaxy. This data set will allow us to improve our understanding of the mechanisms that drive the evolution of disks. We investigated the properties of 62 H II regions and concentric rings in NGC 5668 and derived maps in ionized-gas attenuation and chemical (oxygen) abundances. We find that while inward of r {approx}36'' {approx} 4.4 kpc {approx} 0.36 (D{sub 25}/2) the derived O/H ratio follows the radial gradient typical of spiral galaxies, the abundance gradient beyond r {approx} 36'' flattens out. The analysis of the multi-wavelength surface brightness profiles of NGC 5668 is performed by fitting these profiles with those predicted by chemo-spectrophotometric evolutionary models of galaxy disks. From this, we infer a spin and circular velocity of {lambda} = 0.053 and v{sub c} = 167 km s{sup -1}, respectively. The metallicity gradient and rotation curve predicted by this best-fitting galaxy model nicely match the values derived from the IFU observations, especially within r {approx}36''. The same is true for the colors despite some small offsets and a reddening in the bluest colors beyond that radius. On the other hand, deviations of some of these properties in the outer disk indicate that a secondary mechanism, possibly gas transfer induced by the presence of a young bar, must have played a role in shaping the recent chemical and star formation histories of NGC 5668.

  12. HST/COS SPECTRA OF THREE QSOs THAT PROBE THE CIRCUMGALACTIC MEDIUM OF A SINGLE SPIRAL GALAXY: EVIDENCE FOR GAS RECYCLING AND OUTFLOW

    Energy Technology Data Exchange (ETDEWEB)

    Keeney, Brian A.; Stocke, John T.; Danforth, Charles W.; Shull, J. Michael; Green, James C. [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Rosenberg, Jessica L. [Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030 (United States); Ryan-Weber, Emma V. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H30, P.O. Box 218, Hawthorn, 3122 VIC (Australia); Savage, Blair D., E-mail: brian.keeney@colorado.edu [Department of Astronomy, University of Wisconsin-Madison, 5534 Sterling Hall, 475 North Charter Street, Madison, WI 53706 (United States)

    2013-03-01

    We have used the Cosmic Origins Spectrograph (COS) to obtain far-UV spectra of three closely spaced QSO sight lines that probe the circumgalactic medium (CGM) of an edge-on spiral galaxy, ESO 157-49, at impact parameters of 74 and 93 h {sup -1} {sub 70} kpc near its major axis and 172 h {sup -1} {sub 70} kpc along its minor axis. H I Ly{alpha} absorption is detected at the galaxy redshift in the spectra of all three QSOs, and metal lines of Si III, Si IV, and C IV are detected along the two major-axis sight lines. Photoionization models of these clouds suggest metallicities close to the galaxy metallicity, cloud sizes of {approx}1 kpc, and gas masses of {approx}10{sup 4} M {sub Sun }. Given the high covering factor of these clouds, ESO 157-49 could harbor {approx}2 Multiplication-Sign 10{sup 9} M {sub Sun} of warm CGM gas. We detect no metals in the sight line that probes the galaxy along its minor axis, but gas at the galaxy metallicity would not have detectable metal absorption with ionization conditions similar to the major-axis clouds. The kinematics of the major-axis clouds favor these being portions of a 'galactic fountain' of recycled gas, while two of the three minor-axis clouds are constrained geometrically to be outflowing gas. In addition, one of our QSO sight lines probes a second more distant spiral, ESO 157-50, along its major axis at an impact parameter of 88 h {sup -1} {sub 70} kpc. Strong H I Ly{alpha} and C IV absorption only are detected in the QSO spectrum at the redshift of ESO 157-50.

  13. Star formation properties in barred galaxies. III. Statistical study of bar-driven secular evolution using a sample of nearby barred spirals

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Zhi-Min; Wu, Hong [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Cao, Chen, E-mail: zmzhou@bao.ac.cn, E-mail: hwu@bao.ac.cn, E-mail: caochen@sdu.edu.cn [School of Space Science and Physics, Shandong University at Weihai, Weihai, Shandong 264209 (China)

    2015-01-01

    Stellar bars are important internal drivers of secular evolution in disk galaxies. Using a sample of nearby spiral galaxies with weak and strong bars, we explore the relationships between the star formation feature and stellar bars in galaxies. We find that galaxies with weak bars tend coincide with low concentrical star formation activity, while those with strong bars show a large scatter in the distribution of star formation activity. We find enhanced star formation activity in bulges toward stronger bars, although not predominantly, consistent with previous studies. Our results suggest that different stages of the secular process and many other factors may contribute to the complexity of the secular evolution. In addition, barred galaxies with intense star formation in bars tend to have active star formation in their bulges and disks, and bulges have higher star formation densities than bars and disks, indicating the evolutionary effects of bars. We then derived a possible criterion to quantify the different stages of the bar-driven physical process, while future work is needed because of the uncertainties.

  14. The GALEX/S4G UV-IR color-color diagram: Catching spiral galaxies away from the Blue Sequence

    CERN Document Server

    Bouquin, Alexandre Y K; Boissier, Samuel; Muñoz-Mateos, Juan-Carlos; Sheth, Kartik; Zaritsky, Dennis; Laine, Jarkko; Gallego, Jesús; Peletier, Reynier F; Röck, Benjamin R; Knapen, Johan H

    2015-01-01

    We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6$\\mu$m photometry for > 2000 galaxies, available for 90% of the S4G sample. We find a very tight "GALEX Blue Sequence (GBS)" in the (FUV-NUV) versus (NUV-[3.6]) color-color diagram which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale ($\\tau$) and a degeneracy between $\\tau$ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the "GALEX Green Valley (GGV)". At the red end of the GBS, at (NUV-[3.6]) > 5, we find a wider "GALEX Red Sequence (GRS)" mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by $\\rm{M}_{[3.6]}$), since both massive ($M_{\\star} > 10^{11} M_{\\odot}$) blue and red sequence galaxies are identified. The type that is proportionally more often foun...

  15. The VIRUS-P Exploration of Nearby Galaxies (VENGA): spatially resolved gas-phase metallicity distributions in barred and unbarred spirals

    Science.gov (United States)

    Kaplan, Kyle F.; Jogee, Shardha; Kewley, Lisa; Blanc, Guillermo A.; Weinzirl, Tim; Song, Mimi; Drory, Niv; Luo, Rongxin; van den Bosch, Remco C. E.

    2016-10-01

    We present a study of the excitation conditions and metallicity of ionized gas (Zgas) in eight nearby barred and unbarred spiral galaxies from the VIRUS-P Exploration of Nearby Galaxies (VENGA) survey, which provides high spatial sampling and resolution (median ˜387 pc), large coverage from the bulge to outer disc, broad wavelength range (3600-6800 Å), and medium spectral resolution (˜120 km s-1 at 5000 Å). Our results are: (1) We present high resolution gas excitation maps to differentiate between regions with excitation typical of Seyfert, LINER, or recent star formation. We find LINER-type excitation at large distances (3-10 kpc) from the centre, and associate this excitation with diffuse ionized gas (DIG). (2) After excluding spaxels dominated by Seyfert, LINER, or DIG, we produce maps with the best spatial resolution and sampling to date of the ionization parameter q, star formation rate, and Zgas using common strong line diagnostics. We find that isolated barred and unbarred spirals exhibit similarly shallow Zgas profiles from the inner kpc out to large radii (7-10 kpc or 0.5-1.0 R25). This implies that if profiles had steeper gradients at earlier epochs, then the present-day bar is not the primary driver flattening gradients over time. This result contradicts earlier claims, but agrees with recent IFU studies. (3) The Zgas gradients in our z ˜ 0 massive spirals are markedly shallower, by ˜0.2 dex kpc-1, than published gradients for lensed lower mass galaxies at z ˜ 1.5-2.0. Cosmologically motivated hydrodynamical simulations best match this inferred evolution, but the match is sensitive to adopted stellar feedback prescriptions.

  16. Rotating shallow water modeling of planetary,astrophysical and plasma vortical structures (plasma transport across a magnetic field,model of the jupiter's GRS, prediction of existence of giant vortices in spiral galaxies

    Directory of Open Access Journals (Sweden)

    M. V. Nezlin

    1999-01-01

    Full Text Available Three kinds of results have been described in this paper. Firstly, an experimental study of the Rossby vortex meridional drift on the rotating shallow water has been carried out. Owing to the stringent physical analogy between the Rossby vortices and drift vortices in the magnetized plasma, the results obtained have allowed one to make a conclusion that the transport rate of the plasma, trapped by the drift vortices, across the magnetic field is equivalent to the “gyro-Bohm” diffusion coefficient. Secondly, a model of big vortices of the type of the Great Red Spot of Jupiter, dominating in the atmospheres of the outer planets, has been produced. Thirdly, the rotating shallow water modeling has been carried out of the hydrodynamical generation mechanism of spiral structures in galaxies. Trailing spiral waves of various azimuthal modes, generated by a shear flow between fast rotating “nucleus” and slow rotating periphery, were produced. The spirals are similar to those existing in the real galaxies. The hydrodynamical concept of the spiral structure formation in galaxies has been substantiated. Strong anticyclonic vortices between the spiral arms of the structures under study have been discovered for the first time. The existence of analogous vortices in real galaxies has been predicted. (This prediction has been reliably confirmed recently in special astronomical observations, carried out on the basis of the mentioned laboratory modeling and the prediction made – see the paper by A. Fridman et al. (Astrophysics and Space Science, 1997, 252, 115.

  17. Simulations of the grand design galaxy M51: a case study for analysing tidally induced spiral structure

    CERN Document Server

    Dobbs, C L; Pringle, J E; Bate, M R

    2009-01-01

    We present hydrodynamical models of the grand design spiral M51 (NGC 5194), and its interaction with its companion NGC 5195. Despite the simplicity of our models, our simulations capture the present day spiral structure of M51 remarkably well, and even reproduce details such as a kink along one spiral arm, and spiral arm bifurcations. We investigate the offset between the stellar and gaseous spiral arms, and find at most times (including the present day) there is no offset between the stars and gas to within our error bars. We also compare our simulations with recent observational analysis of M51. We compute the pattern speed versus radius, and like the observations, find no single global pattern speed. We also show that the spiral arms cannot be fitted well by logarithmic spirals. We interpret these findings as evidence that M51 does not exhibit a quasi-steady density wave, as would be predicted by density wave theory. The internal structure of M51 derives from the complicated and dynamical interaction with ...

  18. The Influence of a Kinematically Cold Young Component on Disc-Halo Decompositions in Spiral Galaxies: Insights from Solar Neighbourhood K-giants

    CERN Document Server

    Aniyan, S; Gerhard, O E; Arnaboldi, M; Flynn, C

    2015-01-01

    In decomposing the HI rotation curves of disc galaxies, it is necessary to break a degeneracy between the gravitational fields of the disc and the dark halo by estimating the disc surface density. This is done by combining measurements of the vertical velocity dispersion of the disc with the disc scale height. The vertical velocity dispersion of the discs is measured from absorption lines (near the V-band) of near-face-on spiral galaxies, with the light coming from a mixed population of giants of all ages. However, the scale heights for these galaxies are estimated statistically from near-IR surface photometry of edge-on galaxies. The scale height estimate is therefore dominated by a population of older (> 2 Gyr) red giants. In this paper, we demonstrate the importance of measuring the velocity dispersion for the same older population of stars that is used to estimate the vertical scale height. We present an analysis of the vertical kinematics of K-giants in the solar vicinity. We find the vertical velocity d...

  19. The SWELLS survey. II. Breaking the disk-halo degeneracy in the spiral galaxy gravitational lens SDSS J2141-0001

    CERN Document Server

    Dutton, A A; Marshall, P J; Auger, M W; Treu, T; Koo, D C; Bolton, A S; Holden, B P; Koopmans, L V E

    2011-01-01

    The degeneracy among the disk, bulge and halo contributions to galaxy rotation curves prevents an understanding of the distribution of baryons and dark matter in disk galaxies. In an attempt to break this degeneracy, we present an analysis of the spiral galaxy strong gravitational lens SDSS J2141-0001, discovered as part of the SLACS survey. We present new Hubble Space Telescope multicolor imaging, gas and stellar kinematics data derived from long-slit spectroscopy, and K-band LGS adaptive optics imaging, both from the Keck telescopes. We model the galaxy as a sum of concentric axisymmetric bulge, disk and halo components and infer the contribution of each component, using information from gravitational lensing and gas kinematics. This analysis yields a best-fitting total (disk plus bulge) stellar mass of log_{10}(Mstar/Msun)=10.99(+0.11,-0.25). The photometric data combined with stellar population synthesis models yield log_{10}(Mstar/Msun)=10.97\\pm0.07, and 11.21\\pm0.07 for the Chabrier and Salpeter IMFs, r...

  20. A revised host galaxy association for GRB 020819B: a high-redshift dusty starburst, not a low-redshift gas-poor spiral

    Science.gov (United States)

    Perley, Daniel A.; Krühler, Thomas; Schady, Patricia; Michałowski, Michał J.; Thöne, Christina C.; Petry, Dirk; Graham, John F.; Greiner, Jochen; Klose, Sylvio; Schulze, Steve; Kim, Sam

    2017-02-01

    The purported spiral host galaxy of GRB 020819B at z = 0.41 has been seminal in establishing our view of the diversity of long-duration gamma-ray burst environments: Optical spectroscopy of this host provided evidence that gamma-ray bursts (GRBs) can form even at high metallicities, whereas millimetric observations suggested that GRBs may preferentially form in regions with minimal molecular gas. We report new observations from the Very Large Telescope (Multi Unit Spectroscopic Explorer and X-shooter), which demonstrate that the purported host is an unrelated foreground galaxy. The probable radio afterglow is coincident with a compact, highly star forming, dusty galaxy at z = 1.9621. The revised redshift naturally explains the apparent non-detection of CO(3-2) line emission at the afterglow site from the Atacama Large Millimetre Observatory. There is no evidence that molecular gas properties in GRB host galaxies are unusual, and limited evidence that GRBs can form readily at a super-Solar metallicity.

  1. GHASP: an Hα kinematic survey of spiral galaxies - X. Surface photometry, decompositions and the Tully-Fisher relation in the Rc band

    Science.gov (United States)

    Barbosa, C. E.; Mendes de Oliveira, C.; Amram, P.; Ferrari, F.; Russeil, D.; Epinat, B.; Perret, V.; Adami, C.; Marcelin, M.

    2015-11-01

    We present Rc-band surface photometry for 170 of the 203 galaxies in GHASP, the Gassendi H-alpha survey of spirals, a sample of late-type galaxies for which high-resolution Fabry-Perot Hα maps have previously been obtained. Our data set is constructed using new Rc-band observations taken at the Observatoire de Haute-Provence, supplemented with Sloan Digital Sky Survey archival data, obtained with the purpose of deriving homogeneous photometric profiles and parameters. Our results include Rc-band surface brightness profiles for 170 galaxies and ugriz profiles for 108 of these objects. We catalogue several parameters of general interest for further reference, such as total magnitude, effective radius and isophotal parameters (magnitude, position angle, ellipticity and inclination). We also perform a structural decomposition of the surface brightness profiles using a multi-component method to separate discs from bulges and bars, and to observe the main scaling relations involving luminosities, sizes and maximum velocities. We determine the Rc-band Tully-Fisher relation using maximum velocities derived solely from Hα rotation curves for a sample of 80 galaxies, resulting in a slope of -8.1 ± 0.5, zero-point of -3.0 ± 1.0 and an estimated intrinsic scatter of 0.28 ± 0.07. We note that, unlike the Tully-Fisher relation in the near-infrared derived for the same sample, no change in the slope of the relation is seen at the low-mass end (for galaxies with Vmax power law while the near-infrared has two), may be caused by differences in the stellar mass-to-light ratio for galaxies with Vmax < 125 km s-1.

  2. THE GALEX/S{sup 4}G UV–IR COLOR–COLOR DIAGRAM: CATCHING SPIRAL GALAXIES AWAY FROM THE BLUE SEQUENCE

    Energy Technology Data Exchange (ETDEWEB)

    Bouquin, Alexandre Y. K.; Gil de Paz, Armando; Gallego, Jesús [Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Boissier, Samuel [Aix Marseille Université, CNGRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Muñoz-Mateos, Juan-Carlos [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Sheth, Kartik [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Zaritsky, Dennis [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Laine, Jarkko [Astronomy Division, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland); Peletier, Reynier F. [Kapteyn Astronomical Institute, Postbus 800, NL-9700 AV Groningen (Netherlands); Röck, Benjamin R.; Knapen, Johan H., E-mail: abouquin@fis.ucm.es [Instituto de Astrofísica de Canarias, Vía Láctea, S/N, E-38205 La Laguna (Spain)

    2015-02-10

    We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6 μm photometry for >2000 galaxies, available for 90% of the S{sup 4}G sample. We find a very tight GALEX blue sequence (GBS) in the (FUV–NUV) versus (NUV–[3.6]) color–color diagram, which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale (τ) and a degeneracy between τ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the GALEX green valley (GGV). At the red end of the GBS, at (NUV–[3.6]) > 5, we find a wider GALEX red sequence (GRS) mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by M{sub [3.6]}) since both massive (M{sub ⋆}>10{sup 11}M{sub ⊙}) blue- and red-sequence galaxies are identified. The type that is proportionally more often found in the GGV is the S0-Sa’s, and most of these are located in high-density environments. We discuss evolutionary models of galaxies that show a rapid transition from the blue to the red sequence on a timescale of 10{sup 8} yr.

  3. The spiral galaxy M33 mapped in the FIR by ISOPHOT: A spatially resolved study of the warm and cold dust

    CERN Document Server

    Hippelein, H; Tuffs, R J; Lemke, D; Stickel, M; Klaas, U; Völk, H J

    2003-01-01

    The Sc galaxy M33 has been mapped with ISOPHOT in the far-infrared, at 60, 100, and 170mue. The spatial resolution of these FIR maps allows the separation of spiral arms and interarm regions and the isolation of a large number of star-forming regions. The spectral energy distribution in the FIR indicates a superposition of two components, a warm one originating from dust at ~45K, and a cold one, at ~16K. The warm component is concentrated towards the spiral arms and the star-forming regions, and is likely heated by the UV radiation from OB stars. The cold component is more smoothly distributed over the disk, and heated by the diffuse interstellar radiation. For the about 60 star-forming regions detected the H-alpha/FIR flux ratio increases significantly with the distance from the galaxy center, probably due to decreasing extinction. An anti-correlation of F_Ha/F_60 with F_170 suggests the intrinsic extinction to be related to the cold dust surface brightness according to A_V/S_170~0.03mag/MJy*sr. For the tota...

  4. Star Formation in Irregular Galaxies.

    Science.gov (United States)

    Hunter, Deidre; Wolff, Sidney

    1985-01-01

    Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

  5. The Spatially Resolved Dynamics of Dusty Starburst Galaxies in a z ~ 0.4 Cluster: Beginning the Transition from Spirals to S0s

    CERN Document Server

    Johnson, H L; Swinbank, A M; Bower, R G; Smail, Ian; Koyama, Y; Geach, J E

    2016-01-01

    To investigate what drives the reversal of the morphology-density relation at intermediate/high redshift, we present a multi-wavelength analysis of 27 dusty starburst galaxies in the massive cluster Cl 0024+17 at z = 0.4. We combine H-alpha dynamical maps from the VLT/FLAMES multi-IFU system with far-infrared imaging using Herschel SPIRE and millimetre spectroscopy from IRAM/NOEMA, in order to measure the dynamics, star formation rates and gas masses of this sample. Most galaxies appear to be rotationally supported, with a median ratio of rotational support to line-of-sight velocity dispersion v/sigma ~ 5 +/- 2, and specific angular momentum lambda_R = 0.83 +/- 0.06 - comparable to field spirals of a similar mass at this redshift. The star formation rates of 3 - 26 M_solar/yr and average 12 CO derived gas mass of 1 x 10^10 M_solar suggest gas depletion timescales of ~ 1Gyr (~ 0.25 of the cluster crossing time). We derive characteristic dust temperatures (mean T_dust = 26 +/- 1 K) consistent with local galaxie...

  6. GHASP: an H$\\alpha$ kinematic survey of spiral galaxies - X. Surface photometry, decompositions and the Tully-Fisher relation in the Rc-band

    CERN Document Server

    Barbosa, C E; Amram, P; Ferrari, F; Russeil, D; Epinat, B; Perret, V; Adami, C; Marcelin, M

    2015-01-01

    We present Rc-band surface photometry for 170 of the 203 galaxies in GHASP, Gassendi H-Alpha survey of SPirals, a sample of late-type galaxies for which high-resolution Fabry-Perot H{\\alpha} maps have previously been obtained. Our data set is constructed by new Rc-band observations taken at the Observatoire de Haute-Provence (OHP), supplemented with Sloan Digital Sky Survey (SDSS) archival data, obtained with the purpose of deriving homogeneous photometric profiles and parameters. Our results include Rc-band surface brightness profiles for 170 galaxies and $ugriz$ profiles for 108 of these objects. We catalogue several parameters of general interest for further reference, such as total magnitude, effective radius and isophotal parameters -- magnitude, position angle, ellipticity and inclination. We also perform a structural decomposition of the surface brightness profiles using a multi-component method in order to separate disks from bulges and bars, and to observe the main scaling relations involving luminos...

  7. Extragalactic chemical abundances: do HII regions and young stars tell the same story? The case of the spiral galaxy NGC 300

    CERN Document Server

    Bresolin, Fabio; Kudritzki, Rolf-Peter; Pietrzynski, Grzegorz; Urbaneja, Miguel A; Carraro, Giovanni

    2009-01-01

    (Abridged) We have obtained new spectrophotometric data for 28 HII regions in the spiral galaxy NGC 300, a member of the nearby Sculptor Group. The detection of auroral lines, including [OIII]4363, [SIII]6312 and [NII]5755, has allowed us to measure electron temperatures and direct chemical abundances for the whole sample. We determine for the first time in this galaxy a radial gas-phase oxygen abundance gradient based solely on auroral lines, and obtain the following least-square solution: 12+log(O/H)=8.57-0.41 R/R25, where the galactocentric distance is expressed in terms of the isophotal radius R25. The gradient corresponds to -0.077 dex/kpc, and agrees very well with the galactocentric trend in metallicity obtained for 29 B and A supergiants in the same galaxy. The intercept of the regression for the nebular data virtually coincides with the intercept obtained from the stellar data. This allows little room for depletion of nebular oxygen onto dust grains, although in this kind of comparison we are somewha...

  8. The influence of a kinematically cold young component on disc-halo decompositions in spiral galaxies: insights from solar neighbourhood K-giants

    Science.gov (United States)

    Aniyan, S.; Freeman, K. C.; Gerhard, O. E.; Arnaboldi, M.; Flynn, C.

    2016-02-01

    In decomposing the H I rotation curves of disc galaxies, it is necessary to break a degeneracy between the gravitational fields of the disc and the dark halo by estimating the disc surface density. This is done by combining measurements of the vertical velocity dispersion of the disc with the disc scaleheight. The vertical velocity dispersion of the discs is measured from absorption lines (near the V band) of near-face-on spiral galaxies, with the light coming from a mixed population of giants of all ages. However, the scaleheights for these galaxies are estimated statistically from near-IR surface photometry of edge-on galaxies. The scaleheight estimate is therefore dominated by a population of older (>2 Gyr) red giants. In this paper, we demonstrate the importance of measuring the velocity dispersion for the same older population of stars that is used to estimate the vertical scaleheight. We present an analysis of the vertical kinematics of K-giants in the solar vicinity. We find the vertical velocity distribution best fitted by two components with dispersions of 9.6 ± 0.5 km s-1 and 18.6 ± 1.0 km s-1, which we interpret as the dispersions of the young and old disc populations, respectively. Combining the (single) measured velocity dispersion of the total young + old disc population (13.0 ± 0.1 km s-1) with the scaleheight estimated for the older population would underestimate the disc surface density by a factor of ˜2. Such a disc would have a peak rotational velocity that is only 70 per cent of that for the maximal disc, thus making it appear submaximal.

  9. Absorption-line detections of 10{sup 5}-10{sup 6} K gas in spiral-rich groups of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Stocke, John T.; Keeney, Brian A.; Danforth, Charles W.; Syphers, David; Yamamoto, H.; Shull, J. Michael; Green, James C.; Froning, Cynthia [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Savage, Blair D.; Wakker, Bart; Kim, Tae-Sun [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Ryan-Weber, Emma V.; Kacprzak, Glenn G., E-mail: john.stocke@colorado.edu [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, VIC 3122 (Australia)

    2014-08-20

    Using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, the COS Science Team has conducted a high signal-to-noise survey of 14 bright QSOs. In a previous paper, these far-UV spectra were used to discover 14 'warm' (T ≥ 10{sup 5} K) absorbers using a combination of broad Lyα and broad O VI absorptions. A reanalysis of a few of this new class of absorbers using slightly relaxed fitting criteria finds as many as 20 warm absorbers could be present in this sample. A shallow, wide spectroscopic galaxy redshift survey has been conducted around these sight lines to investigate the warm absorber environment, which is found to be spiral-rich groups or cluster outskirts with radial velocity dispersions σ = 250-750 km s{sup –1}. While 2σ evidence is presented favoring the hypothesis that these absorptions are associated with the galaxy groups and not with the individual, nearest galaxies, this evidence has considerable systematic uncertainties and is based on a small sample size so it is not entirely conclusive. If the associations are with galaxy groups, the observed frequency of warm absorbers (dN/dz = 3.5-5 per unit redshift) requires them to be very extended as an ensemble on the sky (∼1 Mpc in radius at high covering factor). Most likely these warm absorbers are interface gas clouds whose presence implies the existence of a hotter (T ∼ 10{sup 6.5} K), diffuse, and probably very massive (>10{sup 11} M {sub ☉}) intra-group medium which has yet to be detected directly.

  10. First results from the Dragonfly Telephoto Array: the apparent lack of a stellar halo in the massive spiral galaxy M101

    CERN Document Server

    van Dokkum, Pieter; Merritt, Allison

    2014-01-01

    We use a new telescope concept, the Dragonfly Telephoto Array, to study the low surface brightness outskirts of the spiral galaxy M101. The radial surface brightness profile is measured down to mu_g ~ 32 mag/arcsec^2, a depth that approaches the sensitivity of star count studies in the Local Group. We convert surface brightness to surface mass density using the radial g-r color profile. The mass density profile shows no significant upturn at large radius and is well-approximated by a simple bulge + disk model out to R = 70 kpc, corresponding to 18 disk scale lengths. Fitting a bulge + disk + halo model we find that the best-fitting halo mass M_halo ~ 1.7 x 10^8 M_sun. The total stellar mass of M101 is M_tot,* ~ 5.3 x 10^10 Msun, and we infer that the halo mass fraction f_halo = M_halo / M_tot,* ~ 0.003. This mass fraction is lower than that of the Milky Way (f_halo ~ 0.02) and M31 (f_halo ~ 0.04). All three galaxies fall below the f_halo - M_tot,* relation predicted by recent cosmological simulations that tra...

  11. The Relationship between the Dense Neutral and Diffuse Ionized Gas in the Thick Disks of Two Edge-on Spiral Galaxies

    Science.gov (United States)

    Rueff, Katherine M.; Howk, J. Christopher; Pitterle, Marissa; Hirschauer, Alec S.; Fox, Andrew J.; Savage, Blair D.

    2013-03-01

    We present high-resolution, optical images (BVI + Hα) of the multiphase interstellar medium (ISM) in the thick disks of the edge-on spiral galaxies NGC 4013 and NGC 4302. Our images from the Hubble Space Telescope (HST), Large Binocular Telescope, and WIYN 3.5 m telescope reveal an extensive population of filamentary dust absorption seen to z ~2-2.5 kpc. Many of these dusty thick disk structures have characteristics reminiscent of molecular clouds found in the Milky Way disk. Our Hα images show that the extraplanar diffuse ionized gas (DIG) in these galaxies is dominated by a smooth, diffuse component. The strongly filamentary morphologies of the dust absorption have no counterpart in the smoothly distributed Hα emission. We argue that the thick disk DIG and dust-bearing filaments trace physically distinct phases of the thick disk ISM, the latter tracing a dense, warm or cold neutral medium. The dense, dusty matter in the thick disks of spiral galaxies is largely tracing matter ejected from the thin disk via energetic feedback from massive stars. The high densities of the gas may be a result of converging gas flows. This dense material fuels some thick disk star formation, as evidenced by the presence of thick disk H II regions. Based on observations obtained with the NASA/ESA Hubble Space Telescope operated at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Also, based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the US, Italy, and Germany. LBT Corporation partners are the University of Arizona, on behalf of the Arizona University System; Instituto Nazionale do Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute of Potsdam, and Heidelberg University; Ohio State University, and the Research Corporation, on

  12. The UVJ Selection of Quiescent and Star Forming Galaxies: Separating Early and Late-Type Galaxies and Isolating Edge-on Spirals

    CERN Document Server

    Patel, Shannon G; Kelson, Daniel D; Franx, Marijn; van der Wel, Arjen; Illingworth, Garth D

    2011-01-01

    We utilize for the first time HST ACS 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 0.610.25). 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 Sersic 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 Sersic indices. Interestingly, most UVJ-selected SFGs with high Sersic 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 a SFG on the sequence of UVJ colors is determined to a large degree by the mass of ...

  13. 棒对旋涡星系中央恒星形成的作用%The Effects of Bar Sturcture on the Central sSFR of Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    林野

    2014-01-01

    We investigate the effects of bars in spiral galaxies on galaxy central specific Star Formation Rate (sSFR) using a sample of over 9000 spiral galaxies drawn from Sloan Digital Sky Survey, with morphological classifications assigned by visual inspection. Our sample includes three types: none-barred galaxies and galaxies hosting long or short bars, respectively. By identifying star-forming and quiescent population, we find barred spiral galaxies tend to be central quiescent. However, the star-forming barred spiral galaxies tend to have stronger central star forming activities than the unbarred spiral galaxies. In order to find the connection between central sSFR and the presence of a bar within the spiral galaxy, we construct control samples where barred and unbarred ones are closely matched by stellar mass. We then find the same proportion of central quiescent galaxies for barred and unbarred ones. Furthermore, the star-forming barred ones still have stronger central star forming activities than the unbarred ones with the signal mainly coming from the long barred ones. These results demonstrate that bars may have no influence on central star quiescence, but bars can induce the central star formation in their host spiral galaxies where the effect are mainly contributed by long bars.%使用了目前最大的棒旋星系样本之一,着重于研究旋涡星系中央的比恒星形成率(sSFR)和棒结构的关系。我们用lg sSFR =−11 a−1作为星系宁静态和活跃态的分界,统计对比了棒旋星系和非棒旋星系中央的sSFR,发现相对于非棒旋星系,棒旋星系处于中央宁静态的比重更大,而在中央活跃态其恒星形成活动更剧烈。为消除星系样本恒星质量差异对星系中央sSFR统计结果的影响,获得控制样本,使棒旋星系和非棒旋星系具有相同的恒星质量分布。随后发现这两类星系在中央宁静态中的统计差异消失,而在中央活跃态棒旋星系的恒星

  14. Spirality: A Noval Way to Measure Spiral Arm Pitch Angle

    Science.gov (United States)

    Shields, Douglas W.; Boe, Benjamin; Henderson, Casey L.; Hartley, Matthew; Davis, Benjamin L.; Pour Imani, Hamed; Kennefick, Daniel; Kennefick, Julia D.

    2015-01-01

    We present the MATLAB code Spirality, a novel method for measuring spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. For a given pitch angle template, the mean pixel value is found along each of typically 1000 spiral axes. The fitting function, which shows a local maximum at the best-fit pitch angle, is the variance of these means. Error bars are found by varying the inner radius of the measurement annulus and finding the standard deviation of the best-fit pitches. Computation time is typically on the order of 2 minutes per galaxy, assuming at least 8 GB of working memory. We tested the code using 128 synthetic spiral images of known pitch. These spirals varied in the number of spiral arms, pitch angle, degree of logarithmicity, radius, SNR, inclination angle, bar length, and bulge radius. A correct result is defined as a result that matches the true pitch within the error bars, with error bars no greater than ±7°. For the non-logarithmic spiral sample, the correct answer is similarly defined, with the mean pitch as function of radius in place of the true pitch. For all synthetic spirals, correct results were obtained so long as SNR > 0.25, the bar length was no more than 60% of the spiral's diameter (when the bar was included in the measurement), the input center of the spiral was no more than 6% of the spiral radius away from the true center, and the inclination angle was no more than 30°. The synthetic spirals were not deprojected prior to measurement. The code produced the correct result for all barred spirals when the measurement annulus was placed outside the bar. Additionally, we compared the code's results against 2DFFT results for 203 visually selected spiral galaxies in GOODS North and South. Among the entire sample, Spirality's error bars overlapped 2DFFT's error bars 64% of the time. For those galaxies in which Source code is available by email request from the primary author.

  15. THE STRUCTURE OF NUCLEAR STAR CLUSTERS IN NEARBY LATE-TYPE SPIRAL GALAXIES FROM HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 IMAGING

    Energy Technology Data Exchange (ETDEWEB)

    Carson, Daniel J.; Barth, Aaron J. [Department of Physics and Astronomy, University of California Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Seth, Anil C.; Brok, Mark den [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Cappellari, Michele [Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Peyton Hall—Ivy Lane, Princeton, NJ 08544 (United States); Ho, Luis C. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Neumayer, Nadine [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)

    2015-05-15

    We obtained Hubble Space Telescope/Wide Field Camera 3 imaging of a sample of ten of the nearest and brightest nuclear clusters (NCs) residing in late-type spiral galaxies, in seven bands that span the near-UV to the near-IR. Structural properties of the clusters were measured by fitting two-dimensional surface brightness profiles to the images using GALFIT. The clusters exhibit a wide range of structural properties, with F814W absolute magnitudes that range from −11.2 to −15.1 mag and F814W effective radii that range from 1.4 to 8.3 pc. For 6 of the 10 clusters in our sample, we find changes in the effective radius with wavelength, suggesting radially varying stellar populations. In four of the objects, the effective radius increases with wavelength, indicating the presence of a younger population that is more concentrated than the bulk of the stars in the cluster. However, we find a general decrease in effective radius with wavelength in two of the objects in our sample, which may indicate extended, circumnuclear star formation. We also find a general trend of increasing roundness of the clusters at longer wavelengths, as well as a correlation between the axis ratios of the NCs and their host galaxies. These observations indicate that blue disks aligned with the host galaxy plane are a common feature of NCs in late-type galaxies, but are difficult to detect in galaxies that are close to face-on. In color–color diagrams spanning the near-UV through the near-IR, most of the clusters lie far from single-burst evolutionary tracks, showing evidence for multi-age populations. Most of the clusters have integrated colors consistent with a mix of an old population (>1 Gyr) and a young population (∼100–300 Myr). The wide wavelength coverage of our data provides a sensitivity to populations with a mix of ages that would not be possible to achieve with imaging in optical bands only. The surface brightness profiles presented in this work will be used for future

  16. FIRST RESULTS FROM THE DRAGONFLY TELEPHOTO ARRAY: THE APPARENT LACK OF A STELLAR HALO IN THE MASSIVE SPIRAL GALAXY M101

    Energy Technology Data Exchange (ETDEWEB)

    Van Dokkum, Pieter G.; Merritt, Allison [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Abraham, Roberto [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H8 (Canada)

    2014-02-20

    We use a new telescope concept, the Dragonfly Telephoto Array, to study the low surface brightness outskirts of the spiral galaxy M101. The radial surface brightness profile is measured down to μ {sub g} ∼ 32 mag arcsec{sup –2}, a depth that approaches the sensitivity of star count studies in the Local Group. We convert surface brightness to surface mass density using the radial g – r color profile. The mass density profile shows no significant upturn at large radius and is well-approximated by a simple bulge + disk model out to R = 70 kpc, corresponding to 18 disk scale lengths. Fitting a bulge + disk + halo model we find that the best-fitting halo mass M{sub halo}=1.7{sub −1.7}{sup +3.4}×10{sup 8} M {sub ☉}. The total stellar mass of M101 is M{sub tot,∗}=5.3{sub −1.3}{sup +1.7}×10{sup 10} M {sub ☉}, and we infer that the halo mass fraction f{sub halo}=M{sub halo}/M{sub tot,∗}=0.003{sub −0.003}{sup +0.006}. This mass fraction is lower than that of the Milky Way (f {sub halo} ∼ 0.02) and M31 (f {sub halo} ∼ 0.04). All three galaxies fall below the f {sub halo}-M {sub tot,} {sub *} relation predicted by recent cosmological simulations that trace the light of disrupted satellites, with M101's halo mass a factor of ∼10 below the median expectation. However, the predicted scatter in this relation is large, and more galaxies are needed to better quantify this possible tension with galaxy formation models. Dragonfly is well suited for this project: as integrated-light surface brightness is independent of distance, large numbers of galaxies can be studied in a uniform way.

  17. The Herschel Virgo Cluster Survey. IX. Dust-to-gas mass ratio and metallicity gradients in four Virgo spiral galaxies

    CERN Document Server

    Magrini, Laura; Corbelli, Edvige; Cortese, Luca; Hunt, Leslie; Smith, Matthew; Vlahakis, Catherine; Davies, Jonathan; Bendo, George J; Baes, Maarten; Boselli, Alessandro; Clemens, Marcel; Casasola, Viviana; De Looze, Ilse; Fritz, Jacopo; Giovanardi, Carlo; Grossi, Marco; Hughes, Thomas; Madden, Suzanne; Pappalardo, Ciro; Pohlen, Michael; Alighieri, Sperello di Serego; Verstappen, Joris

    2011-01-01

    Using Herschel data from the Open Time Key Project the Herschel Virgo Cluster Survey (HeViCS), we investigated the relationship between the metallicity gradients expressed by metal abundances in the gas phase as traced by the chemical composition of HII regions, and in the solid phase, as traced by the dust-to-gas mass ratio. We derived the radial gradient of the dust-to-gas mass ratio for all galaxies observed by HeViCS whose metallicity gradients are available in the literature. They are all late type Sbc galaxies, namely NGC4254, NGC4303, NGC4321, and NGC4501. We examined different dependencies on metallicity of the CO-to-H$_2$ conversion factor (\\xco), used to transform the $^{12}$CO observations into the amount of molecular hydrogen. We found that in these galaxies the dust-to-gas mass ratio radial profile is extremely sensitive to choice of the \\xco\\ value, since the molecular gas is the dominant component in the inner parts. We found that for three galaxies of our sample, namely NGC4254, NGC4321, and N...

  18. The SWELLS survey. IV. Precision measurements of the stellar and dark matter distributions in a spiral lens galaxy

    CERN Document Server

    Barnabè, Matteo; Marshall, Philip J; Auger, Matthew W; Brewer, Brendon J; Treu, Tommaso; Bolton, Adam S; Koo, David C; Koopmans, Léon V E

    2012-01-01

    We construct a fully self-consistent mass model for the lens galaxy J2141 at z=0.14, and use it to improve on previous studies by modelling its gravitational lensing effect, gas rotation curve and stellar kinematics simultaneously. We adopt a very flexible axisymmetric mass model constituted by a generalized NFW dark matter halo and a stellar mass distribution obtained by deprojecting the MGE fit to the high-resolution K'-band LGSAO imaging data of the galaxy, with the (spatially constant) M/L ratio as a free parameter. We model the stellar kinematics by solving the anisotropic Jeans equations. We find that the inner logarithmic slope of the dark halo is weakly constrained (gamma = 0.82^{+0.65}_{-0.54}), and consistent with an unmodified NFW profile. We infer the galaxy to have (i) a dark matter fraction within 2.2 disk radii of 0.28^{+0.15}_{-0.10}, independent of the galaxy stellar population, implying a maximal disk for J2141; (ii) an apparently uncontracted dark matter halo, with concentration c_{-2} = 7....

  19. The star cluster - field star connection in nearby spiral galaxies. II. Field star and cluster formation histories and their relation

    NARCIS (Netherlands)

    Silva-Villa, E.; Larsen, S.S.

    2011-01-01

    Context. Recent studies have started to cast doubt on the assumption that most stars are formed in clusters. Observational studies of field stars and star cluster systems in nearby galaxies can lead to better constraints on the fraction of stars forming in clusters. Ultimately this may lead to a bet

  20. How Different are Normal and Barred Spirals?

    CERN Document Server

    Bergh, Sidney van den

    2011-01-01

    No significant color differences are found between normal and barred spirals over the range of Hubble stages a - ab - b - bc. Furthermore, no significant difference is seen between the luminosity distributions of normal and barred galaxies over the same range of Hubble stages. However, SBc galaxies are found to be systematically fainter than Sc galaxies at 99% confidence. The observation that normal and barred spirals with Hubble stages a - ab - b - bc have indistinguishable intrinsic colors hints at the possibility that the bars in such spiral galaxies might be ephemeral structures. Finally, it is pointed out that lenticular galaxies of types S0 and SB0 are systematically fainter than are other early-type galaxies, suggesting that such galaxies are situated on evolutionary tracks that differ systematically from those of galaxies that lie along the E - Sa - Sb -Sc and E - SBa - SBb - SBc sequences.

  1. 棒对星系核区恒星形成活动的影响%The Effect of Bar on Nuclear Star-forming Activities in Nearby Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    汪潋

    2009-01-01

    利用SDSS光谱,研究了IRAS卫星亮红外源星表中的盘状星系中的恒星形成性质,并着重探讨了棒对星系核区恒星形成活动的影响.利用星族合成的方法得到了每个样本星系核区的恒星组成性质、恒星形成活动的强度等信息,并比较了星系整体和核区恒星形成性质的差异.得到的结论:除去相互作用,样本中的棒星系显示出比非棒旋星系更强的核区恒星形成活动和更多的年轻星族成分.%By using SDSS spectra, we have studied nuclear star-forming properties of nearby spiral galaxies selected from Infrared Revised Bright Galaxy Sample, and try to find the effect of bar structure on star-forming activities in the nuclear regions of nearby galaxies. The composition of stellar population and the strength of star formation activities in the sample galaxies are acquired by using stellar population synthesis code ?STARLIGHT, and the star formation properties in nuclear regions are compared with that of the whole galaxies. We find that the star formation in barred spiral galaxies is more intensive than non-barred ones and barred spirals show much younger stellar populations.

  2. Featured Image: The Birth of Spiral Arms

    Science.gov (United States)

    Kohler, Susanna

    2017-01-01

    In this figure, the top panels show three spiral galaxies in the Virgo cluster, imaged with the Sloan Digital Sky Survey. The bottom panels provide a comparison with three morphologically similar galaxies generated insimulations. The simulations run by Marcin Semczuk, Ewa okas, and Andrs del Pino (Nicolaus Copernicus Astronomical Center, Poland) were designed to examine how the spiral arms of galaxies like the Milky Way may have formed. In particular, the group exploredthe possibility that so-called grand-design spiral arms are caused by tidal effects as a Milky-Way-like galaxy orbits a cluster of galaxies. The authors show that the gravitational potential of the cluster can trigger the formation of two spiral arms each time the galaxy passes through the pericenter of its orbit around the cluster. Check out the original paper below for more information!CitationMarcin Semczuk et al 2017 ApJ 834 7. doi:10.3847/1538-4357/834/1/7

  3. 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

  4. The star cluster - field star connection in nearby spiral galaxies. II. Field star and cluster formation histories and their relation

    Science.gov (United States)

    Silva-Villa, E.; Larsen, S. S.

    2011-05-01

    Context. Recent studies have started to cast doubt on the assumption that most stars are formed in clusters. Observational studies of field stars and star cluster systems in nearby galaxies can lead to better constraints on the fraction of stars forming in clusters. Ultimately this may lead to a better understanding of star formation in galaxies, and galaxy evolution in general. Aims: We aim to constrain the amount of star formation happening in long-lived clusters for four galaxies through the homogeneous, simultaneous study of field stars and star clusters. Methods: Using HST/ACS and HST/WFPC2 images of the galaxies NGC 45, NGC 1313, NGC 5236, and NGC 7793, we estimate star formation histories by means of the synthetic CMD method. Masses and ages of star clusters are estimated using simple stellar population model fitting. Comparing observed and modeled luminosity functions, we estimate cluster formation rates. By randomly sampling the stellar initial mass function (SIMF), we construct artificial star clusters and quantify how stochastic effects influence cluster detection, integrated colors, and age estimates. Results: Star formation rates appear to be constant over the past 107 - 108 years within the fields covered by our observations. The number of clusters identified per galaxy varies, with a few detected massive clusters (M ≥ 105 M⊙) and a few older than 1 Gyr. Among our sample of galaxies, NGC 5236 and NGC 1313 show high star and cluster formation rates, while NGC 7793 and NGC 45 show lower values. We find that stochastic sampling of the SIMF has a strong impact on the estimation of ages, colors, and completeness for clusters with masses ≤ 103 - 104 M⊙, while the effect is less pronounced for high masses. Stochasticity also makes size measurements highly uncertain at young ages (τ ≲ 108 yr), making it difficult to distinguish between clusters and stars based on sizes. Conclusions: The ratio of star formation happening in clusters (Γ) compared to

  5. Star Formation in Spiral Arms

    CERN Document Server

    Elmegreen, Bruce G

    2011-01-01

    The origin and types of spiral arms are reviewed with an emphasis on the connections between these arms and star formation. Flocculent spiral arms are most likely the result of transient instabilities in the gas that promote dense cloud formation, star formation, and generate turbulence. Long irregular spiral arms are usually initiated by gravitational instabilities in the stars, with the gas contributing to and following these instabilities, and star formation in the gas. Global spiral arms triggered by global perturbations, such as a galaxy interaction, can be wavemodes with wave reflection in the inner regions. They might grow and dominate the disk for several rotations before degenerating into higher-order modes by non-linear effects. Interstellar gas flows through these global arms, and through the more transient stellar spiral arms as well, where it can reach a high density and low shear, thereby promoting self-gravitational instabilities. The result is the formation of giant spiral arm cloud complexes,...

  6. The star cluster - field star connection in nearby spiral galaxies. II. Field star and cluster formation histories and their relation

    CERN Document Server

    Silva-Villa, Esteban

    2011-01-01

    Recent studies have started to cast doubt on the assumption that most stars are formed in clusters. Observational studies of field stars and star cluster systems in nearby galaxies can lead to better constraints on the fraction of stars forming in clusters. We aim to constrain the amount of star formation happening in long-lived clusters for four galaxies through the homogeneous study of field stars and star clusters. Using HST/ACS-WFPC2 images of the galaxies NGC45, NGC1313, NGC5236 and NGC7793, we estimate star formation histories by means of the synthetic CMD method. Masses and ages of star clusters are estimated using simple stellar population model fitting. Comparing observed and modeled luminosity functions we estimate cluster formation rates. By randomly sampling the stellar IMF, we construct artificial star clusters and quantify how stochastic effects influence cluster detection, integrated colors and age estimates. Star formation rates appear to be constant over the past 10-100 Myr. The number of clu...

  7. VIRUS-W: commissioning and first-year results of a new integral field unit spectrograph dedicated to the study of spiral galaxy bulges

    Science.gov (United States)

    Fabricius, Maximilian H.; Grupp, Frank; Bender, Ralf; Drory, Niv; Arns, Jim; Barnes, Stuart; Gössl, Claus; Snigula, Jan; Hill, Gary J.; Hopp, Ulrich; Lang-Bardl, Florian; MacQueen, Phillip J.; Saglia, Roberto; Wullstein, Philipp

    2012-09-01

    In November and December 2010 we successfully commissioned a new optical fibre-based Integral Field Unit (IFU) spectrograph at the 2.7m Harlan J. Smith Telescope of the McDonald Observatory in Texas. Regular science observations commenced in spring 2011. The instrument achieves a spectral resolution of λ/Δλ = 8700 with a spectral coverage of 4850Å - 5480Å and a spectacular throughput of 37% including the telescope optics. The design is related to the VIRUS-P instrument that was developed for the HETDEX experiment, but was modified significantly in order to achieve the large spectral resolution that is needed to recover the dynamical properties of disk galaxies. In addition to the high resolution mode, VIRUS-W offers a stellar population mode with a resolution of λ/Δλ = 3300 and a spectral coverage of 4340Å - 6040Å. The IFU is comprised out of 267 150 μm-core optical fibers with a fill factor of 1/3. With a beam of f/3.65, the core diameter translates to 3.2" on sky and a large field of view of 105" x 55" that is ideally suited to study the bulge regions of local spiral galaxies. The large throughput is due to a design that operates close to the numerical aperture of the fibers, a large 200mm aperture refractive camera with no central obscuration, highly efficient volume phase holographic gratings, and a high-QE CCD. We will discuss the design, the performance and briefly present an example for the very up-to-date science that is possible with such instruments at 2m class telescopes.

  8. Galaxy Disks

    NARCIS (Netherlands)

    van der Kruit, P. C.; Freeman, K. C.

    The disks of disk galaxies contain a substantial fraction of their baryonic matter and angular momentum, and much of the evolutionary activity in these galaxies, such as the formation of stars, spiral arms, bars and rings, and the various forms of secular evolution, takes place in their disks. The

  9. The Structure of Nuclear Star Clusters in Nearby Late-type Spiral Galaxies from Hubble Space Telescope Wide Field Camera 3 Imaging

    CERN Document Server

    Carson, Daniel J; Seth, Anil C; Brok, Mark den; Cappelari, Michele; Greene, Jenny E; Ho, Luis C; Neumayer, Nadine

    2015-01-01

    We obtained Hubble Space Telescope/Wide Field Camera 3 imaging of a sample of ten of the nearest and brightest nuclear clusters residing in late-type spiral galaxies, in seven bands that span the near-ultraviolet to the near-infrared. Structural properties of the clusters were measured by fitting two-dimensional surface brightness profiles to the images using GALFIT. The clusters exhibit a wide range of structural properties. For six of the ten clusters in our sample, we find changes in the effective radius with wavelength, suggesting radially varying stellar populations. In four of the objects, the effective radius increases with wavelength, indicating the presence of a younger population which is more concentrated than the bulk of the stars in the cluster. However, we find a general decrease in effective radius with wavelength in two of the objects in our sample, which may indicate extended, circumnuclear star formation. We also find a general trend of increasing roundness of the clusters at longer waveleng...

  10. A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974: signature of an inner bar

    CERN Document Server

    Emsellem, E; Ferruit, P; Emsellem, Eric; Goudfrooij, Paul; Ferruit, Pierre

    2003-01-01

    TIGER integral-field spectrography and HST/WFPC2 imaging of the E3 galaxy NGC 2974 are used to derive the kinematics of the stellar and ionized gas components in its central 500 pc. We derive a numerical two-integral distribution function from a MGE mass model using the HQ formalism. The TIGER as well as published long-slit stellar kinematics are well fitted with this self-consistent model, requiring neither the addition of a significant mass contribution from a hidden disc structure, nor the presence of a central dark mass. The data reveal the presence of a striking, highly contrasted, two-arm gaseous spiral structure within a radius of ~200 pc, corresponding to a total mass of 6.8x10^4 Msun of ionized gas. We use a deconvolved TIGER datacube to probe its kinematics at a resolution of about 0.35 arcsec. Strong departures from circular motions are observed, as well as high velocity dispersion values on the inner side of the arms. We interpret the observed gas morphology and kinematics as the signature of stre...

  11. Unveiling the Nature of an X-ray flare from 3XMM J014528.9+610729: A candidate spiral galaxy

    CERN Document Server

    Bhatt, Himali; Bhatt, Nilay; Pandey, J C

    2014-01-01

    We report an X-ray flare from 3XMM J014528.9+610729, serendipitously detected during the observation of the open star cluster NGC 663. The colour-colour space technique using optical and infrared data reveals the X-ray source as a candidate spiral galaxy. The flare shows fast rise and exponential decay shape with a ratio of the peak and the quiescent count rates of $\\sim$60 and duration of $\\sim$5.4 ks. The spectrum during the flaring state is well fitted with a combination of thermal ({\\sc Apec}) model with a plasma temperature of $\\rm{1.3\\pm0.1}$ keV and non-thermal ({\\sc Power-law}) model with power-law index of $\\rm{1.9\\pm0.2}$. However, no firm conclusion can be made for the spectrum during the quiescent state. The temporal behavior, plasma temperature and spectral evolution during flare suggest that the flare from 3XMM J014528.9+610729 can not be associated with tidal disruption events.

  12. Observational Confirmations of Spiral Density Wave Theory

    Science.gov (United States)

    Kennefick, Julia D.; Kennefick, Daniel; Shameer Abdeen, Mohamed; Berrier, Joel; Davis, Benjamin; Fusco, Michael; Pour Imani, Hamed; Shields, Doug; DMS, SINGS

    2017-01-01

    Using two techniques to reliably and accurately measure the pitch angles of spiral arms in late-type galaxies, we have compared pitch angles to directly measured black hole masses in local galaxies and demonstrated a strong correlation between them. Using the relation thus established we have developed a pitch angle distribution function of a statistically complete volume limited sample of nearby galaxies and developed a central black hole mass function for nearby spiral galaxies.We have further shown that density wave theory leads us to a three-way correlation between bulge mass, pitch angle, and disk gas density, and have used data from the Galaxy Disk Mass Survey to confirm this possible fundamental plane. Density wave theory also predicts that the pitch angle of spiral arms should change with observed waveband as each waveband is sampling a different stage in stellar population formation and evolution. We present evidence that this is indeed the case using a sample of galaxies from the Spitzer Infrared Nearby Galaxy Survey. Furthermore, the evolved spiral arms cross at the galaxy co-rotation radius. This gives a new method for determining the co-rotation radius of spiral galaxies that is found to agree with those found using previous methods.

  13. The perfect shape spiral stories

    CERN Document Server

    Hammer, Øyvind

    2016-01-01

    This book uses the spiral shape as a key to a multitude of strange and seemingly disparate stories about art, nature, science, mathematics, and the human endeavour. In a way, the book is itself organized as a spiral, with almost disconnected chapters circling around and closing in on the common theme. A particular strength of the book is its extremely cross-disciplinary nature - everything is fun, and everything is connected! At the same time, the author puts great emphasis on mathematical and scientific correctness, in contrast, perhaps, with some earlier books on spirals. Subjects include the mathematical properties of spirals, sea shells, sun flowers, Greek architecture, air ships, the history of mathematics, spiral galaxies, the anatomy of the human hand, the art of prehistoric Europe, Alfred Hitchcock, and spider webs, to name a few.

  14. A 15.65-solar-mass black hole in an eclipsing binary in the nearby spiral galaxy M 33.

    Science.gov (United States)

    Orosz, Jerome A; McClintock, Jeffrey E; Narayan, Ramesh; Bailyn, Charles D; Hartman, Joel D; Macri, Lucas; Liu, Jiefeng; Pietsch, Wolfgang; Remillard, Ronald A; Shporer, Avi; Mazeh, Tsevi

    2007-10-18

    Stellar-mass black holes are found in X-ray-emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty producing black holes in close binaries with masses more than ten times that of the Sun (>10; ref. 4), which is consistent with the fact that the most massive stellar black holes known so far all have masses within one standard deviation of 10. Here we report a mass of (15.65 +/- 1.45) for the black hole in the recently discovered system M 33 X-7, which is located in the nearby galaxy Messier 33 (M 33) and is the only known black hole that is in an eclipsing binary. To produce such a massive black hole, the progenitor star must have retained much of its outer envelope until after helium fusion in the core was completed. On the other hand, in order for the black hole to be in its present 3.45-day orbit about its (70.0 +/- 6.9) companion, there must have been a 'common envelope' phase of evolution in which a significant amount of mass was lost from the system. We find that the common envelope phase could not have occurred in M 33 X-7 unless the amount of mass lost from the progenitor during its evolution was an order of magnitude less than what is usually assumed in evolutionary models of massive stars.

  15. Spiral Arm of the Perseus Is Closer than Thought

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ It is easy for us to observe the magnificent spiral galaxies outside the Milky Way with a telescope. Although our own galaxy is also believed to have similar spiral arms to those observed in the universe, astronomers have difficulties in rendering the structure because we are living inside it.

  16. Measurements of the equivalent thicknesses of three-dimensional spiral galactic disks

    Institute of Scientific and Technical Information of China (English)

    Gang Li; Zhi-Quan Luo; Qiu-He Peng

    2009-01-01

    Spiral arms are fitted after the data from the latest spiral galactic images re-leased by the Sloan Digital Sky Survey are processed. Equivalent thicknesses of 42 spiral galactic disks are derived, which increase the foundational data for further research about spiral galaxies.

  17. Effect of bars on the galaxy properties

    Science.gov (United States)

    Vera, Matias; Alonso, Sol; Coldwell, Georgina

    2016-10-01

    Aims: With the aim of assessing the effects of bars on disk galaxy properties, we present an analysis of different characteristics of spiral galaxies with strong bars, weak bars and without bars. Methods: We identified barred galaxies from the Sloan Digital Sky Survey (SDSS). By visual inspection of SDSS images we classified the face-on spiral galaxies brighter than glog (M∗/M⊙) processing, reflected in the significant changes in the physical properties of the host galaxies.

  18. MEASUREMENT OF GALACTIC LOGARITHMIC SPIRAL ARM PITCH ANGLE USING TWO-DIMENSIONAL FAST FOURIER TRANSFORM DECOMPOSITION

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Benjamin L.; Berrier, Joel C.; Shields, Douglas W.; Kennefick, Julia; Kennefick, Daniel; Seigar, Marc S.; Lacy, Claud H. S. [Arkansas Center for Space and Planetary Sciences, 202 Field House, University of Arkansas, Fayetteville, AR 72701 (United States); Puerari, Ivanio [Instituto Nacional de Astrofisica, Optica y Electronica, Calle Luis Enrique Erro 1, 72840 Santa Maria Tonantzintla, Puebla (Mexico)

    2012-04-01

    A logarithmic spiral is a prominent feature appearing in a majority of observed galaxies. This feature has long been associated with the traditional Hubble classification scheme, but historical quotes of pitch angle of spiral galaxies have been almost exclusively qualitative. We have developed a methodology, utilizing two-dimensional fast Fourier transformations of images of spiral galaxies, in order to isolate and measure the pitch angles of their spiral arms. Our technique provides a quantitative way to measure this morphological feature. This will allow comparison of spiral galaxy pitch angle to other galactic parameters and test spiral arm genesis theories. In this work, we detail our image processing and analysis of spiral galaxy images and discuss the robustness of our analysis techniques.

  19. Measurement of Galactic Logarithmic Spiral Arm Pitch Angle Using Two-Dimensional Fast Fourier Transform Decomposition

    CERN Document Server

    Davis, Benjamin L; Shields, Douglas W; Kennefick, Julia; Kennefick, Daniel; Seigar, Marc S; Lacy, Claud H S; Puerari, Ivânio

    2012-01-01

    A logarithmic spiral is a prominent feature appearing in a majority of observed galaxies. This feature has long been associated with the traditional Hubble classification scheme, but historical quotes of pitch angle of spiral galaxies have been almost exclusively qualitative. We have developed a methodology, utilizing two-dimensional fast Fourier transformations of images of spiral galaxies, in order to isolate and measure the pitch angles of their spiral arms. Our technique provides a quantitative way to measure this morphological feature. This will allow comparison of spiral galaxy pitch angle to other galactic parameters and test spiral arm genesis theories. In this work, we detail our image processing and analysis of spiral galaxy images and discuss the robustness of our analysis techniques.

  20. The spiral

    DEFF Research Database (Denmark)

    Bibace, Roger; Kharlamov, Nikita

    2013-01-01

    At the core of Heinz Werner’s concept of development is what he called “the genetic principle of spirality:” over the course of ontogenetic development, lower levels, processes, and functions do not disappear, and can even resurface again under specific conditions, normal and pathological. Werner...