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Sample records for flux-limited galaxy sample

  1. A Faint Flux-limited Ly α Emitter Sample at z ∼ 0.3

    Energy Technology Data Exchange (ETDEWEB)

    Wold, Isak G. B.; Finkelstein, Steven L. [Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712 (United States); Barger, Amy J.; Rosenwasser, Benjamin [Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States); Cowie, Lennox L., E-mail: wold@astro.as.utexas.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2017-10-20

    We present a flux-limited sample of z ∼ 0.3 Ly α emitters (LAEs) from Galaxy Evolution Explorer ( GALEX ) grism spectroscopic data. The published GALEX z ∼ 0.3 LAE sample is pre-selected from continuum-bright objects and thus is biased against high equivalent width (EW) LAEs. We remove this continuum pre-selection and compute the EW distribution and the luminosity function of the Ly α emission line directly from our sample. We examine the evolution of these quantities from z ∼ 0.3 to 2.2 and find that the EW distribution shows little evidence for evolution over this redshift range. As shown by previous studies, the Ly α luminosity density from star-forming (SF) galaxies declines rapidly with declining redshift. However, we find that the decline in Ly α luminosity density from z = 2.2 to z = 0.3 may simply mirror the decline seen in the H α luminosity density from z = 2.2 to z = 0.4, implying little change in the volumetric Ly α escape fraction. Finally, we show that the observed Ly α luminosity density from AGNs is comparable to the observed Ly α luminosity density from SF galaxies at z = 0.3. We suggest that this significant contribution from AGNs to the total observed Ly α luminosity density persists out to z ∼ 2.2.

  2. A Faint Flux-limited Lyα Emitter Sample at z ˜ 0.3

    Science.gov (United States)

    Wold, Isak G. B.; Finkelstein, Steven L.; Barger, Amy J.; Cowie, Lennox L.; Rosenwasser, Benjamin

    2017-10-01

    We present a flux-limited sample of z ˜ 0.3 Lyα emitters (LAEs) from Galaxy Evolution Explorer (GALEX) grism spectroscopic data. The published GALEX z ˜ 0.3 LAE sample is pre-selected from continuum-bright objects and thus is biased against high equivalent width (EW) LAEs. We remove this continuum pre-selection and compute the EW distribution and the luminosity function of the Lyα emission line directly from our sample. We examine the evolution of these quantities from z ˜ 0.3 to 2.2 and find that the EW distribution shows little evidence for evolution over this redshift range. As shown by previous studies, the Lyα luminosity density from star-forming (SF) galaxies declines rapidly with declining redshift. However, we find that the decline in Lyα luminosity density from z = 2.2 to z = 0.3 may simply mirror the decline seen in the Hα luminosity density from z = 2.2 to z = 0.4, implying little change in the volumetric Lyα escape fraction. Finally, we show that the observed Lyα luminosity density from AGNs is comparable to the observed Lyα luminosity density from SF galaxies at z = 0.3. We suggest that this significant contribution from AGNs to the total observed Lyα luminosity density persists out to z ˜ 2.2. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  3. Galaxies

    International Nuclear Information System (INIS)

    1989-01-01

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

  4. On the fairness of the main galaxy sample of SDSS

    International Nuclear Information System (INIS)

    Meng Kelai; Pan Jun; Feng Longlong; Ma Bin

    2011-01-01

    Flux-limited and volume-limited galaxy samples are constructed from the Sloan Digital Sky Survey (SDSS) data releases DR4, DR6 and DR7 for statistical analysis. The two-point correlation functions ξ(s), monopole of three-point correlation functions ζ 0 , projected two-point correlation function w p and pairwise velocity dispersion σ 12 are measured to test if galaxy samples are fair for these statistics. We find that with the increment of sky coverage of subsequent data releases in SDSS, ξ(s) of the flux-limited sample is extremely robust and insensitive to local structures at low redshift. However, for volume-limited samples fainter than L* at large scales s > or approx. 10 h -1 Mpc, the deviation of ξ(s) from different SDSS data releases (DR7, DR6 and DR4) increases with the increment of absolute magnitude. The case of ζ 0 (s) is similar to that of ξ(s). In the weakly nonlinear regime, there is no agreement between ζ 0 of different data releases in all luminosity bins. Furthermore, w p of volume-limited samples of DR7 in luminosity bins fainter than -M r,0.1 = [18.5, 19.5] are significantly larger and σ 12 of the two faintest volume-limited samples of DR7 display a very different scale dependence than results from DR4 and DR6. Our findings call for caution in understanding clustering analysis results of SDSS faint galaxy samples and higher order statistics of SDSS volume-limited samples in the weakly nonlinear regime. The first zero-crossing points of ξ(s) from volume-limited samples are also investigated and discussed. (research papers)

  5. A redshift survey of IRAS galaxies. I. Sample selection

    International Nuclear Information System (INIS)

    Strauss, M.A.; Davis, M.; Yahil, A.; Huchra, J.P.

    1990-01-01

    A complete all-sky sample of objects, flux-limited at 60 microns, has been extracted from the data base of the IRAS. The sample consists of 5014 objects, of which 2649 are galaxies and 13 are not yet identified. In order to study large-scale structure with this sample, it must be free of systematic biases. Corrections are applied for a major systematic effect in the flux densities listed in the IRAS Point Source Catalog: sources resolved by the IRAS beam have flux densities systematically underestimated. In addition, accurate flux densities are obtained for sources flagged as variable, or of moderate flux quality at 60 microns. The IRAS detectors suffered radiation-induced responsivity enhancement (hysteresis) due to crossings of the satellite scans across the Galactic plane; this effect is measured and is shown to be negligible. 53 refs

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

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  7. Galaxy redshift surveys with sparse sampling

    International Nuclear Information System (INIS)

    Chiang, Chi-Ting; Wullstein, Philipp; Komatsu, Eiichiro; Jee, Inh; Jeong, Donghui; Blanc, Guillermo A.; Ciardullo, Robin; Gronwall, Caryl; Hagen, Alex; Schneider, Donald P.; Drory, Niv; Fabricius, Maximilian; Landriau, Martin; Finkelstein, Steven; Jogee, Shardha; Cooper, Erin Mentuch; Tuttle, Sarah; Gebhardt, Karl; Hill, Gary J.

    2013-01-01

    Survey observations of the three-dimensional locations of galaxies are a powerful approach to measure the distribution of matter in the universe, which can be used to learn about the nature of dark energy, physics of inflation, neutrino masses, etc. A competitive survey, however, requires a large volume (e.g., V survey ∼ 10Gpc 3 ) to be covered, and thus tends to be expensive. A ''sparse sampling'' method offers a more affordable solution to this problem: within a survey footprint covering a given survey volume, V survey , we observe only a fraction of the volume. The distribution of observed regions should be chosen such that their separation is smaller than the length scale corresponding to the wavenumber of interest. Then one can recover the power spectrum of galaxies with precision expected for a survey covering a volume of V survey (rather than the volume of the sum of observed regions) with the number density of galaxies given by the total number of observed galaxies divided by V survey (rather than the number density of galaxies within an observed region). We find that regularly-spaced sampling yields an unbiased power spectrum with no window function effect, and deviations from regularly-spaced sampling, which are unavoidable in realistic surveys, introduce calculable window function effects and increase the uncertainties of the recovered power spectrum. On the other hand, we show that the two-point correlation function (pair counting) is not affected by sparse sampling. While we discuss the sparse sampling method within the context of the forthcoming Hobby-Eberly Telescope Dark Energy Experiment, the method is general and can be applied to other galaxy surveys

  8. IR Observations of a Complete Unbiased Sample of Bright Seyfert Galaxies

    Science.gov (United States)

    Malkan, Matthew; Bendo, George; Charmandaris, Vassilis; Smith, Howard; Spinoglio, Luigi; Tommasin, Silvia

    2008-03-01

    IR spectra will measure the 2 main energy-generating processes by which galactic nuclei shine: black hole accretion and star formation. Both of these play roles in galaxy evolution, and they appear connected. To obtain a complete sample of AGN, covering the range of luminosities and column-densities, we will combine 2 complete all-sky samples with complementary selections, minimally biased by dust obscuration: the 116 IRAS 12um AGN and the 41 Swift/BAT hard Xray AGN. These galaxies have been extensively studied across the entire EM spectrum. Herschel observations have been requested and will be synergistic with the Spitzer database. IRAC and MIPS imaging will allow us to separate the nuclear and galactic continua. We are completing full IR observations of the local AGN population, most of which have already been done. The only remaining observations we request are 10 IRS/HIRES, 57 MIPS-24 and 30 IRAC pointings. These high-quality observations of bright AGN in the bolometric-flux-limited samples should be completed, for the high legacy value of complete uniform datasets. We will measure quantitatively the emission at each wavelength arising from stars and from accretion in each galactic center. Since our complete samples come from flux-limited all-sky surveys in the IR and HX, we will calculate the bi-variate AGN and star formation Luminosity Functions for the local population of active galaxies, for comparison with higher redshifts.Our second aim is to understand the physical differences between AGN classes. This requires statistical comparisons of full multiwavelength observations of complete representative samples. If the difference between Sy1s and Sy2s is caused by orientation, their isotropic properties, including those of the surrounding galactic centers, should be similar. In contrast, if they are different evolutionary stages following a galaxy encounter, then we may find observational evidence that the circumnuclear ISM of Sy2s is relatively younger.

  9. The Arecibo Galaxy Environment Survey IX: the isolated galaxy sample

    Czech Academy of Sciences Publication Activity Database

    Minchin, R.F.; Auld, R.; Davies, J.I.; Karachentsev, I.D.; Keenan, O.; Momjian, E.; Rodriguez, R.; Taber, T.; Taylor, Rhys

    2016-01-01

    Roč. 455, č. 4 (2016), s. 3430-3435 ISSN 0035-8711 R&D Projects: GA MŠk LG14013; GA ČR GAP209/12/1795 Institutional support: RVO:67985815 Keywords : individual galaxies NGC 1156 * individual galaxies NGC 5523 * individual galaxies UGC 2082 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.961, year: 2016

  10. HICOSMO - cosmology with a complete sample of galaxy clusters - I. Data analysis, sample selection and luminosity-mass scaling relation

    Science.gov (United States)

    Schellenberger, G.; Reiprich, T. H.

    2017-08-01

    The X-ray regime, where the most massive visible component of galaxy clusters, the intracluster medium, is visible, offers directly measured quantities, like the luminosity, and derived quantities, like the total mass, to characterize these objects. The aim of this project is to analyse a complete sample of galaxy clusters in detail and constrain cosmological parameters, like the matter density, Ωm, or the amplitude of initial density fluctuations, σ8. The purely X-ray flux-limited sample (HIFLUGCS) consists of the 64 X-ray brightest galaxy clusters, which are excellent targets to study the systematic effects, that can bias results. We analysed in total 196 Chandra observations of the 64 HIFLUGCS clusters, with a total exposure time of 7.7 Ms. Here, we present our data analysis procedure (including an automated substructure detection and an energy band optimization for surface brightness profile analysis) that gives individually determined, robust total mass estimates. These masses are tested against dynamical and Planck Sunyaev-Zeldovich (SZ) derived masses of the same clusters, where good overall agreement is found with the dynamical masses. The Planck SZ masses seem to show a mass-dependent bias to our hydrostatic masses; possible biases in this mass-mass comparison are discussed including the Planck selection function. Furthermore, we show the results for the (0.1-2.4) keV luminosity versus mass scaling relation. The overall slope of the sample (1.34) is in agreement with expectations and values from literature. Splitting the sample into galaxy groups and clusters reveals, even after a selection bias correction, that galaxy groups exhibit a significantly steeper slope (1.88) compared to clusters (1.06).

  11. Multidimensional flux-limited advection schemes

    International Nuclear Information System (INIS)

    Thuburn, J.

    1996-01-01

    A general method for building multidimensional shape preserving advection schemes using flux limiters is presented. The method works for advected passive scalars in either compressible or incompressible flow and on arbitrary grids. With a minor modification it can be applied to the equation for fluid density. Schemes using the simplest form of the flux limiter can cause distortion of the advected profile, particularly sideways spreading, depending on the orientation of the flow relative to the grid. This is partly because the simple limiter is too restrictive. However, some straightforward refinements lead to a shape-preserving scheme that gives satisfactory results, with negligible grid-flow angle-dependent distortion

  12. TURBULENCE AND STAR FORMATION IN A SAMPLE OF SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Maier, Erin; Chien, Li-Hsin [Department of Physics and Astronomy, Northern Arizona University 527 S Beaver Street, Flagstaff, AZ 86011 (United States); Hunter, Deidre A., E-mail: erin-maier@uiowa.edu, E-mail: Lisa.Chien@nau.edu, E-mail: dah@lowell.edu [Lowell Observatory 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States)

    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.

  13. Flux Limiter Lattice Boltzmann for Compressible Flows

    International Nuclear Information System (INIS)

    Chen Feng; Li Yingjun; Xu Aiguo; Zhang Guangcai

    2011-01-01

    In this paper, a new flux limiter scheme with the splitting technique is successfully incorporated into a multiple-relaxation-time lattice Boltzmann (LB) model for shacked compressible flows. The proposed flux limiter scheme is efficient in decreasing the artificial oscillations and numerical diffusion around the interface. Due to the kinetic nature, some interface problems being difficult to handle at the macroscopic level can be modeled more naturally through the LB method. Numerical simulations for the Richtmyer-Meshkov instability show that with the new model the computed interfaces are smoother and more consistent with physical analysis. The growth rates of bubble and spike present a satisfying agreement with the theoretical predictions and other numerical simulations. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  14. Panchromatic properties of 99 000 galaxies detected by SDSS, and (some by) ROSAT, GALEX, 2MASS, IRAS, GB6, FIRST, NVSS and WENSS surveys

    NARCIS (Netherlands)

    Obric, M.; Ivezic, Z.; Best, P. N.; Lupton, R. H.; Tremonti, C.; Brinchmann, J.; Agueeros, M. A.; Knapp, G. R.; Gunn, J. E.; Rockosi, C. M.; Schlegel, D.; Finkbeiner, D.; Gacesa, M.; Smolcic, V.; Anderson, S. F.; Voges, W.; Juric, M.; Siverd, R. J.; Steinhardt, W.; Jagoda, A. S.; Blanton, M. R.; Schneider, D. P.

    2006-01-01

    We discuss the panchromatic properties of 99 088 galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 1 'main' spectroscopic sample ( a flux-limited sample for 1360 deg(2)). These galaxies are positionally matched to sources detected by ROSAT, Galaxy Evolution Explorer (GALEX),

  15. The limitation and modification of flux-limited diffusion theory

    International Nuclear Information System (INIS)

    Liu Chengan; Huang Wenkai

    1986-01-01

    The limitation of various typical flux-limited diffusion theory and advantages of asymptotic diffusion theory with time absorption constant are analyzed and compared. The conclusions are as following: Though the flux-limited problem in neutron diffusion theory are theoretically solved by derived flux-limited diffusion equation, it's going too far to limit flux due to the inappropriate assumption in deriving flux-limited diffusion equation. The asymptotic diffusion theory with time absorption constant has eliminated the above-mentioned limitation, and it is more accurate than flux-limited diffusion theory in describing neutron transport problem

  16. Dependence of the clustering properties of galaxies on stellar velocity dispersion in the Main galaxy sample of SDSS DR10

    Science.gov (United States)

    Deng, Xin-Fa; Song, Jun; Chen, Yi-Qing; Jiang, Peng; Ding, Ying-Ping

    2014-08-01

    Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 10 (SDSS DR10), we investigate the dependence of the clustering properties of galaxies on stellar velocity dispersion by cluster analysis. It is found that in the luminous volume-limited Main galaxy sample, except at r=1.2, richer and larger systems can be more easily formed in the large stellar velocity dispersion subsample, while in the faint volume-limited Main galaxy sample, at r≥0.9, an opposite trend is observed. According to statistical analyses of the multiplicity functions, we conclude in two volume-limited Main galaxy samples: small stellar velocity dispersion galaxies preferentially form isolated galaxies, close pairs and small group, while large stellar velocity dispersion galaxies preferentially inhabit the dense groups and clusters. However, we note the difference between two volume-limited Main galaxy samples: in the faint volume-limited Main galaxy sample, at r≥0.9, the small stellar velocity dispersion subsample has a higher proportion of galaxies in superclusters ( n≥200) than the large stellar velocity dispersion subsample.

  17. Flux-limited diffusion models in radiation hydrodynamics

    International Nuclear Information System (INIS)

    Pomraning, G.C.; Szilard, R.H.

    1993-01-01

    The authors discuss certain flux-limited diffusion theories which approximately describe radiative transfer in the presence of steep spatial gradients. A new formulation is presented which generalizes a flux-limited description currently in widespread use for large radiation hydrodynamic calculations. This new formation allows more than one Case discrete mode to be described by a flux-limited diffusion equation. Such behavior is not extant in existing formulations. Numerical results predicted by these flux-limited diffusion models are presented for radiation penetration into an initially cold halfspace. 37 refs., 5 figs

  18. A homogeneous sample of binary galaxies: Basic observational properties

    Science.gov (United States)

    Karachentsev, I. D.

    1990-01-01

    A survey of optical characteristics for 585 binary systems, satisfying a condition of apparent isolation on the sky, is presented. Influences of various selection effects distorting the average parameters of the sample are noted. The pair components display mutual similarity over all the global properties: luminosity, diameter, morphological type, mass-to-luminosity ratio, angular momentum etc., which is not due only to selection effects. The observed correlations must be caused by common origin of pair members. Some features (nuclear activity, color index) could acquire similarity during synchronous evolution of double galaxies. Despite the observed isolation, the sample of double systems is seriously contaminated by accidental pairs, and also by members of groups and clusters. After removing false pairs estimates of orbital mass-to-luminosity ratio range from 0 to 30 f(solar), with the mean value (7.8 plus or minus 0.7) f(solar). Binary galaxies possess nearly circular orbits with a typical eccentrity e = 0.25, probably resulting from evolutionary selection driven by component mergers under dynamical friction. The double-galaxy population with space abundance 0.12 plus or minus 0.02 and characteristic merger timescale 0.2 H(exp -1) may significantly influence the rate of dynamical evolution of galaxies.

  19. HERSCHEL-ATLAS: TOWARD A SAMPLE OF {approx}1000 STRONGLY LENSED GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Nuevo, J.; Lapi, A.; Bressan, S.; Danese, L.; De Zotti, G.; Cai, Z.-Y.; Fan, L. [SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Fleuren, S.; Sutherland, W. [School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom); Negrello, M. [Department of Physical Sciences, Open University, Milton Keynes MK7 6AA (United Kingdom); Baes, M. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Baker, A. J. [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States); Clements, D. L. [Astrophysics Group, Imperial College, Blackett Lab, Prince Consort Road, London SW7 2AZ (United Kingdom); Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Dannerbauer, H. [Institut fuer Astronomie, Universitaet Wien, Tuerkenschanzstrasse 17, 1180 Wien, Oesterreich (Austria); Dunne, L.; Dye, S. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Eales, S. [School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA (United Kingdom); Frayer, D. T. [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Harris, A. I., E-mail: gnuevo@sissa.it [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); and others

    2012-04-10

    While the selection of strongly lensed galaxies (SLGs) with 500 {mu}m flux density S{sub 500} > 100 mJy has proven to be rather straightforward, for many applications it is important to analyze samples larger than the ones obtained when confining ourselves to such a bright limit. Moreover, only by probing to fainter flux densities is it possible to exploit strong lensing to investigate the bulk of the high-z star-forming galaxy population. We describe HALOS (the Herschel-ATLAS Lensed Objects Selection), a method for efficiently selecting fainter candidate SLGs, reaching a surface density of {approx_equal} 1.5-2 deg{sup -2}, i.e., a factor of about 4-6 higher than that at the 100 mJy flux limit. HALOS will allow the selection of up to {approx}1000 candidate SLGs (with amplifications {mu} {approx}> 2) over the full H-ATLAS survey area. Applying HALOS to the H-ATLAS Science Demonstration Phase field ({approx_equal} 14.4 deg{sup 2}) we find 31 candidate SLGs, whose candidate lenses are identified in the VIKING near-infrared catalog. Using the available information on candidate sources and candidate lenses we tentatively estimate a {approx_equal} 72% purity of the sample. As expected, the purity decreases with decreasing flux density of the sources and with increasing angular separation between candidate sources and lenses. The redshift distribution of the candidate lensed sources is close to that reported for most previous surveys for lensed galaxies, while that of candidate lenses extends to redshifts substantially higher than found in the other surveys. The counts of candidate SLGs are also in good agreement with model predictions. Even though a key ingredient of the method is the deep near-infrared VIKING photometry, we show that H-ATLAS data alone allow the selection of a similarly deep sample of candidate SLGs with an efficiency close to 50%; a slightly lower surface density ({approx_equal} 1.45 deg{sup -2}) can be reached with a {approx}70% efficiency.

  20. Variable Eddington factors and flux-limiting diffusion coefficients

    International Nuclear Information System (INIS)

    Whalen, P.P.

    1982-01-01

    Variable Eddington factors and flux limiting diffusion coefficients arise in two common techniques of closing the moment equations of transport. The first two moment equations of the full transport equation are still frequently used to solve many problems of radiative or particle transport. An approximate analysis, developed by Levermore, exhibits the relation between the coefficients of the two different techniques. This analysis is described and then used to test the validity of several commonly used flux limiters and Eddington factors. All of the ad-hoc flux limiters have limited validity. All of the variable Eddington factors derived from some underlying description of the angular distribution function are generally valid. The use of coefficients from Minerbo's elegant maximum entropy Eddington factor analysis is suggested for use in either flux limited diffusion or variable Eddington factor equations

  1. Flux-limited diffusion coefficients in reactor physics applications

    International Nuclear Information System (INIS)

    Pounders, J.; Rahnema, F.; Szilard, R.

    2007-01-01

    Flux-limited diffusion theory has been successfully applied to problems in radiative transfer and radiation hydrodynamics, but its relevance to reactor physics has not yet been explored. The current investigation compares the performance of a flux-limited diffusion coefficient against the traditionally defined transport cross section. A one-dimensional BWR benchmark problem is examined at both the assembly and full-core level with varying degrees of heterogeneity. (authors)

  2. Chapman--Enskog approach to flux-limited diffusion theory

    International Nuclear Information System (INIS)

    Levermore, C.D.

    1979-01-01

    Using the technique developed by Chapman and Enskog for deriving the Navier--Stokes equations from the Boltzmann equation, a framework is set up for deriving diffusion theories from the transport equation. The procedure is first applied to give a derivation of isotropic diffusion theory and then of a completely new theory which is naturally flux-limited. This new flux-limited diffusion theory is then compared with asymptotic diffusion theory

  3. Galaxies

    International Nuclear Information System (INIS)

    1981-01-01

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

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

    Science.gov (United States)

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

    2017-11-01

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

  5. Nonoscillatory shock capturing scheme using flux limited dissipation

    International Nuclear Information System (INIS)

    Jameson, A.

    1985-01-01

    A method for modifying the third order dissipative terms by the introduction of flux limiters is proposed. The first order dissipative terms can then be eliminated entirely, and in the case of a scalar conservation law the scheme is converted into a total variation diminishing scheme provided that an appropriate value is chosen for the dissipative coefficient. Particular attention is given to: (1) the treatment of the scalar conservation law; (2) the treatment of the Euler equations for inviscid compressible flow; (3) the boundary conditions; and (4) multistage time stepping and multigrid schemes. Numerical results for transonic flows suggest that a central difference scheme augmented by flux limited dissipative terms can lead to an effective nonoscillatory shock capturing method. 20 references

  6. The clustering evolution of distant red galaxies in the GOODS-MUSIC sample

    Science.gov (United States)

    Grazian, A.; Fontana, A.; Moscardini, L.; Salimbeni, S.; Menci, N.; Giallongo, E.; de Santis, C.; Gallozzi, S.; Nonino, M.; Cristiani, S.; Vanzella, E.

    2006-07-01

    Aims.We study the clustering properties of Distant Red Galaxies (DRGs) to test whether they are the progenitors of local massive galaxies. Methods.We use the GOODS-MUSIC sample, a catalog of ~3000 Ks-selected galaxies based on VLT and HST observation of the GOODS-South field with extended multi-wavelength coverage (from 0.3 to 8~μm) and accurate estimates of the photometric redshifts to select 179 DRGs with J-Ks≥ 1.3 in an area of 135 sq. arcmin.Results.We first show that the J-Ks≥ 1.3 criterion selects a rather heterogeneous sample of galaxies, going from the targeted high-redshift luminous evolved systems, to a significant fraction of lower redshift (1mass, like groups or small galaxy clusters. Low-z DRGs, on the other hand, will likely evolve into slightly less massive field galaxies.

  7. Galaxies

    International Nuclear Information System (INIS)

    1987-01-01

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

  8. Space density and clustering properties of a new sample of emission-line galaxies

    International Nuclear Information System (INIS)

    Wasilewski, A.J.

    1982-01-01

    A moderate-dispersion objective-prism survey for low-redshift emission-line galaxies has been carried out in an 825 sq. deg. region of sky with the Burrell Schmidt telescope of Case Western Reserve University. A 4 0 prism (300 A/mm at H#betta#) was used with the Illa-J emulsion to show that a new sample of emission-line galaxies is available even in areas already searched with the excess uv-continuum technique. The new emission-line galaxies occur quite commonly in systems with peculiar morphology indicating gravitational interaction with a close companion or other disturbance. About 10 to 15% of the sample are Seyfert galaxies. It is suggested that tidal interaction involving matter infall play a significant role in the generation of an emission-line spectrum. The space density of the new galaxies is found to be similar to the space density of the Makarian galaxies. Like the Markarian sample, the galaxies in the present survey represent about 10% of all galaxies in the absolute magnitude range M/sub p/ = -16 to -22. The observations also indicate that current estimates of dwarf galaxy space densities may be too low. The clustering properties of the new galaxies have been investigated using two approaches: cluster contour maps and the spatial correlation function. These tests suggest that there is weak clustering and possibly superclustering within the sample itself and that the galaxies considered here are about as common in clusters of ordinary galaxies as in the field

  9. Direct comparison of observed magnitude-redshift relations in complete galaxy samples with systematic predictions of alternative redshift-distance laws

    International Nuclear Information System (INIS)

    Segal, I.E.

    1989-01-01

    The directly observed average apparent magnitude (or in one case, angular diameter) as a function of redshift in each of a number of large complete galaxy samples is compared with the predictions of hypothetical redshift-distance power laws, as a systematic statistical question. Due account is taken of observational flux limits by an entirely objective and reproducible optimal statistical procedure, and no assumptions are made regarding the distribution of the galaxies in space. The laws considered are of the form z varies as r p , where r denotes the distance, for p = 1, 2 and 3. The comparative fits of the various redshift-distance laws are similar in all the samples. Overall, the cubic law fits better than the linear law, but each shows substantial systematic deviations from observation. The quadratic law fits extremely well except at high redshifts in some of the samples, where no power law fits closely and the correlation of apparent magnitude with redshift is small or negative. In all cases, the luminosity function required for theoretical prediction was estimated from the sample by the non-parametric procedure ROBUST, whose intrinsic neutrality as programmed was checked by comprehensive computer simulations. (author)

  10. Exploring cosmic homogeneity with the BOSS DR12 galaxy sample

    Energy Technology Data Exchange (ETDEWEB)

    Ntelis, Pierros; Hamilton, Jean-Christophe; Busca, Nicolas Guillermo; Aubourg, Eric [APC, Université Paris Diderot-Paris 7, CNRS/IN2P3, CEA, Observatoire de Paris, 10, rue A. Domon and L. Duquet, Paris (France); Goff, Jean-Marc Le; Burtin, Etienne; Laurent, Pierre; Rich, James; Bourboux, Hélion du Mas des; Delabrouille, Nathalie Palanque [CEA, Centre de Saclay, IRFU/SPP, F-91191 Gif-sur-Yvette (France); Tinker, Jeremy [Department of Physics and Center for Cosmology and Particle Physics, New York University, 726 Broadway, New York (United States); Bautista, Julian [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Delubac, Timothée [Laboratoire d' astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, CH-1290 Versoix (Switzerland); Eftekharzadeh, Sarah; Myers, Adam [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Hogg, David W. [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, Meyer Hall of Physics, New York, NY 10003 (United States); Vargas-Magaña, Mariana [Instituto de Física, Universidad Nacional Autónoma de México, Apdo. Postal 20-364, México (Mexico); Pâris, Isabelle [Aix Marseille Universite, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, 13388, Marseille (France); Petitjean, Partick [Institut d' Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, Paris, 75014 France (France); Rossi, Graziano, E-mail: pntelis@apc.in2p3.fr, E-mail: jchamilton75@gmail.com [Department of Astronomy and Space Science, Sejong University, Seoul, 143-747 (Korea, Republic of); and others

    2017-06-01

    In this study, we probe the transition to cosmic homogeneity in the Large Scale Structure (LSS) of the Universe using the CMASS galaxy sample of BOSS spectroscopic survey which covers the largest effective volume to date, 3 h {sup −3} Gpc{sup 3} at 0.43 ≤ z ≤ 0.7. We study the scaled counts-in-spheres, N(< r ), and the fractal correlation dimension, D{sub 2}( r ), to assess the homogeneity scale of the universe using a Landy and Szalay inspired estimator. Defining the scale of transition to homogeneity as the scale at which D{sub 2}( r ) reaches 3 within 1%, i.e. D{sub 2}( r )>2.97 for r >R {sub H} , we find R {sub H} = (63.3±0.7) h {sup −1} Mpc, in agreement at the percentage level with the predictions of the ΛCDM model R {sub H} =62.0 h {sup −1} Mpc. Thanks to the large cosmic depth of the survey, we investigate the redshift evolution of the transition to homogeneity scale and find agreement with the ΛCDM prediction. Finally, we find that D{sub 2} is compatible with 3 at scales larger than 300 h {sup −1} Mpc in all redshift bins. These results consolidate the Cosmological Principle and represent a precise consistency test of the ΛCDM model.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-10

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

  13. The Ultraviolet and Infrared Star Formation Rates of Compact Group Galaxies: An Expanded Sample

    Science.gov (United States)

    Lenkic, Laura; Tzanavaris, Panayiotis; Gallagher, Sarah C.; Desjardins, Tyler D.; Walker, Lisa May; Johnson, Kelsey E.; Fedotov, Konstantin; Charlton, Jane; Cardiff, Ann H.; Durell, Pat R.

    2016-01-01

    Compact groups of galaxies provide insight into the role of low-mass, dense environments in galaxy evolution because the low velocity dispersions and close proximity of galaxy members result in frequent interactions that take place over extended time-scales. We expand the census of star formation in compact group galaxies by Tzanavaris et al. (2010) and collaborators with Swift UVOT, Spitzer IRAC and MIPS 24 m photometry of a sample of 183 galaxies in 46 compact groups. After correcting luminosities for the contribution from old stellar populations, we estimate the dust-unobscured star formation rate (SFRUV) using the UVOT uvw2 photometry. Similarly, we use the MIPS 24 m photometry to estimate the component of the SFR that is obscured by dust (SFRIR). We find that galaxies which are MIR-active (MIR-red), also have bluer UV colours, higher specific SFRs, and tend to lie in Hi-rich groups, while galaxies that are MIR-inactive (MIR-blue) have redder UV colours, lower specific SFRs, and tend to lie in Hi-poor groups. We find the SFRs to be continuously distributed with a peak at about 1 M yr1, indicating this might be the most common value in compact groups. In contrast, the specific SFR distribution is bimodal, and there is a clear distinction between star-forming and quiescent galaxies. Overall, our results suggest that the specific SFR is the best tracer of gas depletion and galaxy evolution in compact groups.

  14. SDSS-IV MaNGA: faint quenched galaxies - I. Sample selection and evidence for environmental quenching

    Science.gov (United States)

    Penny, Samantha J.; Masters, Karen L.; Weijmans, Anne-Marie; Westfall, Kyle B.; Bershady, Matthew A.; Bundy, Kevin; Drory, Niv; Falcón-Barroso, Jesús; Law, David; Nichol, Robert C.; Thomas, Daniel; Bizyaev, Dmitry; Brownstein, Joel R.; Freischlad, Gordon; Gaulme, Patrick; Grabowski, Katie; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Roman-Lopes, Alexandre; Pan, Kaike; Simmons, Audrey; Wake, David A.

    2016-11-01

    Using kinematic maps from the Sloan Digital Sky Survey (SDSS) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, we reveal that the majority of low-mass quenched galaxies exhibit coherent rotation in their stellar kinematics. Our sample includes all 39 quenched low-mass galaxies observed in the first year of MaNGA. The galaxies are selected with Mr > -19.1, stellar masses 109 M⊙ 1.9. They lie on the size-magnitude and σ-luminosity relations for previously studied dwarf galaxies. Just six (15 ± 5.7 per cent) are found to have rotation speeds ve, rot 5 × 1010 M⊙), supporting the hypothesis that galaxy-galaxy or galaxy-group interactions quench star formation in low-mass galaxies. The local bright galaxy density for our sample is ρproj = 8.2 ± 2.0 Mpc-2, compared to ρproj = 2.1 ± 0.4 Mpc-2 for a star-forming comparison sample, confirming that the quenched low-mass galaxies are preferentially found in higher density environments.

  15. Hidden Broad Line Seyfert 2 Galaxies in the CfA and 12micron Samples

    OpenAIRE

    Tran, Hien D.

    2001-01-01

    We report the results of a spectropolarimetric survey of the CfA and 12micron samples of Seyfert 2 galaxies (S2s). Polarized (hidden) broad line regions (HBLRs) are confirmed in a number of galaxies, and several new cases (F02581-1136, MCG -3-58-7, NGC 5995, NGC 6552, NGC 7682) are reported. The 12micron S2 sample shows a significantly higher incidence of HBLR (50%) than its CfA counterpart (30%), suggesting that the latter may be incomplete in hidden AGNs. Compared to the non-HBLR S2s, the H...

  16. Updated 34-band Photometry for the SINGS/KINGFISH Samples of Nearby Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Dale, D. A.; Turner, J. A. [Department of Physics and Astronomy, University of Wyoming, Laramie WY (United States); Cook, D. O. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena CA (United States); Roussel, H. [Institut d’Astrophysique de Paris, Sorbonne Universités, Paris (France); Armus, L.; Helou, G. [Spitzer Science Center, California Institute of Technology, Pasadena, CA (United States); Bolatto, A. D. [Department of Astronomy, University of Maryland, College Park, MD (United States); Boquien, M. [Unidad de Astronomía, Universidad de Antofagasta, Antofagasta (Chile); Brown, M. J. I. [School of Physics and Astronomy, Monash University, Victoria 3800 (Australia); Calzetti, D. [Department of Astronomy, University of Massachusetts, Amherst MA (United States); Looze, I. De [Sterrenkundig Observatorium, Universiteit Gent, Gent (Belgium); Galametz, M. [European Southern Observatory, Garching (Germany); Gordon, K. D. [Space Telescope Science Institute, Baltimore MD (United States); Groves, B. A. [Research School of Astronomy and Astrophysics, Australian National University, Canberra (Australia); Jarrett, T. H. [Astronomy Department, University of Capetown, Rondebosch (South Africa); Herrera-Camus, R. [Max-Planck-Institut für Extraterrestrische Physik, Garching (Germany); Hinz, J. L. [Steward Observatory, University of Arizona, Tucson AZ (United States); Hunt, L. K. [INAF—Osservatorio Astrofisico di Arcetri, Firenze (Italy); Kennicutt, R. C. [Institute of Astronomy, University of Cambridge, Cambridge (United Kingdom); Murphy, E. J., E-mail: ddale@uwyo.edu [National Radio Astronomy Observatory, Charlottesville, VA (United States); and others

    2017-03-01

    We present an update to the ultraviolet-to-radio database of global broadband photometry for the 79 nearby galaxies that comprise the union of the KINGFISH (Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel ) and SINGS ( Spitzer Infrared Nearby Galaxies Survey) samples. The 34-band data set presented here includes contributions from observational work carried out with a variety of facilities including GALEX , SDSS, Pan-STARRS1, NOAO , 2MASS, Wide-Field Infrared Survey Explorer , Spitzer , Herschel , Planck , JCMT , and the VLA. Improvements of note include recalibrations of previously published SINGS BVR {sub C} I {sub C} and KINGFISH far-infrared/submillimeter photometry. Similar to previous results in the literature, an excess of submillimeter emission above model predictions is seen primarily for low-metallicity dwarf or irregular galaxies. This 33-band photometric data set for the combined KINGFISH+SINGS sample serves as an important multiwavelength reference for the variety of galaxies observed at low redshift. A thorough analysis of the observed spectral energy distributions is carried out in a companion paper.

  17. Updated 34-band Photometry for the SINGS/KINGFISH Samples of Nearby Galaxies

    International Nuclear Information System (INIS)

    Dale, D. A.; Turner, J. A.; Cook, D. O.; Roussel, H.; Armus, L.; Helou, G.; Bolatto, A. D.; Boquien, M.; Brown, M. J. I.; Calzetti, D.; Looze, I. De; Galametz, M.; Gordon, K. D.; Groves, B. A.; Jarrett, T. H.; Herrera-Camus, R.; Hinz, J. L.; Hunt, L. K.; Kennicutt, R. C.; Murphy, E. J.

    2017-01-01

    We present an update to the ultraviolet-to-radio database of global broadband photometry for the 79 nearby galaxies that comprise the union of the KINGFISH (Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel ) and SINGS ( Spitzer Infrared Nearby Galaxies Survey) samples. The 34-band data set presented here includes contributions from observational work carried out with a variety of facilities including GALEX , SDSS, Pan-STARRS1, NOAO , 2MASS, Wide-Field Infrared Survey Explorer , Spitzer , Herschel , Planck , JCMT , and the VLA. Improvements of note include recalibrations of previously published SINGS BVR C I C and KINGFISH far-infrared/submillimeter photometry. Similar to previous results in the literature, an excess of submillimeter emission above model predictions is seen primarily for low-metallicity dwarf or irregular galaxies. This 33-band photometric data set for the combined KINGFISH+SINGS sample serves as an important multiwavelength reference for the variety of galaxies observed at low redshift. A thorough analysis of the observed spectral energy distributions is carried out in a companion paper.

  18. The Swift Gamma-Ray Burst Host Galaxy Legacy Survey. I. Sample Selection and Redshift Distribution

    Science.gov (United States)

    Perley, D. A.; Kruhler, T.; Schulze, S.; Postigo, A. De Ugarte; Hjorth, J.; Berger, E.; Cenko, S. B.; Chary, R.; Cucchiara, A.; Ellis, R.; hide

    2016-01-01

    We introduce the Swift Gamma-Ray Burst Host Galaxy Legacy Survey (SHOALS), a multi-observatory high redshift galaxy survey targeting the largest unbiased sample of long-duration gamma-ray burst (GRB) hosts yet assembled (119 in total). We describe the motivations of the survey and the development of our selection criteria, including an assessment of the impact of various observability metrics on the success rate of afterglow-based redshift measurement. We briefly outline our host galaxy observational program, consisting of deep Spitzer/IRAC imaging of every field supplemented by similarly deep, multicolor optical/near-IR photometry, plus spectroscopy of events without preexisting redshifts. Our optimized selection cuts combined with host galaxy follow-up have so far enabled redshift measurements for 110 targets (92%) and placed upper limits on all but one of the remainder. About 20% of GRBs in the sample are heavily dust obscured, and at most 2% originate from z > 5.5. Using this sample, we estimate the redshift-dependent GRB rate density, showing it to peak at z approx. 2.5 and fall by at least an order of magnitude toward low (z = 0) redshift, while declining more gradually toward high (z approx. 7) redshift. This behavior is consistent with a progenitor whose formation efficiency varies modestly over cosmic history. Our survey will permit the most detailed examination to date of the connection between the GRB host population and general star-forming galaxies, directly measure evolution in the host population over cosmic time and discern its causes, and provide new constraints on the fraction of cosmic star formation occurring in undetectable galaxies at all redshifts.

  19. The SAGES Legacy Unifying Globulars and Galaxies survey (SLUGGS): sample definition, methods, and initial results

    Energy Technology Data Exchange (ETDEWEB)

    Brodie, Jean P.; Romanowsky, Aaron J.; Jennings, Zachary G.; Pota, Vincenzo; Kader, Justin; Roediger, Joel C.; Villaume, Alexa; Arnold, Jacob A.; Woodley, Kristin A. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Forbes, Duncan A.; Pastorello, Nicola; Usher, Christopher; Blom, Christina; Kartha, Sreeja S. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Foster, Caroline; Spitler, Lee R., E-mail: jbrodie@ucsc.edu [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia)

    2014-11-20

    We introduce and provide the scientific motivation for a wide-field photometric and spectroscopic chemodynamical survey of nearby early-type galaxies (ETGs) and their globular cluster (GC) systems. The SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey is being carried out primarily with Subaru/Suprime-Cam and Keck/DEIMOS. The former provides deep gri imaging over a 900 arcmin{sup 2} field-of-view to characterize GC and host galaxy colors and spatial distributions, and to identify spectroscopic targets. The NIR Ca II triplet provides GC line-of-sight velocities and metallicities out to typically ∼8 R {sub e}, and to ∼15 R {sub e} in some cases. New techniques to extract integrated stellar kinematics and metallicities to large radii (∼2-3 R {sub e}) are used in concert with GC data to create two-dimensional (2D) velocity and metallicity maps for comparison with simulations of galaxy formation. The advantages of SLUGGS compared with other, complementary, 2D-chemodynamical surveys are its superior velocity resolution, radial extent, and multiple halo tracers. We describe the sample of 25 nearby ETGs, the selection criteria for galaxies and GCs, the observing strategies, the data reduction techniques, and modeling methods. The survey observations are nearly complete and more than 30 papers have so far been published using SLUGGS data. Here we summarize some initial results, including signatures of two-phase galaxy assembly, evidence for GC metallicity bimodality, and a novel framework for the formation of extended star clusters and ultracompact dwarfs. An integrated overview of current chemodynamical constraints on GC systems points to separate, in situ formation modes at high redshifts for metal-poor and metal-rich GCs.

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

    Science.gov (United States)

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

    2017-02-01

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

  1. The Galaxy mass function up to z =4 in the GOODS-MUSIC sample: into the epoch of formation of massive galaxies

    Science.gov (United States)

    Fontana, A.; Salimbeni, S.; Grazian, A.; Giallongo, E.; Pentericci, L.; Nonino, M.; Fontanot, F.; Menci, N.; Monaco, P.; Cristiani, S.; Vanzella, E.; de Santis, C.; Gallozzi, S.

    2006-12-01

    Aims.The goal of this work is to measure the evolution of the Galaxy Stellar Mass Function and of the resulting Stellar Mass Density up to redshift ≃4, in order to study the assembly of massive galaxies in the high redshift Universe. Methods: .We have used the GOODS-MUSIC catalog, containing 3000 Ks-selected galaxies with multi-wavelength coverage extending from the U band to the Spitzer 8 μm band, of which 27% have spectroscopic redshifts and the remaining fraction have accurate photometric redshifts. On this sample we have applied a standard fitting procedure to measure stellar masses. We compute the Galaxy Stellar Mass Function and the resulting Stellar Mass Density up to redshift ≃4, taking into proper account the biases and incompleteness effects. Results: .Within the well known trend of global decline of the Stellar Mass Density with redshift, we show that the decline of the more massive galaxies may be described by an exponential timescale of ≃6 Gyr up to z≃ 1.5, and proceeds much faster thereafter, with an exponential timescale of ≃0.6 Gyr. We also show that there is some evidence for a differential evolution of the Galaxy Stellar Mass Function, with low mass galaxies evolving faster than more massive ones up to z≃ 1{-}1.5 and that the Galaxy Stellar Mass Function remains remarkably flat (i.e. with a slope close to the local one) up to z≃ 1{-}1.3. Conclusions: .The observed behaviour of the Galaxy Stellar Mass Function is consistent with a scenario where about 50% of present-day massive galaxies formed at a vigorous rate in the epoch between redshift 4 and 1.5, followed by a milder evolution until the present-day epoch.

  2. Why are classical bulges more common in S0 galaxies than in spiral galaxies?

    Science.gov (United States)

    Mishra, Preetish K.; Wadadekar, Yogesh; Barway, Sudhanshu

    2018-05-01

    In this paper, we try to understand why the classical bulge fraction observed in S0 galaxies is significantly higher than that in spiral galaxies. We carry out a comparative study of the bulge and global properties of a sample of spiral and S0 galaxies in a fixed environment. Our sample is flux limited and contains 262 spiral and 155 S0 galaxies drawn from the Sloan Digital Sky Survey. We have classified bulges into classical and pseudobulge categories based on their position on the Kormendy diagram. Dividing our sample into bins of galaxy stellar mass, we find that the fraction of S0 galaxies hosting a classical bulge is significantly higher than the classical bulge fraction seen in spirals even at fixed stellar mass. We have compared the bulge and the global properties of spirals and S0 galaxies in our sample and find indications that spiral galaxies which host a classical bulge, preferentially get converted into S0 population as compared to pseudobulge hosting spirals. By studying the star formation properties of our galaxies in the NUV - r color-mass diagram, we find that the pseudobulge hosting spirals are mostly star forming while the majority of classical bulge host spirals are in the green valley or in the passive sequence. We suggest that some internal process, such as AGN feedback or morphological quenching due to the massive bulge, quenches these classical bulge hosting spirals and transforms them into S0 galaxies, thus resulting in the observed predominance of the classical bulge in S0 galaxies.

  3. Age bimodality in the central region of pseudo-bulges in S0 galaxies

    Science.gov (United States)

    Mishra, Preetish K.; Barway, Sudhanshu; Wadadekar, Yogesh

    2017-11-01

    We present evidence for bimodal stellar age distribution of pseudo-bulges of S0 galaxies as probed by the Dn(4000) index. We do not observe any bimodality in age distribution for pseudo-bulges in spiral galaxies. Our sample is flux limited and contains 2067 S0 and 2630 spiral galaxies drawn from the Sloan Digital Sky Survey. We identify pseudo-bulges in S0 and spiral galaxies, based on the position of the bulge on the Kormendy diagram and their central velocity dispersion. Dividing the pseudo-bulges of S0 galaxies into those containing old and young stellar populations, we study the connection between global star formation and pseudo-bulge age on the u - r colour-mass diagram. We find that most old pseudo-bulges are hosted by passive galaxies while majority of young bulges are hosted by galaxies that are star forming. Dividing our sample of S0 galaxies into early-type S0s and S0/a galaxies, we find that old pseudo-bulges are mainly hosted by early-type S0 galaxies while most of the pseudo-bulges in S0/a galaxies are young. We speculate that morphology plays a strong role in quenching of star formation in the disc of these S0 galaxies, which stops the growth of pseudo-bulges, giving rise to old pseudo-bulges and the observed age bimodality.

  4. A sample of galaxy pairs identified from the LAMOST spectral survey and the Sloan Digital Sky Survey

    International Nuclear Information System (INIS)

    Shen, Shi-Yin; Argudo-Fernández, Maria; Chen, Li; Feng, Shuai; Hou, Jin-Liang; Shao, Zheng-Yi; Chen, Xiao-Yan; Luo, A-Li; Wu, Hong; Yang, Hai-Feng; Yang, Ming; Hou, Yong-Hui; Wang, Yue-Fei; Jiang, Peng; Wang, Ting-Gui; Jing, Yi-Peng; Kong, Xu; Wang, Wen-Ting; Luo, Zhi-Jian; Wu, Xue-Bing

    2016-01-01

    A small fraction (< 10%) of the SDSS main galaxy (MG) sample has not been targeted with spectroscopy due to the effect of fiber collisions. These galaxies have been compiled into the input catalog of the LAMOST ExtraGAlactic Surveys and named the complementary galaxy sample. In this paper, we introduce this project and status of the spectroscopies associated with the complementary galaxies in the first two years of the LAMOST spectral survey (till Sep. of 2014). Moreover, we present a sample of 1102 galaxy pairs identified from the LAMOST complementary galaxies and SDSS MGs, which are defined as two members that have a projected distance smaller than 100 h −1 70 kpc and a recessional velocity difference smaller than 500 km s −1 . Compared with galaxy pairs that are only selected from SDSS, the LAMOST-SDSS pairs have the advantages of not being biased toward large separations and therefore act as a useful supplement in statistical studies of galaxy interaction and galaxy merging. (paper)

  5. Comparison of some properties of star forming galaxies and active galactic nuclei between two BOSS galaxy samples from SDSS DR9

    International Nuclear Information System (INIS)

    Deng Xin-Fa

    2014-01-01

    Using the LOWZ and CMASS samples of the ninth data release (DR9) from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), I investigate properties of star forming galaxies and active galactic nuclei (AGNs). The CMASS sample seriously suffers from the radial selection effect, even within the redshift 0.44 ≤ z ≤ 0.6, which will likely lead to statistical conclusions in the CMASS sample being less robust. In the LOWZ sample, the fraction of star-forming galaxies is nearly constant from the least dense regime to the densest regime; the AGN fraction is also insensitive to the local environment. In addition, I note that in the LOWZ sample, the distributions of stellar mass and stellar velocity dispersion for star forming galaxies and AGNs are nearly the same

  6. Superwind Outflows in Seyfert Galaxies? : Large-Scale Radio Maps of an Edge-On Sample

    Science.gov (United States)

    Colbert, E.; Gallimore, J.; Baum, S.; O'Dea, C.

    1995-03-01

    Large-scale galactic winds (superwinds) are commonly found flowing out of the nuclear region of ultraluminous infrared and powerful starburst galaxies. Stellar winds and supernovae from the nuclear starburst provide the energy to drive these superwinds. The outflowing gas escapes along the rotation axis, sweeping up and shock-heating clouds in the halo, which produces optical line emission, radio synchrotron emission, and X-rays. These features can most easily be studied in edge-on systems, so that the wind emission is not confused by that from the disk. We have begun a systematic search for superwind outflows in Seyfert galaxies. In an earlier optical emission-line survey, we found extended minor axis emission and/or double-peaked emission line profiles in >~30% of the sample objects. We present here large-scale (6cm VLA C-config) radio maps of 11 edge-on Seyfert galaxies, selected (without bias) from a distance-limited sample of 23 edge-on Seyferts. These data have been used to estimate the frequency of occurrence of superwinds. Preliminary results indicate that four (36%) of the 11 objects observed and six (26%) of the 23 objects in the distance-limited sample have extended radio emission oriented perpendicular to the galaxy disk. This emission may be produced by a galactic wind blowing out of the disk. Two (NGC 2992 and NGC 5506) of the nine objects for which we have both radio and optical data show good evidence for a galactic wind in both datasets. We suggest that galactic winds occur in >~30% of all Seyferts. A goal of this work is to find a diagnostic that can be used to distinguish between large-scale outflows that are driven by starbursts and those that are driven by an AGN. The presence of starburst-driven superwinds in Seyferts, if established, would have important implications for the connection between starburst galaxies and AGN.

  7. THE CLUSTERING OF ALFALFA GALAXIES: DEPENDENCE ON H I MASS, RELATIONSHIP WITH OPTICAL SAMPLES, AND CLUES OF HOST HALO PROPERTIES

    Energy Technology Data Exchange (ETDEWEB)

    Papastergis, Emmanouil; Giovanelli, Riccardo; Haynes, Martha P.; Jones, Michael G. [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Rodríguez-Puebla, Aldo, E-mail: papastergis@astro.cornell.edu, E-mail: riccardo@astro.cornell.edu, E-mail: haynes@astro.cornell.edu, E-mail: jonesmg@astro.cornell.edu, E-mail: apuebla@astro.unam.mx [Instituto de Astronomía, Universidad Nacional Autónoma de México, A. P. 70-264, 04510 México, D.F. (Mexico)

    2013-10-10

    We use a sample of ≈6000 galaxies detected by the Arecibo Legacy Fast ALFA (ALFALFA) 21 cm survey to measure the clustering properties of H I-selected galaxies. We find no convincing evidence for a dependence of clustering on galactic atomic hydrogen (H I) mass, over the range M{sub H{sub I}} ≈ 10{sup 8.5}-10{sup 10.5} M{sub ☉}. We show that previously reported results of weaker clustering for low H I mass galaxies are probably due to finite-volume effects. In addition, we compare the clustering of ALFALFA galaxies with optically selected samples drawn from the Sloan Digital Sky Survey (SDSS). We find that H I-selected galaxies cluster more weakly than even relatively optically faint galaxies, when no color selection is applied. Conversely, when SDSS galaxies are split based on their color, we find that the correlation function of blue optical galaxies is practically indistinguishable from that of H I-selected galaxies. At the same time, SDSS galaxies with red colors are found to cluster significantly more than H I-selected galaxies, a fact that is evident in both the projected as well as the full two-dimensional correlation function. A cross-correlation analysis further reveals that gas-rich galaxies 'avoid' being located within ≈3 Mpc of optical galaxies with red colors. Next, we consider the clustering properties of halo samples selected from the Bolshoi ΛCDM simulation. A comparison with the clustering of ALFALFA galaxies suggests that galactic H I mass is not tightly related to host halo mass and that a sizable fraction of subhalos do not host H I galaxies. Lastly, we find that we can recover fairly well the correlation function of H I galaxies by just excluding halos with low spin parameter. This finding lends support to the hypothesis that halo spin plays a key role in determining the gas content of galaxies.

  8. UV TO FAR-IR CATALOG OF A GALAXY SAMPLE IN NEARBY CLUSTERS: SPECTRAL ENERGY DISTRIBUTIONS AND ENVIRONMENTAL TRENDS

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Fernandez, Jonathan D.; Iglesias-Paramo, J.; Vilchez, J. M., E-mail: jonatan@iaa.es [Instituto de Astrofisica de Andalucia, Glorieta de la Astronomia s/n, 18008 Granada (Spain)

    2012-03-01

    In this paper, we present a sample of cluster galaxies devoted to study the environmental influence on the star formation activity. This sample of galaxies inhabits in clusters showing a rich variety in their characteristics and have been observed by the SDSS-DR6 down to M{sub B} {approx} -18, and by the Galaxy Evolution Explorer AIS throughout sky regions corresponding to several megaparsecs. We assign the broadband and emission-line fluxes from ultraviolet to far-infrared to each galaxy performing an accurate spectral energy distribution for spectral fitting analysis. The clusters follow the general X-ray luminosity versus velocity dispersion trend of L{sub X} {proportional_to} {sigma}{sup 4.4}{sub c}. The analysis of the distributions of galaxy density counting up to the 5th nearest neighbor {Sigma}{sub 5} shows: (1) the virial regions and the cluster outskirts share a common range in the high density part of the distribution. This can be attributed to the presence of massive galaxy structures in the surroundings of virial regions. (2) The virial regions of massive clusters ({sigma}{sub c} > 550 km s{sup -1}) present a {Sigma}{sub 5} distribution statistically distinguishable ({approx}96%) from the corresponding distribution of low-mass clusters ({sigma}{sub c} < 550 km s{sup -1}). Both massive and low-mass clusters follow a similar density-radius trend, but the low-mass clusters avoid the high density extreme. We illustrate, with ABELL 1185, the environmental trends of galaxy populations. Maps of sky projected galaxy density show how low-luminosity star-forming galaxies appear distributed along more spread structures than their giant counterparts, whereas low-luminosity passive galaxies avoid the low-density environment. Giant passive and star-forming galaxies share rather similar sky regions with passive galaxies exhibiting more concentrated distributions.

  9. A large sample of Kohonen selected E+A (post-starburst) galaxies from the Sloan Digital Sky Survey

    Science.gov (United States)

    Meusinger, H.; Brünecke, J.; Schalldach, P.; in der Au, A.

    2017-01-01

    Context. The galaxy population in the contemporary Universe is characterised by a clear bimodality, blue galaxies with significant ongoing star formation and red galaxies with only a little. The migration between the blue and the red cloud of galaxies is an issue of active research. Post starburst (PSB) galaxies are thought to be observed in the short-lived transition phase. Aims: We aim to create a large sample of local PSB galaxies from the Sloan Digital Sky Survey (SDSS) to study their characteristic properties, particularly morphological features indicative of gravitational distortions and indications for active galactic nuclei (AGNs). Another aim is to present a tool set for an efficient search in a large database of SDSS spectra based on Kohonen self-organising maps (SOMs). Methods: We computed a huge Kohonen SOM for ∼106 spectra from SDSS data release 7. The SOM is made fully available, in combination with an interactive user interface, for the astronomical community. We selected a large sample of PSB galaxies taking advantage of the clustering behaviour of the SOM. The morphologies of both PSB galaxies and randomly selected galaxies from a comparison sample in SDSS Stripe 82 (S82) were inspected on deep co-added SDSS images to search for indications of gravitational distortions. We used the Portsmouth galaxy property computations to study the evolutionary stage of the PSB galaxies and archival multi-wavelength data to search for hidden AGNs. Results: We compiled a catalogue of 2665 PSB galaxies with redshifts z 3 Å and z cloud, in agreement with the idea that PSB galaxies represent the transitioning phase between actively and passively evolving galaxies. The relative frequency of distorted PSB galaxies is at least 57% for EW(Hδ) > 5 Å, significantly higher than in the comparison sample. The search for AGNs based on conventional selection criteria in the radio and MIR results in a low AGN fraction of ∼2-3%. We confirm an MIR excess in the mean SED of

  10. Isolated galaxies

    International Nuclear Information System (INIS)

    Einasto, Maret

    1990-01-01

    To test for the possible presence of really isolated galaxies, which form a randomly distributed population in voids, we compare the distribution of most isolated galaxies in an observed sample with distributions of the same number of random points using the nearest neighbour test. The results show that the random population of really isolated galaxies does not exist - even the most isolated galaxies are connected with systems of galaxies, forming their outlying parts. (author)

  11. Dark Energy Survey Year 1 Results: Galaxy Sample for BAO Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Crocce, M.; et al.

    2017-12-17

    We define and characterise a sample of 1.3 million galaxies extracted from the first year of Dark Energy Survey data, optimised to measure Baryon Acoustic Oscillations in the presence of significant redshift uncertainties. The sample is dominated by luminous red galaxies located at redshifts $z \\gtrsim 0.6$. We define the exact selection using color and magnitude cuts that balance the need of high number densities and small photometric redshift uncertainties, using the corresponding forecasted BAO distance error as a figure-of-merit in the process. The typical photo-$z$ uncertainty varies from $2.3\\%$ to $3.6\\%$ (in units of 1+$z$) from $z=0.6$ to $1$, with number densities from $200$ to $130$ galaxies per deg$^2$ in tomographic bins of width $\\Delta z = 0.1$. Next we summarise the validation of the photometric redshift estimation. We characterise and mitigate observational systematics including stellar contamination, and show that the clustering on large scales is robust in front of those contaminants. We show that the clustering signal in the auto-correlations and cross-correlations is generally consistent with theoretical models, which serves as an additional test of the redshift distributions.

  12. Galaxy power-spectrum responses and redshift-space super-sample effect

    Science.gov (United States)

    Li, Yin; Schmittfull, Marcel; Seljak, Uroš

    2018-02-01

    As a major source of cosmological information, galaxy clustering is susceptible to long-wavelength density and tidal fluctuations. These long modes modulate the growth and expansion rate of local structures, shifting them in both amplitude and scale. These effects are often named the growth and dilation effects, respectively. In particular the dilation shifts the baryon acoustic oscillation (BAO) peak and breaks the assumption of the Alcock-Paczynski (AP) test. This cannot be removed with reconstruction techniques because the effect originates from long modes outside the survey. In redshift space, the long modes generate a large-scale radial peculiar velocity that affects the redshift-space distortion (RSD) signal. We compute the redshift-space response functions of the galaxy power spectrum to long density and tidal modes at leading order in perturbation theory, including both the growth and dilation terms. We validate these response functions against measurements from simulated galaxy mock catalogs. As one application, long density and tidal modes beyond the scale of a survey correlate various observables leading to an excess error known as the super-sample covariance, and thus weaken their constraining power. We quantify the super-sample effect on BAO, AP, and RSD measurements, and study its impact on current and future surveys.

  13. GALAXIES IN FILAMENTS HAVE MORE SATELLITES: THE INFLUENCE OF THE COSMIC WEB ON THE SATELLITE LUMINOSITY FUNCTION IN THE SDSS

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Quan; Libeskind, N. I. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Tempel, E., E-mail: qguo@aip.de [Tartu Observatory, Observatooriumi 1, 61602 Tõravere (Estonia)

    2015-02-20

    We investigate whether the satellite luminosity function (LF) of primary galaxies identified in the Sloan Digital Sky Survey (SDSS) depends on whether the host galaxy is in a filament or not. Isolated primary galaxies are identified in the SDSS spectroscopic sample, and potential satellites (that are up to four magnitudes fainter than their hosts) are searched for in the much deeper photometric sample. Filaments are constructed from the galaxy distribution by the Bisous process. Isolated primary galaxies are divided into two subsamples: those in filaments and those not in filaments. We examine the stacked mean satellite LF of both the filament and nonfilament samples and find that, on average, the satellite LF of galaxies in filaments is significantly higher than those of galaxies not in filaments. The filamentary environment can increase the abundance of the brightest satellites (M {sub sat.} < M {sub prim.} + 2.0) by a factor of ∼2 compared with nonfilament isolated galaxies. This result is independent of the primary galaxy magnitude, although the satellite LF of galaxies in the faintest magnitude bin is too noisy to determine if such a dependence exists. Because our filaments are extracted from a spectroscopic flux-limited sample, we consider the possibility that the difference in satellite LF is due to a redshift, color, or environmental bias, finding these to be insufficient to explain our result. The dependence of the satellite LF on the cosmic web suggests that the filamentary environment may have a strong effect on the efficiency of galaxy formation.

  14. GALAXIES IN FILAMENTS HAVE MORE SATELLITES: THE INFLUENCE OF THE COSMIC WEB ON THE SATELLITE LUMINOSITY FUNCTION IN THE SDSS

    International Nuclear Information System (INIS)

    Guo, Quan; Libeskind, N. I.; Tempel, E.

    2015-01-01

    We investigate whether the satellite luminosity function (LF) of primary galaxies identified in the Sloan Digital Sky Survey (SDSS) depends on whether the host galaxy is in a filament or not. Isolated primary galaxies are identified in the SDSS spectroscopic sample, and potential satellites (that are up to four magnitudes fainter than their hosts) are searched for in the much deeper photometric sample. Filaments are constructed from the galaxy distribution by the Bisous process. Isolated primary galaxies are divided into two subsamples: those in filaments and those not in filaments. We examine the stacked mean satellite LF of both the filament and nonfilament samples and find that, on average, the satellite LF of galaxies in filaments is significantly higher than those of galaxies not in filaments. The filamentary environment can increase the abundance of the brightest satellites (M sat. < M prim. + 2.0) by a factor of ∼2 compared with nonfilament isolated galaxies. This result is independent of the primary galaxy magnitude, although the satellite LF of galaxies in the faintest magnitude bin is too noisy to determine if such a dependence exists. Because our filaments are extracted from a spectroscopic flux-limited sample, we consider the possibility that the difference in satellite LF is due to a redshift, color, or environmental bias, finding these to be insufficient to explain our result. The dependence of the satellite LF on the cosmic web suggests that the filamentary environment may have a strong effect on the efficiency of galaxy formation

  15. Superwind Outflow in Seyfert Galaxies? : Optical Observations of an Edge-On Sample

    Science.gov (United States)

    Colbert, E.; Gallimore, J.; Baum, S.; O'Dea, C.; Lehnert, M.

    1994-12-01

    Large-scale galactic winds (superwinds) are commonly found flowing out of the nuclear region of ultraluminous infrared and powerful starburst galaxies. Stellar winds and supernovae from the nuclear starburst are thought to provide the energy to drive these superwinds. The outflowing gas escapes along the rotation axis, sweeping up and shock-heating clouds in the halo, which produces optical line emission, X-rays and radio synchrotron emission. These features can most easily be studied in edge-on systems, so that the wind emission is not confused by that from the disk. Diffuse radio emission has been found (Baum et al. 1993, ApJ, 419, 553) to extend out to kpc-scales in a number of edge-on Seyfert galaxies. We have therefore launched a systematic search for superwind outflows in Seyferts. We present here narrow-band optical images and optical spectra for a sample of edge-on Seyferts. These data have been used to estimate the frequency of occurence of superwinds. Approximately half of the sample objects show evidence for extended emission-line regions which are preferentially oriented perpendicular to the galaxy disk. It is possible that these emission-line regions may be energized by a superwind outflow from a circumnuclear starburst, although there may also be a contribution from the AGN itself. A goal of this work is to find a diagnostic that can be used to distinguish between large-scale outflows that are driven by starbursts and those that are driven by an AGN. The presence of starburst-driven superwinds in Seyferts, if established, would have important implications for the connection between starburst galaxies and AGN.

  16. A multigroup flux-limited asymptotic diffusion Fokker-Planck equation

    International Nuclear Information System (INIS)

    Liu Chengan

    1987-01-01

    A more perfrect flux-limited method is applied to combine with asymptotic diffusion theory of the radiation transpore, and the high peaked component in the scattering angle is treated with Fokker-Planck methods, thus the flux-limited asymptotic diffusion Fokker-Planck equation has been founded. Since the equation is of diffusion form, it retains the simplity and the convenience of the classical diffusion theory, and improves precision in describing radiation transport problems

  17. Spectroscopic Properties of Star-Forming Host Galaxies and Type Ia Supernova Hubble Residuals in a Nearly Unbiased Sample

    Energy Technology Data Exchange (ETDEWEB)

    D' Andrea, Chris B. [Univ. of Pennsylvania, Philadelphia, PA (United States); et al.

    2011-12-20

    We examine the correlation between supernova host galaxy properties and their residuals on the Hubble diagram. We use supernovae discovered during the Sloan Digital Sky Survey II - Supernova Survey, and focus on objects at a redshift of z < 0.15, where the selection effects of the survey are known to yield a complete Type Ia supernova sample. To minimize the bias in our analysis with respect to measured host-galaxy properties, spectra were obtained for nearly all hosts, spanning a range in magnitude of -23 < M_r < -17. In contrast to previous works that use photometric estimates of host mass as a proxy for global metallicity, we analyze host-galaxy spectra to obtain gas-phase metallicities and star-formation rates from host galaxies with active star formation. From a final sample of ~ 40 emission-line galaxies, we find that light-curve corrected Type Ia supernovae are ~ 0.1 magnitudes brighter in high-metallicity hosts than in low-metallicity hosts. We also find a significant (> 3{\\sigma}) correlation between the Hubble residuals of Type Ia supernovae and the specific star-formation rate of the host galaxy. We comment on the importance of supernova/host-galaxy correlations as a source of systematic bias in future deep supernova surveys.

  18. Diversity in the stellar velocity dispersion profiles of a large sample of brightest cluster galaxies z ≤ 0.3

    Science.gov (United States)

    Loubser, S. I.; Hoekstra, H.; Babul, A.; O'Sullivan, E.

    2018-06-01

    We analyse spatially resolved deep optical spectroscopy of brightestcluster galaxies (BCGs) located in 32 massive clusters with redshifts of 0.05 ≤ z ≤ 0.30 to investigate their velocity dispersion profiles. We compare these measurements to those of other massive early-type galaxies, as well as central group galaxies, where relevant. This unique, large sample extends to the most extreme of massive galaxies, spanning MK between -25.7 and -27.8 mag, and host cluster halo mass M500 up to 1.7 × 1015 M⊙. To compare the kinematic properties between brightest group and cluster members, we analyse similar spatially resolved long-slit spectroscopy for 23 nearby brightest group galaxies (BGGs) from the Complete Local-Volume Groups Sample. We find a surprisingly large variety in velocity dispersion slopes for BCGs, with a significantly larger fraction of positive slopes, unique compared to other (non-central) early-type galaxies as well as the majority of the brightest members of the groups. We find that the velocity dispersion slopes of the BCGs and BGGs correlate with the luminosity of the galaxies, and we quantify this correlation. It is not clear whether the full diversity in velocity dispersion slopes that we see is reproduced in simulations.

  19. CORRELATION ANALYSIS OF A LARGE SAMPLE OF NARROW-LINE SEYFERT 1 GALAXIES: LINKING CENTRAL ENGINE AND HOST PROPERTIES

    International Nuclear Information System (INIS)

    Xu Dawei; Komossa, S.; Wang Jing; Yuan Weimin; Zhou Hongyan; Lu Honglin; Li Cheng; Grupe, Dirk

    2012-01-01

    We present a statistical study of a large, homogeneously analyzed sample of narrow-line Seyfert 1 (NLS1) galaxies, accompanied by a comparison sample of broad-line Seyfert 1 (BLS1) galaxies. Optical emission-line and continuum properties are subjected to correlation analyses, in order to identify the main drivers of the correlation space of active galactic nuclei (AGNs), and of NLS1 galaxies in particular. For the first time, we have established the density of the narrow-line region as a key parameter in Eigenvector 1 space, as important as the Eddington ratio L/L Edd . This is important because it links the properties of the central engine with the properties of the host galaxy, i.e., the interstellar medium (ISM). We also confirm previously found correlations involving the line width of Hβ and the strength of the Fe II and [O III] λ5007 emission lines, and we confirm the important role played by L/L Edd in driving the properties of NLS1 galaxies. A spatial correlation analysis shows that large-scale environments of the BLS1 and NLS1 galaxies of our sample are similar. If mergers are rare in our sample, accretion-driven winds, on the one hand, or bar-driven inflows, on the other hand, may account for the strong dependence of Eigenvector 1 on ISM density.

  20. HICOSMO - X-ray analysis of a complete sample of galaxy clusters

    Science.gov (United States)

    Schellenberger, G.; Reiprich, T.

    2017-10-01

    Galaxy clusters are known to be the largest virialized objects in the Universe. Based on the theory of structure formation one can use them as cosmological probes, since they originate from collapsed overdensities in the early Universe and witness its history. The X-ray regime provides the unique possibility to measure in detail the most massive visible component, the intra cluster medium. Using Chandra observations of a local sample of 64 bright clusters (HIFLUGCS) we provide total (hydrostatic) and gas mass estimates of each cluster individually. Making use of the completeness of the sample we quantify two interesting cosmological parameters by a Bayesian cosmological likelihood analysis. We find Ω_{M}=0.3±0.01 and σ_{8}=0.79±0.03 (statistical uncertainties) using our default analysis strategy combining both, a mass function analysis and the gas mass fraction results. The main sources of biases that we discuss and correct here are (1) the influence of galaxy groups (higher incompleteness in parent samples and a differing behavior of the L_{x} - M relation), (2) the hydrostatic mass bias (as determined by recent hydrodynamical simulations), (3) the extrapolation of the total mass (comparing various methods), (4) the theoretical halo mass function and (5) other cosmological (non-negligible neutrino mass), and instrumental (calibration) effects.

  1. A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies. II. The SDSS DR7 Sample

    Science.gov (United States)

    Liu, He-Yang; Yuan, Weimin; Dong, Xiao-Bo; Zhou, Hongyan; Liu, Wen-Juan

    2018-04-01

    A new sample of 204 low-mass black holes (LMBHs) in active galactic nuclei (AGNs) is presented with black hole masses in the range of (1–20) × 105 M ⊙. The AGNs are selected through a systematic search among galaxies in the Seventh Data Release (DR7) of the Sloan Digital Sky Survey (SDSS), and careful analyses of their optical spectra and precise measurement of spectral parameters. Combining them with our previous sample selected from SDSS DR4 makes it the largest LMBH sample so far, totaling over 500 objects. Some of the statistical properties of the combined LMBH AGN sample are briefly discussed in the context of exploring the low-mass end of the AGN population. Their X-ray luminosities follow the extension of the previously known correlation with the [O III] luminosity. The effective optical-to-X-ray spectral indices α OX, albeit with a large scatter, are broadly consistent with the extension of the relation with the near-UV luminosity L 2500 Å. Interestingly, a correlation of α OX with black hole mass is also found, with α OX being statistically flatter (stronger X-ray relative to optical) for lower black hole masses. Only 26 objects, mostly radio loud, were detected in radio at 20 cm in the FIRST survey, giving a radio-loud fraction of 4%. The host galaxies of LMBHs have stellar masses in the range of 108.8–1012.4 M ⊙ and optical colors typical of Sbc spirals. They are dominated by young stellar populations that seem to have undergone continuous star formation history.

  2. Bulgeless galaxies at intermediate redshift: Sample selection, color properties, and the existence of powerful active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Bizzocchi, Luca; Leonardo, Elvira; Grossi, Marco; Afonso, José; Fernandes, Cristina; Retrê, João [Centro de Astronomia e Astrofísica da Universidade de Lisboa, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisbon (Portugal); Filho, Mercedes E.; Lobo, Catarina [Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Griffith, Roger L. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Anton, Sonia [Centro de Investigação em Ciências Geo-Espaciais, Faculdade de Ciências da Universidade do Porto, Porto (Portugal); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Brinchmann, Jarle [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Henriques, Bruno [Max-Planck-Institut für Astrophysik, Karl Schwarzschild Straße 1, D-85748 Garching bei München (Germany); Messias, Hugo [Departamento de astronomía, Av. Esteban Iturra 6to piso, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción (Chile)

    2014-02-10

    We present a catalog of bulgeless galaxies, which includes 19,225 objects selected in four of the deepest, largest multi-wavelength data sets available—COSMOS, AEGIS, GEMS, and GOODS—at intermediate redshift (0.4 ≤ z ≤ 1.0). The morphological classification was provided by the Advanced Camera for Surveys General Catalog (ACS-GC), which used publicly available data obtained with the ACS instrument on the Hubble Space Telescope. Rest-frame photometric quantities were derived using kcorrect. We analyze the properties of the sample and the evolution of pure-disk systems with redshift. Very massive [log (M {sub *}/M {sub ☉}) > 10.5] bulgeless galaxies contribute to ∼30% of the total galaxy population number density at z ≥ 0.7, but their number density drops substantially with decreasing redshift. We show that only a negligible fraction of pure disks appear to be quiescent systems, and red sequence bulgeless galaxies show indications of dust-obscured star formation. X-ray catalogs were used to search for X-ray emission within our sample. After visual inspection and detailed parametric morphological fitting we identify 30 active galactic nuclei (AGNs) that reside in galaxies without a classical bulge. The finding of such peculiar objects at intermediate redshift shows that while AGN growth in merger-free systems is a rare event (0.2% AGN hosts in this sample of bulgeless galaxies), it can indeed happen relatively early in the history of the universe.

  3. Cleaning spectroscopic samples of stars in nearby dwarf galaxies : The use of the nIR Mg I line to weed out Milky Way contaminants

    NARCIS (Netherlands)

    Battaglia, G.; Starkenburg, E.

    Dwarf galaxies provide insight into the processes of star formation and chemical enrichment at the low end of the galaxy mass function, as well as into the clustering of dark matter on small scales. In studies of Local Group dwarf galaxies, spectroscopic samples of individual stars are used to

  4. Multi-spectral study of a new sample of blue compact dwarf galaxies

    CERN Document Server

    Doublier, V; Comte, G

    1999-01-01

    For pt.I see ibid., vol.124, no.3, p.405-24 (1997). We present the results of surface photometry on a new sample of blue compact dwarf galaxies (BCDGs), in continuation to a previous paper (Doublier et al. 1997). The 22 galaxies $9 (plus two companions) discussed in the present paper have been selected in the Southern Hemisphere, from several lists. An atlas containing isophotal maps, surface brightnesses and B-R color profiles of the sample is given, together $9 with the tables containing the photometric parameters. The results are consistent with those for objects selected from the Byurakan surveys in the Northern Hemisphere. Similarly, we find about one fourth of the BCDGs showing a $9 dominant r/sup 1/4/ brightness distribution component, one fourth of the BCDGs showing a dominant exponential surface brightness profile, and about half of them show composite brightness distributions. Integrated properties, colors, $9 mean surface brightnesses and luminosity-radius relations are investigated and discussed f...

  5. A SAMPLE OF SEYFERT-2 GALAXIES WITH ULTRALUMINOUS GALAXY-WIDE NARROW-LINE REGIONS: QUASAR LIGHT ECHOES?

    International Nuclear Information System (INIS)

    Schirmer, M.; Diaz, R.; Levenson, N. A.; Winge, C.; Holhjem, K.

    2013-01-01

    We report the discovery of Seyfert-2 galaxies in SDSS-DR8 with galaxy-wide, ultraluminous narrow-line regions (NLRs) at redshifts z = 0.2-0.6. With a space density of 4.4 Gpc –3 at z ∼ 0.3, these 'green beans' (GBs) are amongst the rarest objects in the universe. We are witnessing an exceptional and/or short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). The main focus of this paper is on a detailed analysis of the GB prototype galaxy J2240–0927 (z = 0.326). Its NLR extends over 26 × 44 kpc and is surrounded by an extended NLR. With a total [O III] λ5008 luminosity of (5.7 ± 0.9) × 10 43 erg s –1 , this is one of the most luminous NLRs known around any type-2 galaxy. Using VLT/XSHOOTER, we show that the NLR is powered by an AGN, and we derive resolved extinction, density, and ionization maps. Gas kinematics is disturbed on a global scale, and high-velocity outflows are absent or faint. This NLR is unlike any other NLR or extended emission line region known. Spectroscopy with Gemini/GMOS reveals extended, high-luminosity [O III] emission also in other GBs. WISE 24 μm luminosities are 5-50 times lower than predicted by the [O III] fluxes, suggesting that the NLRs reflect earlier, very active quasar states that have strongly subsided in less than a galaxy's light-crossing time. These light echoes, or ionization echoes, are about 100 times more luminous than any other such echo known to date. X-ray data are needed for photoionization modeling and to verify the light echoes.

  6. The optimally sampled galaxy-wide stellar initial mass function. Observational tests and the publicly available GalIMF code

    Science.gov (United States)

    Yan, Zhiqiang; Jerabkova, Tereza; Kroupa, Pavel

    2017-11-01

    Here we present a full description of the integrated galaxy-wide initial mass function (IGIMF) theory in terms of the optimal sampling and compare it with available observations. Optimal sampling is the method we use to discretize the IMF deterministically into stellar masses. Evidence indicates that nature may be closer to deterministic sampling as observations suggest a smaller scatter of various relevant observables than random sampling would give, which may result from a high level of self-regulation during the star formation process. We document the variation of IGIMFs under various assumptions. The results of the IGIMF theory are consistent with the empirical relation between the total mass of a star cluster and the mass of its most massive star, and the empirical relation between the star formation rate (SFR) of a galaxy and the mass of its most massive cluster. Particularly, we note a natural agreement with the empirical relation between the IMF power-law index and the SFR of a galaxy. The IGIMF also results in a relation between the SFR of a galaxy and the mass of its most massive star such that, if there were no binaries, galaxies with SFR first time, we show optimally sampled galaxy-wide IMFs (OSGIMF) that mimic the IGIMF with an additional serrated feature. Finally, a Python module, GalIMF, is provided allowing the calculation of the IGIMF and OSGIMF dependent on the galaxy-wide SFR and metallicity. A copy of the python code model is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A126

  7. THE CIRCUMGALACTIC MEDIUM OF SUBMILLIMETER GALAXIES. I. FIRST RESULTS FROM A RADIO-IDENTIFIED SAMPLE

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Hai; Mutel, R.; Isbell, J.; Lang, C.; McGinnis, D. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Hennawi, J. F. [Max-Planck-Institut fur Astronomie, Heidelberg (Germany); Prochaska, J. X. [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Casey, C. [Department of Astronomy, the University of Texas at Austin, 2515 Speedway Blvd, Stop C1400, Austin, TX 78712 (United States); Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Kereš, D. [Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Zhang, Z.-Y.; Michałowski, M. J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Clements, D. [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Mooley, K. [Oxford Centre For Astrophysical Surveys, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United States); Perley, D. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 København Ø (Denmark); Stockton, A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Thompson, D. [Large Binocular Telescope Observatory, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721 (United States)

    2016-11-20

    We present the first results from an ongoing survey to characterize the circumgalactic medium (CGM) of massive high-redshift galaxies detected as submillimeter galaxies (SMGs). We constructed a parent sample of 163 SMG–QSO pairs with separations less than ∼36″ by cross-matching far-infrared-selected galaxies from Herschel with spectroscopically confirmed QSOs. The Herschel sources were selected to match the properties of the SMGs. We determined the sub-arcsecond positions of six Herschel sources with the Very Large Array and obtained secure redshift identification for three of those with near-infrared spectroscopy. The QSO sightlines probe transverse proper distances of 112, 157, and 198 kpc at foreground redshifts of 2.043, 2.515, and 2.184, respectively, which are comparable to the virial radius of the ∼10{sup 13} M {sub ⊙} halos expected to host SMGs. High-quality absorption-line spectroscopy of the QSOs reveals systematically strong H i Ly α absorption around all three SMGs, with rest-frame equivalent widths of ∼2–3 Å. However, none of the three absorbers exhibit compelling evidence for optically thick H i gas or metal absorption, in contrast to the dominance of strong neutral absorbers in the CGM of luminous z ∼ 2 QSOs. The low covering factor of optically thick H i gas around SMGs tentatively indicates that SMGs may not have as prominent cool gas reservoirs in their halos as the coeval QSOs and that they may inhabit less massive halos than previously thought.

  8. Understanding of flux-limited behaviors of heat transport in nonlinear regime

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yangyu, E-mail: yangyuhguo@gmail.com [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics and CNMM, Tsinghua University, Beijing 100084 (China); Jou, David, E-mail: david.jou@uab.es [Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia (Spain); Wang, Moran, E-mail: mrwang@tsinghua.edu [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics and CNMM, Tsinghua University, Beijing 100084 (China)

    2016-01-28

    The classical Fourier's law of heat transport breaks down in highly nonequilibrium situations as in nanoscale heat transport, where nonlinear effects become important. The present work is aimed at exploring the flux-limited behaviors based on a categorization of existing nonlinear heat transport models in terms of their theoretical foundations. Different saturation heat fluxes are obtained, whereas the same qualitative variation trend of heat flux versus exerted temperature gradient is got in diverse nonlinear models. The phonon hydrodynamic model is proposed to act as a standard to evaluate other heat flux limiters because of its more rigorous physical foundation. A deeper knowledge is thus achieved about the phenomenological generalized heat transport models. The present work provides deeper understanding and accurate modeling of nonlocal and nonlinear heat transport beyond the diffusive limit. - Highlights: • Exploring flux-limited behaviors based on a categorization of existing nonlinear heat transport models. • Proposing phonon hydrodynamic model as a standard to evaluate heat flux limiters. • Providing accurate modeling of nonlocal and nonlinear heat transport beyond the diffusive limit.

  9. A multigrid Newton-Krylov method for flux-limited radiation diffusion

    International Nuclear Information System (INIS)

    Rider, W.J.; Knoll, D.A.; Olson, G.L.

    1998-01-01

    The authors focus on the integration of radiation diffusion including flux-limited diffusion coefficients. The nonlinear integration is accomplished with a Newton-Krylov method preconditioned with a multigrid Picard linearization of the governing equations. They investigate the efficiency of the linear and nonlinear iterative techniques

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

    International Nuclear Information System (INIS)

    Barton, Elizabeth J.; Cooke, Jeff

    2009-01-01

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

  11. A Catalog Sample of Low-mass Galaxies Observed in X-Rays with Central Candidate Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Nucita, A. A.; Manni, L.; Paolis, F. De; Giordano, M.; Ingrosso, G., E-mail: nucita@le.infn.it [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, Via per Arnesano, CP 193, I-73100, Lecce (Italy)

    2017-03-01

    We present a sample of X-ray-selected candidate black holes in 51 low-mass galaxies with z ≤ 0.055 and masses up to 10{sup 10} M {sub ⊙} obtained by cross-correlating the NASA-SLOAN Atlas with the 3XMM catalog. We have also searched in the available catalogs for radio counterparts of the black hole candidates and find that 19 of the previously selected sources also have a radio counterpart. Our results show that about 37% of the galaxies of our sample host an X-ray source (associated with a radio counterpart) spatially coincident with the galaxy center, in agreement with other recent works. For these nuclear sources, the X-ray/radio fundamental plane relation allows one to estimate the mass of the (central) candidate black holes, which are in the range of 10{sup 4}–2 × 10{sup 8} M {sub ⊙} (with a median value of ≃3 × 10{sup 7} M {sub ⊙} and eight candidates having masses below 10{sup 7} M {sub ⊙}). This result, while suggesting that X-ray emitting black holes in low-mass galaxies may have had a key role in the evolution of such systems, makes it even more urgent to explain how such massive objects formed in galaxies. Of course, dedicated follow-up observations both in the X-ray and radio bands, as well as in the optical, are necessary in order to confirm our results.

  12. LOCAL BENCHMARKS FOR THE EVOLUTION OF MAJOR-MERGER GALAXIES-SPITZER OBSERVATIONS OF A K-BAND SELECTED SAMPLE

    International Nuclear Information System (INIS)

    Xu, C. Kevin; Cheng Yiwen; Lu Nanyao; Mazzarella, Joseph M.; Cutri, Roc; Domingue, Donovan; Huang Jiasheng; Gao Yu; Sun, W.-H.; Surace, Jason

    2010-01-01

    We present Spitzer observations for a sample of close major-merger galaxy pairs (KPAIR sample) selected from cross-matches between the Two Micron All Sky Survey and Sloan Digital Sky Survey Data Release 3. The goals are to study the star formation activity in these galaxies and to set a local bench mark for the cosmic evolution of close major mergers. The Spitzer KPAIR sample (27 pairs, 54 galaxies) includes all spectroscopically confirmed spiral-spiral (S+S) and spiral-elliptical (S+E) pairs in a parent sample that is complete for primaries brighter than K = 12.5 mag, projected separations of 5 h -1 kpc ≤ s ≤ 20 h -1 kpc, and mass ratios ≤2.5. The Spitzer data, consisting of images in seven bands (3.6, 4.5, 5.8, 8, 24, 70, 160 μm), show very diversified IR emission properties. Compared to single spiral galaxies in a control sample, only spiral galaxies in S+S pairs show significantly enhanced specific star formation rate (sSFR = SFR/M), whereas spiral galaxies in S+E pairs do not. Furthermore, the SFR enhancement of spiral galaxies in S+S pairs is highly mass-dependent. Only those with M ∼> 10 10.5 M sun show significant enhancement. Relatively low-mass (M ∼ 10 10 M sun ) spirals in S+S pairs have about the same SFR/M compared to their counterparts in the control sample, while those with 10 11 M sun have on average a ∼3 times higher SFR/M than single spirals. There is evidence for a correlation between the global star formation activities (but not the nuclear activities) of the component galaxies in massive S+S major-merger pairs (the H olmberg effect ) . There is no significant difference in the SFR/M between the primaries and the secondaries, nor between spirals of SEP KPAIR =2.54 x 10 -4 (M sun yr -1 Mpc -3 ).

  13. Photometric redshift requirements for lens galaxies in galaxy-galaxy lensing analyses

    Science.gov (United States)

    Nakajima, R.; Mandelbaum, R.; Seljak, U.; Cohn, J. D.; Reyes, R.; Cool, R.

    2012-03-01

    Weak gravitational lensing is a valuable probe of galaxy formation and cosmology. Here we quantify the effects of using photometric redshifts (photo-z) in galaxy-galaxy lensing, for both sources and lenses, both for the immediate goal of using galaxies with photo-z as lenses in the Sloan Digital Sky Survey (SDSS) and as a demonstration of methodology for large, upcoming weak lensing surveys that will by necessity be dominated by lens samples with photo-z. We calculate the bias in the lensing mass calibration as well as consequences for absolute magnitude (i.e. k-corrections) and stellar mass estimates for a large sample of SDSS Data Release 8 (DR8) galaxies. The redshifts are obtained with the template-based photo-z code ZEBRA on the SDSS DR8 ugriz photometry. We assemble and characterize the calibration samples (˜9000 spectroscopic redshifts from four surveys) to obtain photometric redshift errors and lensing biases corresponding to our full SDSS DR8 lens and source catalogues. Our tests of the calibration sample also highlight the impact of observing conditions in the imaging survey when the spectroscopic calibration covers a small fraction of its footprint; atypical imaging conditions in calibration fields can lead to incorrect conclusions regarding the photo-z of the full survey. For the SDSS DR8 catalogue, we find σΔz/(1+z)= 0.096 and 0.113 for the lens and source catalogues, with flux limits of r= 21 and 21.8, respectively. The photo-z bias and scatter is a function of photo-z and template types, which we exploit to apply photo-z quality cuts. By using photo-z rather than spectroscopy for lenses, dim blue galaxies and L* galaxies up to z˜ 0.4 can be used as lenses, thus expanding into unexplored areas of parameter space. We also explore the systematic uncertainty in the lensing signal calibration when using source photo-z, and both lens and source photo-z; given the size of existing training samples, we can constrain the lensing signal calibration (and

  14. Occurrence of Radio Minihalos in a Mass-limited Sample of Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Giacintucci, Simona; Clarke, Tracy E. [Naval Research Laboratory, 4555 Overlook Avenue SW, Code 7213, Washington, DC 20375 (United States); Markevitch, Maxim [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Cassano, Rossella; Venturi, Tiziana; Brunetti, Gianfranco, E-mail: simona.giacintucci@nrl.navy.mil [INAF—Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy)

    2017-06-01

    We investigate the occurrence of radio minihalos—diffuse radio sources of unknown origin observed in the cores of some galaxy clusters—in a statistical sample of 58 clusters drawn from the Planck Sunyaev–Zel’dovich cluster catalog using a mass cut ( M {sub 500} > 6 × 10{sup 14} M {sub ⊙}). We supplement our statistical sample with a similarly sized nonstatistical sample mostly consisting of clusters in the ACCEPT X-ray catalog with suitable X-ray and radio data, which includes lower-mass clusters. Where necessary (for nine clusters), we reanalyzed the Very Large Array archival radio data to determine whether a minihalo is present. Our total sample includes all 28 currently known and recently discovered radio minihalos, including six candidates. We classify clusters as cool-core or non-cool-core according to the value of the specific entropy floor in the cluster center, rederived or newly derived from the Chandra X-ray density and temperature profiles where necessary (for 27 clusters). Contrary to the common wisdom that minihalos are rare, we find that almost all cool cores—at least 12 out of 15 (80%)—in our complete sample of massive clusters exhibit minihalos. The supplementary sample shows that the occurrence of minihalos may be lower in lower-mass cool-core clusters. No minihalos are found in non-cool cores or “warm cores.” These findings will help test theories of the origin of minihalos and provide information on the physical processes and energetics of the cluster cores.

  15. THE SL2S GALAXY-SCALE LENS SAMPLE. V. DARK MATTER HALOS AND STELLAR IMF OF MASSIVE EARLY-TYPE GALAXIES OUT TO REDSHIFT 0.8

    Energy Technology Data Exchange (ETDEWEB)

    Sonnenfeld, Alessandro; Treu, Tommaso [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Marshall, Philip J. [Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 20450, MS29, Stanford, CA 94309 (United States); Suyu, Sherry H. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Gavazzi, Raphaël [Institut d' Astrophysique de Paris, UMR7095 CNRS-Université Pierre et Marie Curie, 98bis bd Arago, F-75014 Paris (France); Auger, Matthew W. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Nipoti, Carlo, E-mail: sonnen@physics.ucsb.edu [Department of Physics and Astronomy, Bologna University, viale Berti-Pichat 6/2, I-40127 Bologna (Italy)

    2015-02-20

    We investigate the cosmic evolution of the internal structure of massive early-type galaxies over half of the age of the universe. We perform a joint lensing and stellar dynamics analysis of a sample of 81 strong lenses from the Strong Lensing Legacy Survey and Sloan ACS Lens Survey and combine the results with a hierarchical Bayesian inference method to measure the distribution of dark matter mass and stellar initial mass function (IMF) across the population of massive early-type galaxies. Lensing selection effects are taken into account. We find that the dark matter mass projected within the inner 5 kpc increases for increasing redshift, decreases for increasing stellar mass density, but is roughly constant along the evolutionary tracks of early-type galaxies. The average dark matter slope is consistent with that of a Navarro-Frenk-White profile, but is not well constrained. The stellar IMF normalization is close to a Salpeter IMF at log M {sub *} = 11.5 and scales strongly with increasing stellar mass. No dependence of the IMF on redshift or stellar mass density is detected. The anti-correlation between dark matter mass and stellar mass density supports the idea of mergers being more frequent in more massive dark matter halos.

  16. Dark Matter Profiles in Dwarf Galaxies: A Statistical Sample Using High-Resolution Hα Velocity Fields from PCWI

    Science.gov (United States)

    Relatores, Nicole C.; Newman, Andrew B.; Simon, Joshua D.; Ellis, Richard; Truong, Phuongmai N.; Blitz, Leo

    2018-01-01

    We present high quality Hα velocity fields for a sample of nearby dwarf galaxies (log M/M⊙ = 8.4-9.8) obtained as part of the Dark Matter in Dwarf Galaxies survey. The purpose of the survey is to investigate the cusp-core discrepancy by quantifying the variation of the inner slope of the dark matter distributions of 26 dwarf galaxies, which were selected as likely to have regular kinematics. The data were obtained with the Palomar Cosmic Web Imager, located on the Hale 5m telescope. We extract rotation curves from the velocity fields and use optical and infrared photometry to model the stellar mass distribution. We model the total mass distribution as the sum of a generalized Navarro-Frenk-White dark matter halo along with the stellar and gaseous components. We present the distribution of inner dark matter density profile slopes derived from this analysis. For a subset of galaxies, we compare our results to an independent analysis based on CO observations. In future work, we will compare the scatter in inner density slopes, as well as their correlations with galaxy properties, to theoretical predictions for dark matter core creation via supernovae feedback.

  17. Size effects in non-linear heat conduction with flux-limited behaviors

    Science.gov (United States)

    Li, Shu-Nan; Cao, Bing-Yang

    2017-11-01

    Size effects are discussed for several non-linear heat conduction models with flux-limited behaviors, including the phonon hydrodynamic, Lagrange multiplier, hierarchy moment, nonlinear phonon hydrodynamic, tempered diffusion, thermon gas and generalized nonlinear models. For the phonon hydrodynamic, Lagrange multiplier and tempered diffusion models, heat flux will not exist in problems with sufficiently small scale. The existence of heat flux needs the sizes of heat conduction larger than their corresponding critical sizes, which are determined by the physical properties and boundary temperatures. The critical sizes can be regarded as the theoretical limits of the applicable ranges for these non-linear heat conduction models with flux-limited behaviors. For sufficiently small scale heat conduction, the phonon hydrodynamic and Lagrange multiplier models can also predict the theoretical possibility of violating the second law and multiplicity. Comparisons are also made between these non-Fourier models and non-linear Fourier heat conduction in the type of fast diffusion, which can also predict flux-limited behaviors.

  18. Examining the X-ray Properties of Lenticular Galaxies: Rollins S0 X-ray Sample (RS0X)

    Science.gov (United States)

    Fuse, Christopher R.; Malespina, Alysa

    2017-01-01

    Lenticular galaxies represent a complex morphology in which many questions remain. The S0 morphology possesses spiral galaxy attributes, such as a disk, while also displaying the luminosity and old stellar population indicative of an elliptical galaxy. The proposed formation mechanisms for lenticulars are also varied, with the absence of gas suggesting a faded spiral and the high masses and luminosities implying a merger formation. The star formation and high-energy emission from a sample of S0s will be used to better understand the properties and formation mechanisms of this unique subset of galaxies.We use the Chandra X-ray Observatory archives cycle 1 - 16 to identify a sample of seventeen lenticular galaxies residing in a variety of environments. Data was analyzed using the CIAO software to produce true color images, radial profiles of the halo gas, gas contours, as well as determine the X-ray luminosities of the point sources and gas.The X-ray gas temperature of the sample S0s varied over a narrow range between 0.61 and 0.96 keV, with one outlier, NGC 4382 at 2.0 keV. The X-ray luminosity of the halo gas varies by four dex. The gas temperatures and X-ray luminosities do not vary by environment, with the majority of sample S0s displaying values of typical elliptical galaxies. The S0 sample is X-ray under-luminous relative to the optical luminosity as compared to the sample of early-type galaxies of Ellis & O’Sullivan (2006).The halo gas exhibited some distinct morphological features, such as multiple X-ray peaks, which may indicate a merger event, and highly concentrated gas, suggesting limited gravitational disturbance. Isolated S0, NGC 4406, displays an asymmetric halo, which could be interpreted as gas stripping. An isolated lenticular experiencing gas redistribution due to gravitational perturbation or a cluster-like medium could be interpreted as NGC 4406 forming in a higher galactic density environment than the field.

  19. Extreme emission-line galaxies out to z ~ 1 in zCOSMOS. I. Sample and characterization of global properties

    Science.gov (United States)

    Amorín, R.; Pérez-Montero, E.; Contini, T.; Vílchez, J. M.; Bolzonella, M.; Tasca, L. A. M.; Lamareille, F.; Zamorani, G.; Maier, C.; Carollo, C. M.; Kneib, J.-P.; Le Fèvre, O.; Lilly, S.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Bongiorno, A.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Kovač, K.; Le Borgne, J.-F.; Le Brun, V.; Mignoli, M.; Pellò, R.; Peng, Y.; Presotto, V.; Ricciardelli, E.; Silverman, J. D.; Tanaka, M.; Tresse, L.; Vergani, D.; Zucca, E.

    2015-06-01

    Context. The study of large and representative samples of low-metallicity star-forming galaxies at different cosmic epochs is of great interest to the detailed understanding of the assembly history and evolution of low-mass galaxies. Aims: We present a thorough characterization of a large sample of 183 extreme emission-line galaxies (EELGs) at redshift 0.11 ≤ z ≤ 0.93 selected from the 20k zCOSMOS bright survey because of their unusually large emission line equivalent widths. Methods: We use multiwavelength COSMOS photometry, HST-ACS I-band imaging, and optical zCOSMOS spectroscopy to derive the main global properties of star-forming EELGs, such as sizes, stellar masses, star formation rates (SFR), and reliable oxygen abundances using both "direct" and "strong-line" methods. Results: The EELGs are extremely compact (r50 ~ 1.3 kpc), low-mass (M∗ ~ 107-1010 M⊙) galaxies forming stars at unusually high specific star formation rates (sSFR ≡ SFR/M⋆ up to 10-7 yr-1) compared to main sequence star-forming galaxies of the same stellar mass and redshift. At rest-frame UV wavelengths, the EELGs are luminous and show high surface brightness and include strong Lyα emitters, as revealed by GALEX spectroscopy. We show that zCOSMOS EELGs are high-ionization, low-metallicity systems, with median 12+log (O/H) = 8.16 ± 0.21 (0.2 Z⊙) including a handful of extremely metal-deficient (Universe, EELGs are most often found in relative isolation. While only very few EELGs belong to compact groups, almost one third of them are found in spectroscopically confirmed loose pairs or triplets. Conclusions: The zCOSMOS EELGs are galaxies caught in a transient and probably early period of their evolution, where they are efficiently building up a significant fraction of their present-day stellar mass in an ongoing, galaxy-wide starburst. Therefore, the EELGs constitute an ideal benchmark for comparison studies between low- and high-redshift low-mass star-forming galaxies. Full

  20. THE NONLINEAR BIASING OF THE zCOSMOS GALAXIES UP TO z ∼ 1 FROM THE 10k SAMPLE

    International Nuclear Information System (INIS)

    Kovac, K.; Porciani, C.; Lilly, S. J.; Oesch, P.; Peng, Y.; Carollo, C. M.; Marinoni, C.; Guzzo, L.; Iovino, A.; Cucciati, O.; Kneib, J.-P.; Le Fevre, O.; Zamorani, G.; Bolzonella, M.; Zucca, E.; Bardelli, S.; Meneux, B.; Contini, T.; Mainieri, V.; Renzini, A.

    2011-01-01

    We use the zCOSMOS galaxy overdensity field to study the biasing of galaxies in the COSMOS field. By comparing the probability distribution function of the galaxy density contrast δ g to the lognormal approximation of the mass density contrast δ, we obtain the mean biasing function b(δ, z, R) between the galaxy and matter overdensity fields and its second moments b-hat and b-tilde. Over the redshift interval 0.4 g |δ) = b(δ, z, R)δ is of a characteristic shape, requiring nonlinear biasing in the most overdense and underdense regions. Taking into account the uncertainties due to cosmic variance, we do not detect any significant evolution in the (δ g |δ) function, but we do detect a significant redshift evolution in the linear biasing parameter b-hat from 1.23 ± 0.11 at z ∼ 0.55 to 1.62 ± 0.14 at z ∼ 0.75, for a luminosity-complete sample of M B -1 Mpc, but increases systematically with luminosity (at 2σ-3σ significance between the M B B B 12 M sun with a small dependence on the adopted bias-mass relation. Our detailed error analysis and comparison with previous studies lead us to conclude that cosmic variance is the main contributor to the differences in the linear bias measured from different surveys. While our results support the general picture of biased galaxy formation up to z ∼ 1, the fine-tuning of the galaxy formation models is still limited by the restrictions of the current spectroscopic surveys at these redshifts.

  1. HEAO A-1 observations of x ray emitting clusters of galaxies

    International Nuclear Information System (INIS)

    Johnson, M.W.

    1990-01-01

    Clusters of galaxies were known to be sources of x ray emission. Statistical analysis of how the x ray emission from clusters is related to other cluster properties was limited by the small number of clusters observed in the x ray region and the completeness of the x ray sample being considered. Both of these limitations are solved by producing a flux-limited catalog of x ray emitting Abell clusters of galaxies and using this catalog to investigate how the x ray emission correlates with other cluster properties. X ray data from the HEAO A-1 experiment were used to search for x ray emission from Abell clusters of galaxies. Selection criteria were chosen to ensure that the resulting catalog was complete and as free as possible from selection effects. The resulting identifications and x ray luminosities were used to check correlations with other cluster properties. Special consideration was given to observational selection effects and consistency checks. The data were consistent with all clusters of galaxies being x ray emitters beyond some limiting luminosity, which depends on cluster richness. Furthermore, the x ray luminosity of clusters is correlated with the richness of the cluster, its galaxy content, and the spacial distribution and galaxy content of galaxies within the cluster. It is concluded that the x ray emission from clusters of galaxies depends not only on the richness of the cluster but also the morphology of the cluster

  2. A multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters

    Science.gov (United States)

    Eskridge, Paul B.; Fabbiano, Giuseppina; Kim, Dong-Woo

    1995-01-01

    We have conducted bivariate and multivariate statistical analysis of data measuring the luminosity and interstellar medium of the Einstein sample of early-type galaxies (presented by Fabbiano, Kim, & Trinchieri 1992). We find a strong nonlinear correlation between L(sub B) and L(sub X), with a power-law slope of 1.8 +/- 0.1, steepening to 2.0 +/- if we do not consider the Local Group dwarf galaxies M32 and NGC 205. Considering only galaxies with log L(sub X) less than or equal to 40.5, we instead find a slope of 1.0 +/- 0.2 (with or without the Local Group dwarfs). Although E and S0 galaxies have consistent slopes for their L(sub B)-L(sub X) relationships, the mean values of the distribution functions of both L(sub X) and L(sub X)/L(sub B) for the S0 galaxies are lower than those for the E galaxies at the 2.8 sigma and 3.5 sigma levels, respectively. We find clear evidence for a correlation between L(sub X) and the X-ray color C(sub 21), defined by Kim, Fabbiano, & Trinchieri (1992b), which indicates that X-ray luminosity is correlated with the spectral shape below 1 keV in the sense that low-L(sub X) systems have relatively large contributions from a soft component compared with high-L(sub X) systems. We find evidence from our analysis of the 12 micron IRAS data for our sample that our S0 sample has excess 12 micron emission compared with the E sample, scaled by their optical luminosities. This may be due to emission from dust heated in star-forming regions in S0 disks. This interpretation is reinforced by the existence of a strong L(sub 12)-L(sub 100) correlation for our S0 sample that is not found for the E galaxies, and by an analysis of optical-IR colors. We find steep slopes for power-law relationships between radio luminosity and optical, X-ray, and far-IR (FIR) properties. This last point argues that the presence of an FIR-emitting interstellar medium (ISM) in early-type galaxies is coupled to their ability to generate nonthermal radio continuum, as

  3. The FUR to near-IR morphologies of luminous infrared galaxies in the goals sample

    International Nuclear Information System (INIS)

    Petty, S. M.; Armus, L.; Díaz-Santos, T.; Howell, J. H.; Surace, J. A.; Charmandaris, V.; Psychogyios, A.; Evans, A. S.; Stierwalt, S.; Floc’h, E. Le; Bridge, C.; Inami, H.

    2014-01-01

    We compare the morphologies of a sample of 20 luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey (GOALS) in the FUV, B, I, and H bands, using the Gini (G) and M 20 parameters to quantitatively estimate the distribution and concentration of flux as a function of wavelength. Hubble Space Telescope (HST) images provide an average spatial resolution of ∼80 pc. While our LIRGs can be reliably classified as mergers across the entire range of wavelengths studied here, there is a clear shift toward more negative M 20 (more bulge-dominated) and a less significant decrease in G values at longer wavelengths. We find no correlation between the derived FUV G-M 20 parameters and the global measures of the IR to FUV flux ratio (IRX). Given the fine resolution in our HST data, this suggests either that the UV morphology and IRX are correlated on very small scales, or that the regions emitting the bulk of the IR emission emit almost no FUV light. We use our multi-wavelength data to simulate how merging LIRGs would appear from z∼0.5–3 in deep optical and near-infrared images such as the Hubble Ultra-Deep Field, and use these simulations to measure the G-M 20 at these redshifts. Our simulations indicate a noticeable decrease in G, which flattens at z⩾2 by as much as 40%, resulting in mis-classifying our LIRGs as disk-like, even in the rest-frame FUV. The higher redshift values of M 20 for the GOALS sources do not appear to change more than about 10% from the values at z∼0. The change in G-M 20 is caused by the surface brightness dimming of extended tidal features and asymmetries, and also the decreased spatial resolution which reduced the number of individual clumps identified. This effect, seen as early as z∼0.5, could easily lead to an underestimate of the number of merging galaxies at high-redshift in the rest-frame FUV.

  4. The FUV to Near-IR Morphologies of Luminous Infrared Galaxies in the Goals Sample

    Science.gov (United States)

    Petty, S. M.; Armus, L.; Charmandaris, V.; Evans, A. S.; Le Floc'h, E.; Bridge, C.; Díaz-Santos, T.; Howell, J. H.; Inami, H.; Psychogyios, A.; Stierwalt, S.; Surace, J. A.

    2014-12-01

    We compare the morphologies of a sample of 20 luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey (GOALS) in the FUV, B, I, and H bands, using the Gini (G) and M20 parameters to quantitatively estimate the distribution and concentration of flux as a function of wavelength. Hubble Space Telescope (HST) images provide an average spatial resolution of ˜ 80 pc. While our LIRGs can be reliably classified as mergers across the entire range of wavelengths studied here, there is a clear shift toward more negative M20 (more bulge-dominated) and a less significant decrease in G values at longer wavelengths. We find no correlation between the derived FUV G-M20 parameters and the global measures of the IR to FUV flux ratio (IRX). Given the fine resolution in our HST data, this suggests either that the UV morphology and IRX are correlated on very small scales, or that the regions emitting the bulk of the IR emission emit almost no FUV light. We use our multi-wavelength data to simulate how merging LIRGs would appear from z˜ 0.5-3 in deep optical and near-infrared images such as the Hubble Ultra-Deep Field, and use these simulations to measure the G-M20 at these redshifts. Our simulations indicate a noticeable decrease in G, which flattens at z≥slant 2 by as much as 40%, resulting in mis-classifying our LIRGs as disk-like, even in the rest-frame FUV. The higher redshift values of M20 for the GOALS sources do not appear to change more than about 10% from the values at z˜ 0. The change in G-M20 is caused by the surface brightness dimming of extended tidal features and asymmetries, and also the decreased spatial resolution which reduced the number of individual clumps identified. This effect, seen as early as z˜ 0.5, could easily lead to an underestimate of the number of merging galaxies at high-redshift in the rest-frame FUV.

  5. C II 158 ??bservations of a Sample of Late-type Galaxies from the Virgo Cluster

    Science.gov (United States)

    Leech, K.; Volk, H.; Heinrichsen, I.; Hippelein, H.; Metcalfe, L.; Pierini, D.; Popescu, C.; Tuffs, R.; Xu, C.

    1999-01-01

    We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESAs Infrared Space Observatory (ISO) obtaining spectra around the [CII] 157.741 ??ine structure line.

  6. Galaxy Clustering in Early SDSS Redshift Data

    CERN Document Server

    Zehavi, I.; Frieman, Joshua A.; Weinberg, David H.; Mo, Houjun J.; Anderson, Scott F.; Strauss, Michael A.; Annis, James; Bahcall, Neta A.; Bernardi, Mariangela; Briggs, John W.; Brinkmann, Jon; Burles, Scott; Carey, Larry; Castander, Francisco J.; Connolly, J.; Csabai, Istvan; Dalcanton, Julianne J.; Dodelson,Scott; Doi,Mamoru; Eisenstein, Daniel; Evans, Michael L.; Finkbeiner, Douglas P.; Friedman, Scott; Fukugita, Masataka; Gunn, James E.; Hennessy, Greg S.; Hindsley, Robert B.; Ivezic, Zeljko; Kent,Stephen; Knapp, Gillian R.; Kron, Richard; Kunszt, Peter; Lamb, Donald; French Leger, R.; Long, Daniel C.; Loveday, Jon.; Lupton, Robert H.; McKay, Timothy; Meiksin, Avery; Merrelli, Aronne; Munn, Jeffrey A.; Narayanan, Vijay; Newcomb, Matt; Nichol, Robert C.; Owen, Russell; Peoples, John; Pope, Adrian; Rockosi, Constance M.; Schlegel, David; Schneider, Donald P.; Scoccimarro, Roman; Sheth, Ravi K.; Siegmund, Walter; Smee, Stephen; Snir, Yehuda; Stebbins, Albert; Stoughton, Christopher; SubbaRao, Mark; Szalay, Alexander S.; Szapudi, Istvan; Tegmark, Max; Tucker, Douglas L.; Uomoto, Alan; Vanden Berk, Dan; Vogeley, Michael S.; Waddell,Patrick; Yanny, Brian; York, Donald G.; Zehavi, Idit; Blanton, Michael R.; Frieman, Joshua A.; Weinberg, David H.; Mo, Houjun J.; Strauss, Michael A.

    2002-01-01

    We present the first measurements of clustering in the Sloan Digital Sky Survey (SDSS) galaxy redshift survey. Our sample consists of 29,300 galaxies with redshifts 5,700 km/s < cz < 39,000 km/s, distributed in several long but narrow (2.5-5 degree) segments, covering 690 square degrees. For the full, flux-limited sample, the redshift-space correlation length is approximately 8 Mpc/h. The two-dimensional correlation function \\xi(r_p,\\pi) shows clear signatures of both the small-scale, ``fingers-of-God'' distortion caused by velocity dispersions in collapsed objects and the large-scale compression caused by coherent flows, though the latter cannot be measured with high precision in the present sample. The inferred real-space correlation function is well described by a power law, \\xi(r)=(r/6.1+/-0.2 Mpc/h)^{-1.75+/-0.03}, for 0.1 Mpc/h < r < 16 Mpc/h. The galaxy pairwise velocity dispersion is \\sigma_{12} ~ 600+/-100 km/s for projected separations 0.15 Mpc/h < r_p < 5 Mpc/h. When we divide the...

  7. Redshifts for a sample of fainter galaxies in the first CfA survey slice

    Science.gov (United States)

    Thorstensen, J. R.; Wegner, G. A.; Hamwey, R.; Boley, F.; Geller, M. J.

    1989-01-01

    Redshifts were measured for 93 of the 94 galaxies in the Zwicky-Nilson merged catalog with the value of m(B/01) between 15.5 and 15.7 and with right ascension alpha between 8(h) and 17(h) and declination delta between 29 and 30 deg. This region is within the one covered by the first slice of the CfA (Center for Astrophysics) survey. The galaxies reinforce features already visible in the earlier survey.

  8. X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine

    Science.gov (United States)

    Torresi, E.; Grandi, P.; Capetti, A.; Baldi, R. D.; Giovannini, G.

    2018-06-01

    Fanaroff-Riley type 0 radio galaxies (FR0s) are compact radio sources that represent the bulk of the radio-loud active galactic nuclei (AGN) population, but they are still poorly understood. Pilot studies on these sources have been already performed at radio and optical wavelengths: here we present the first X-ray study of a sample of 19 FR0 radio galaxies selected from the Sloan Digital Sky Survey/NRAO VLA Sky Survey/Faint Images of the Radio Sky at Twenty-cm sample of Best & Heckman, with redshift ≤0.15, radio size ≤10 kpc, and optically classified as low-excitation galaxies. The X-ray spectra are modelled with a power-law component absorbed by Galactic column density with, in some cases, a contribution from thermal extended gas. The X-ray photons are likely produced by the jet as attested by the observed correlation between X-ray (2-10 keV) and radio (5 GHz) luminosities, similar to Fanaroff-Riley type I radio galaxies (FRIs). The estimated Eddington-scaled luminosities indicate a low accretion rate. Overall, we find that the X-ray properties of FR0s are indistinguishable from those of FRIs, thus adding another similarity between AGN associated with compact and extended radio sources. A comparison between FR0s and low-luminosity BL Lacs rules out important beaming effects in the X-ray emission of the compact radio galaxies. FR0s have different X-ray properties with respect to young radio sources (e.g. gigahertz-peaked spectrum/compact steep spectrum sources), generally characterized by higher X-ray luminosities and more complex spectra. In conclusion, the paucity of extended radio emission in FR0s is probably related to the intrinsic properties of their jets that prevent the formation of extended structures, and/or to intermittent activity of their engines.

  9. THE SL2S GALAXY-SCALE LENS SAMPLE. II. COSMIC EVOLUTION OF DARK AND LUMINOUS MASS IN EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Ruff, Andrea J.; Marshall, Philip J.; Treu, Tommaso; Auger, Matthew W.; Gavazzi, Raphael; Brault, Florence

    2011-01-01

    We present a joint gravitational lensing and stellar-dynamical analysis of 11 early-type galaxies (median deflector redshift z d = 0.5) from Strong Lenses in the Legacy Survey (SL2S). Using newly measured redshifts and stellar velocity dispersions from Keck spectroscopy with lens models from Paper I, we derive the total mass-density slope inside the Einstein radius for each of the 11 lenses. The average total density slope is found to be (γ') = 2.16 +0.09 -0.09 (ρ tot ∝r -γ ' ), with an intrinsic scatter of 0.25 +0.10 -0.07 . We also determine the dark matter fraction for each lens within half the effective radius, R eff /2, and find the average-projected dark matter mass fraction to be 0.42 +0.08 -0.08 with a scatter of 0.20 +0.09 -0.07 for a Salpeter initial mass function. By combining the SL2S results with those from the Sloan Lens ACS Survey (median z d = 0.2) and the Lenses Structure and Dynamics Survey (median z d = 0.8), we investigate cosmic evolution of γ' and find a mild trend ∂(γ')/∂z d = -0.25 +0.10 -0.12 . This suggests that the total density profile of massive galaxies has become slightly steeper over cosmic time. If this result is confirmed by larger samples, it would indicate that dissipative processes played some role in the growth of massive galaxies since z ∼ 1.

  10. The X-Ray Weakness of GPS Radio Galaxies: A Volume-Limited Complete Sample

    Science.gov (United States)

    Mushotzky, Richard F. (Technical Monitor); Siemiginowska, Aneta (Principal Investigator)

    2004-01-01

    The XMM observations of Mkn 668 have been analyzed. We found soft X-ray signatures of a hot plasma (kT approximately 10^7 approximately K) and a hard X-ray emission from the nucleus. The X-ray spectrum above 2.5 approximately keV is characterized by a very flat (observed photon index, Gamma approximately 0.5) power-law continuum, alongside with a strong Fe-K-alpha neutral iron fluorescent line (EW approximately 600 approximately eV). The best explanation for the origin of this high energy X-ray emission is in terms of the Compton-reflection of the nuclear emission. The primary X-ray emission is obscured by a Compton-thick (N_H approximately 10^24 approximately cm-2) matter which becomes transparent at higher energies. The observed above 2.5-keV X-rays are mostly due to reflection which is indicated by a strong Fe-K-alpha line. This represents the second hard X-ray detection of the GPS galaxy ever (the first one being 1345+125; O Dea et al. 2000). Interestingly, the both such trend is confirmed by our on going XMM-Newton observations of a larger GPS sample, it would lead us to looking into the question on how the dense nuclear environment impacts the nature and evolution of a GPS source, and more generally, on the history of radio power in the universe. The paper summarizing the results has been submitted to Astronomy and Astrophysics in December 2003.

  11. The BRAVE Program. I. Improved Bulge Stellar Velocity Dispersion Estimates for a Sample of Active Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Batiste, Merida; Bentz, Misty C.; Manne-Nicholas, Emily R. [Department of Physics and Astronomy, Georgia State University, 25 Park Place, Atlanta, GA 30303 (United States); Onken, Christopher A. [Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia); Bershady, Matthew A., E-mail: batiste@astro.gsu.edu [Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53706 (United States)

    2017-02-01

    We present new bulge stellar velocity dispersion measurements for 10 active galaxies with secure M {sub BH} determinations from reverberation mapping. These new velocity dispersion measurements are based on spatially resolved kinematics from integral-field (IFU) spectroscopy. In all but one case, the field of view of the IFU extends beyond the effective radius of the galaxy, and in the case of Mrk 79 it extends to almost one half the effective radius. This combination of spatial resolution and field of view allows for secure determinations of stellar velocity dispersion within the effective radius for all 10 target galaxies. Spatially resolved maps of the first ( V ) and second ( σ {sub ⋆}) moments of the line of sight velocity distribution indicate the presence of kinematic substructure in most cases. In future projects we plan to explore methods of correcting for the effects of kinematic substructure in the derived bulge stellar velocity dispersion measurements.

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

    Science.gov (United States)

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

    2018-02-01

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

  13. A MULTIWAVELENGTH STUDY OF A SAMPLE OF 70 μm SELECTED GALAXIES IN THE COSMOS FIELD. II. THE ROLE OF MERGERS IN GALAXY EVOLUTION

    International Nuclear Information System (INIS)

    Kartaltepe, Jeyhan S.; Sanders, D. B.; Le Floc'h, E.; Frayer, D. T.; Aussel, H.; Arnouts, S.; Ilbert, O.; Cassata, P.; Le Fevre, O.; Salvato, M.; Scoville, N. Z.; Capak, P.; Surace, J.; Yan, L.; Caputi, K.; Carollo, C. M.; Lilly, S.; Civano, F.; Hasinger, G.; Koekemoer, A. M.

    2010-01-01

    We analyze the morphological properties of a large sample of 1503 70 μm selected galaxies in the COSMOS field spanning the redshift range 0.01 8 IR (8 - 1000 μm) 14 L sun with a median luminosity of 10 11.4 L sun . In general, these galaxies are massive, with a stellar mass range of 10 10 -10 12 M sun , and luminous, with -25 K IR , with the fraction at the highest luminosity (L IR > 10 12 L sun ) being up to ∼50%. We also find that the fraction of spirals drops dramatically with L IR . Minor mergers likely play a role in boosting the infrared luminosity for sources with low luminosities (L IR 11.5 L sun ). The precise fraction of mergers in any given L IR bin varies by redshift due to sources at z > 1 being difficult to classify and subject to the effects of bandpass shifting; therefore, these numbers can only be considered lower limits. At z 1, the fraction of major mergers is lower, but is at least 30%-40% for ULIRGs. In a comparison of our visual classifications with several automated classification techniques we find general agreement; however, the fraction of identified mergers is underestimated due to automated classification methods being sensitive to only certain timescales of a major merger. Although the general morphological trends agree with what has been observed for local (U)LIRGs, the fraction of major mergers is slightly lower than seen locally. This is in part due to the difficulty of identifying merger signatures at high redshift. The distribution of the U - V color of the galaxies in our sample peaks in the green valley ((U - V) = 1.1) with a large spread at bluer and redder colors and with the major mergers peaking more strongly in the green valley than the rest of the morphological classes. We argue that, given the number of major gas-rich mergers observed and the relatively short timescale that they would be observable in the (U)LIRG phase, it is plausible for the observed red sequence of massive ellipticals ( 12 M sun ) to have been

  14. The X-ray luminosity-temperature relation of a complete sample of low-mass galaxy clusters

    DEFF Research Database (Denmark)

    Zou, S.; Maughan, B. J.; Giles, P. A.

    2016-01-01

    found for massive clusters to a steeper slope for the lower mass sample studied here. Thanks to our rigorous treatment of selection biases, these measurements provide a robust reference against which to compare predictions of models of the impact of feedback on the X-ray properties of galaxy groups....... (T), taking selection biases fully into account. The logarithmic slope of the bolometric L-T relation was found to be 3.29 ± 0.33, consistent with values typically found for samples of more massive clusters. In combination with other recent studies of the L-T relation, we show...

  15. A statistical analysis of the Einstein normal galaxy sample. III - Radio and X-ray properties of elliptical and S0 galaxies

    Science.gov (United States)

    Fabbiano, G.; Klein, U.; Trinchieri, G.; Wielebinski, R.

    1987-01-01

    Radioastronomy, optical and X-ray data were used to probe the cause of high X-ray luminosities of 28 radio-quiet elliptical galaxies (RQE) and S0 galaxies previously scanned by the Einstein Observatory. Comparisons were made with similar data on double-lobed 3CR galaxies. Radio luminosities were highly correlated with the X-ray luminosities, agreeing with models of radio nuclear sources in early-type galaxies as accreting compact objects. Additionally, 3CR galaxies seemed to be large-scale versions of normal RQE. The significance of interstellar medium/intracluster medium interactions for high correlations between the core and total radio power from X-ray emitting galaxies is discussed.

  16. Statistical analysis of the Einstein normal galaxy sample. III. Radio and X-ray properties of elliptical and S0 galaxies

    International Nuclear Information System (INIS)

    Fabbiano, G.; Klein, U.; Trinchieri, G.; Wielebinski, R.; Bonn Universitaet, West Germany; Arcetri, Osservatorio Astrofisico, Florence, Italy; Max-Planck-Institut fuer Radioastronomie, Bonn, West Germany)

    1987-01-01

    Radioastronomy, optical and X-ray data were used to probe the cause of high X-ray luminosities of 28 radio-quiet elliptical galaxies (RQE) and S0 galaxies previously scanned by the Einstein Observatory. Comparisons were made with similar data on double-lobed 3CR galaxies. Radio luminosities were highly correlated with the X-ray luminosities, agreeing with models of radio nuclear sources in early-type galaxies as accreting compact objects. Additionally, 3CR galaxies seemed to be large-scale versions of normal RQE. The significance of interstellar medium/intracluster medium interactions for high correlations between the core and total radio power from X-ray emitting galaxies is discussed. 54 references

  17. SPITZER INFRARED LOW-RESOLUTION SPECTROSCOPIC STUDY OF BURIED ACTIVE GALACTIC NUCLEI IN A COMPLETE SAMPLE OF NEARBY ULTRALUMINOUS INFRARED GALAXIES

    International Nuclear Information System (INIS)

    Imanishi, Masatoshi; Maiolino, Roberto; Nakagawa, Takao

    2010-01-01

    We present the results of Spitzer Infrared Spectrograph low-resolution infrared 5-35 μm spectroscopy of 17 nearby ultraluminous infrared galaxies (ULIRGs) at z 12 L sun , are found in eight sources. We combine these results with those of our previous research to investigate the energy function of buried AGNs in a complete sample of optically non-Seyfert ULIRGs in the local universe at z < 0.3 (85 sources). We confirm a trend that we previously discovered: that buried AGNs are more common in galaxies with higher infrared luminosities. Because optical Seyferts also show a similar trend, we argue more generally that the energetic importance of AGNs is intrinsically higher in more luminous galaxies, suggesting that the AGN-starburst connections are luminosity dependent. This may be related to the stronger AGN feedback scenario in currently more massive galaxy systems, as a possible origin of the galaxy downsizing phenomenon.

  18. The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological analysis of the DR12 galaxy sample

    Science.gov (United States)

    Alam, Shadab; Ata, Metin; Bailey, Stephen; Beutler, Florian; Bizyaev, Dmitry; Blazek, Jonathan A.; Bolton, Adam S.; Brownstein, Joel R.; Burden, Angela; Chuang, Chia-Hsun; Comparat, Johan; Cuesta, Antonio J.; Dawson, Kyle S.; Eisenstein, Daniel J.; Escoffier, Stephanie; Gil-Marín, Héctor; Grieb, Jan Niklas; Hand, Nick; Ho, Shirley; Kinemuchi, Karen; Kirkby, David; Kitaura, Francisco; Malanushenko, Elena; Malanushenko, Viktor; Maraston, Claudia; McBride, Cameron K.; Nichol, Robert C.; Olmstead, Matthew D.; Oravetz, Daniel; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pellejero-Ibanez, Marcos; Percival, Will J.; Petitjean, Patrick; Prada, Francisco; Price-Whelan, Adrian M.; Reid, Beth A.; Rodríguez-Torres, Sergio A.; Roe, Natalie A.; Ross, Ashley J.; Ross, Nicholas P.; Rossi, Graziano; Rubiño-Martín, Jose Alberto; Saito, Shun; Salazar-Albornoz, Salvador; Samushia, Lado; Sánchez, Ariel G.; Satpathy, Siddharth; Schlegel, David J.; Schneider, Donald P.; Scóccola, Claudia G.; Seo, Hee-Jong; Sheldon, Erin S.; Simmons, Audrey; Slosar, Anže; Strauss, Michael A.; Swanson, Molly E. C.; Thomas, Daniel; Tinker, Jeremy L.; Tojeiro, Rita; Magaña, Mariana Vargas; Vazquez, Jose Alberto; Verde, Licia; Wake, David A.; Wang, Yuting; Weinberg, David H.; White, Martin; Wood-Vasey, W. Michael; Yèche, Christophe; Zehavi, Idit; Zhai, Zhongxu; Zhao, Gong-Bo

    2017-09-01

    We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises 1.2 million massive galaxies over an effective area of 9329 deg2 and volume of 18.7 Gpc3, divided into three partially overlapping redshift slices centred at effective redshifts 0.38, 0.51 and 0.61. We measure the angular diameter distance DM and Hubble parameter H from the baryon acoustic oscillation (BAO) method, in combination with a cosmic microwave background prior on the sound horizon scale, after applying reconstruction to reduce non-linear effects on the BAO feature. Using the anisotropic clustering of the pre-reconstruction density field, we measure the product DMH from the Alcock-Paczynski (AP) effect and the growth of structure, quantified by fσ8(z), from redshift-space distortions (RSD). We combine individual measurements presented in seven companion papers into a set of consensus values and likelihoods, obtaining constraints that are tighter and more robust than those from any one method; in particular, the AP measurement from sub-BAO scales sharpens constraints from post-reconstruction BAOs by breaking degeneracy between DM and H. Combined with Planck 2016 cosmic microwave background measurements, our distance scale measurements simultaneously imply curvature ΩK = 0.0003 ± 0.0026 and a dark energy equation-of-state parameter w = -1.01 ± 0.06, in strong affirmation of the spatially flat cold dark matter (CDM) model with a cosmological constant (ΛCDM). Our RSD measurements of fσ8, at 6 per cent precision, are similarly consistent with this model. When combined with supernova Ia data, we find H0 = 67.3 ± 1.0 km s-1 Mpc-1 even for our most general dark energy model, in tension with some direct measurements. Adding extra relativistic species as a degree of freedom loosens the constraint only slightly, to H0 = 67.8 ± 1.2 km s-1 Mpc-1. Assuming flat

  19. New observations of z ∼ 7 galaxies: evidence for a patchy reionization

    International Nuclear Information System (INIS)

    Pentericci, L.; Fontana, A.; Castellano, M.; Grazian, A.; Galametz, A.; Giallongo, E.; Paris, D.; Santini, P.; Vanzella, E.; Treu, T.; Mesinger, A.; Dijkstra, M.; Bradač, M.; Conselice, C.; Cristiani, S.; Dunlop, J.; McLure, R.; Giavalisco, M.; Koekemoer, A.; Maiolino, R.

    2014-01-01

    We present new results from our search for z ∼ 7 galaxies from deep spectroscopic observations of candidate z dropouts in the CANDELS fields. Despite the extremely low flux limits achieved by our sensitive observations, only two galaxies have robust redshift identifications, one from its Lyα emission line at z = 6.65, the other from its Lyman break, i.e., the continuum discontinuity at the Lyα wavelength consistent with a redshift of 6.42 but with no emission line. In addition, for 23 galaxies we present deep limits in the Lyα equivalent width derived from the nondetections in ultradeep observations. Using this new data as well as previous samples, we assemble a total of 68 candidate z ∼ 7 galaxies with deep spectroscopic observations, of which 12 have a line detection. With this much enlarged sample we can place solid constraints on the declining fraction of Lyα emission in z ∼ 7 Lyman-break galaxies compared to z ∼ 6, both for bright and faint galaxies. Applying a simple analytical model, we show that the present data favor a patchy reionization process rather than a smooth one.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  1. THE BOSS EMISSION-LINE LENS SURVEY (BELLS). I. A LARGE SPECTROSCOPICALLY SELECTED SAMPLE OF LENS GALAXIES AT REDSHIFT {approx}0.5

    Energy Technology Data Exchange (ETDEWEB)

    Brownstein, Joel R.; Bolton, Adam S.; Pandey, Parul [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Schlegel, David J. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Eisenstein, Daniel J. [Harvard College Observatory, 60 Garden Street, MS 20, Cambridge, MA 02138 (United States); Kochanek, Christopher S. [Department of Astronomy and Center for Cosmology and Astroparticle Physics, Ohio State University, Columbus, OH 43210 (United States); Connolly, Natalia [Department of Physics, Hamilton College, Clinton, NY 13323 (United States); Maraston, Claudia [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom); Seitz, Stella [University Observatory Munich, Scheinstrasse 1, 81679 Muenchen (Germany); Wake, David A. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Wood-Vasey, W. Michael [Pittsburgh Center for Particle Physics, Astrophysics, and Cosmology (PITT-PACC), Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Brinkmann, Jon [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics and Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA 16802 (United States); Weaver, Benjamin A. [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States)

    2012-01-01

    We present a catalog of 25 definite and 11 probable strong galaxy-galaxy gravitational lens systems with lens redshifts 0.4 {approx}< z {approx}< 0.7, discovered spectroscopically by the presence of higher-redshift emission lines within the Baryon Oscillation Spectroscopic Survey (BOSS) of luminous galaxies, and confirmed with high-resolution Hubble Space Telescope (HST) images of 44 candidates. Our survey extends the methodology of the Sloan Lens Advanced Camera for Surveys survey (SLACS) to higher redshift. We describe the details of the BOSS spectroscopic candidate detections, our HST ACS image processing and analysis methods, and our strong gravitational lens modeling procedure. We report BOSS spectroscopic parameters and ACS photometric parameters for all candidates, and mass-distribution parameters for the best-fit singular isothermal ellipsoid models of definite lenses. Our sample to date was selected using only the first six months of BOSS survey-quality spectroscopic data. The full five-year BOSS database should produce a sample of several hundred strong galaxy-galaxy lenses and in combination with SLACS lenses at lower redshift, strongly constrain the redshift evolution of the structure of elliptical, bulge-dominated galaxies as a function of luminosity, stellar mass, and rest-frame color, thereby providing a powerful test for competing theories of galaxy formation and evolution.

  2. The Evolution of the Stellar Hosts of Radio Galaxies

    International Nuclear Information System (INIS)

    Lacy, Mark; Bunker, Andrew J.; Ridgway, Susan E.

    2000-01-01

    We present new near-infrared images of z>0.8 radio galaxies from the flux-limited 7C-iii sample of radio sources for which we have recently obtained almost complete spectroscopic redshifts. The 7C objects have radio luminosities ≅20 times fainter than 3C radio galaxies at a given redshift. The absolute magnitudes of the underlying host galaxies and their scale sizes are only weakly dependent on radio luminosity. Radio galaxy hosts at z∼2 are significantly brighter than the hosts of radio-quiet quasars at similar redshifts and the recent model AGN hosts of Kauffmann and Haehnelt. There is no evidence for strong evolution in scale size, which shows a large scatter at all redshifts. The hosts brighten significantly with redshift, consistent with the passive evolution of a stellar population that formed at z(greater-or-similar sign)3. This scenario is consistent with studies of host galaxy morphology and submillimeter continuum emission, both of which show strong evolution at z(greater-or-similar sign)2.5. The lack of a strong ''redshift cutoff'' in the radio luminosity function to z>4 suggests that the formation epoch of the radio galaxy host population lasts (greater-or-similar sign)1 Gyr, from z(greater-or-similar sign)5 to z∼3. We suggest these facts are best explained by models in which the most massive galaxies and their associated AGN form early because of high baryon densities in the centers of their dark matter haloes. (c) 2000 The American Astronomical Society

  3. Spot the difference. Impact of different selection criteria on observed properties of passive galaxies in zCOSMOS-20k sample

    Science.gov (United States)

    Moresco, M.; Pozzetti, L.; Cimatti, A.; Zamorani, G.; Bolzonella, M.; Lamareille, F.; Mignoli, M.; Zucca, E.; Lilly, S. J.; Carollo, C. M.; Contini, T.; Kneib, J.-P.; Le Fèvre, O.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Bongiorno, A.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Kovač, K.; Le Borgne, J.-F.; Le Brun, V.; Maier, C.; Pelló, R.; Peng, Y.; Perez-Montero, E.; Presotto, V.; Silverman, J. D.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Barnes, L.; Bordoloi, R.; Cappi, A.; Diener, C.; Koekemoer, A. M.; Le Floc'h, E.; López-Sanjuan, C.; McCracken, H. J.; Nair, P.; Oesch, P.; Scarlata, C.; Scoville, N.; Welikala, N.

    2013-10-01

    Aims: We present the analysis of photometric, spectroscopic, and morphological properties for differently selected samples of passive galaxies up to z = 1 extracted from the zCOSMOS-20k spectroscopic survey. This analysis intends toexplore the dependence of galaxy properties on the selection criterion adopted, study the degree of contamination due to star-forming outliers, and provide a comparison between different commonly used selection criteria. This work is a first step to fully investigating the selection effects of passive galaxies for future massive surveys such as Euclid. Methods: We extracted from the zCOSMOS-20k catalog six different samples of passive galaxies, based on morphology (3336 "morphological" early-type galaxies), optical colors (4889 "red-sequence" galaxies and 4882 "red UVJ" galaxies), specific star-formation rate (2937 "quiescent" galaxies), a best fit to the observed spectral energy distribution (2603 "red SED" galaxies), and a criterion that combines morphological, spectroscopic, and photometric information (1530 "red & passive early-type galaxies"). For all the samples, we studied optical and infrared colors, morphological properties, specific star-formation rates (SFRs), and the equivalent widths of the residual emission lines; this analysis was performed as a function of redshift and stellar mass to inspect further possible dependencies. Results: We find that each passive galaxy sample displays a certain level of contamination due to blue/star-forming/nonpassive outliers. The morphological sample is the one that presents the higher percentage of contamination, with ~12-65% (depending on the mass range) of galaxies not located in the red sequence, ~25-80% of galaxies with a specific SFR up to ~25 times higher than the adopted definition of passive, and significant emission lines found in the median stacked spectra, at least for log (M/M⊙) contamination in color 10.25, very limited tails in sSFR, a median value ~20% higher than the

  4. Profile modifications in laser-driven temperature fronts using flux-limiters and delocalization models

    Science.gov (United States)

    Colombant, Denis; Manheimer, Wallace; Busquet, Michel

    2004-11-01

    A simple steady-state model using flux-limiters by Day et al [1] showed that temperature profiles could formally be double-valued. Stability of temperature profiles in laser-driven temperature fronts using delocalization models was also discussed by Prasad and Kershaw [2]. We have observed steepening of the front and flattening of the maximum temperature in laser-driven implosions [3]. Following the simple model first proposed in [1], we solve for a two-boundary value steady-state heat flow problem for various non-local heat transport models. For the more complicated models [4,5], we obtain the steady-state solution as the asymptotic limit of the time-dependent solution. Solutions will be shown and compared for these various models. 1.M.Day, B.Merriman, F.Najmabadi and R.W.Conn, Contrib. Plasma Phys. 36, 419 (1996) 2.M.K.Prasad and D.S.Kershaw, Phys. Fluids B3, 3087 (1991) 3.D.Colombant, W.Manheimer and M.Busquet, Bull. Amer. Phys. Soc. 48, 326 (2003) 4.E.M.Epperlein and R.W.Short, Phys. Fluids B3, 3092 (1991) 5.W.Manheimer and D.Colombant, Phys. Plasmas 11, 260 (2004)

  5. A flux-limited treatment for the conductive evaporation of spherical interstellar gas clouds

    Science.gov (United States)

    Dalton, William W.; Balbus, Steven A.

    1993-01-01

    In this work, we present and analyze a new analytic solution for the saturated (flux-limited) thermal evaporation of a spherical cloud. This work is distinguished from earlier analytic studies by allowing the thermal conductivity to change continuously from a diffusive to a saturated form, in a manner usually employed only in numerical calculations. This closed form solution will be of interest as a computational benchmark. Using our calculated temperature profiles and mass-loss rates, we model the thermal evaporation of such a cloud under typical interstellar medium (ISM) conditions, with some restrictions. We examine the ionization structure of the cloud-ISM interface and evaluate column densities of carbon, nitrogen, oxygen, neon, and silicon ions toward the cloud. In accord with other investigations, we find that ionization equilibrium is far from satisfied under the assumed conditions. Since the inclusion of saturation effects in the heat flux narrows the thermal interface relative to its classical structure, we also find that saturation effects tend to lower predicted column densities.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-20

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

  7. Galaxy angular momentum

    International Nuclear Information System (INIS)

    Thompson, L.A.

    1974-01-01

    In order to test the theories which purport to explain the origin of galaxy angular momentum, this study presents new data for about 1000 individual galaxies in eight rich clusters. The clusters which are studied include Virgo, A 119, A 400, A 1656 (Coma), A 2147, A 2151 (Hercules), A 2197, and A 2199. Selected samples of these data are used to investigate systematic alignment effects in clusters of galaxies and to investigate the intrinsic ellipticities of E, SO, and spiral galaxies. The following new results are reported: Galaxies in the cluster A 2197 show a significant alignment effect (chi 2 probability less than 0.0002), and the preferential direction of alignment corresponds approximately to the major axis of the overall cluster elongation. None of the other seven clusters show any significant alignment trends. The spiral galaxy samples in four clusters (Virgo, A 1656, A 2151, and A 2197) were large enough to analyze the number distributions of forward and reverse winding spirals. Large and small spiral galaxies have identical ellipticity distributions. Large E and SO galaxies tend to be more spherical, and small E and SO galaxies more flattened. The intrinsic ellipticities of E, SO, and spiral galaxies are the same for galaxies in the ''field'' and for galaxies in rich clusters. Six models of galaxy formation are reviewed, and the major []mphasis is placed on how each model explains the origin of galaxy angular momentum. (Diss. Abstr. Int., B)

  8. H α IMAGING OF NEARBY SEYFERT HOST GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-01

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

  9. EmpiriciSN: Re-sampling Observed Supernova/Host Galaxy Populations Using an XD Gaussian Mixture Model

    Energy Technology Data Exchange (ETDEWEB)

    Holoien, Thomas W.-S.; /Ohio State U., Dept. Astron. /Ohio State U., CCAPP /KIPAC, Menlo Park /SLAC; Marshall, Philip J.; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC

    2017-05-11

    We describe two new open-source tools written in Python for performing extreme deconvolution Gaussian mixture modeling (XDGMM) and using a conditioned model to re-sample observed supernova and host galaxy populations. XDGMM is new program that uses Gaussian mixtures to perform density estimation of noisy data using extreme deconvolution (XD) algorithms. Additionally, it has functionality not available in other XD tools. It allows the user to select between the AstroML and Bovy et al. fitting methods and is compatible with scikit-learn machine learning algorithms. Most crucially, it allows the user to condition a model based on the known values of a subset of parameters. This gives the user the ability to produce a tool that can predict unknown parameters based on a model that is conditioned on known values of other parameters. EmpiriciSN is an exemplary application of this functionality, which can be used to fit an XDGMM model to observed supernova/host data sets and predict likely supernova parameters using a model conditioned on observed host properties. It is primarily intended to simulate realistic supernovae for LSST data simulations based on empirical galaxy properties.

  10. EmpiriciSN: Re-sampling Observed Supernova/Host Galaxy Populations Using an XD Gaussian Mixture Model

    Science.gov (United States)

    Holoien, Thomas W.-S.; Marshall, Philip J.; Wechsler, Risa H.

    2017-06-01

    We describe two new open-source tools written in Python for performing extreme deconvolution Gaussian mixture modeling (XDGMM) and using a conditioned model to re-sample observed supernova and host galaxy populations. XDGMM is new program that uses Gaussian mixtures to perform density estimation of noisy data using extreme deconvolution (XD) algorithms. Additionally, it has functionality not available in other XD tools. It allows the user to select between the AstroML and Bovy et al. fitting methods and is compatible with scikit-learn machine learning algorithms. Most crucially, it allows the user to condition a model based on the known values of a subset of parameters. This gives the user the ability to produce a tool that can predict unknown parameters based on a model that is conditioned on known values of other parameters. EmpiriciSN is an exemplary application of this functionality, which can be used to fit an XDGMM model to observed supernova/host data sets and predict likely supernova parameters using a model conditioned on observed host properties. It is primarily intended to simulate realistic supernovae for LSST data simulations based on empirical galaxy properties.

  11. Modeling Well Sampled Composite Spectral Energy Distributions of Distant Galaxies via an MCMC-driven Inference Framework

    Science.gov (United States)

    Pasha, Imad; Kriek, Mariska; Johnson, Benjamin; Conroy, Charlie

    2018-01-01

    Using a novel, MCMC-driven inference framework, we have modeled the stellar and dust emission of 32 composite spectral energy distributions (SEDs), which span from the near-ultraviolet (NUV) to far infrared (FIR). The composite SEDs were originally constructed in a previous work from the photometric catalogs of the NEWFIRM Medium-Band Survey, in which SEDs of individual galaxies at 0.5 MIPS 24 μm was added for each SED type, and in this work, PACS 100 μm, PACS160 μm, SPIRE 25 μm, and SPIRE 350 μm photometry have been added to extend the range of the composite SEDs into the FIR. We fit the composite SEDs with the Prospector code, which utilizes an MCMC sampling to explore the parameter space for models created by the Flexible Stellar Population Synthesis (FSPS) code, in order to investigate how specific star formation rate (sSFR), dust temperature, and other galaxy properties vary with SED type.This work is also being used to better constrain the SPS models within FSPS.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  13. CHANG-ES. IX. Radio scale heights and scale lengths of a consistent sample of 13 spiral galaxies seen edge-on and their correlations

    Science.gov (United States)

    Krause, Marita; Irwin, Judith; Wiegert, Theresa; Miskolczi, Arpad; Damas-Segovia, Ancor; Beck, Rainer; Li, Jiang-Tao; Heald, George; Müller, Peter; Stein, Yelena; Rand, Richard J.; Heesen, Volker; Walterbos, Rene A. M.; Dettmar, Ralf-Jürgen; Vargas, Carlos J.; English, Jayanne; Murphy, Eric J.

    2018-03-01

    Aim. The vertical halo scale height is a crucial parameter to understand the transport of cosmic-ray electrons (CRE) and their energy loss mechanisms in spiral galaxies. Until now, the radio scale height could only be determined for a few edge-on galaxies because of missing sensitivity at high resolution. Methods: We developed a sophisticated method for the scale height determination of edge-on galaxies. With this we determined the scale heights and radial scale lengths for a sample of 13 galaxies from the CHANG-ES radio continuum survey in two frequency bands. Results: The sample average values for the radio scale heights of the halo are 1.1 ± 0.3 kpc in C-band and 1.4 ± 0.7 kpc in L-band. From the frequency dependence analysis of the halo scale heights we found that the wind velocities (estimated using the adiabatic loss time) are above the escape velocity. We found that the halo scale heights increase linearly with the radio diameters. In order to exclude the diameter dependence, we defined a normalized scale height h˜ which is quite similar for all sample galaxies at both frequency bands and does not depend on the star formation rate or the magnetic field strength. However, h˜ shows a tight anticorrelation with the mass surface density. Conclusions: The sample galaxies with smaller scale lengths are more spherical in the radio emission, while those with larger scale lengths are flatter. The radio scale height depends mainly on the radio diameter of the galaxy. The sample galaxies are consistent with an escape-dominated radio halo with convective cosmic ray propagation, indicating that galactic winds are a widespread phenomenon in spiral galaxies. While a higher star formation rate or star formation surface density does not lead to a higher wind velocity, we found for the first time observational evidence of a gravitational deceleration of CRE outflow, e.g. a lowering of the wind velocity from the galactic disk.

  14. High-Resolution Near-Infrared Spectroscopy of an Equivalent Width-Selected Sample of Starbursting Dwarf Galaxies

    Science.gov (United States)

    Maseda, Michael V.; VanDerWeL, Arjen; DaChuna, Elisabete; Rix, Hans-Walter; Pacafichi, Camilla; Momcheva, Ivelina; Brammer, Gabriel B.; Franx, Marijn; VanDokkum, Pieter; Bell, Eric F.; hide

    2013-01-01

    Spectroscopic observations from the Large Binocular Telescope and the Very Large Telescope reveal kinematically narrow lines (approx. 50 km/s) for a sample of 14 Extreme Emission Line Galaxies (EELGs) at redshifts 1.4 < zeta < 2.3. These measurements imply that the total dynamical masses of these systems are low ( 3 × 10(exp 9) M). Their large [O III]5007 equivalent widths (500 - 1100 A) and faint blue continuum emission imply young ages of 10-100 Myr and stellar masses of 10(exp 8)-10(exp 9) M, confirming the presence of a violent starburst. The stellar mass formed in this vigorous starburst phase thus represents a large fraction of the total (dynamical) mass, without a significantly massive underlying population of older stars. The occurrence of such intense events in shallow potentials strongly suggests that supernova-driven winds must be of critical importance in the subsequent evolution of these systems.

  15. A comparison of LBGs, DRGs, and BzK galaxies: their contribution to the stellar mass density in the GOODS-MUSIC sample

    Science.gov (United States)

    Grazian, A.; Salimbeni, S.; Pentericci, L.; Fontana, A.; Nonino, M.; Vanzella, E.; Cristiani, S.; de Santis, C.; Gallozzi, S.; Giallongo, E.; Santini, P.

    2007-04-01

    Context: The classification scheme for high redshift galaxies is complex at the present time, with simple colour-selection criteria (i.e. EROs, IEROs, LBGs, DRGs, BzKs), resulting in ill-defined properties for the stellar mass and star formation rate of these distant galaxies. Aims: The goal of this work is to investigate the properties of different classes of high-z galaxies, focusing in particular on the stellar masses of LBGs, DRGs, and BzKs, in order to derive their contribution to the total mass budget of the distant Universe. Methods: We used the GOODS-MUSIC catalog, containing ~3000 Ks-selected (~10 000 z-selected) galaxies with multi-wavelength coverage extending from the U band to the Spitzer 8~μm band, with spectroscopic or accurate photometric redshifts. We selected samples of BM/BX/LBGs, DRGs, and BzK galaxies to discuss the overlap and the limitations of these criteria, which can be overridden by a selection criterion based on physical parameters. We then measured the stellar masses of these galaxies and computed the stellar mass density (SMD) for the different samples up to redshift ≃4. Results: We show that the BzK-PE criterion is not optimal for selecting early type galaxies at the faint end. On the other hand, BzK-SF is highly contaminated by passively evolving galaxies at red z-Ks colours. We find that LBGs and DRGs contribute almost equally to the global SMD at z≥ 2 and, in general, that star-forming galaxies form a substantial fraction of the universal SMD. Passively evolving galaxies show a strong negative density evolution from redshift 2 to 3, indicating that we are witnessing the epoch of mass assembly of such objects. Finally we have indications that by pushing the selection to deeper magnitudes, the contribution of less massive DRGs could overtake that of LBGs. Deeper surveys, like the HUDF, are required to confirm this suggestion.

  16. Measures of star formation rates from infrared (Herschel) and UV (GALEX) emissions of galaxies in the HerMES fields

    Science.gov (United States)

    Buat, V.; Giovannoli, E.; Burgarella, D.; Altieri, B.; Amblard, A.; Arumugam, V.; Aussel, H.; Babbedge, T.; Blain, A.; Bock, J.; Boselli, A.; Castro-Rodríguez, N.; Cava, A.; Chanial, P.; Clements, D. L.; Conley, A.; Conversi, L.; Cooray, A.; Dowell, C. D.; Dwek, E.; Eales, S.; Elbaz, D.; Fox, M.; Franceschini, A.; Gear, W.; Glenn, J.; Griffin, M.; Halpern, M.; Hatziminaoglou, E.; Heinis, S.; Ibar, E.; Isaak, K.; Ivison, R. J.; Lagache, G.; Levenson, L.; Lonsdale, C. J.; Lu, N.; Madden, S.; Maffei, B.; Magdis, G.; Mainetti, G.; Marchetti, L.; Morrison, G. E.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Omont, A.; Owen, F. N.; Page, M. J.; Pannella, M.; Panuzzo, P.; Papageorgiou, A.; Pearson, C. P.; Pérez-Fournon, I.; Pohlen, M.; Rigopoulou, D.; Rizzo, D.; Roseboom, I. G.; Rowan-Robinson, M.; Sánchez Portal, M.; Schulz, B.; Seymour, N.; Shupe, D. L.; Smith, A. J.; Stevens, J. A.; Strazzullo, V.; Symeonidis, M.; Trichas, M.; Tugwell, K. E.; Vaccari, M.; Valiante, E.; Valtchanov, I.; Vigroux, L.; Wang, L.; Ward, R.; Wright, G.; Xu, C. K.; Zemcov, M.

    2010-11-01

    The reliability of infrared (IR) and ultraviolet (UV) emissions to measure star formation rates (SFRs) in galaxies is investigated for a large sample of galaxies observed with the Spectral and Photometric Imaging Receiver (SPIRE) and the Photodetector Array Camera and Spectrometer (PACS) instruments on Herschel as part of the Herschel Multi-Tiered Extragalactic Survey (HerMES) project. We build flux-limited 250-μm samples of sources at redshift z 500 μm. Dust attenuation is discussed on the basis of commonly used diagnostics: the LIR/LUV ratio and the slope, β, of the UV continuum. A mean dust attenuation AUV of mag is measured in the samples. LIR/LUV is found to correlate with LIR. Galaxies with and 0.5 recipe commonly applied to local starbursts is found to overestimate the dust attenuation correction in our galaxy sample by a factor of ~2-3. The SFRs deduced from LIR are found to account for about 90 per cent of the total SFR; this percentage drops to 71 per cent for galaxies with (or ). For these faint objects, one needs to combine UV and IR emissions to obtain an accurate measure of the SFR.

  17. THE SL2S GALAXY-SCALE LENS SAMPLE. IV. THE DEPENDENCE OF THE TOTAL MASS DENSITY PROFILE OF EARLY-TYPE GALAXIES ON REDSHIFT, STELLAR MASS, AND SIZE

    International Nuclear Information System (INIS)

    Sonnenfeld, Alessandro; Treu, Tommaso; Suyu, Sherry H.; Gavazzi, Raphaël; Marshall, Philip J.; Auger, Matthew W.; Nipoti, Carlo

    2013-01-01

    We present optical and near-infrared spectroscopy obtained at Keck, Very Large Telescope, and Gemini for a sample of 36 secure strong gravitational lens systems and 17 candidates identified as part of the Strong Lensing Legacy Survey. The deflectors are massive early-type galaxies in the redshift range z d = 0.2-0.8, while the lensed sources are at z s = 1-3.5. We combine these data with photometric and lensing measurements presented in the companion paper III and with lenses from the Sloan Lens Advanced Camera for Surveys and Lènses Structure and Dynamics surveys to investigate the cosmic evolution of the internal structure of massive early-type galaxies over half the age of the universe. We study the dependence of the slope of the total mass density profile, γ' (ρ(r)∝r -γ ' ), on stellar mass, size, and redshift. We find that two parameters are sufficient to determine γ' with less than 6% residual scatter. At fixed redshift, γ' depends solely on the surface stellar mass density ∂γ'/∂Σ * = 0.38 ± 0.07, i.e., galaxies with denser stars also have steeper slopes. At fixed M * and R eff , γ' depends on redshift, in the sense that galaxies at a lower redshift have steeper slopes (∂γ'/∂z = –0.31 ± 0.10). However, the mean redshift evolution of γ' for an individual galaxy is consistent with zero dγ'/dz = –0.10 ± 0.12. This result is obtained by combining our measured dependencies of γ' on z, M * ,R eff with the evolution of the R eff -M * taken from the literature, and is broadly consistent with current models of the formation and evolution of massive early-type galaxies. Detailed quantitative comparisons of our results with theory will provide qualitatively new information on the detailed physical processes at work

  18. THE FMOS-COSMOS SURVEY OF STAR-FORMING GALAXIES AT z ∼ 1.6. III. SURVEY DESIGN, PERFORMANCE, AND SAMPLE CHARACTERISTICS

    Energy Technology Data Exchange (ETDEWEB)

    Silverman, J. D.; Sugiyama, N. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, 277-8583 (Japan); Kashino, D. [Division of Particle and Astrophysical Science, Graduate School of Science, Nagoya University, Nagoya, 464-8602 (Japan); Sanders, D.; Zahid, J.; Kewley, L. J.; Chu, J.; Hasinger, G. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, 96822 (United States); Kartaltepe, J. S. [National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ, 85719 (United States); Arimoto, N. [Subaru Telescope, 650 North A’ohoku Place, Hilo, Hawaii, 96720 (United States); Renzini, A. [Instituto Nazionale de Astrofisica, Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, I-35122, Padova, Italy, EU (Italy); Rodighiero, G.; Baronchelli, I. [Dipartimento di Fisica e Astronomia, Universita di Padova, vicolo Osservatorio, 3, I-35122, Padova (Italy); Daddi, E.; Juneau, S. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d’Astrophysique, CEA Saclay (France); Nagao, T. [Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan); Lilly, S. J.; Carollo, C. M. [Institute of Astronomy, ETH Zürich, CH-8093, Zürich (Switzerland); Capak, P. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Ilbert, O., E-mail: john.silverman@ipmu.jp [Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); and others

    2015-09-15

    We present a spectroscopic survey of galaxies in the COSMOS field using the Fiber Multi-object Spectrograph (FMOS), a near-infrared instrument on the Subaru Telescope. Our survey is specifically designed to detect the Hα emission line that falls within the H-band (1.6–1.8 μm) spectroscopic window from star-forming galaxies with 1.4 < z < 1.7 and M{sub stellar} ≳ 10{sup 10} M{sub ⊙}. With the high multiplex capability of FMOS, it is now feasible to construct samples of over 1000 galaxies having spectroscopic redshifts at epochs that were previously challenging. The high-resolution mode (R ∼ 2600) effectively separates Hα and [N ii]λ6585, thus enabling studies of the gas-phase metallicity and photoionization state of the interstellar medium. The primary aim of our program is to establish how star formation depends on stellar mass and environment, both recognized as drivers of galaxy evolution at lower redshifts. In addition to the main galaxy sample, our target selection places priority on those detected in the far-infrared by Herschel/PACS to assess the level of obscured star formation and investigate, in detail, outliers from the star formation rate (SFR)—stellar mass relation. Galaxies with Hα detections are followed up with FMOS observations at shorter wavelengths using the J-long (1.11–1.35 μm) grating to detect Hβ and [O iii]λ5008 which provides an assessment of the extinction required to measure SFRs not hampered by dust, and an indication of embedded active galactic nuclei. With 460 redshifts measured from 1153 spectra, we assess the performance of the instrument with respect to achieving our goals, discuss inherent biases in the sample, and detail the emission-line properties. Our higher-level data products, including catalogs and spectra, are available to the community.

  19. A new method to measure galaxy bias by combining the density and weak lensing fields

    Energy Technology Data Exchange (ETDEWEB)

    Pujol, Arnau; Chang, Chihway; Gaztañaga, Enrique; Amara, Adam; Refregier, Alexandre; Bacon, David J.; Carretero, Jorge; Castander, Francisco J.; Crocce, Martin; Fosalba, Pablo; Manera, Marc; Vikram, Vinu

    2016-07-29

    We present a new method to measure redshift-dependent galaxy bias by combining information from the galaxy density field and the weak lensing field. This method is based on the work of Amara et al., who use the galaxy density field to construct a bias-weighted convergence field κg. The main difference between Amara et al.'s work and our new implementation is that here we present another way to measure galaxy bias, using tomography instead of bias parametrizations. The correlation between κg and the true lensing field κ allows us to measure galaxy bias using different zero-lag correlations, such as <κgκ>/<κκ> or <κgκg>/<κgκ>. Our method measures the linear bias factor on linear scales, under the assumption of no stochasticity between galaxies and matter. We use the Marenostrum Institut de Ciències de l'Espai (MICE) simulation to measure the linear galaxy bias for a flux-limited sample (i < 22.5) in tomographic redshift bins using this method. This article is the first that studies the accuracy and systematic uncertainties associated with the implementation of the method and the regime in which it is consistent with the linear galaxy bias defined by projected two-point correlation functions (2PCF). We find that our method is consistent with a linear bias at the per cent level for scales larger than 30 arcmin, while non-linearities appear at smaller scales. This measurement is a good complement to other measurements of bias, since it does not depend strongly on σ8 as do the 2PCF measurements. We will apply this method to the Dark Energy Survey Science Verification data in a follow-up article.

  20. The ATLAS3D project - I. A volume-limited sample of 260 nearby early-type galaxies: science goals and selection criteria

    Science.gov (United States)

    Cappellari, Michele; Emsellem, Eric; Krajnović, Davor; McDermid, Richard M.; Scott, Nicholas; Verdoes Kleijn, G. A.; Young, Lisa M.; Alatalo, Katherine; Bacon, R.; Blitz, Leo; Bois, Maxime; Bournaud, Frédéric; Bureau, M.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Khochfar, Sadegh; Kuntschner, Harald; Lablanche, Pierre-Yves; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Serra, Paolo; Weijmans, Anne-Marie

    2011-05-01

    The ATLAS3D project is a multiwavelength survey combined with a theoretical modelling effort. The observations span from the radio to the millimetre and optical, and provide multicolour imaging, two-dimensional kinematics of the atomic (H I), molecular (CO) and ionized gas (Hβ, [O III] and [N I]), together with the kinematics and population of the stars (Hβ, Fe5015 and Mg b), for a carefully selected, volume-limited (1.16 × 105 Mpc3) sample of 260 early-type (elliptical E and lenticular S0) galaxies (ETGs). The models include semi-analytic, N-body binary mergers and cosmological simulations of galaxy formation. Here we present the science goals for the project and introduce the galaxy sample and the selection criteria. The sample consists of nearby (D 15°) morphologically selected ETGs extracted from a parent sample of 871 galaxies (8 per cent E, 22 per cent S0 and 70 per cent spirals) brighter than MK statistically representative of the nearby galaxy population. We present the size-luminosity relation for the spirals and ETGs and show that the ETGs in the ATLAS3D sample define a tight red sequence in a colour-magnitude diagram, with few objects in the transition from the blue cloud. We describe the strategy of the SAURON integral field observations and the extraction of the stellar kinematics with the pPXF method. We find typical 1σ errors of ΔV≈ 6 km s-1, Δσ≈ 7 km s-1, Δh3≈Δh4≈ 0.03 in the mean velocity, the velocity dispersion and Gauss-Hermite (GH) moments for galaxies with effective dispersion σe≳ 120 km s-1. For galaxies with lower σe (≈40 per cent of the sample) the GH moments are gradually penalized by pPXF towards zero to suppress the noise produced by the spectral undersampling and only V and σ can be measured. We give an overview of the characteristics of the other main data sets already available for our sample and of the ongoing modelling projects.

  1. The Sloan Lens ACS Survey. I. A large spectroscopically selected sample of massive early-type lens galaxies

    NARCIS (Netherlands)

    Bolton, AS; Burles, S; Koopmans, LVE; Treu, T; Moustakas, LA

    2006-01-01

    The Sloan Lens ACS (SLACS) Survey is an efficient Hubble Space Telescope (HST) Snapshot imaging survey for new galaxy-scale strong gravitational lenses. The targeted lens candidates are selected spectroscopically from the Sloan Digital Sky Survey (SDSS) database of galaxy spectra for having multiple

  2. The relation between specific baryon angular momentum and mass for a sample of nearby low-mass galaxies with resolved H I kinematics

    Science.gov (United States)

    Elson, E. C.

    2017-12-01

    This paper investigates the relationship between specific baryon angular momentum jb and baryon mass Mb for a sample of nearby late-type galaxies with resolved H I kinematics. This work roughly doubles the number of galaxies with Mb ≲ 1010 M⊙ used to study the jb-Mb relation. Most of the galaxies in the sample have their baryon mass dominated by their gas content, thereby offering jb and Mb measures that are relatively unaffected by uncertainties arising from the stellar mass-to-light ratio. Measured H I surface density radial profiles together with optical and rotation curve data from the literature are used to derive a best-fitting relation given by j_b=qM_b^{α }, with α = 0.62 ± 0.02 and log10 q = -3.35 ± 0.25. This result is consistent with the j_b∝ M_b^{2/3} relation that is theoretically expected and also measured by Obreschkow & Glazebrook for their full sample of THINGS spiral galaxies, yet differs to their steeper relation found for subsets with fixed bulge fraction. The 30 arcsec spatial resolution of the H I imaging used in this study is significantly lower than that of the THINGS imaging used by Obreschkow & Glazebrook, yet the results presented in this work are clearly shown to contain no significant systematic errors due to the low-resolution imaging.

  3. Evidence for ubiquitous high-equivalent-width nebular emission in z ∼ 7 galaxies: toward a clean measurement of the specific star-formation rate using a sample of bright, magnified galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Smit, R.; Bouwens, R. J.; Labbé, I. [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); Zheng, W.; Lemze, D.; Ford, H. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Bradley, L.; Coe, D.; Postman, M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Donahue, M. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Moustakas, J. [Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States); Umetsu, K. [Institute of Astronomy and Astrophysics, Academia Sinica, P. O. Box 23-141, Taipei 10617, Taiwan (China); Zitrin, A.; Bartelmann, M. [Institut fur Theoretische Astrophysik, ZAH, Albert-Ueberle-Straß e 2, 69120 Heidelberg (Germany); Gonzalez, V. [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Benítez, N.; Jimenez-Teja, Y. [Instituto de Astrofisica de Andalucia (CSIC), C/Camino Bajo de Huetor 24, Granada 18008 (Spain); Broadhurst, T. [Department of Theoretical Physics, University of the Basque Country, P. O. Box 644, 48080 Bilbao (Spain); Grillo, C. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Infante, L. [Departamento de Astronoia y Astrofisica, Pontificia Universidad Catolica de Chile, V. Mackenna 4860, Santiago 22 (Chile); and others

    2014-03-20

    Growing observational evidence indicates that nebular line emission has a significant impact on the rest-frame optical fluxes of z ∼ 5-7 galaxies. This line emission makes z ∼ 5-7 galaxies appear more massive, with lower specific star-formation rates (sSFRs). However, corrections for this line emission have been difficult to perform reliably because of huge uncertainties on the strength of such emission at z ≳ 5.5. In this paper, we present the most direct observational evidence thus far for ubiquitous high-equivalent-width (EW) [O III] + Hβ line emission in Lyman-break galaxies at z ∼ 7, and we present a strategy for an improved measurement of the sSFR at z ∼ 7. We accomplish this through the selection of bright galaxies in the narrow redshift window z ∼ 6.6-7.0 where the Spitzer/Infrared Array Camera (IRAC) 4.5 μm flux provides a clean measurement of the stellar continuum light, in contrast with the 3.6 μm flux, which is contaminated by the prominent [O III] + Hβ lines. To ensure a high signal-to-noise ratio for our IRAC flux measurements, we consider only the brightest (H {sub 160} < 26 mag) magnified galaxies we have identified behind galaxy clusters. It is remarkable that the mean rest-frame optical color for our bright seven-source sample is very blue, [3.6]-[4.5] = –0.9 ± 0.3. Such blue colors cannot be explained by the stellar continuum light and require that the rest-frame EW of [O III] + Hβ is greater than 637 Å for the average source. The four bluest sources from our seven-source sample require an even more extreme EW of 1582 Å. We can also set a robust lower limit of ≳ 4 Gyr{sup –1} on the sSFR of our sample based on the mean spectral energy distribution.

  4. A Principle Component Analysis of Galaxy Properties from a Large, Gas-Selected Sample

    Directory of Open Access Journals (Sweden)

    Yu-Yen Chang

    2012-01-01

    concluded that this is in conflict with the CDM model. Considering the importance of the issue, we reinvestigate the problem using the principal component analysis on a fivefold larger sample and additional near-infrared data. We use databases from the Arecibo Legacy Fast Arecibo L-band Feed Array Survey for the gas properties, the Sloan Digital Sky Survey for the optical properties, and the Two Micron All Sky Survey for the near-infrared properties. We confirm that the parameters are indeed correlated where a single physical parameter can explain 83% of the variations. When color (g-i is included, the first component still dominates but it develops a second principal component. In addition, the near-infrared color (i-J shows an obvious second principal component that might provide evidence of the complex old star formation. Based on our data, we suggest that it is premature to pronounce the failure of the CDM model and it motivates more theoretical work.

  5. THE SL2S GALAXY-SCALE LENS SAMPLE. IV. THE DEPENDENCE OF THE TOTAL MASS DENSITY PROFILE OF EARLY-TYPE GALAXIES ON REDSHIFT, STELLAR MASS, AND SIZE

    Energy Technology Data Exchange (ETDEWEB)

    Sonnenfeld, Alessandro; Treu, Tommaso; Suyu, Sherry H. [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Gavazzi, Raphaël [Institut d' Astrophysique de Paris, UMR7095 CNRS-Université Pierre et Marie Curie, 98bis bd Arago, F-75014 Paris (France); Marshall, Philip J. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305 (United States); Auger, Matthew W. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Nipoti, Carlo, E-mail: sonnen@physics.ucsb.edu [Astronomy Department, University of Bologna, via Ranzani 1, I-40127 Bologna (Italy)

    2013-11-10

    We present optical and near-infrared spectroscopy obtained at Keck, Very Large Telescope, and Gemini for a sample of 36 secure strong gravitational lens systems and 17 candidates identified as part of the Strong Lensing Legacy Survey. The deflectors are massive early-type galaxies in the redshift range z{sub d} = 0.2-0.8, while the lensed sources are at z{sub s} = 1-3.5. We combine these data with photometric and lensing measurements presented in the companion paper III and with lenses from the Sloan Lens Advanced Camera for Surveys and Lènses Structure and Dynamics surveys to investigate the cosmic evolution of the internal structure of massive early-type galaxies over half the age of the universe. We study the dependence of the slope of the total mass density profile, γ' (ρ(r)∝r{sup -γ{sup '}}), on stellar mass, size, and redshift. We find that two parameters are sufficient to determine γ' with less than 6% residual scatter. At fixed redshift, γ' depends solely on the surface stellar mass density ∂γ'/∂Σ{sub *} = 0.38 ± 0.07, i.e., galaxies with denser stars also have steeper slopes. At fixed M{sub *} and R{sub eff}, γ' depends on redshift, in the sense that galaxies at a lower redshift have steeper slopes (∂γ'/∂z = –0.31 ± 0.10). However, the mean redshift evolution of γ' for an individual galaxy is consistent with zero dγ'/dz = –0.10 ± 0.12. This result is obtained by combining our measured dependencies of γ' on z, M{sub *},R{sub eff} with the evolution of the R{sub eff}-M{sub *} taken from the literature, and is broadly consistent with current models of the formation and evolution of massive early-type galaxies. Detailed quantitative comparisons of our results with theory will provide qualitatively new information on the detailed physical processes at work.

  6. H1 in RSA galaxies

    Science.gov (United States)

    Richter, OTTO-G.

    1993-01-01

    The original Revised Shapley-Ames (RSA) galaxy sample of almost 1300 galaxies has been augmented with further bright galaxies from the RSA appendix as well as newer galaxy catalogs. A complete and homogeneous, strictly magnitude-limited all-sky sample of 2345 galaxies brighter than 13.4 in apparent blue magnitude was formed. New 21 cm H1 line observations for more than 600 RSA galaxies have been combined with all previously available H1 data from the literature. This new extentise data act allows detailed tests of widely accepted 'standard' reduction and analysis techniques.

  7. Kolmogorov similarity hypotheses for scalar fields: sampling intermittent turbulent mixing in the ocean and galaxy

    International Nuclear Information System (INIS)

    Gibson, C.H.

    1991-01-01

    Kolmogorov's three universal similarity hypotheses are extrapolated to describe scalar fields like temperature mixed by turbulence. The analogous first and second hypotheses for scalars include the effects of Prandtl number and rate-of-strain mixing. Application of velocity and scalar similarity hypotheses to the ocean must take into account the damping of active turbulence by density stratification and the Earth's rotation to form fossil turbulence. By the analogous Kolmogorov third hypothesis for scalars, temperature dissipation rates χ averaged over lengths r > L K should be lognormally distributed with intermittency factors σ 2 that increase with increasing turbulence energy length scales L O as σ ln r 2 approx = μ θ ln(L O /r). Tests of kolmogorovian velocity and scalar universal similarity hypotheses for very large ranges of turbulence length and timescales are provided by data from the ocean and the galactic interstellar medium. These ranges are from 1 to 9 decades in the ocean, and over 12 decades in the interstellar medium. The universal constant for turbulent mixing intermittency μ θ is estimated from oceanic data to be 0.44±0.01, which is remarkably close to estimates for Kolmorgorov's turbulence intermittency constant μ of 0.45±0.05 from galactic as well as atmospheric data. Extreme intermittency complicates the oceanic sampling problem, and may lead to quantitative and qualitative undersampling errors in estimates of mean oceanic dissipation rates and fluxes. Intermittency of turbulence and mixing in the interstellar medium may be a factor in the formation of stars. (author)

  8. BOOSTING LY α   AND He ii λ 1640 LINE FLUXES FROM POPULATION III GALAXIES: STOCHASTIC IMF SAMPLING AND DEPARTURES FROM CASE-B

    International Nuclear Information System (INIS)

    Mas-Ribas, Lluís; Dijkstra, Mark; Forero-Romero, Jaime E.

    2016-01-01

    We revisit calculations of nebular hydrogen Ly α and He ii λ 1640 line strengths for Population III (Pop III) galaxies, undergoing continuous, and bursts of, star formation. We focus on initial mass functions (IMFs) motivated by recent theoretical studies, which generally span a lower range of stellar masses than earlier works. We also account for case-B departures and the stochastic sampling of the IMF. In agreement with previous work, we find that departures from case-B can enhance the Ly α flux by a factor of a few, but we argue that this enhancement is driven mainly by collisional excitation and ionization, and not due to photoionization from the n  = 2 state of atomic hydrogen. The increased sensitivity of the Ly α flux to the high-energy end of the galaxy spectrum makes it more subject to stochastic sampling of the IMF. The latter introduces a dispersion in the predicted nebular line fluxes around the deterministic value by as much as a factor of ∼4. In contrast, the stochastic sampling of the IMF has less impact on the emerging Lyman Werner photon flux. When case-B departures and stochasticity effects are combined, nebular line emission from Pop III galaxies can be up to one order of magnitude brighter than predicted by “standard” calculations that do not include these effects. This enhances the prospects for detection with future facilities such as the James Webb Space Telescope and large, ground-based telescopes.

  9. Boosting Lyα and He II λ1640 Line Fluxes from Population III Galaxies: Stochastic IMF Sampling and Departures from Case-B

    Science.gov (United States)

    Mas-Ribas, Lluís; Dijkstra, Mark; Forero-Romero, Jaime E.

    2016-12-01

    We revisit calculations of nebular hydrogen Lyα and He II λ1640 line strengths for Population III (Pop III) galaxies, undergoing continuous, and bursts of, star formation. We focus on initial mass functions (IMFs) motivated by recent theoretical studies, which generally span a lower range of stellar masses than earlier works. We also account for case-B departures and the stochastic sampling of the IMF. In agreement with previous work, we find that departures from case-B can enhance the Lyα flux by a factor of a few, but we argue that this enhancement is driven mainly by collisional excitation and ionization, and not due to photoionization from the n = 2 state of atomic hydrogen. The increased sensitivity of the Lyα flux to the high-energy end of the galaxy spectrum makes it more subject to stochastic sampling of the IMF. The latter introduces a dispersion in the predicted nebular line fluxes around the deterministic value by as much as a factor of ˜4. In contrast, the stochastic sampling of the IMF has less impact on the emerging Lyman Werner photon flux. When case-B departures and stochasticity effects are combined, nebular line emission from Pop III galaxies can be up to one order of magnitude brighter than predicted by “standard” calculations that do not include these effects. This enhances the prospects for detection with future facilities such as the James Webb Space Telescope and large, ground-based telescopes.

  10. HIghMass-high H I mass, H I-rich galaxies at z ∼ 0 sample definition, optical and Hα imaging, and star formation properties

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Shan; Matsushita, Satoki [Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, National Taiwan University, Taipei 10617, Taiwan (China); Haynes, Martha P.; Giovanelli, Riccardo; Hallenbeck, Gregory; Jones, Michael G.; Adams, Elizabeth A. K. [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Brinchmann, Jarle [Sterrewacht Leiden, Leiden University, NL-2300 RA Leiden (Netherlands); Chengalur, Jayaram N. [National Centre for Radio Astrophysics, Tata Institute for Fundamental Research, Pune 411007 (India); Hunt, Leslie K. [INAF-Osservatorio Astrofisico di Arcetri, Largo East Fermi 5, I-50125, Firenze (Italy); Masters, Karen L. [Institute of Cosmology and Gravitation, Dennis Sciama Building, Burnaby Road, Portsmouth POI 3FX (United Kingdom); Saintonge, Amelie [Department of Physics and Astronomy, University College London, Gower Place, London WC1E 6BT (United Kingdom); Spekkens, Kristine, E-mail: shan@asiaa.sinica.edu.tw [Royal Military College of Canada, Department of Physics, P.O. Box 17000, Station Forces, Kingston, ON K7K 7B4 (Canada)

    2014-09-20

    We present first results of the study of a set of exceptional H I sources identified in the 40% ALFALFA extragalactic H I survey catalog α.40 as both being H I massive (M{sub HI}>10{sup 10} M{sub ⊙}) and having high gas fractions for their stellar masses: the HIghMass galaxy sample. We analyze UV- and optical-broadband and Hα images to understand the nature of their relatively underluminous disks in optical and to test whether their high gas fractions can be tracked to higher dark matter halo spin parameters or late gas accretion. Estimates of their star formation rates (SFRs) based on spectral energy distribution fitting agree within uncertainties with the Hα luminosity inferred current massive SFRs. The H II region luminosity functions, parameterized as dN/dlog L∝L {sup α}, have standard slopes at the luminous end (α ∼ –1). The global SFRs demonstrate that the HIghMass galaxies exhibit active ongoing star formation (SF) with moderate SF efficiency but, relative to normal spirals, a lower integrated SFR in the past. Because the SF activity in these systems is spread throughout their extended disks, they have overall lower SFR surface densities and lower surface brightness in the optical bands. Relative to normal disk galaxies, the majority of HIghMass galaxies have higher Hα equivalent widths and are bluer in their outer disks, implying an inside-out disk growth scenario. Downbending double exponential disks are more frequent than upbending disks among the gas-rich galaxies, suggesting that SF thresholds exist in the downbending disks, probably as a result of concentrated gas distribution.

  11. Xray cavities in a sample of 83 SPT-selected clusters galaxies. Tracing the evolution of AGN feedback in clusters of galaxies out to z=1.2

    Energy Technology Data Exchange (ETDEWEB)

    Hlavacek-Larrondo, J.; McDonald, M.; Benson, B. A.; Forman, W. R.; Allen, S. W.; Bleem, L. E.; Ashby, M. L. N.; Bocquet, S.; Brodwin, M.; Dietrich, J. P.; Jones, C.; Liu, J.; Reichardt, C. L.; Saliwanchik, B. R.; Saro, A.; Schrabback, T.; Song, J.; Stalder, B.; Vikhlinin, A.; Zenteno, A.

    2015-05-18

    X-ray cavities are key tracers of mechanical (or radio mode) heating arising from the active galactic nuclei (AGNs) in brightest cluster galaxies (BCGs). We report on a survey for X-ray cavities in 83 massive, high-redshift ($0.4\\lt z\\lt 1.2$) clusters of galaxies selected by their Sunyaev-Zel’dovich signature in the South Pole Telescope data. Based on Chandra X-ray images, we find a total of six clusters having symmetric pairs of surface brightness depressions consistent with the picture of radio jets inflating X-ray cavities in the intracluster medium (ICM). The majority of these detections are of relatively low significance and require deeper follow-up data in order to be confirmed. Further, this search will miss small (<10 kpc) X-ray cavities that are unresolved by Chandra at high ($z\\gtrsim 0.5$) redshift. Despite these limitations, our results suggest that the power generated by AGN feedback in BCGs has remained unchanged for over half of the age of the universe ($\\gt 7$ Gyr at $z\\sim 0.8$). On average, the detected X-ray cavities have powers of $(0.8-5)\\times {{10}^{45}}\\ {\\rm erg}\\ {{{\\rm s}}^{-1}}$, enthalpies of $(3-6)\\times {{10}^{59}}\\ {\\rm erg}$, and radii of ~17 kpc. Integrating over 7 Gyr, we find that the supermassive black holes in BCGs may have accreted 10(8) to several ${{10}^{9}}\\,{{M}_{\\odot }}$ of material to power these outflows. This level of accretion indicates that significant supermassive black hole growth may occur not only at early times, in the quasar era, but at late times as well. We also find that X-ray cavities at high redshift may inject an excess heat of 0.1–1.0 keV per particle into the hot ICM above and beyond the energy needed to offset cooling. Although this result needs to be confirmed, we note that the magnitude of excess heating is similar to the energy needed to preheat clusters, break self-similarity, and explain the excess entropy in hot atmospheres.

  12. VLBI observations of the nuclei of a mixed sample of bright galaxies and quasars at 327 MHz

    International Nuclear Information System (INIS)

    Ananthakrishnan, S.; Kulkarni, V.K.

    1989-01-01

    The first VLBI observations using the Ooty telescope are presented. An array consisting of telescopes at Ooty (India), Crimea (USSR), Torun (Poland), Westerbork (Netherlands) and Jodrell Bank (United Kingdom) was operated in 1983 December at a frequency of 327 MHz. Nearby galaxies, compact quasars and SS433 were observed in this pilot experiment. Most of the galaxies were found to be well resolved. The structure of SS433 (visible only on the shortest baseline) is consistent with that obtained in previous high-frequency VLBI work. The visibilities of the compact quasars indicate that large-scale scattering may be taking place in the interplanetary medium. (author)

  13. Surface oxygen vacancy and oxygen permeation flux limits of perovskite ion transport membranes

    KAUST Repository

    Hunt, Anton

    2015-09-01

    © 2015 Elsevier B.V. The mechanisms and quantitative models for how oxygen is separated from air using ion transport membranes (ITMs) are not well understood, largely due to the experimental complexity for determining surface exchange reactions at extreme temperatures (>800°C). This is especially true when fuels are present at the permeate surface. For both inert and reactive (fuels) operations, solid-state oxygen surface vacancies (δ) are ultimately responsible for driving the oxygen flux, JO2. In the inert case, the value of δ at either surface is a function of the local PO2 and temperature, whilst the magnitude of δ dictates both the JO2 and the inherent stability of the material. In this study values of δ are presented based on experimental measurements under inert (CO2) sweep: using a permeation flux model and local PO2 measurements, collected by means of a local gas-sampling probe in our large-scale reactor, we can determine δ directly. The ITM assessed was La0.9Ca0.1FeO3-δ (LCF); the relative resistances to JO2 were quantified using the pre-defined permeation flux model and local PO2 values. Across a temperature range from 825°C to 1056°C, δ was found to vary from 0.007 to 0.029 (<1%), safely within material stability limits, whilst the permeate surface exchange resistance dominates. An inert JO2 limit was identified owing to a maximum sweep surface δ, δmaxinert. The physical presence of δmaxinert is attributed to a rate limiting step shift from desorption to associative electron transfer steps on the sweep surface as PO2 is reduced. Permeate surface exchange limitations under non-reactive conditions suggest that reactive (fuel) operation is necessary to accelerate surface chemistry for future work, to reduce flux resistance and push δpast δmaxinert in a stable manner.

  14. The Lyman alpha reference sample VI. Lyman alpha escape from the edge-on disk galaxy Mrk 1486

    Czech Academy of Sciences Publication Activity Database

    Duval, F.; Ostlin, G.; Hayes, M.; Zackrisson, E.; Verhamme, A.; Orlitová, Ivana; Adamo, A.; Guaita, L.; Melinder, J.; Cannon, J.M.; Laursen, P.; Rivera-Thorsen, T.; Herenz, E.Ch.; Gruyters, P.; Mas-Hesse, J. M.; Kunth, D.; Sandberg, A.; Schaerer, D.; Mansson, J.-E.

    2016-01-01

    Roč. 587, March (2016), A77/1-A77/24 ISSN 0004-6361 R&D Projects: GA ČR(CZ) GP14-20666P Institutional support: RVO:67985815 Keywords : galaxies * starburst * submillimeter Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

  15. Bright galaxies at z=9-11 from pure-parallel HST observations: Building a unique sample for JWST with Spitzer/IRAC

    Science.gov (United States)

    Bouwens, Rychard; Morashita, Takahiro; Stefanon, Mauro; Magee, Dan

    2018-05-01

    The combination of observations taken by Hubble and Spitzer revealed the unexpected presence of sources as bright as our own Milky Way as early as 400 Myr after the Big Bang, potentially highlighting a new highly efficient regime for star formation in L>L* galaxies at very early times. Yet, the sample of high-quality z>8 galaxies with both HST and Spitzer/IRAC imaging is still small, particularly at the highest luminosities. We propose here to remedy this situation and use Spitzer/IRAC to efficiently follow up the most promising z>8 sources from our Hubble Brightest of Reionizing Galaxies (BoRG) survey, which covers a footprint on the sky similar to CANDELS, provides a deeper search than ground-based surveys like UltraVISTA, and is robust against cosmic variance because of its 210 independent lines of sight. The proposed new 3.6 micron observations will continue our Spitzer cycle 12 and 13 BORG911 programs, targeting 15 additional fields, leveraging over 200 new HST orbits to identify a final sample of about 8 bright galaxies at z >= 8.5. For optimal time use (just 20 hours), our goal is to readily discriminate between z>8 sources (undetected or marginally detected in IRAC) and z 2 interlopers (strongly detected in IRAC) with just 1-2 hours per pointing. The high-quality candidates that we will identify with IRAC will be ideal targets for further studies investigating the ionization state of the distant universe through near-IR Keck/VLT spectroscopy. They will also be uniquely suited to measurement of the redshift and stellar population properties through JWST/NIRSPEC observations, with the potential to elucidate how the first generations of stars are assembled in the earliest stages of the epoch of reionization.

  16. Galaxy Zoo: dust in spiral galaxies star

    OpenAIRE

    Masters, Karen L.; Nichol, Robert; Bamford, Steven; Mosleh, Moein; Lintott, Chris J.; Andreescu, Dan; Edmondson, Edward M.; Keel, William C.; Murray, Phil; Raddick, M. Jordan; Schawinski, Kevin; Slosar, Anze; Szalay, Alexander S.; Thomas, Daniel; Vandenberg, Jan

    2010-01-01

    We investigate the effect of dust on spiral galaxies by measuring the inclination dependence of optical colours for 24 276 well-resolved Sloan Digital Sky Survey (SDSS) galaxies visually classified via the Galaxy Zoo project. We find clear trends of reddening with inclination which imply a total extinction from face-on to edge-on of 0.7, 0.6, 0.5 and 0.4 mag for the ugri passbands (estimating 0.3 mag of extinction in z band). We split the sample into ‘bulgy’ (early-type) and ‘discy’ (late-typ...

  17. Heat flux limiting sleeves

    Science.gov (United States)

    Harris, William G.

    1985-01-01

    A heat limiting tubular sleeve extending over only a portion of a tube having a generally uniform outside diameter, the sleeve being open on both ends, having one end thereof larger in diameter than the other end thereof and having a wall thickness which decreases in the same direction as the diameter of the sleeve decreases so that the heat transfer through the sleeve and tube is less adjacent the large diameter end of the sleeve than adjacent the other end thereof.

  18. Galaxy collisions

    International Nuclear Information System (INIS)

    Combes, F.

    1987-01-01

    Galaxies are not isolated systems of stars and gas, ''independent universes'' as believed by astronomers about ten years ago, but galaxies are formed and evolve by interaction with their environment, and in particular with their nearest neighbors. Gravitational interactions produce enormous tides in the disk of spiral galaxies, generate spiral arms and trigger bursts of star formation. Around elliptical galaxies, the collision with a small companion produces a series of waves, or shells. A galaxy interaction leads, in most cases, to the coalescence of the two coliders; therefore all galaxies are not formed just after the Big-Bang, when matter recombines: second generation galaxies are still forming now by galaxy mergers, essentially elliptical galaxies, but also compact dwarfs. Collisions between galaxies could also trigger activity in nuclei for radiogalaxies and quasars [fr

  19. The Gemini/HST Galaxy Cluster Project: Redshift 0.2–1.0 Cluster Sample, X-Ray Data, and Optical Photometry Catalog

    Science.gov (United States)

    Jørgensen, Inger; Chiboucas, Kristin; Hibon, Pascale; Nielsen, Louise D.; Takamiya, Marianne

    2018-04-01

    The Gemini/HST Galaxy Cluster Project (GCP) covers 14 z = 0.2–1.0 clusters with X-ray luminosity of {L}500≥slant {10}44 {erg} {{{s}}}-1 in the 0.1–2.4 keV band. In this paper, we provide homogeneously calibrated X-ray luminosities, masses, and radii, and we present the complete catalog of the ground-based photometry for the GCP clusters. The clusters were observed with either Gemini North or South in three or four of the optical passbands g‧, r‧, i‧, and z‧. The photometric catalog includes consistently calibrated total magnitudes, colors, and geometrical parameters. The photometry reaches ≈25 mag in the passband closest to the rest-frame B band. We summarize comparisons of our photometry with data from the Sloan Digital Sky Survey. We describe the sample selection for our spectroscopic observations, and establish the calibrations to obtain rest-frame magnitudes and colors. Finally, we derive the color–magnitude relations for the clusters, and briefly discuss these in the context of evolution with redshift. Consistent with our results based on spectroscopic data, the color–magnitude relations support passive evolution of the red sequence galaxies. The absence of change in the slope with redshift constrains the allowable age variation along the red sequence to <0.05 dex between the brightest cluster galaxies and those four magnitudes fainter. This paper serves as the main reference for the GCP cluster and galaxy selection, X-ray data, and ground-based photometry.

  20. Carbon monoxide emission from small galaxies

    Science.gov (United States)

    Thronson, Harley A., Jr.; Bally, John

    1987-01-01

    A search was conducted for J = 1 yields 0 CO emission from 22 galaxies, detecting half, as part of a survey to study star formation in small to medium size galaxies. Although substantial variation was found in the star formation efficiencies of the sample galaxies, there is no apparent systematic trend with galaxy size.

  1. The Atacama Cosmology Telescope: Physical Properties and Purity of a Galaxy Cluster Sample Selected Via the Sunyaev-Zel'Dovich Effect

    Science.gov (United States)

    Menanteau, Felipe; Gonzalez, Jorge; Juin, Jean-Baptiste; Marriage, Tobias; Reese, Erik D.; Acquaviva, Viviana; Aguirre, Paula; Appel, John Willam; Baker, Andrew J.; Barrientos, L. Felipe; hide

    2010-01-01

    We present optical and X-ray properties for the first confirmed galaxy cluster sample selected by the Sunyaev-Zel'dovich Effect from 148 GHz maps over 455 square degrees of sky made with the Atacama Cosmology Telescope. These maps. coupled with multi-band imaging on 4-meter-class optical telescopes, have yielded a sample of 23 galaxy clusters with redshifts between 0.118 and 1.066. Of these 23 clusters, 10 are newly discovered. The selection of this sample is approximately mass limited and essentially independent of redshift. We provide optical positions, images, redshifts and X-ray fluxes and luminosities for the full sample, and X-ray temperatures of an important subset. The mass limit of the full sample is around 8.0 x 10(exp 14) Stellar Mass. with a number distribution that peaks around a redshift of 0.4. For the 10 highest significance SZE-selected cluster candidates, all of which are optically confirmed, the mass threshold is 1 x 10(exp 15) Stellar Mass and the redshift range is 0.167 to 1.066. Archival observations from Chandra, XMM-Newton. and ROSAT provide X-ray luminosities and temperatures that are broadly consistent with this mass threshold. Our optical follow-up procedure also allowed us to assess the purity of the ACT cluster sample. Eighty (one hundred) percent of the 148 GHz candidates with signal-to-noise ratios greater than 5.1 (5.7) are confirmed as massive clusters. The reported sample represents one of the largest SZE-selected sample of massive clusters over all redshifts within a cosmologically-significant survey volume, which will enable cosmological studies as well as future studies on the evolution, morphology, and stellar populations in the most massive clusters in the Universe.

  2. On the use of flux limiters in the discrete ordinates method for 3D radiation calculations in absorbing and scattering media

    International Nuclear Information System (INIS)

    Godoy, William F.; DesJardin, Paul E.

    2010-01-01

    The application of flux limiters to the discrete ordinates method (DOM), S N , for radiative transfer calculations is discussed and analyzed for 3D enclosures for cases in which the intensities are strongly coupled to each other such as: radiative equilibrium and scattering media. A Newton-Krylov iterative method (GMRES) solves the final systems of linear equations along with a domain decomposition strategy for parallel computation using message passing libraries in a distributed memory system. Ray effects due to angular discretization and errors due to domain decomposition are minimized until small variations are introduced by these effects in order to focus on the influence of flux limiters on errors due to spatial discretization, known as numerical diffusion, smearing or false scattering. Results are presented for the DOM-integrated quantities such as heat flux, irradiation and emission. A variety of flux limiters are compared to 'exact' solutions available in the literature, such as the integral solution of the RTE for pure absorbing-emitting media and isotropic scattering cases and a Monte Carlo solution for a forward scattering case. Additionally, a non-homogeneous 3D enclosure is included to extend the use of flux limiters to more practical cases. The overall balance of convergence, accuracy, speed and stability using flux limiters is shown to be superior compared to step schemes for any test case.

  3. Spectroscopy of the galaxy components of N and Seyfert galaxies

    International Nuclear Information System (INIS)

    Boroson, T.A.; Oke, J.B.; Palomar Observatory, Pasadena, CA)

    1987-01-01

    Nuclear and off-nuclear spectra of nine active galaxies are presented. The sample consists of four Seyfert galaxies, two N galaxies, one Seyfert radio galaxy, and one liner/Seyfert 2 galaxy. All of the objects show continuum emission off the nucleus. Four clearly show absorption features from a stellar population. Velocities have been measured for the off-nuclear emission and absorption lines. In the case of I Zw 1, the absorption-line velocities are inconsistent with 21-cm H I measurements of this object. 26 references

  4. THE ORIGIN OF THE INFRARED EMISSION IN RADIO GALAXIES. II. ANALYSIS OF MID- TO FAR-INFRARED SPITZER OBSERVATIONS OF THE 2JY SAMPLE

    International Nuclear Information System (INIS)

    Dicken, D.; Tadhunter, C.; Axon, D.; Morganti, R.; Inskip, K. J.; Holt, J.; Groves, B.; Delgado, R. Gonzalez

    2009-01-01

    We present an analysis of deep mid- to far-infrared (MFIR) Spitzer photometric observations of the southern 2Jy sample of powerful radio sources (0.05 < z < 0.7), conducting a statistical investigation of the links between radio jet, active galactic nucleus (AGN), starburst activity and MFIR properties. This is part of an ongoing extensive study of powerful radio galaxies that benefits from both complete optical emission line information and a uniquely high detection rate in the far-infrared (far-IR). We find tight correlations between the MFIR and [O III]λ5007 emission luminosities, which are significantly better than those between MFIR and extended radio luminosities, or between radio and [O III] luminosities. Since [O III] is a known indicator of intrinsic AGN power, these correlations confirm AGN illumination of the circumnuclear dust as the primary heating mechanism for the dust producing thermal MFIR emission at both 24 and 70 μm. We demonstrate that AGN heating is energetically feasible, and identify the narrow-line region clouds as the most likely location of the cool, far-IR emitting dust. Starbursts make a major contribution to the heating of the cool dust in only 15%-28% of our targets. We also investigate the orientation dependence of the continuum properties, finding that the broad- and narrow-line objects in our sample with strong emission lines have similar distributions of MFIR luminosities and colors. Therefore our results are entirely consistent with the orientation-based unified schemes for powerful radio galaxies. However, the weak line radio galaxies form a separate class of objects with intrinsically low-luminosity AGNs in which both the optical emission lines and the MFIR continuum are weak.

  5. Galaxy mergers

    International Nuclear Information System (INIS)

    Roos, N.

    1981-01-01

    This thesis contains a series of four papers dealing with the effects of interactions among galaxies during the epoch of cluster formation. Galaxy interactions are investigated and the results incorporated in numerical simulations of the formation of groups and clusters of galaxies. The role of galaxy interactions is analysed in the more general context of simulations of an expanding universe. The evolution of galaxies in rich clusters is discussed. The results of the investigations are presented and their relation to other work done in the field are briefly reviewed and an attempt is made to link galaxy mergers to the occurrence of activity in galactic nuclei. (Auth.)

  6. Flux Limiter Lattice Boltzmann Scheme Approach to Compressible Flows with Flexible Specific-Heat Ratio and Prandtl Number

    International Nuclear Information System (INIS)

    Gan Yanbiao; Li Yingjun; Xu Aiguo; Zhang Guangcai

    2011-01-01

    We further develop the lattice Boltzmann (LB) model [Physica A 382 (2007) 502] for compressible flows from two aspects. Firstly, we modify the Bhatnagar-Gross-Krook (BGK) collision term in the LB equation, which makes the model suitable for simulating flows with different Prandtl numbers. Secondly, the flux limiter finite difference (FLFD) scheme is employed to calculate the convection term of the LB equation, which makes the unphysical oscillations at discontinuities be effectively suppressed and the numerical dissipations be significantly diminished. The proposed model is validated by recovering results of some well-known benchmarks, including (i) The thermal Couette flow; (ii) One- and two-dimensional Riemann problems. Good agreements are obtained between LB results and the exact ones or previously reported solutions. The flexibility, together with the high accuracy of the new model, endows the proposed model considerable potential for tracking some long-standing problems and for investigating nonlinear nonequilibrium complex systems. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  7. Parallel Jacobian-free Newton Krylov solution of the discrete ordinates method with flux limiters for 3D radiative transfer

    International Nuclear Information System (INIS)

    Godoy, William F.; Liu Xu

    2012-01-01

    The present study introduces a parallel Jacobian-free Newton Krylov (JFNK) general minimal residual (GMRES) solution for the discretized radiative transfer equation (RTE) in 3D, absorbing, emitting and scattering media. For the angular and spatial discretization of the RTE, the discrete ordinates method (DOM) and the finite volume method (FVM) including flux limiters are employed, respectively. Instead of forming and storing a large Jacobian matrix, JFNK methods allow for large memory savings as the required Jacobian-vector products are rather approximated by semiexact and numerical formulations, for which convergence and computational times are presented. Parallelization of the GMRES solution is introduced in a combined memory-shared/memory-distributed formulation that takes advantage of the fact that only large vector arrays remain in the JFNK process. Results are presented for 3D test cases including a simple homogeneous, isotropic medium and a more complex non-homogeneous, non-isothermal, absorbing–emitting and anisotropic scattering medium with collimated intensities. Additionally, convergence and stability of Gram–Schmidt and Householder orthogonalizations for the Arnoldi process in the parallel GMRES algorithms are discussed and analyzed. Overall, the introduction of JFNK methods results in a parallel, yet scalable to the tested 2048 processors, and memory affordable solution to 3D radiative transfer problems without compromising the accuracy and convergence of a Newton-like solution.

  8. MULTIPLE GALAXY COLLISIONS

    Science.gov (United States)

    2002-01-01

    Here is a sampling of 15 ultraluminous infrared galaxies viewed by NASA's Hubble Space Telescope. Hubble's sharp vision reveals more complexity within these galaxies, which astronomers are interpreting as evidence of a multiple-galaxy pileup. These images, taken by the Wide Field and Planetary Camera 2, are part of a three-year study of 123 galaxies within 3 billion light-years of Earth. The study was conducted in 1996, 1997, and 1999. False colors were assigned to these photos to enhance fine details within these coalescing galaxies. Credits: NASA, Kirk Borne (Raytheon and NASA Goddard Space Flight Center, Greenbelt, Md.), Luis Colina (Instituto de Fisica de Cantabria, Spain), and Howard Bushouse and Ray Lucas (Space Telescope Science Institute, Baltimore, Md.)

  9. THE ATACAMA COSMOLOGY TELESCOPE: DYNAMICAL MASSES AND SCALING RELATIONS FOR A SAMPLE OF MASSIVE SUNYAEV-ZEL'DOVICH EFFECT SELECTED GALAXY CLUSTERS ,

    International Nuclear Information System (INIS)

    Sifón, Cristóbal; Barrientos, L. Felipe; González, Jorge; Infante, Leopoldo; Dünner, Rolando; Menanteau, Felipe; Hughes, John P.; Baker, Andrew J.; Hasselfield, Matthew; Marriage, Tobias A.; Crichton, Devin; Gralla, Megan B.; Addison, Graeme E.; Dunkley, Joanna; Battaglia, Nick; Bond, J. Richard; Hajian, Amir; Das, Sudeep; Devlin, Mark J.; Hilton, Matt

    2013-01-01

    We present the first dynamical mass estimates and scaling relations for a sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample consists of 16 massive clusters detected with the Atacama Cosmology Telescope (ACT) over a 455 deg 2 area of the southern sky. Deep multi-object spectroscopic observations were taken to secure intermediate-resolution (R ∼ 700-800) spectra and redshifts for ≈60 member galaxies on average per cluster. The dynamical masses M 200c of the clusters have been calculated using simulation-based scaling relations between velocity dispersion and mass. The sample has a median redshift z = 0.50 and a median mass M 200c ≅12×10 14 h 70 -1 M sun with a lower limit M 200c ≅6×10 14 h 70 -1 M sun , consistent with the expectations for the ACT southern sky survey. These masses are compared to the ACT SZE properties of the sample, specifically, the match-filtered central SZE amplitude y 0 -tilde, the central Compton parameter y 0 , and the integrated Compton signal Y 200c , which we use to derive SZE-mass scaling relations. All SZE estimators correlate with dynamical mass with low intrinsic scatter (∼< 20%), in agreement with numerical simulations. We explore the effects of various systematic effects on these scaling relations, including the correlation between observables and the influence of dynamically disturbed clusters. Using the three-dimensional information available, we divide the sample into relaxed and disturbed clusters and find that ∼50% of the clusters are disturbed. There are hints that disturbed systems might bias the scaling relations, but given the current sample sizes, these differences are not significant; further studies including more clusters are required to assess the impact of these clusters on the scaling relations

  10. PRIMUS: CONSTRAINTS ON STAR FORMATION QUENCHING AND GALAXY MERGING, AND THE EVOLUTION OF THE STELLAR MASS FUNCTION FROM z = 0-1

    Energy Technology Data Exchange (ETDEWEB)

    Moustakas, John [Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States); Coil, Alison L.; Mendez, Alexander J. [Center for Astrophysics and Space Sciences, Department of Physics, University of California, 9500 Gilman Dr., La Jolla, CA 92093 (United States); Aird, James [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Cool, Richard J. [MMT Observatory, University of Arizona, 1540 E Second Street, Tucson, AZ 85721 (United States); Eisenstein, Daniel J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Wong, Kenneth C. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Zhu, Guangtun [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Arnouts, Stephane, E-mail: jmoustakas@siena.edu [Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States)

    2013-04-10

    We measure the evolution of the stellar mass function (SMF) from z = 0-1 using multi-wavelength imaging and spectroscopic redshifts from the PRism MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey (SDSS). From PRIMUS we construct an i < 23 flux-limited sample of {approx}40, 000 galaxies at z = 0.2-1.0 over five fields totaling Almost-Equal-To 5.5 deg{sup 2}, and from the SDSS we select {approx}170, 000 galaxies at z = 0.01-0.2 that we analyze consistently with respect to PRIMUS to minimize systematic errors in our evolutionary measurements. We find that the SMF of all galaxies evolves relatively little since z = 1, although we do find evidence for mass assembly downsizing; we measure a Almost-Equal-To 30% increase in the number density of {approx}10{sup 10} M{sub sun} galaxies since z Almost-Equal-To 0.6, and a {approx}< 10% change in the number density of all {approx}> 10{sup 11} M{sub sun} galaxies since z Almost-Equal-To 1. Dividing the sample into star-forming and quiescent using an evolving cut in specific star formation rate, we find that the number density of {approx}10{sup 10} M{sub sun} star-forming galaxies stays relatively constant since z Almost-Equal-To 0.6, whereas the space density of {approx}> 10{sup 11} M{sub sun} star-forming galaxies decreases by Almost-Equal-To 50% between z Almost-Equal-To 1 and z Almost-Equal-To 0. Meanwhile, the number density of {approx}10{sup 10} M{sub sun} quiescent galaxies increases steeply toward low redshift, by a factor of {approx}2-3 since z Almost-Equal-To 0.6, while the number of massive quiescent galaxies remains approximately constant since z Almost-Equal-To 1. These results suggest that the rate at which star-forming galaxies are quenched increases with decreasing stellar mass, but that the bulk of the stellar mass buildup within the quiescent population occurs around {approx}10{sup 10.8} M{sub sun}. In addition, we conclude that mergers do not appear to be a dominant channel for the stellar mass

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-05-01

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

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

  13. The Seyfert galaxy population

    International Nuclear Information System (INIS)

    Meurs, E.

    1982-01-01

    A large sample of Seyfert galaxies, many of which are Markarian galaxies, has been observed with the WSRT in lambda 21 cm continuum radiation. The results are presented, and the number of radio detected Seyferts has now increased considerably. A number of accurate optical positions are given that were needed to identify radio sources with the Seyfert galaxies observed. Optical and radio luminosity functions of Seyfert galaxies are derived. The results are compared with such functions for other categories of objects that may be related to these galaxies. The discussions focus on the possible connections between normal galaxies, Seyferts, and optically selected quasars. Three investigations are reported on individual objects that are related to Seyfert galaxies. WSRT observations of four bright, optically selected quasars are presented. The identification of an X-ray discovered BL Lacertae object is discussed. Its radio emission is on a much lower level than for other BL Lacs. Perhaps it is a radio-quiet object in this class, suggesting a comparable difference in radio emission for BL Lacs as is known for quasars. Photo-electric photometry for the Seyfert galaxy NGC 1566 is reported. Besides a monitoring programme, multi-aperture photometry is described. (Auth.)

  14. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

    Galaxy formation is an enormously complex discipline due to the many physical processes that play a role in shaping galaxies. The objective of this thesis is to study galaxy formation with two different approaches: First, numerical simulations are used to study the structure of dark matter and how...... galaxies form stars throughout the history of the Universe, and secondly it is shown that observations of gamma-ray bursts (GRBs) can be used to probe galaxies with active star formation in the early Universe. A conclusion from the hydrodynamical simulations is that the galaxies from the stateof...... is important, since it helps constraining chemical evolution models at high redshift. A new project studying how the population of galaxies hosting GRBs relate to other galaxy population is outlined in the conclusion of this thesis. The core of this project will be to quantify how the stellar mass function...

  15. Statistics of galaxy warps in the HDF North and South

    NARCIS (Netherlands)

    Reshetnikov, [No Value; Battaner, E; Combes, F; Jimenez-Vicente, J

    We present a statistical study of the presence of galaxy warps in the Hubble deep fields. Among a complete sample of 45 edge-on galaxies above a diameter of 1."3, we find 5 galaxies to be certainly warped and 6 galaxies as good candidates. In addition, 4 galaxies reveal a characteristic U-warp.

  16. Transport methods: general. 6. A Flux-Limited Diffusion Theory Derived from the Maximum Entropy Eddington Factor

    International Nuclear Information System (INIS)

    Yin, Chukai; Su, Bingjing

    2001-01-01

    The Minerbo's maximum entropy Eddington factor (MEEF) method was proposed as a low-order approximation to transport theory, in which the first two moment equations are closed for the scalar flux f and the current F through a statistically derived nonlinear Eddington factor f. This closure has the ability to handle various degrees of anisotropy of angular flux and is well justified both numerically and theoretically. Thus, a lot of efforts have been made to use this approximation in transport computations, especially in the radiative transfer and astrophysics communities. However, the method suffers numerical instability and may lead to anomalous solutions if the equations are solved by certain commonly used (implicit) mesh schemes. Studies on numerical stability in one-dimensional cases show that the MEEF equations can be solved satisfactorily by an implicit scheme (of treating δΦ/δx) if the angular flux is not too anisotropic so that f 32 , the classic diffusion solution P 1 , the MEEF solution f M obtained by Riemann solvers, and the NFLD solution D M for the two problems, respectively. In Fig. 1, NFLD and MEEF quantitatively predict very close results. However, the NFLD solution is qualitatively better because it is continuous while MEEF predicts unphysical jumps near the middle of the slab. In Fig. 2, the NFLD and MEEF solutions are almost identical, except near the material interface. In summary, the flux-limited diffusion theory derived from the MEEF description is quantitatively as accurate as the MEEF method. However, it is more qualitatively correct and user-friendly than the MEEF method and can be applied efficiently to various steady-state problems. Numerical tests show that this method is widely valid and overall predicts better results than other low-order approximations for various kinds of problems, including eigenvalue problems. Thus, it is an appealing approximate solution technique that is fast computationally and yet is accurate enough for a

  17. Galaxies in the Early Universe

    DEFF Research Database (Denmark)

    Krogager, Jens-Kristian

    Understanding how galaxies evolved from the early Universe through cosmic time is a fundamental part of modern astrophysics. In order to study this evolution it is important to sample the galaxies at various times in a consistent way through time. In regular luminosity selected samples, our...

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

    Science.gov (United States)

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

    1997-07-01

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

  19. The L_X-M relation of Clusters of Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Rykoff, E.S.; Evrard, A.E.; McKay, T.A.; Becker, M.R.; Johnston, D.E.; Koester, B.P.; Nord, B.; Rozo, E.; Sheldon, E.S.; Stanek, R.; Wechsler, R.H.

    2008-05-16

    We present a new measurement of the scaling relation between X-ray luminosity and total mass for 17,000 galaxy clusters in the maxBCG cluster sample. Stacking sub-samples within fixed ranges of optical richness, N200, we measure the mean 0.1-2.4 keV X-ray luminosity, , from the ROSAT All-Sky Survey. The mean mass, , is measured from weak gravitational lensing of SDSS background galaxies (Johnston et al. 2007). For 9 {le} N{sub 200} < 200, the data are well fit by a power-law, /10{sup 42} h{sup -2} ergs{sup -1} = (12.6{sub -1.3}{sup +1.4}(stat) {+-} 1.6 (sys)) (/10{sup 14} h{sup -1} M{sub {circle_dot}}){sup 1.65{+-}0.13}. The slope agrees to within 10% with previous estimates based on X-ray selected catalogs, implying that the covariance in L{sub X} and N{sub 200} at fixed halo mass is not large. The luminosity intercept is 30%, or 2{sigma}, lower than determined from the X-ray flux-limited sample of Reiprich & Boehringer (2002), assuming hydrostatic equilibrium. This slight difference could arise from a combination of Malmquist bias and/or systematic error in hydrostatic mass estimates, both of which are expected. The intercept agrees with that derived by Stanek et al. (2006) using a model for the statistical correspondence between clusters and halos in a WMAP3 cosmology with power spectrum normalization {sigma}{sub 8} = 0.85. Similar exercises applied to future data sets will allow constraints on the covariance among optical and hot gas properties of clusters at fixed mass.

  20. Galaxy Zoo: dust in spiral galaxies

    Science.gov (United States)

    Masters, Karen L.; Nichol, Robert; Bamford, Steven; Mosleh, Moein; Lintott, Chris J.; Andreescu, Dan; Edmondson, Edward M.; Keel, William C.; Murray, Phil; Raddick, M. Jordan; Schawinski, Kevin; Slosar, Anže; Szalay, Alexander S.; Thomas, Daniel; Vandenberg, Jan

    2010-05-01

    We investigate the effect of dust on spiral galaxies by measuring the inclination dependence of optical colours for 24276 well-resolved Sloan Digital Sky Survey (SDSS) galaxies visually classified via the Galaxy Zoo project. We find clear trends of reddening with inclination which imply a total extinction from face-on to edge-on of 0.7, 0.6, 0.5 and 0.4mag for the ugri passbands (estimating 0.3mag of extinction in z band). We split the sample into `bulgy' (early-type) and `discy' (late-type) spirals using the SDSS fracdeV (or fDeV) parameter and show that the average face-on colour of `bulgy' spirals is redder than the average edge-on colour of `discy' spirals. This shows that the observed optical colour of a spiral galaxy is determined almost equally by the spiral type (via the bulge-disc ratio and stellar populations), and reddening due to dust. We find that both luminosity and spiral type affect the total amount of extinction, with discy spirals at Mr ~ -21.5mag having the most reddening - more than twice as much as both the lowest luminosity and most massive, bulge-dominated spirals. An increase in dust content is well known for more luminous galaxies, but the decrease of the trend for the most luminous has not been observed before and may be related to their lower levels of recent star formation. We compare our results with the latest dust attenuation models of Tuffs et al. We find that the model reproduces the observed trends reasonably well but overpredicts the amount of u-band attenuation in edge-on galaxies. This could be an inadequacy in the Milky Way extinction law (when applied to external galaxies), but more likely indicates the need for a wider range of dust-star geometries. We end by discussing the effects of dust on large galaxy surveys and emphasize that these effects will become important as we push to higher precision measurements of galaxy properties and their clustering. This publication has been made possible by the participation of more than

  1. The environments of Markarian galaxies

    International Nuclear Information System (INIS)

    Mackenty, J.W.; Simpson, C.; Mclean, B.

    1990-01-01

    The extensively studied Markarian sample of 1500 ultraviolet excess galaxies contains many Seyfert, starburst, and peculiar galaxies. Using the 20 minute V plates obtained for the construction of the Hubble Space Telescope Guide Star Catalog, the authors investigated the morphologies of the Markarian galaxies and the environments in which they are located. The relationship between the types of nuclear activity and the morphologies and environments of the Markarian galaxies is discussed. The authors conclude that the type of nuclear activity present in the galaxies of the Markarian sample is not dependent on either the morphology or the local environment of the galaxy. This is not to imply that nuclear activity per se is not influenced by the environment in which the nucleus is located. Rather the type of nuclear activity (at least in the Markarian population) does not appear to be determined by the environment

  2. THE ATACAMA COSMOLOGY TELESCOPE: DYNAMICAL MASSES AND SCALING RELATIONS FOR A SAMPLE OF MASSIVE SUNYAEV-ZEL'DOVICH EFFECT SELECTED GALAXY CLUSTERS {sup ,}

    Energy Technology Data Exchange (ETDEWEB)

    Sifon, Cristobal; Barrientos, L. Felipe; Gonzalez, Jorge; Infante, Leopoldo; Duenner, Rolando [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Menanteau, Felipe; Hughes, John P.; Baker, Andrew J. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Hasselfield, Matthew [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Marriage, Tobias A.; Crichton, Devin; Gralla, Megan B. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218-2686 (United States); Addison, Graeme E.; Dunkley, Joanna [Sub-department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Battaglia, Nick; Bond, J. Richard; Hajian, Amir [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Das, Sudeep [Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States); Devlin, Mark J. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Hilton, Matt [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); and others

    2013-07-20

    We present the first dynamical mass estimates and scaling relations for a sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample consists of 16 massive clusters detected with the Atacama Cosmology Telescope (ACT) over a 455 deg{sup 2} area of the southern sky. Deep multi-object spectroscopic observations were taken to secure intermediate-resolution (R {approx} 700-800) spectra and redshifts for Almost-Equal-To 60 member galaxies on average per cluster. The dynamical masses M{sub 200c} of the clusters have been calculated using simulation-based scaling relations between velocity dispersion and mass. The sample has a median redshift z = 0.50 and a median mass M{sub 200c}{approx_equal}12 Multiplication-Sign 10{sup 14} h{sub 70}{sup -1} M{sub sun} with a lower limit M{sub 200c}{approx_equal}6 Multiplication-Sign 10{sup 14} h{sub 70}{sup -1} M{sub sun}, consistent with the expectations for the ACT southern sky survey. These masses are compared to the ACT SZE properties of the sample, specifically, the match-filtered central SZE amplitude y{sub 0}-tilde, the central Compton parameter y{sub 0}, and the integrated Compton signal Y{sub 200c}, which we use to derive SZE-mass scaling relations. All SZE estimators correlate with dynamical mass with low intrinsic scatter ({approx}< 20%), in agreement with numerical simulations. We explore the effects of various systematic effects on these scaling relations, including the correlation between observables and the influence of dynamically disturbed clusters. Using the three-dimensional information available, we divide the sample into relaxed and disturbed clusters and find that {approx}50% of the clusters are disturbed. There are hints that disturbed systems might bias the scaling relations, but given the current sample sizes, these differences are not significant; further studies including more clusters are required to assess the impact of these clusters on the scaling relations.

  3. Galaxy formation

    International Nuclear Information System (INIS)

    Gribbin, J.

    1979-01-01

    The current debate on the origin and evolution of galaxies is reviewed and evidence to support the so-called 'isothermal' and 'adiabatic' fluctuation models considered. It is shown that new theories have to explain the formation of both spiral and elliptical galaxies and the reason for their differences. It is stated that of the most recent models the best indicates that rotating spiral galaxies are formed naturally when gas concentrates in the centre of a great halo and forms stars while ellipticals are explained by later interactions between spiral galaxies and merging, which can cancel out the rotation while producing an elliptical galaxy in which the stars, coming from two original galaxies, follow very elliptical, anisotropic orbits. (UK)

  4. DISCOVERY OF ULTRA-FAST OUTFLOWS IN A SAMPLE OF BROAD-LINE RADIO GALAXIES OBSERVED WITH SUZAKU

    International Nuclear Information System (INIS)

    Tombesi, F.; Sambruna, R. M.; Mushotzky, R. F.; Reeves, J. N.; Gofford, J.; Braito, V.; Ballo, L.; Cappi, M.

    2010-01-01

    We present the results of a uniform and systematic search for blueshifted Fe K absorption lines in the X-ray spectra of five bright broad-line radio galaxies observed with Suzaku. We detect, for the first time in radio-loud active galactic nuclei (AGNs) at X-rays, several absorption lines at energies greater than 7 keV in three out of five sources, namely, 3C 111, 3C 120, and 3C 390.3. The lines are detected with high significance according to both the F-test and extensive Monte Carlo simulations. Their likely interpretation as blueshifted Fe XXV and Fe XXVI K-shell resonance lines implies an origin from highly ionized gas outflowing with mildly relativistic velocities, in the range v ≅ 0.04-0.15c. A fit with specific photoionization models gives ionization parameters in the range log ξ ≅ 4-5.6 erg s -1 cm and column densities of N H ≅ 10 22 -10 23 cm -2 . These characteristics are very similar to those of the ultra-fast outflows (UFOs) previously observed in radio-quiet AGNs. Their estimated location within ∼0.01-0.3 pc of the central super-massive black hole suggests a likely origin related with accretion disk winds/outflows. Depending on the absorber covering fraction, the mass outflow rate of these UFOs can be comparable to the accretion rate and their kinetic power can correspond to a significant fraction of the bolometric luminosity and is comparable to their typical jet power. Therefore, these UFOs can play a significant role in the expected feedback from the AGN to the surrounding environment and can give us further clues on the relation between the accretion disk and the formation of winds/jets in both radio-quiet and radio-loud AGNs.

  5. Orientations of galaxies in the Local Supercluster

    International Nuclear Information System (INIS)

    MacGillivray, H.T.; Dodd, R.J.; McNally, B.V.; Corwin, H.G. Jr.

    1982-01-01

    The distribution of position angles and ellipticities for a sample of 727 spiral and irregular galaxies, selected on the basis of brightness and radial velocity from the Second Reference Catalogue of Bright Galaxies, is analysed for non-random effects. A marginally significant tendency is found for galaxies to be aligned along the plane of the Local Supercluster. This preferential alignment effect is found to exist mainly for galaxies at high supergalactic latitude and for galaxies which are seen nearly edge-on. The results are interpreted as supporting the view that superclusters formed prior to the formation of the constituent galaxies and clusters. (author)

  6. Low surface brightness spiral galaxies

    International Nuclear Information System (INIS)

    Romanishin, W.

    1980-01-01

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

  7. The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements. II. The Full Sample of Reverberation-Mapped AGNs

    DEFF Research Database (Denmark)

    Bentz, Misty C.; Peterson, Bradley M.; Netzer, Hagai

    2009-01-01

    We present high-resolution Hubble Space Telescope images of all 35 active galactic nuclei (AGNs) with optical reverberation-mapping results, which we have modeled to create a nucleus-free image of each AGN host galaxy. From the nucleus-free images, we determine the host-galaxy contribution to gro...

  8. Galaxy formation

    International Nuclear Information System (INIS)

    Silk, J.; Di Cintio, A.; Dvorkin, I.

    2014-01-01

    Galaxy formation is at the forefront of observation and theory in cosmology. An improved understanding is essential for improving our knowledge both of the cosmological parameters, of the contents of the universe, and of our origins. In these lectures intended for graduate students, galaxy formation theory is reviewed and confronted with recent observational issues. In lecture 1, the following topics are presented: star formation considerations, including IMF, star formation efficiency and star formation rate, the origin of the galaxy luminosity function, and feedback in dwarf galaxies. In lecture 2, we describe formation of disks and massive spheroids, including the growth of supermassive black holes, negative feedback in spheroids, the AGN-star formation connection, star formation rates at high redshift and the baryon fraction in galaxies.

  9. SURFACE PHOTOMETRY OF LOW SURFACE BRIGHTNESS GALAXIES

    NARCIS (Netherlands)

    DEBLOK, WJG; VANDERHULST, JM; BOTHUN, GD

    1995-01-01

    Low surface brightness (LSB) galaxies are galaxies dominated by an exponential disc whose central surface brightness is much fainter than the value of mu(B)(0) = 21.65 +/- 0.30 mag arcsec(-2) found by Freeman. In this paper we present broadband photometry of a sample of 21 late-type LSB galaxies.

  10. The Metallicity of Void Dwarf Galaxies

    Science.gov (United States)

    Kreckel, K.; Croxall, K.; Groves, B.; van de Weygaert, R.; Pogge, R. W.

    2015-01-01

    The current ΛCDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the assumption that void galaxies are more pristine, we compare the evolutionary properties of a sample of dwarf galaxies selected specifically to lie in voids with a sample of similar isolated dwarf galaxies in average density environments. We measure gas-phase oxygen abundances and gas fractions for eight dwarf galaxies (Mr > -16.2), carefully selected to reside within the lowest density environments of seven voids, and apply the same calibrations to existing samples of isolated dwarf galaxies. We find no significant difference between these void dwarf galaxies and the isolated dwarf galaxies, suggesting that dwarf galaxy chemical evolution proceeds independent of the large-scale environment. While this sample is too small to draw strong conclusions, it suggests that external gas accretion is playing a limited role in the chemical evolution of these systems, and that this evolution is instead dominated mainly by the internal secular processes that are linking the simultaneous growth and enrichment of these galaxies.

  11. Dark matter halo properties from galaxy-galaxy lensing

    International Nuclear Information System (INIS)

    Brimioulle, Fabrice

    2013-01-01

    redshift and galaxy shape catalogs. The complete galaxy sample consists of a total number of 5 x 10 6 lens galaxies within a redshift range of 0.05 phot ≤1 and 1.7 x 10 6 corresponding source galaxies with redshifts of 0.05 phot ≤2 and successfully extracted shapes. Assuming that the galaxy halos can be described by analytic profiles, the scaling relations with absolute luminosity for the galaxy masses, their mass-to-light ratios and the corresponding halo parameters have been extracted. Based on the obtained scaling relations, the average values for the corresponding halo parameters and the mean galaxy masses for a given luminosity were derived as a function of considered halo model, the galaxy SED and the local environment density. We obtain a total mass of M total =23.2 +2.8 -2.5 x 10 11 h -1 M s un for an average galaxy with chosen reference luminosity of L * =1.6 x 10 10 h -2 L s un. In contrast, the mean total masses for red galaxies of same luminosity exceed the value of the average galaxy about 130%, while the mass of a blue galaxy is about 65% below the value of an average fiducial galaxy. Investigating the influence of the environmental density on the galaxy properties we observe a significant increase of the total integrated masses with galaxy density, however the velocity dispersions are not affected. This indicates that the central galaxy matter density mostly depends on the galaxy luminosity but not on the environment. Simulations based on the extracted scientific results were built, verifying the robustness of the scientific results. They give a clear hint that multiple deflections on different lens galaxies have to be properly accounted for in order to avoid systematically biased results.

  12. The intrinsic shape of galaxies in SDSS/Galaxy Zoo

    Science.gov (United States)

    Rodríguez, Silvio; Padilla, Nelson D.

    2013-09-01

    By modelling the axis ratio distribution of Sloan Digital Sky Survey (SDSS) Data Release 8 galaxies, we find the intrinsic 3D shapes of spirals and ellipticals. We use morphological information from the Galaxy Zoo project and assume a non-parametric distribution intrinsic of shapes, while taking into account dust extinction. We measure the dust extinction of the full sample of spiral galaxies and find a smaller value than previous estimations, with an edge-on extinction of E_0 = 0.284^{+0.015}_{-0.026} in the SDSS r band. We also find that the distribution of minor to major axis ratio has a mean value of 0.267 ± 0.009, slightly larger than previous estimates mainly due to the lower extinction used; the same affects the circularity of galactic discs, which are found to be less round in shape than in previous studies, with a mean ellipticity of 0.215 ± 0.013. For elliptical galaxies, we find that the minor to major axis ratio, with a mean value of 0.584 ± 0.006, is larger than previous estimations due to the removal of spiral interlopers present in samples with morphological information from photometric profiles. These interlopers are removed when selecting ellipticals using Galaxy Zoo data. We find that the intrinsic shapes of galaxies and their dust extinction vary with absolute magnitude, colour and physical size. We find that bright elliptical galaxies are more spherical than faint ones, a trend that is also present with galaxy size, and that there is no dependence of elliptical galaxy shape with colour. For spiral galaxies, we find that the reddest ones have higher dust extinction as expected, due to the fact that this reddening is mainly due to dust. We also find that the thickness of discs increases with luminosity and size, and that brighter, smaller and redder galaxies have less round discs.

  13. Accretion Properties of a Sample of Hard X-Ray (<60 keV) Selected Seyfert 1 Galaxies

    Science.gov (United States)

    Wang, J.; Mao, Y. F.; Wei, J. Y.

    2009-02-01

    We examine the accretion properties in a sample of 42 hard (3-60 keV) X-ray selected nearby broad-line active galactic nuclei (AGNs). The energy range in the sample is harder than that usually used in similar previous studies. These AGNs are mainly complied from the RXTE All Sky Survey, and complemented by the released INTEGRAL AGN catalog. The black hole masses, bolometric luminosities of AGN, and Eddington ratios are derived from their optical spectra in terms of the broad Hβ emission line. The tight correlation between the hard X-ray (3-20 keV) and bolometric/line luminosity is well identified in our sample. Also identified is a strong inverse Baldwin relationship of the Hβ emission line. In addition, all of these hard X-ray AGNs are biased toward luminous objects with a high Eddington ratio (mostly between 0.01 and 0.1) and a low column density (Simbol-X, and NeXT. Finally, the correlation between RFe (= optical Fe II/Hβ) and disk temperature as assessed by T vprop (L/L Edd)M -1 BH leads us to suggest that the strength of the Fe II emission is mainly determined by the shape of the ionizing spectrum.

  14. Filaments and clusters of galaxies

    International Nuclear Information System (INIS)

    Soltan, A.

    1987-01-01

    A statistical test to investigate filaments of galaxies is performed. Only particular form of filaments is considered, viz. filaments connecting Abell clusters of galaxies. Relative position of triplets ''cluster - field object - cluster'' is analysed. Though neither cluster sample nor field object sample are homogeneous and complete only peculiar form of selection effects could affect the present statistics. Comparison of observational data with simulations shows that less than 15 per cent of all field galaxies is concentrated in filaments connecting rich clusters. Most of the field objects used in the analysis are not normal galaxies and it is possible that this conclusion is not in conflict with apparent filaments seen in the Lick counts and in some nearby 3D maps of the galaxy distribution. 26 refs., 2 figs. (author)

  15. The Carnegie-Spitzer-IMACS redshift survey of galaxy evolution since z = 1.5. I. Description and methodology

    Energy Technology Data Exchange (ETDEWEB)

    Kelson, Daniel D.; Williams, Rik J.; Dressler, Alan; McCarthy, Patrick J.; Shectman, Stephen A.; Mulchaey, John S.; Villanueva, Edward V.; Crane, Jeffrey D.; Quadri, Ryan F. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2014-03-10

    We describe the Carnegie-Spitzer-IMACS (CSI) Survey, a wide-field, near-IR selected spectrophotometric redshift survey with the Inamori Magellan Areal Camera and Spectrograph (IMACS) on Magellan-Baade. By defining a flux-limited sample of galaxies in Spitzer Infrared Array Camera 3.6 μm imaging of SWIRE fields, the CSI Survey efficiently traces the stellar mass of average galaxies to z ∼ 1.5. This first paper provides an overview of the survey selection, observations, processing of the photometry and spectrophotometry. We also describe the processing of the data: new methods of fitting synthetic templates of spectral energy distributions are used to derive redshifts, stellar masses, emission line luminosities, and coarse information on recent star formation. Our unique methodology for analyzing low-dispersion spectra taken with multilayer prisms in IMACS, combined with panchromatic photometry from the ultraviolet to the IR, has yielded high-quality redshifts for 43,347 galaxies in our first 5.3 deg{sup 2} of the SWIRE XMM-LSS field. We use three different approaches to estimate our redshift errors and find robust agreement. Over the full range of 3.6 μm fluxes of our selection, we find typical redshift uncertainties of σ {sub z}/(1 + z) ≲ 0.015. In comparisons with previously published spectroscopic redshifts we find scatters of σ {sub z}/(1 + z) = 0.011 for galaxies at 0.7 ≤ z ≤ 0.9, and σ {sub z}/(1 + z) = 0.014 for galaxies at 0.9 ≤ z ≤ 1.2. For galaxies brighter and fainter than i = 23 mag, we find σ {sub z}/(1 + z) = 0.008 and σ {sub z}/(1 + z) = 0.022, respectively. Notably, our low-dispersion spectroscopy and analysis yields comparable redshift uncertainties and success rates for both red and blue galaxies, largely eliminating color-based systematics that can seriously bias observed dependencies of galaxy evolution on environment.

  16. Deficiency of normal galaxies among Markaryan galaxies

    International Nuclear Information System (INIS)

    Iyeveer, M.M.

    1986-01-01

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

  17. Baryon Content in a Sample of 91 Galaxy Clusters Selected by the South Pole Telescope at 0.2 < z < 1.25

    Science.gov (United States)

    Chiu, I.; Mohr, J. J.; McDonald, M.; Bocquet, S.; Desai, S.; Klein, M.; Israel, H.; Ashby, M. L. N.; Stanford, A.; Benson, B. A.; Brodwin, M.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bayliss, M.; Benoit-Lévy, A.; Bertin, E.; Bleem, L.; Brooks, D.; Buckley-Geer, E.; Bulbul, E.; Capasso, R.; Carlstrom, J. E.; Rosell, A. Carnero; Carretero, J.; Castander, F. J.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Davis, C.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Drlica-Wagner, A.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; García-Bellido, J.; Garmire, G.; Gaztanaga, E.; Gerdes, D. W.; Gonzalez, A.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gupta, N.; Gutierrez, G.; Hlavacek-L, J.; Honscheid, K.; James, D. J.; Jeltema, T.; Kraft, R.; Krause, E.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lahav, O.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Miquel, R.; Murray, S.; Nord, B.; Ogando, R. L. C.; Plazas, A. A.; Rapetti, D.; Reichardt, C. L.; Romer, A. K.; Roodman, A.; Sanchez, E.; Saro, A.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sharon, K.; Smith, R. C.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Stalder, B.; Stern, C.; Strazzullo, V.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Vikram, V.; Walker, A. R.; Weller, J.; Zhang, Y.

    2018-05-01

    We estimate total mass (M500), intracluster medium (ICM) mass (MICM) and stellar mass (M⋆) in a Sunyaev-Zel'dovich effect (SZE) selected sample of 91 galaxy clusters with masses M500 ≳ 2.5 × 1014M⊙ and redshift 0.2 baryonic mass and the cold baryonic fraction with cluster halo mass and redshift. We find significant departures from self-similarity in the mass scaling for all quantities, while the redshift trends are all statistically consistent with zero, indicating that the baryon content of clusters at fixed mass has changed remarkably little over the past ≈9 Gyr. We compare our results to the mean baryon fraction (and the stellar mass fraction) in the field, finding that these values lie above (below) those in cluster virial regions in all but the most massive clusters at low redshift. Using a simple model of the matter assembly of clusters from infalling groups with lower masses and from infalling material from the low density environment or field surrounding the parent halos, we show that the measured mass trends without strong redshift trends in the stellar mass scaling relation could be explained by a mass and redshift dependent fractional contribution from field material. Similar analyses of the ICM and baryon mass scaling relations provide evidence for the so-called "missing baryons" outside cluster virial regions.

  18. Galaxy Formation

    CERN Document Server

    Longair, Malcolm S

    2008-01-01

    This second edition of Galaxy Formation is an up-to-date text on astrophysical cosmology, expounding the structure of the classical cosmological models from a contemporary viewpoint. This forms the background to a detailed study of the origin of structure and galaxies in the Universe. The derivations of many of the most important results are derived by simple physical arguments which illuminate the results of more advanced treatments. A very wide range of observational data is brought to bear upon these problems, including the most recent results from WMAP, the Hubble Space Telescope, galaxy surveys like the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey, studies of Type 1a supernovae, and many other observations.

  19. Polarimetry and Unification of Low-Redshift Radio Galaxies

    International Nuclear Information System (INIS)

    Cohen, Marshall H.; Ogle, Patrick M.; Tran, Hien D.; Goodrich, Robert W.; Miller, Joseph S.

    1999-01-01

    We have made high-quality measurements of the polarization spectra of 13 FR II radio galaxies and taken polarization images for 11 of these with the Keck telescopes. Seven of the eight narrow-line radio galaxies (NLRGs) are polarized, and six of the seven show prominent broad Balmer lines in polarized light. The broad lines are also weakly visible in total flux. Some of the NLRGs show bipolar regions with roughly circumferential polarization vectors, revealing a large reflection nebula illuminated by a central source. Our observations powerfully support the hidden quasar hypothesis for some NLRGs. According to this hypothesis, the continuum and broad lines are blocked by a dusty molecular torus, but can be seen by reflected, hence polarized, light. Classification as a NLRG, a broad-line radio galaxy (BLRG), or a quasar therefore depends on orientation. However, not all objects fit into this unification scheme. Our sample is biased toward objects known in advance to be polarized, but the combination of our results with the 1996 findings of Hill, Goodrich, and DePoy show that at least six out of a complete, volume and flux-limited sample of nine FR II NLRGs have broad lines, seen either in polarization or Pα.The BLRGs in our sample range from 3C 382, which has a quasar-like spectrum, to the highly reddened IRAS source FSC 2217+259. This reddening sequence suggests a continuous transition from unobscured quasar to reddened BLRG to NLRG. Apparently the obscuring torus does not have a distinct edge. The BLRGs have polarization images that are consistent with a point source broadened by seeing and diluted by starlight. We do not detect extended nebular or scattered emission, perhaps because it is swamped by the nuclear source. Our starlight-corrected BLRG spectra can be explained with a two-component model: a quasar viewed through dust and quasar light scattered by dust. The direct flux is more reddened than the scattered flux, causing the polarization to rise steeply

  20. Polarimetry and Unification of Low-Redshift Radio Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Marshall H.; Ogle, Patrick M.; Tran, Hien D.; Goodrich, Robert W.; Miller, Joseph S.

    1999-11-01

    We have made high-quality measurements of the polarization spectra of 13 FR II radio galaxies and taken polarization images for 11 of these with the Keck telescopes. Seven of the eight narrow-line radio galaxies (NLRGs) are polarized, and six of the seven show prominent broad Balmer lines in polarized light. The broad lines are also weakly visible in total flux. Some of the NLRGs show bipolar regions with roughly circumferential polarization vectors, revealing a large reflection nebula illuminated by a central source. Our observations powerfully support the hidden quasar hypothesis for some NLRGs. According to this hypothesis, the continuum and broad lines are blocked by a dusty molecular torus, but can be seen by reflected, hence polarized, light. Classification as a NLRG, a broad-line radio galaxy (BLRG), or a quasar therefore depends on orientation. However, not all objects fit into this unification scheme. Our sample is biased toward objects known in advance to be polarized, but the combination of our results with the 1996 findings of Hill, Goodrich, and DePoy show that at least six out of a complete, volume and flux-limited sample of nine FR II NLRGs have broad lines, seen either in polarization or P{alpha}.The BLRGs in our sample range from 3C 382, which has a quasar-like spectrum, to the highly reddened IRAS source FSC 2217+259. This reddening sequence suggests a continuous transition from unobscured quasar to reddened BLRG to NLRG. Apparently the obscuring torus does not have a distinct edge. The BLRGs have polarization images that are consistent with a point source broadened by seeing and diluted by starlight. We do not detect extended nebular or scattered emission, perhaps because it is swamped by the nuclear source. Our starlight-corrected BLRG spectra can be explained with a two-component model: a quasar viewed through dust and quasar light scattered by dust. The direct flux is more reddened than the scattered flux, causing the polarization to rise

  1. Stellar Populations in Elliptical Galaxies

    Science.gov (United States)

    Angeletti, Lucio; Giannone, Pietro

    The R1/n law for the radial surface brightness of elliptical galaxies and the "Best Accretion Model" together with the "Concentration Model" have been combined in order to determine the mass and dynamical structure of largely-populated star systems. Families of models depending on four parameters have been used to fit the observed surface radial profiles of some spectro-photometric indices of a sample of eleven galaxies. We present the best agreements of the spectral index Mg2 with observations for three selected galaxies representative of the full sample. For them we have also computed the spatial distributions of the metal abundances, which are essential to achieve a population synthesis.

  2. HUBBLE SPACE TELESCOPE ACS IMAGING OF THE GOALS SAMPLE: QUANTITATIVE STRUCTURAL PROPERTIES OF NEARBY LUMINOUS INFRARED GALAXIES WITH L{sub IR} > 10{sup 11.4} L{sub Sun}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.-C.; Evans, A. S.; Privon, G. C., E-mail: dkim@nrao.edu, E-mail: aevans@virginia.edu, E-mail: gcp8y@virginia.edu [Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904 (United States); and others

    2013-05-10

    A Hubble Space Telescope/Advanced Camera for Surveys study of the structural properties of 85 luminous and ultraluminous (L{sub IR} > 10{sup 11.4} L{sub Sun }) infrared galaxies (LIRGs and ULIRGs) in the Great Observatories All-sky LIRG Survey (GOALS) sample is presented. Two-dimensional GALFIT analysis has been performed on F814W ''I-band'' images to decompose each galaxy, as appropriate, into bulge, disk, central point-spread function (PSF) and stellar bar components. The fraction of bulge-less disk systems is observed to be higher in LIRGs (35%) than in ULIRGs (20%), with the disk+bulge systems making up the dominant fraction of both LIRGs (55%) and ULIRGs (45%). Further, bulge+disk systems are the dominant late-stage merger galaxy type and are the dominant type for LIRGs and ULIRGs at almost every stage of galaxy-galaxy nuclear separation. The mean I-band host absolute magnitude of the GOALS galaxies is -22.64 {+-} 0.62 mag (1.8{sup +1.4}{sub -0.4} L{sup *}{sub I}), and the mean bulge absolute magnitude in GOALS galaxies is about 1.1 mag fainter than the mean host magnitude. Almost all ULIRGs have bulge magnitudes at the high end (-20.6 to -23.5 mag) of the GOALS bulge magnitude range. Mass ratios in the GOALS binary systems are consistent with most of the galaxies being the result of major mergers, and an examination of the residual-to-host intensity ratios in GOALS binary systems suggests that smaller companions suffer more tidal distortion than the larger companions. We find approximately twice as many bars in GOALS disk+bulge systems (32.8%) than in pure-disk mergers (15.9%) but most of the disk+bulge systems that contain bars are disk-dominated with small bulges. The bar-to-host intensity ratio, bar half-light radius, and bar ellipticity in GOALS galaxies are similar to those found in nearby spiral galaxies. The fraction of stellar bars decreases toward later merger stages and smaller nuclear separations, indicating that bars are

  3. Photometric properties of galaxies in the SDSS

    Science.gov (United States)

    Hogg, D. W.; Blanton, M.; SDSS Collaboration

    2001-12-01

    We analyze the number density distribution of galaxy properties in a sample of 8x 104 galaxies from the Sloan Digital Sky Survey, in the redshift range 0.02calculated for each galaxy. The photometry is of excellent quality; every galaxy has CCD imaging with signal-to-noise for the flux well above 100. The distribution of galaxies in the (six-dimensional) space spanned by four colors, central surface-brightness, and radial concentration is described and analyzed, with the following results: \\textsl{(1)} The galaxies occupy only a small part of the six-dimensional space. \\textsl{(2)} The distribution of galaxy number density in the space is a strong function of intrinsic galaxy luminosity. \\textsl{(3)} Elliptical (or early type) and spiral (or late type) galaxies are clearly separated in the space. The ratio of early-type to late-type galaxy contributions to the luminosity density of the Universe is computed, as a function of wavelength. At 1 {μm }, early-type galaxies dominate the luminosity density. \\textsl{(4)} Outliers in color tend to be lower surface-brightness galaxies. Funding for the SDSS has been provided by the Alfred P. Sloan Foundation, the SDSS member institutions, NASA, NSF, DOE, the Japanese Monbukagakusho, and the Max Planck Society. This research has been supported by the NYU Faculty of Arts and Sciences.

  4. INFERENCES ON THE DISTRIBUTION OF Ly{alpha} EMISSION OF z {approx} 7 AND z {approx} 8 GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Treu, Tommaso; Auger, Matthew W. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Trenti, Michele [University of Colorado, Center for Astrophysics and Space Astronomy, 389-UCB, Boulder, CO 80309 (United States); Stiavelli, Massimo; Bradley, Larry D., E-mail: tt@physics.ucsb.edu [Space Telescope Science Institute, 3700 San Martin Dr, Baltimore MD 21218 (United States)

    2012-03-01

    Spectroscopic confirmation of galaxies at z {approx} 7 and above has been extremely difficult, owing to a drop in intensity of Ly{alpha} emission in comparison with samples at z {approx} 6. This crucial finding could potentially signal the ending of cosmic reionization. However, it is based on small data sets, often incomplete and heterogeneous in nature. We introduce a flexible Bayesian framework, useful to interpret such evidence. Within this framework, we implement two simple phenomenological models: a smooth one where the distribution of Ly{alpha} is attenuated by a factor {epsilon}{sub s} with respect to z {approx} 6 and a patchy one where a fraction {epsilon}{sub p} is absorbed/non-emitted while the rest is unabsorbed. From a compilation of 39 observed z {approx} 7 galaxies, we find {epsilon}{sub s} = 0.69 {+-} 0.12 and {epsilon}{sub p} = 0.66 {+-} 0.16. The models can be used to compute fractions of emitters above any equivalent width W. For W > 25 A, we find X{sup 25}{sub z=7} = 0.37 {+-} 0.11 (0.14 {+-} 0.06) for galaxies fainter (brighter) than M{sub UV} = -20.25 for the patchy model, consistent with previous work, but with smaller uncertainties by virtue of our full use of the data. At z {approx} 8 we combine new deep (5{sigma} flux limit 10{sup -17} erg s{sup -1} cm{sup -2}) Keck/NIRSPEC observations of a bright Y-dropout identified by our Brightest of Reionization Galaxies Survey, with those of three objects from the literature and find that the inference is inconclusive. We compute predictions for future near-infrared spectroscopic surveys and show that it is challenging but feasible to constrain the distribution of Ly{alpha} emitters at z {approx} 8 and distinguish between models.

  5. INFERENCES ON THE DISTRIBUTION OF Lyα EMISSION OF z ∼ 7 AND z ∼ 8 GALAXIES

    International Nuclear Information System (INIS)

    Treu, Tommaso; Auger, Matthew W.; Trenti, Michele; Stiavelli, Massimo; Bradley, Larry D.

    2012-01-01

    Spectroscopic confirmation of galaxies at z ∼ 7 and above has been extremely difficult, owing to a drop in intensity of Lyα emission in comparison with samples at z ∼ 6. This crucial finding could potentially signal the ending of cosmic reionization. However, it is based on small data sets, often incomplete and heterogeneous in nature. We introduce a flexible Bayesian framework, useful to interpret such evidence. Within this framework, we implement two simple phenomenological models: a smooth one where the distribution of Lyα is attenuated by a factor ε s with respect to z ∼ 6 and a patchy one where a fraction ε p is absorbed/non-emitted while the rest is unabsorbed. From a compilation of 39 observed z ∼ 7 galaxies, we find ε s = 0.69 ± 0.12 and ε p = 0.66 ± 0.16. The models can be used to compute fractions of emitters above any equivalent width W. For W > 25 Å, we find X 25 z=7 = 0.37 ± 0.11 (0.14 ± 0.06) for galaxies fainter (brighter) than M UV = –20.25 for the patchy model, consistent with previous work, but with smaller uncertainties by virtue of our full use of the data. At z ∼ 8 we combine new deep (5σ flux limit 10 –17 erg s –1 cm –2 ) Keck/NIRSPEC observations of a bright Y-dropout identified by our Brightest of Reionization Galaxies Survey, with those of three objects from the literature and find that the inference is inconclusive. We compute predictions for future near-infrared spectroscopic surveys and show that it is challenging but feasible to constrain the distribution of Lyα emitters at z ∼ 8 and distinguish between models.

  6. Baryon Content in a Sample of 91 Galaxy Clusters Selected by the South Pole Telescope at 0.2 < z < 1.25

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, I.; et al.

    2017-11-02

    We estimate total mass ($M_{500}$), intracluster medium (ICM) mass ($M_{\\mathrm{ICM}}$) and stellar mass ($M_{\\star}$) in a Sunyaev-Zel'dovich effect (SZE) selected sample of 91 galaxy clusters with masses $M_{500}\\gtrsim2.5\\times10^{14}M_{\\odot}$ and redshift $0.2 < z < 1.25$ from the 2500 deg$^2$ South Pole Telescope SPT-SZ survey. The total masses $M_{500}$ are estimated from the SZE observable, the ICM masses $M_{\\mathrm{ICM}}$ are obtained from the analysis of $Chandra$ X-ray observations, and the stellar masses $M_{\\star}$ are derived by fitting spectral energy distribution templates to Dark Energy Survey (DES) $griz$ optical photometry and $WISE$ or $Spitzer$ near-infrared photometry. We study trends in the stellar mass, the ICM mass, the total baryonic mass and the cold baryonic fraction with cluster mass and redshift. We find significant departures from self-similarity in the mass scaling for all quantities, while the redshift trends are all statistically consistent with zero, indicating that the baryon content of clusters at fixed mass has changed remarkably little over the past $\\approx9$ Gyr. We compare our results to the mean baryon fraction (and the stellar mass fraction) in the field, finding that these values lie above (below) those in cluster virial regions in all but the most massive clusters at low redshift. Using a simple model of the matter assembly of clusters from infalling groups with lower masses and from infalling material from the low density environment or field surrounding the parent halos, we show that the strong mass and weak redshift trends in the stellar mass scaling relation suggest a mass and redshift dependent fractional contribution from field material. Similar analyses of the ICM and baryon mass scaling relations provide evidence for the so-called 'missing baryons' outside cluster virial regions.

  7. Fundamental Properties of the SHIELD Galaxies

    Science.gov (United States)

    Cannon, John; Adams, Betsey; Giovanelli, Riccardo; Haynes, Martha; Jones, Michael; McQuinn, Kristen; Rhode, Katherine; Salzer, John; Skillman, Evan

    2018-05-01

    The ALFALFA survey has significantly advanced our knowledge of the HI mass function (HIMF), particularly at the low mass end. From the ALFALFA survey, we have constructed a sample of all of the galaxies with HI masses less than 20 million solar masses. Observations of this 82 galaxy sample allow, for the first time, a characterization of the lowest HI mass galaxies at redshift zero. Specifically, this sample can be used to determine the low HI-mass ends of various fundamental scaling relations, including the critical baryonic Tully Fisher relation (BTFR) and the mass-metallicity (M-Z) relation. The M-Z relation and the BTFR are cosmologically important, but current samples leave the low-mass parameter spaces severely underpopulated. A full understanding of these relationships depends critically on accurate stellar masses of this complete sample of uniformly-selected galaxies. Here, we request imaging of the 70 galaxies in our sample that have not been observed with Spitzer. The proposed imaging will allow us to measure stellar masses and inclinations of the sample galaxies using a uniform observational approach. Comparison with (existing and in progress) interferometric HI imaging and with ground-based optical imaging and spectroscopy will enable a robust mass decomposition in each galaxy and accurate placements on the aforementioned scaling relationships. The observations proposed here will allow us to populate the mass continuum between mini-halos and bona fide dwarf galaxies, and to address a range of fundamental questions in galaxy formation and near-field cosmology.

  8. MASS CALIBRATION AND COSMOLOGICAL ANALYSIS OF THE SPT-SZ GALAXY CLUSTER SAMPLE USING VELOCITY DISPERSION σ v AND X-RAY Y X MEASUREMENTS

    International Nuclear Information System (INIS)

    Bocquet, S.; Saro, A.; Mohr, J. J.; Bazin, G.; Chiu, I.; Desai, S.; Aird, K. A.; Ashby, M. L. N.; Bayliss, M.; Bautz, M.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Brodwin, M.; Cho, H. M.; Clocchiatti, A.; De Haan, T.

    2015-01-01

    We present a velocity-dispersion-based mass calibration of the South Pole Telescope Sunyaev-Zel'dovich effect survey (SPT-SZ) galaxy cluster sample. Using a homogeneously selected sample of 100 cluster candidates from 720 deg 2 of the survey along with 63 velocity dispersion (σ v ) and 16 X-ray Y X measurements of sample clusters, we simultaneously calibrate the mass-observable relation and constrain cosmological parameters. Our method accounts for cluster selection, cosmological sensitivity, and uncertainties in the mass calibrators. The calibrations using σ v and Y X are consistent at the 0.6σ level, with the σ v calibration preferring ∼16% higher masses. We use the full SPT CL data set (SZ clusters+σ v +Y X ) to measure σ 8 (Ω m /0.27) 0.3 = 0.809 ± 0.036 within a flat ΛCDM model. The SPT cluster abundance is lower than preferred by either the WMAP9 or Planck+WMAP9 polarization (WP) data, but assuming that the sum of the neutrino masses is ∑m ν = 0.06 eV, we find the data sets to be consistent at the 1.0σ level for WMAP9 and 1.5σ for Planck+WP. Allowing for larger ∑m ν further reconciles the results. When we combine the SPT CL and Planck+WP data sets with information from baryon acoustic oscillations and Type Ia supernovae, the preferred cluster masses are 1.9σ higher than the Y X calibration and 0.8σ higher than the σ v calibration. Given the scale of these shifts (∼44% and ∼23% in mass, respectively), we execute a goodness-of-fit test; it reveals no tension, indicating that the best-fit model provides an adequate description of the data. Using the multi-probe data set, we measure Ω m = 0.299 ± 0.009 and σ 8 = 0.829 ± 0.011. Within a νCDM model we find ∑m ν = 0.148 ± 0.081 eV. We present a consistency test of the cosmic growth rate using SPT clusters. Allowing both the growth index γ and the dark energy equation-of-state parameter w to vary, we find γ = 0.73 ± 0.28 and w = –1.007 ± 0.065, demonstrating that the

  9. The Intrinsic Shape of Galaxies in SDSS/Galaxy Zoo

    OpenAIRE

    Rodríguez, Silvio; Padilla, Nelson D.

    2013-01-01

    By modelling the axis ratio distribution of SDSS DR8 galaxies we find the intrinsic 3D shapes of spirals and ellipticals. We use morphological information from the Galaxy Zoo project and assume a non-parametric distribution intrinsic of shapes, while taking into account dust extinction. We measure the dust extinction of the full sample of spiral galaxies and find a smaller value than previous estimations, with an edge-on extinction of $E_0 = 0.284^{+0.015}_{-0.026}$ in the SDSS r band. We als...

  10. Superclusters and galaxy formation

    International Nuclear Information System (INIS)

    Einasto, J.; Joeveer, M.; Saar, E.

    1979-01-01

    The spatial distribution of Galaxies and Galaxy congestions in the southern galactic hemisphere is studied. The rich galaxy congestions, containing many elliptic Galaxies and radiogalaxies, are linked with each other by chains of scanty congestions with moderate content of elliptic Galaxies and radiogalaxies. The flat formation, linking the density pikes and the intermediate chains, can reasonably be called supercongestion. In the central region of supercongestions there is a thin layer of Galaxies consisting of only spiral Galaxies. The neighbouring supercongestions touch each other, while the intersupercongestion space contains no Galaxy congestions and almost no Galaxies. It is shown that such a structure was, apparently, formed before the formation of Galaxies

  11. The effects of assembly bias on the inference of matter clustering from galaxy-galaxy lensing and galaxy clustering

    Science.gov (United States)

    McEwen, Joseph E.; Weinberg, David H.

    2018-04-01

    The combination of galaxy-galaxy lensing (GGL) and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modeling can extend the approach down to nonlinear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with large scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older halos affects the cutoff of the mean occupation function for central galaxies, with halos in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We introduce an extended, environment dependent HOD (EDHOD) prescription to describe these results and fit galaxy correlation measurements. Crucially, we find that the galaxy-matter cross-correlation coefficient, rgm(r) ≡ ξgm(r) . [ξmm(r)ξgg(r)]-1/2, is insensitive to assembly bias on scales r ≳ 1 h^{-1} Mpc, even though ξgm(r) and ξgg(r) are both affected individually. We can therefore recover the correct ξmm(r) from the HW13 galaxy-galaxy and galaxy-matter correlations using either a standard HOD or EDHOD fitting method. For Mr ≤ -19 or Mr ≤ -20 samples the recovery of ξmm(r) is accurate to 2% or better. For a sample of red Mr ≤ -20 galaxies we achieve 2% recovery at r ≳ 2 h^{-1} Mpc with EDHOD modeling but lower accuracy at smaller scales or with a standard HOD fit. Most of our mock galaxy samples are consistent with rgm = 1 down to r = 1h-1Mpc, to within the uncertainties set by our finite simulation volume.

  12. The effects of assembly bias on the inference of matter clustering from galaxy-galaxy lensing and galaxy clustering

    Science.gov (United States)

    McEwen, Joseph E.; Weinberg, David H.

    2018-07-01

    The combination of galaxy-galaxy lensing and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modelling can extend the approach down to non-linear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with the large-scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older haloes affects the cutoff of the mean occupation function ⟨Ncen(Mmin)⟩ for central galaxies, with haloes in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We introduce an extended, environment-dependent HOD (EDHOD) prescription to describe these results and fit galaxy correlation measurements. Crucially, we find that the galaxy-matter cross-correlation coefficient, rgm(r) ≡ ξgm(r) . [ξmm(r)ξgg(r)]-1/2, is insensitive to assembly bias on scales r ≳ 1 h-1 Mpc, even though ξgm(r) and ξgg(r) are both affected individually. We can therefore recover the correct ξmm(r) from the HW13 galaxy-galaxy and galaxy-matter correlations using either a standard HOD or EDHOD fitting method. For Mr ≤ -19 or Mr ≤ -20 samples the recovery of ξmm(r) is accurate to 2 per cent or better. For a sample of red Mr ≤ -20 galaxies, we achieve 2 per cent recovery at r ≳ 2 h-1 Mpc with EDHOD modelling but lower accuracy at smaller scales or with a standard HOD fit. Most of our mock galaxy samples are consistent with rgm = 1 down to r = 1 h-1 Mpc, to within the uncertainties set by our finite simulation volume.

  13. MID-INFRARED ATOMIC FINE-STRUCTURE EMISSION-LINE SPECTRA OF LUMINOUS INFRARED GALAXIES: SPITZER/IRS SPECTRA OF THE GOALS SAMPLE

    Energy Technology Data Exchange (ETDEWEB)

    Inami, H. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Armus, L.; Stierwalt, S.; Díaz-Santos, T.; Surace, J.; Howell, J.; Marshall, J. [Spitzer Science Center, California Institute of Technology, CA 91125 (United States); Charmandaris, V. [Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, GR-71003 Heraklion (Greece); Groves, B. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Kewley, L. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Petric, A. [Department of Astronomy, California Institute of Technology, MS 320-47, Pasadena, CA 91125 (United States); Rich, J. [The Observatories, Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Haan, S. [CSIRO Astronomy and Space Science, Marsfield, NSW 2122 (Australia); Evans, A. S. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States); Mazzarella, J.; Lord, S. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Appleton, P. [NASA Herschel Science Center, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Spoon, H. [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States); Frayer, D. [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Matsuhara, H., E-mail: inami@noao.edu [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (Japan); and others

    2013-11-10

    We present the data and our analysis of mid-infrared atomic fine-structure emission lines detected in Spitzer/Infrared Spectrograph high-resolution spectra of 202 local Luminous Infrared Galaxies (LIRGs) observed as part of the Great Observatories All-sky LIRG Survey (GOALS). We readily detect emission lines of [S IV], [Ne II], [Ne V], [Ne III], [S III]{sub 18.7{sub μm}}, [O IV], [Fe II], [S III]{sub 33.5{sub μm}}, and [Si II]. More than 75% of these galaxies are classified as starburst-dominated sources in the mid-infrared, based on the [Ne V]/[Ne II] line flux ratios and equivalent width of the 6.2 μm polycyclic aromatic hydrocarbon feature. We compare ratios of the emission-line fluxes to those predicted from stellar photo-ionization and shock-ionization models to constrain the physical and chemical properties of the gas in the starburst LIRG nuclei. Comparing the [S IV]/[Ne II] and [Ne III]/[Ne II] line ratios to the Starburst99-Mappings III models with an instantaneous burst history, the emission-line ratios suggest that the nuclear starbursts in our LIRGs have ages of 1-4.5 Myr, metallicities of 1-2 Z{sub ☉}, and ionization parameters of 2-8 × 10{sup 7} cm s{sup –1}. Based on the [S III]{sub 33.5{sub μm}}/[S III]{sub 18.7{sub μm}} ratios, the electron density in LIRG nuclei is typically one to a few hundred cm{sup –3}, with a median electron density of ∼300 cm{sup –3}, for those sources above the low density limit for these lines. We also find that strong shocks are likely present in 10 starburst-dominated sources of our sample. A significant fraction of the GOALS sources (80) have resolved neon emission-line profiles (FWHM ≥600 km s{sup –1}) and five show clear differences in the velocities of the [Ne III] or [Ne V] emission lines, relative to [Ne II], of more than 200 km s{sup –1}. Furthermore, six starburst and five active galactic nucleus dominated LIRGs show a clear trend of increasing line width with ionization potential

  14. Dark matter in spiral galaxies

    International Nuclear Information System (INIS)

    Persic, M.; Salucci, P.

    1990-01-01

    The Tully-Fisher relation is used to probe dark matter (DM) in the optical regions of spiral galaxies. By establishing it at several different isophotal radii in an appropriate sample of 58 galaxies with good B-band photometry and rotation curves, it is shown that some of its attributes (such as scatter, residuals, nonlinearity, and bias) dramatically decrease moving from the disk edge inward. This behavior challenges any mass model which assumes no DM or a luminosity-independent DM mass fraction interior to the optical radius of spiral galaxies. 58 refs

  15. Substructure in clusters of galaxies

    International Nuclear Information System (INIS)

    Fitchett, M.J.

    1988-01-01

    Optical observations suggesting the existence of substructure in clusters of galaxies are examined. Models of cluster formation and methods used to detect substructure in clusters are reviewed. Consideration is given to classification schemes based on a departure of bright cluster galaxies from a spherically symmetric distribution, evidence for statistically significant substructure, and various types of substructure, including velocity, spatial, and spatial-velocity substructure. The substructure observed in the galaxy distribution in clusters is discussed, focusing on observations from general cluster samples, the Virgo cluster, the Hydra cluster, Centaurus, the Coma cluster, and the Cancer cluster. 88 refs

  16. S0 galaxies in Formax

    DEFF Research Database (Denmark)

    Bedregal...[], A. G.; Aragón-Salamanca, A.; Merrifield, M. R.

    2006-01-01

    Galaxies: elliptical and lenticular, cD: galaxies: kinematics and dynamics Udgivelsesdato: Oct.1......Galaxies: elliptical and lenticular, cD: galaxies: kinematics and dynamics Udgivelsesdato: Oct.1...

  17. The AGN Population in Nearby Galaxies

    International Nuclear Information System (INIS)

    Filho, Mercedes; Barthel, Peter; Ho, Luis

    2006-01-01

    In order to determine the incidence of black hole accretion-driven nuclear activity in nearby galaxies, we have compiled radio data for the LINERs, composite LINER,/Hn and Seyfert galaxies from a complete magnitude-limited sample of bright nearby galaxies (Palomar sample). Our results show an overall radio detection rate of 54% (22% of all bright nearby galaxies) and we estimate that at least ∼50% (∼20% of all bright nearby galaxies) are true AGN. By comparing the radio luminosity function of the LINERs, composite LINER/Hll and Seyferts galaxies in the Palomar sample with those of selected moderate-redshift AGN, we fhd that our sources naturally extend the radio luminosity function of powerful AGN down to powers of about 10 times that of Sgr A*

  18. Stellar populations in distant radio galaxies

    International Nuclear Information System (INIS)

    Lilly, S.J.; Longair, M.S.

    1984-01-01

    A homogeneous data set of infrared observations of 83 3CR galaxies with redshifts 0< z<1.6, selected from a statistically complete sample of 90 radio sources, is used to study the colours and magnitudes of these galaxies as a function of their redshifts. New infrared observations are presented for 66 radio galaxies, in addition to new optical results obtained from a re-analysis of existing CCD images. It is shown that the infrared colours do not deviate from the predicted relations with redshift for a standard giant elliptical galaxy spectrum. The optical to infrared colours, however, show substantial deviations at high redshift. No galaxies have been found that are significantly redder than a passively evolving galaxy, and there is a significant scatter of colours bluewards from this model. The excess of ultraviolet light responsible for these colours is not concentrated at the nucleus, and is interpreted as resulting from bursts of star formation, throughout the galaxy. (author)

  19. IRAC Imaging of LSB Galaxies

    Science.gov (United States)

    Schombert, James; McGaugh, Stacy; Lelli, Federico

    2017-04-01

    We propose a program to observe a large sample of Low Surface Brightness (LSB) galaxies. Large galaxy surveys conducted with Spitzer suffer from the unavoidable selection bias against LSB systems (e.g., the S4G survey). Even those programs thathave specifically targeted LSB galaxies have usually been restricted objects of intermediate surface brightness (between 22 and 23 B mag/ []). Our sample is selected to be of a more extreme LSB nature (with central surface brightness fainter than 23 Bmag/[]). Even warm, Spitzer is the ideal instrument to image these low contrast targets in the near infrared: our sample goes a considerable way towards remedying this hole in the Spitzer legacy archive, also increasing coverage in terms of stellar mass, gas mass, and SFR. The sample will be used to address the newly discovered radial acceleration relation (RAR) in disk galaxies. While issues involving the connection between baryons and dark matter have been known since the development of the global baryonic Tully-Fisher (bTF) relation, it is only in the last six months that the particle physics and theoretical communities have recognized and responded to the local coupling between dark and baryonic matter represented by the RAR. This important new correlation is effectively a new natural law for galaxies. Spitzer photometry has been at the forefront of resolving the stellar mass component in galaxies that make-up the RAR and is the primary reason for the discovery of this new kinematic law.

  20. COMBINED EFFECTS OF GALAXY INTERACTIONS AND LARGE-SCALE ENVIRONMENT ON GALAXY PROPERTIES

    International Nuclear Information System (INIS)

    Park, Changbom; Choi, Yun-Young

    2009-01-01

    We inspect the coupled dependence of physical parameters of the Sloan Digital Sky Survey galaxies on the small-scale (distance to and morphology of the nearest neighbor galaxy) and the large-scale (background density smoothed over 20 nearby galaxies) environments. The impacts of interaction on galaxy properties are detected at least out to the neighbor separation corresponding to the virial radius of galaxies, which is typically between 200 and 400 h -1 kpc for the galaxies in our sample. To detect these long-range interaction effects, it is crucial to divide galaxy interactions into four cases dividing the morphology of target and neighbor galaxies into early and late types. We show that there are two characteristic neighbor-separation scales where the galaxy interactions cause abrupt changes in the properties of galaxies. The first scale is the virial radius of the nearest neighbor galaxy r vir,nei . Many physical parameters start to deviate from those of extremely isolated galaxies at the projected neighbor separation r p of about r vir,nei . The second scale is at r p ∼ 0.05r vir,nei = 10-20 h -1 kpc, and is the scale at which the galaxies in pairs start to merge. We find that late-type neighbors enhance the star formation activity of galaxies while early-type neighbors reduce it, and that these effects occur within r vir,nei . The hot halo gas and cold disk gas must be participating in the interactions at separations less than the virial radius of the galaxy plus dark halo system. Our results also show that the role of the large-scale density in determining galaxy properties is minimal once luminosity and morphology are fixed. We propose that the weak residual dependence of galaxy properties on the large-scale density is due to the dependence of the halo gas property on the large-scale density.

  1. Galaxy-galaxy lensing in EAGLE: comparison with data from 180 deg2 of the KiDS and GAMA surveys

    Science.gov (United States)

    Velliscig, Marco; Cacciato, Marcello; Hoekstra, Henk; Schaye, Joop; Heymans, Catherine; Hildebrandt, Hendrik; Loveday, Jon; Norberg, Peder; Sifón, Cristóbal; Schneider, Peter; van Uitert, Edo; Viola, Massimo; Brough, Sarah; Erben, Thomas; Holwerda, Benne W.; Hopkins, Andrew M.; Kuijken, Konrad

    2017-11-01

    We present predictions for the galaxy-galaxy lensing (GGL) profile from the EAGLE hydrodynamical cosmological simulation at redshift z = 0.18, in the spatial range 0.02 < R/(h- 1 Mpc) < 2, and for five logarithmically equispaced stellar mass bins in the range 10.3 < log10(Mstar/ M⊙) < 11.8. We compare these excess surface density profiles to the observed signal from background galaxies imaged by the Kilo Degree Survey around spectroscopically confirmed foreground galaxies from the Galaxy And Mass Assembly (GAMA) survey. Exploiting the GAMA galaxy group catalogue, the profiles of central and satellite galaxies are computed separately for groups with at least five members to minimize contamination. EAGLE predictions are in broad agreement with the observed profiles for both central and satellite galaxies, although the signal is underestimated at R ≈ 0.5-2 h- 1 Mpc for the highest stellar mass bins. When central and satellite galaxies are considered simultaneously, agreement is found only when the selection function of lens galaxies is taken into account in detail. Specifically, in the case of GAMA galaxies, it is crucial to account for the variation of the fraction of satellite galaxies in bins of stellar mass induced by the flux-limited nature of the survey. We report the inferred stellar-to-halo mass relation and we find good agreement with recent published results. We note how the precision of the GGL profiles in the simulation holds the potential to constrain fine-grained aspects of the galaxy-dark matter connection.

  2. Blueberry Galaxies: The Lowest Mass Young Starbursts

    Science.gov (United States)

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

    2017-09-01

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

  3. Ellipticities of Elliptical Galaxies in Different Environments

    Science.gov (United States)

    Chen, Cheng-Yu; Hwang, Chorng-Yuan; Ko, Chung-Ming

    2016-10-01

    We studied the ellipticity distributions of elliptical galaxies in different environments. From the ninth data release of the Sloan Digital Sky Survey, we selected galaxies with absolute {r}\\prime -band magnitudes between -21 and -22. We used the volume number densities of galaxies as the criterion for selecting the environments of the galaxies. Our samples were divided into three groups with different volume number densities. The ellipticity distributions of the elliptical galaxies differed considerably in these three groups of different density regions. We deprojected the observed 2D ellipticity distributions into intrinsic 3D shape distributions, and the result showed that the shapes of the elliptical galaxies were relatively spherically symmetric in the high density region (HDR) and that relatively more flat galaxies were present in the low density region (LDR). This suggests that the ellipticals in the HDRs and LDRs have different origins or that different mechanisms might be involved. The elliptical galaxies in the LDR are likely to have evolved from mergers in relatively anisotropic structures, such as filaments and webs, and might contain information on the anisotropic spatial distribution of their parent mergers. By contrast, elliptical galaxies in the HDR might be formed in more isotropic structures, such as galaxy clusters, or they might encounter more torqueing effects compared with galaxies in LDRs, thereby becoming rounder.

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

    Science.gov (United States)

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

    2018-05-01

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

  5. Hα Emission Line Morphologies in Markarian Starburst Galaxies A ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging Solutions)

    images of a sample of optically selected starburst galaxies from the Markar- ian lists. .... to the size of the galaxy and the histograms were sky dominated. .... simplest qualitative method is to visually examine the distribution of the emission line.

  6. Typical effect on redshift of galaxies of the Hercules supercluster

    International Nuclear Information System (INIS)

    Giraud, Edmond.

    1981-01-01

    We study dependance of redshift on the morphological type of galaxies in the Hercules supercluster from Tarenghi and al.'s data. We show that S-galaxies have a significant excess in 105 redshift samples [fr

  7. Cosmological parameter constraints from galaxy-galaxy lensing and galaxy clustering with the SDSS DR7

    Science.gov (United States)

    Mandelbaum, Rachel; Slosar, Anže; Baldauf, Tobias; Seljak, Uroš; Hirata, Christopher M.; Nakajima, Reiko; Reyes, Reinabelle; Smith, Robert E.

    2013-06-01

    Recent studies have shown that the cross-correlation coefficient between galaxies and dark matter is very close to unity on scales outside a few virial radii of galaxy haloes, independent of the details of how galaxies populate dark matter haloes. This finding makes it possible to determine the dark matter clustering from measurements of galaxy-galaxy weak lensing and galaxy clustering. We present new cosmological parameter constraints based on large-scale measurements of spectroscopic galaxy samples from the Sloan Digital Sky Survey (SDSS) data release 7. We generalize the approach of Baldauf et al. to remove small-scale information (below 2 and 4 h-1 Mpc for lensing and clustering measurements, respectively), where the cross-correlation coefficient differs from unity. We derive constraints for three galaxy samples covering 7131 deg2, containing 69 150, 62 150 and 35 088 galaxies with mean redshifts of 0.11, 0.28 and 0.40. We clearly detect scale-dependent galaxy bias for the more luminous galaxy samples, at a level consistent with theoretical expectations. When we vary both σ8 and Ωm (and marginalize over non-linear galaxy bias) in a flat Λ cold dark matter model, the best-constrained quantity is σ8(Ωm/0.25)0.57 = 0.80 ± 0.05 (1σ, stat. + sys.), where statistical and systematic errors (photometric redshift and shear calibration) have comparable contributions, and we have fixed ns = 0.96 and h = 0.7. These strong constraints on the matter clustering suggest that this method is competitive with cosmic shear in current data, while having very complementary and in some ways less serious systematics. We therefore expect that this method will play a prominent role in future weak lensing surveys. When we combine these data with Wilkinson Microwave Anisotropy Probe 7-year (WMAP7) cosmic microwave background (CMB) data, constraints on σ8, Ωm, H0, wde and ∑mν become 30-80 per cent tighter than with CMB data alone, since our data break several parameter

  8. Crashing galaxies, cosmic fireworks

    International Nuclear Information System (INIS)

    Keel, W.C.

    1989-01-01

    The study of binary systems is reviewed. The history of the study of interacting galaxies, the behavior of gas in binary systems, studies to identify the processes that occur when galaxies interact, and the relationship of Seyfert galaxies and quasars to binary systems are discussed. The development of an atlas of peculiar galaxies (Arp, 1966) and methods for modeling galaxy interactions are examined

  9. Morphology and Structures of Nearby Dwarf Galaxies

    Science.gov (United States)

    Seo, Mira; Ann, HongBae

    2015-08-01

    We performed an analysis of the structure of nearby dwarf galaxies based on a 2-dimensional decomposition of galaxy images using GALFIT. The present sample consists of ~1,100 dwarf galaxies with redshift less than z = 0.01, which is is derived from the morphology catalog of the Visually classified galaxies in the local universe (Ann, Seo, and Ha 2015). In this catalog, dwarf galaxies are divided into 5 subtypes: dS0, dE, dSph, dEbc, dEblue with distinction of the presence of nucleation in dE, dSph, and dS0. We found that dSph and dEblue galaxies are fainter than other subtypes of dwarf galaxies. In most cases, single component, represented by the Sersic profile with n=1~1.5, well describes the luminosity distribution of dwarf galaxies in the present sample. However, a significant fraction of dS0, dEbc, and dEbue galaxies show sub-structures such as spiral arms and rings. We will discuss the morphology dependent evolutionary history of the local dwarf galaxies.

  10. ULTRAVIOLET HALOS AROUND SPIRAL GALAXIES. I. MORPHOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N., E-mail: hodgeskl@umich.edu [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)

    2016-12-10

    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 ultraviolet (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 10{sup 6}–10{sup 7} M {sub ⊙} of dust within 2–10 kpc of the disk, whose properties may change with height in starburst galaxies.

  11. Infrared galaxies in the IRAS minisurvey

    Science.gov (United States)

    Soifer, B. T.; Neugebauer, G.; Rowan-Robinson, M.; Clegg, P. E.; Emerson, J. P.; Houck, J. R.; De Jong, T.; Aumann, H. H.; Beichman, C. A.; Boggess, N.

    1984-01-01

    A total of 86 galaxies have been detected at 60 microns in the high galactic latitude portion of the IRAS minisurvey. The surface density of detected galaxies with flux densities greater than 0.5 Jy is 0.25 sq deg. Virtually all the galaxies detected are spiral galaxies and have an infrared to blue luminosity ratio ranging from 50 to 0.5. For the infrared-selected sample, no obvious correlation exists between infrared excess and color temperature. The infrared flux from 10 to 100 microns contributes approximately 5 percent of the blue luminosity for galaxies in the magnitude range 14 less than m(pg) less than 18 mag. The fraction of interacting galaxies is between one-eighth and one-fourth of the sample.

  12. Radio emission in peculiar galaxies

    Science.gov (United States)

    Demellorabaca, Dulia F.; Abraham, Zulema

    1990-01-01

    During the last decades a number of surveys of peculiar galaxies have been carried out and accurate positions become available. Since peculiarities are a possible evidence of radio emission (Wright, 1974; Sulentic, 1976; Stocke et al., 1978), the authors selected a sample of 24 peculiar galaxies with optical jet-like features or extensions in different optical catalogues, mainly the Catalogue of Southern Peculiar Galaxies and Associations (Arp and Madore, 1987) and the ESO/Uppsala Survey of the ESO(B) Atlas (Lauberts, 1982) for observation at the radio continuum frequency of 22 GHz. The sample is listed in a table. Sol (1987) studied this sample and concluded that the majority of the jet-like features seem to admit an explanation in terms of interactive galaxies with bridges and/or tails due to tidal effects. Only in a few cases do the jets seem to be possibly linked to some nuclear activity of the host galaxy. The observations were made with the 13.7m-radome enclosed Itapetinga Radiotelescope (HPBW of 4.3 arcmin), in Brazil. The receiver was a 1 GHz d.s.b. super-heterodine mixer operated in total-power mode, with a system temperature of approximately 800 K. The observational technique consisted in scans in right ascention, centralized in the optical position of the galaxy. The amplitude of one scan was 43 arcmin, and its duration time was 20 seconds. The integration time was at least 2 hours (12 ten-minute observations) and the sensibility limit adopted was an antenna temperature greater than 3 times the r.m.s. error of the baseline determination. Virgo A was used as the calibrator source. Three galaxies were detected for the first time as radio sources and four other known galaxies at low frequencies had their flux densities measured at 22 GHz. The results for these sources are presented.

  13. MASS CALIBRATION AND COSMOLOGICAL ANALYSIS OF THE SPT-SZ GALAXY CLUSTER SAMPLE USING VELOCITY DISPERSION σ {sub v} AND X-RAY Y {sub X} MEASUREMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Bocquet, S.; Saro, A.; Mohr, J. J.; Bazin, G.; Chiu, I.; Desai, S. [Department of Physics, Ludwig-Maximilians-Universität, Scheinerstr. 1, D-81679 München (Germany); Aird, K. A. [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Ashby, M. L. N.; Bayliss, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bautz, M. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Benson, B. A. [Fermi National Accelerator Laboratory, Batavia, IL 60510-0500 (United States); Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Cho, H. M. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); Clocchiatti, A. [Departamento de Astronomia y Astrosifica, Pontificia Universidad Catolica (Chile); De Haan, T., E-mail: bocquet@usm.lmu.de [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); and others

    2015-02-01

    We present a velocity-dispersion-based mass calibration of the South Pole Telescope Sunyaev-Zel'dovich effect survey (SPT-SZ) galaxy cluster sample. Using a homogeneously selected sample of 100 cluster candidates from 720 deg{sup 2} of the survey along with 63 velocity dispersion (σ {sub v}) and 16 X-ray Y {sub X} measurements of sample clusters, we simultaneously calibrate the mass-observable relation and constrain cosmological parameters. Our method accounts for cluster selection, cosmological sensitivity, and uncertainties in the mass calibrators. The calibrations using σ {sub v} and Y {sub X} are consistent at the 0.6σ level, with the σ {sub v} calibration preferring ∼16% higher masses. We use the full SPT{sub CL} data set (SZ clusters+σ {sub v}+Y {sub X}) to measure σ{sub 8}(Ω{sub m}/0.27){sup 0.3} = 0.809 ± 0.036 within a flat ΛCDM model. The SPT cluster abundance is lower than preferred by either the WMAP9 or Planck+WMAP9 polarization (WP) data, but assuming that the sum of the neutrino masses is ∑m {sub ν} = 0.06 eV, we find the data sets to be consistent at the 1.0σ level for WMAP9 and 1.5σ for Planck+WP. Allowing for larger ∑m {sub ν} further reconciles the results. When we combine the SPT{sub CL} and Planck+WP data sets with information from baryon acoustic oscillations and Type Ia supernovae, the preferred cluster masses are 1.9σ higher than the Y {sub X} calibration and 0.8σ higher than the σ {sub v} calibration. Given the scale of these shifts (∼44% and ∼23% in mass, respectively), we execute a goodness-of-fit test; it reveals no tension, indicating that the best-fit model provides an adequate description of the data. Using the multi-probe data set, we measure Ω{sub m} = 0.299 ± 0.009 and σ{sub 8} = 0.829 ± 0.011. Within a νCDM model we find ∑m {sub ν} = 0.148 ± 0.081 eV. We present a consistency test of the cosmic growth rate using SPT clusters. Allowing both the growth index γ and the dark energy equation

  14. Automatic Approach to Morphological Classification of Galaxies With Analysis of Galaxy Populations in Clusters

    Science.gov (United States)

    Sultanova, Madina; Barkhouse, Wayne; Rude, Cody

    2018-01-01

    The classification of galaxies based on their morphology is a field in astrophysics that aims to understand galaxy formation and evolution based on their physical differences. Whether structural differences are due to internal factors or a result of local environment, the dominate mechanism that determines galaxy type needs to be robustly quantified in order to have a thorough grasp of the origin of the different types of galaxies. The main subject of my Ph.D. dissertation is to explore the use of computers to automatically classify and analyze large numbers of galaxies according to their morphology, and to analyze sub-samples of galaxies selected by type to understand galaxy formation in various environments. I have developed a computer code to classify galaxies by measuring five parameters from their images in FITS format. The code was trained and tested using visually classified SDSS galaxies from Galaxy Zoo and the EFIGI data set. I apply my morphology software to numerous galaxies from diverse data sets. Among the data analyzed are the 15 Abell galaxy clusters (0.03 Frontier Field galaxy clusters. The high resolution of HST allows me to compare distant clusters with those nearby to look for evolutionary changes in the galaxy cluster population. I use the results from the software to examine the properties (e.g. luminosity functions, radial dependencies, star formation rates) of selected galaxies. Due to the large amount of data that will be available from wide-area surveys in the future, the use of computer software to classify and analyze the morphology of galaxies will be extremely important in terms of efficiency. This research aims to contribute to the solution of this problem.

  15. ALIGNMENTS OF GROUP GALAXIES WITH NEIGHBORING GROUPS

    International Nuclear Information System (INIS)

    Wang Yougang; Chen Xuelei; Park, Changbom; Yang Xiaohu; Choi, Yun-Young

    2009-01-01

    Using a sample of galaxy groups found in the Sloan Digital Sky Survey Data Release 4, we measure the following four types of alignment signals: (1) the alignment between the distributions of the satellites of each group relative to the direction of the nearest neighbor group (NNG); (2) the alignment between the major axis direction of the central galaxy of the host group (HG) and the direction of the NNG; (3) the alignment between the major axes of the central galaxies of the HG and the NNG; and (4) the alignment between the major axes of the satellites of the HG and the direction of the NNG. We find strong signal of alignment between the satellite distribution and the orientation of central galaxy relative to the direction of the NNG, even when the NNG is located beyond 3r vir of the host group. The major axis of the central galaxy of the HG is aligned with the direction of the NNG. The alignment signals are more prominent for groups that are more massive and with early-type central galaxies. We also find that there is a preference for the two major axes of the central galaxies of the HG and NNG to be parallel for the system with both early central galaxies, however, not for the systems with both late-type central galaxies. For the orientation of satellite galaxies, we do not find any significant alignment signals relative to the direction of the NNG. From these four types of alignment measurements, we conclude that the large-scale environment traced by the nearby group affects primarily the shape of the host dark matter halo, and hence also affects the distribution of satellite galaxies and the orientation of central galaxies. In addition, the NNG directly affects the distribution of the satellite galaxies by inducing asymmetric alignment signals, and the NNG at very small separation may also contribute a second-order impact on the orientation of the central galaxy in the HG.

  16. Spectral evolution of galaxies: current views

    International Nuclear Information System (INIS)

    Bruzual, A.G.

    1985-01-01

    A summary of current views on the interpretation of the various evolutionary tests aimed at detecting spectral evolution in galaxies is presented. It is concluded that the evolution taking place in known galaxy samples is a slow process (perhaps consistent with no evolution at all), and that the early phases of rapid spectral evolution in early-type galaxies have not yet been detected. (author)

  17. Connection between Seyfert galaxies and clusters

    International Nuclear Information System (INIS)

    Petrosyan, A.R.

    1988-01-01

    To identify Seyfert galaxies that are members of clusters, the sample of known Seyfert galaxies (464 objects) is tested against the Zwicky, Abell, and southern clusters. On the basis of the criteria adopted in the paper, 67 Seyfert galaxies are selected as probable members of Zwicky clusters, 15 as members of Abell clusters, and 18 as members of southern clusters. Lists of these objects are given

  18. Star formation histories of irregular galaxies

    International Nuclear Information System (INIS)

    Gallagher, J.S. III; Hunter, D.A.; Tutukov, A.V.

    1984-01-01

    We explore the star formation histories of a selection of irregular and spiral galaxies by using three parameters that sample the star formation rate (SFR) at different epochs: (1) the mass of a galaxy in the form of stars measures the SFR integrated over a galaxy's lifetime; (2) the blue luminosity is dominated primarily by stars formed over the past few billion years; and (3) Lyman continuum photon fluxes derived from Hα luminosities give the current ( 8 yr) SFR

  19. Spherical galaxies.

    Science.gov (United States)

    Telles, J. E.; de Souza, R. E.; Penereiro, J. C.

    1990-11-01

    RESUMEN. Presentamos fotometria fotografica de 8 objetos y espectrosco- pla para 3 galaxias, las cuales son buenos candidatos para galaxias esfericas. Los resultados fotometricos se presentan en la forma de iso- fotas y de perfiles radiales promedlo, de los cuales se derivan para- metros estructurales. Estas observaciones combinadas con parametros di- namicos obtenidos de observaciones espectrosc6picas, son consistentes con el plano fundamental derivado por Djorgovski y Davis (1987). ABSTRACT. We present photographic surface photometry for 8 objects and spectroscopy for 3 galaxies which are good candidates for spherical galaxies. Photometric results are presented in the form of isophotes and mean radial profiles from which we derived structural parameters. These observations combined with dynamical parameters obtained from spectroscopic observations are consistent with the fundamental plane derived by Djorgovski and Davis (1987). Keq wo : CALAXIES-ELLIPTICAL

  20. Galaxy bias from galaxy-galaxy lensing in the DES Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Prat, J.; et al.

    2016-09-26

    We present a measurement of galaxy-galaxy lensing around a magnitude-limited ($i_{AB} < 22.5$) sample of galaxies selected from the Dark Energy Survey Science Verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias $b$ and cross-correlation coefficient between the galaxy and dark matter overdensity fields $r$ in each bin, using scales above 4 Mpc/$h$ comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering (Crocce et al. 2016) and CMB lensing (Giannantonio et al. 2016) for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al. (2016), while, in the lowest redshift bin ($z\\sim0.3$), they show some tension with the findings in Giannantonio et al. (2016). Our results are found to be rather insensitive to a large range of systematic effects. We measure $b\\cdot r$ to be $0.87\\pm 0.11$, $1.12 \\pm 0.16$ and $1.24\\pm 0.23$, respectively for the three redshift bins of width $\\Delta z = 0.2$ in the range $0.2sample, TPZ, leads to changes in the measured biases at the 10-20% level, but it does not alter the main conclusion of this work: when comparing with Crocce et al. (2016) we do not find strong evidence for a cross-correlation parameter significantly below one in this galaxy sample, except possibly at the lowest redshift bin ($z\\sim 0.3$), where we find $r = 0.71 \\pm 0.11$ when using TPZ, and $0.83 \\pm 0.12$ with BPZ, assuming the difference between the results from the two probes can be solely attributed to the cross-correlation parameter.

  1. A search for megamaser galaxies

    International Nuclear Information System (INIS)

    Norris, R.P.; Gardner, F.F.; Whiteoak, J.B.

    1989-01-01

    The results are reported of a search for OH megamaser emission from a sample of 32 galaxies selected from the IRAS Point Source Catalog on the basis of their infrared properties. For each galaxy (other than those few already observed elsewhere) we have obtained an optical redshift and have searched for both OH and H I emission. The search yielded one new OH megamaser galaxy and H I was detected towards nine objects. We conclude that there are unlikely to be any OH megamasers in the Southern Hemisphere with flux densities comparable to that of Arp 220 (280 mJy), although there may be a population of weaker megamasers. From the statistics of our search we conclude that no special conditions are required to explain the known OH megamasers other than those expected in a cool, dusty, active galaxy. (author)

  2. LINER galaxy properties and the local environment

    Science.gov (United States)

    Coldwell, Georgina V.; Alonso, Sol; Duplancic, Fernanda; Mesa, Valeria

    2018-05-01

    We analyse the properties of a sample of 5560 low-ionization nuclear emission-line region (LINER) galaxies selected from SDSS-DR12 at low red shift, for a complete range of local density environments. The host LINER galaxies were studied and compared with a well-defined control sample of 5553 non-LINER galaxies matched in red shift, luminosity, morphology and local density. By studying the distributions of galaxy colours and the stellar age population, we find that LINERs are redder and older than the control sample over a wide range of densities. In addition, LINERs are older than the control sample, at a given galaxy colour, indicating that some external process could have accelerated the evolution of the stellar population. The analysis of the host properties shows that the control sample exhibits a strong relation between colours, ages and the local density, while more than 90 per cent of the LINERs are redder and older than the mean values, independently of the neighbourhood density. Furthermore, a detailed study in three local density ranges shows that, while control sample galaxies are redder and older as a function of stellar mass and density, LINER galaxies mismatch the known morphology-density relation of galaxies without low-ionization features. The results support the contribution of hot and old stars to the low-ionization emission although the contribution of nuclear activity is not discarded.

  3. The dwarfs beyond: The stellar-to-halo mass relation for a new sample of intermediate redshift low-mass galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Sarah H.; Ellis, Richard S.; Newman, Andrew B. [California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125 (United States); Benson, Andrew, E-mail: smiller@astro.caltech.edu [Carnegie Observatories, 813 Santa Barbara St, Pasadena, CA 91101 (United States)

    2014-02-20

    A number of recent challenges to the standard ΛCDM paradigm relate to discrepancies that arise in comparing the abundance and kinematics of local dwarf galaxies with the predictions of numerical simulations. Such arguments rely heavily on the assumption that the Local Volume's dwarf and satellite galaxies form a representative distribution in terms of their stellar-to-halo mass ratios. To address this question, we present new, deep spectroscopy using DEIMOS on Keck for 82 low-mass (10{sup 7}-10{sup 9} M {sub ☉}), star-forming galaxies at intermediate redshift (0.2 < z < 1). For 50% of these we are able to determine resolved rotation curves using nebular emission lines and thereby construct the stellar mass Tully-Fisher relation to masses as low as 10{sup 7} M {sub ☉}. Using scaling relations determined from weak lensing data, we convert this to a stellar-to-halo mass relation for comparison with abundance matching predictions. We find a discrepancy between our observations and the predictions from abundance matching in the sense that we observe 3-12 times more stellar mass at a given halo mass. We suggest possible reasons for this discrepancy, as well as improved tests for the future.

  4. THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI: THE EFFECT OF HOST-GALAXY STARLIGHT ON LUMINOSITY MEASUREMENTS. II. THE FULL SAMPLE OF REVERBERATION-MAPPED AGNs

    International Nuclear Information System (INIS)

    Bentz, Misty C.; Peterson, Bradley M.; Pogge, Richard W.; Netzer, Hagai; Vestergaard, Marianne

    2009-01-01

    We present high-resolution Hubble Space Telescope images of all 35 active galactic nuclei (AGNs) with optical reverberation-mapping results, which we have modeled to create a nucleus-free image of each AGN host galaxy. From the nucleus-free images, we determine the host-galaxy contribution to ground-based spectroscopic luminosity measurements at 5100 A. After correcting the luminosities of the AGNs for the contribution from starlight, we re-examine the Hβ R BLR -L relationship. Our best fit for the relationship gives a power-law slope of 0.52 with a range of 0.45-0.59 allowed by the uncertainties. This is consistent with our previous findings, and thus still consistent with the naive assumption that all AGNs are simply luminosity-scaled versions of each other. We discuss various consistency checks relating to the galaxy modeling and starlight contributions, as well as possible systematic errors in the current set of reverberation measurements from which we determine the form of the R BLR -L relationship.

  5. Galaxies in low density regions of the universe

    International Nuclear Information System (INIS)

    Brosch, N.

    1983-01-01

    Until recently, no sample of galaxies has been offered for study as being representative of isolated galaxies. However, lately two such samples have been published; one of them is the subject of this study. Both lists of isolated galaxies contain only a few percent of all galaxies considered in the original sources. The study of the isolated galaxies' sample includes optical UBV photometry, infrared photometry, 6-cm radio continuum observations and ultraviolet spectrophotometry. The results provide a database to compare the properties of isolated galaxies to those of nonisolated ones which have probably been modified since their formation by encounters with gas or with other galaxies. A tentative explanation of the detected difference, the apparently enhanced degree of nuclear activity in isolated galaxies is given. (Auth.)

  6. Dwarf spheroidal galaxies: Keystones of galaxy evolution

    Science.gov (United States)

    Gallagher, John S., III; Wyse, Rosemary F. G.

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  7. Colors and the evolution of amorphous galaxies

    International Nuclear Information System (INIS)

    Gallagher, J.S. III; Hunter, D.A.

    1987-01-01

    UBVRI and H-alpha photometric observations are presented for 16 amorphous galaxies and a comparison sample of Magellanic irregular (Im) and Sc spiral galaxies. These data are analyzed in terms of star-formation rates and histories in amorphous galaxies. Amorphous galaxies have mean global colors and star-formation rates per unit area that are similar to those in giant Im systems, despite differences in spatial distributions of star-forming centers in these two galactic structural classes. Amorphous galaxies differ from giant Im systems in having somewhat wider scatter in relationships between B - V and U - B colors, and between U - B and L(H-alpha)/L(B). This scatter is interpreted as resulting from rapid variations in star-formation rates during the recent past, which could be a natural consequence of the concentration of star-forming activity into centrally located, supergiant young stellar complexes in many amorphous galaxies. While the unusual spatial distribution and intensity of star formation in some amorphous galaxies is due to interactions with other galaxies, several amorphous galaxies are relatively isolated and thus the processes must be internal. The ultimate evolutionary fate of rapidly evolving amorphous galaxies remains unknown. 77 references

  8. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Vigroux, Laurent

    1979-01-01

    This research thesis addresses theories on the chemical evolution of galaxies which aim at explaining abundances of different elements in galaxies, and more particularly aims at improving the model by modifying hypotheses. After a description of the simple model and of its uncertainties, the author shows how it is possible to understand the evolution of the main elements. Predictions obtained with this model are then compared with the present knowledge on galaxies by considering them according to an increasing complexity: Sun's neighbourhood, our galaxy, other spiral galaxies, elliptical galaxies, and finally galaxy clusters. A specific attention is given to irregular galaxies which are the simplest systems [fr

  9. Sampling

    CERN Document Server

    Thompson, Steven K

    2012-01-01

    Praise for the Second Edition "This book has never had a competitor. It is the only book that takes a broad approach to sampling . . . any good personal statistics library should include a copy of this book." —Technometrics "Well-written . . . an excellent book on an important subject. Highly recommended." —Choice "An ideal reference for scientific researchers and other professionals who use sampling." —Zentralblatt Math Features new developments in the field combined with all aspects of obtaining, interpreting, and using sample data Sampling provides an up-to-date treat

  10. Analysis of Sunyaev-Zel'dovich effect mass-observable relations using South Pole Telescope observations of an X-ray selected sample of low-mass galaxy clusters and groups

    Energy Technology Data Exchange (ETDEWEB)

    Liu, J.; Mohr, J.; Saro, A.; Aird, K. A.; Ashby, M. L. N.; Bautz, M.; Bayliss, M.; Benson, B. A.; Bleem, L. E.; Bocquet, S.; Brodwin, M.; Carlstrom, J. E.; Chang, C. L.; Chiu, I.; Cho, H. M.; Clocchiatti, A.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Desai, S.; Dietrich, J. P.; Dobbs, M. A.; Foley, R. J.; Gangkofner, D.; George, E. M.; Gladders, M. D.; Gonzalez, A. H.; Halverson, N. W.; Hennig, C.; Hlavacek-Larrondo, J.; Holder, G. P.; Holzapfel, W. L.; Hrubes, J. D.; Jones, C.; Keisler, R.; Lee, A. T.; Leitch, E. M.; Lueker, M.; Luong-Van, D.; McDonald, M.; McMahon, J. J.; Meyer, S. S.; Mocanu, L.; Murray, S. S.; Padin, S.; Pryke, C.; Reichardt, C. L.; Rest, A.; Ruel, J.; Ruhl, J. E.; Saliwanchik, B. R.; Sayre, J. T.; Schaffer, K. K.; Shirokoff, E.; Spieler, H. G.; Stalder, B.; Staniszewski, Z.; Stark, A. A.; Story, K.;  uhada, R.; Vanderlinde, K.; Vieira, J. D.; Vikhlinin, A.; Williamson, R.; Zahn, O.; Zenteno, A.

    2015-02-25

    We use microwave observations from the South Pole Telescope (SPT) to examine the Sunyaev–Zel'dovich effect (SZE) signatures of a sample of 46 X-ray selected groups and clusters drawn from ~6 deg2 of the XMM–Newton Blanco Cosmology Survey. These systems extend to redshift z = 1.02 and probe the SZE signal to the lowest X-ray luminosities (≥1042 erg s-1) yet; these sample characteristics make this analysis complementary to previous studies. We develop an analysis tool, using X-ray luminosity as a mass proxy, to extract selection-bias-corrected constraints on the SZE significance and Y_500 mass relations. The former is in good agreement with an extrapolation of the relation obtained from high-mass clusters. However, the latter, at low masses, while in good agreement with the extrapolation from the high-mass SPT clusters, is in tension at 2.8σ with the Planck constraints, indicating the low-mass systems exhibit lower SZE signatures in the SPT data. We also present an analysis of potential sources of contamination. For the radio galaxy point source population, we find 18 of our systems have 843 MHz Sydney University Molonglo Sky Survey sources within 2 arcmin of the X-ray centre, and three of these are also detected at significance >4 by SPT. Of these three, two are associated with the group brightest cluster galaxies, and the third is likely an unassociated quasar candidate. We examine the impact of these point sources on our SZE scaling relation analyses and find no evidence of biases. We also examine the impact of dusty galaxies using constraints from the 220 GHz data. The stacked sample provides 2.8σ significant evidence of dusty galaxy flux, which would correspond to an average underestimate of the SPT Y_500 signal that is (17 ± 9)per cent in this sample of low-mass systems. Finally, we explore the impact of future data from SPTpol and XMM-XXL, showing that it will lead to a factor of 4 to 5 tighter

  11. Evidence for AGN feedback in low-mass galaxies

    Science.gov (United States)

    Masters, Karen; Penny, Sam; Smethurst, Rebecca; Krawczyk, Coleman; Nichol, Bob; SDSS-IV MaNGA

    2018-01-01

    Despite being the dominant galaxy population by number in groups and clusters, the formation and quenching mechanism of dwarf galaxies remains unknown. We present evidence for AGN feedback in a subset of 69 quenched low-mass galaxies (M* less than 5e9 Msun, fainter than Mr = -19) selected from the first two years of the MaNGA survey. The majority (85 per cent) of these quenched galaxies appear to reside in a group environment. We find 6 galaxies in our sample that appear to have an active AGN that is preventing on-going star-formation; this is the first time such a feedback mechanism has been observed in this mass range. Interestingly, five of these six galaxies have an ionised gas component that is kinematically offset from their stellar component, suggesting the gas is either recently accreted or outflowing. We hypothesise these six galaxies are low-mass equivalents to the “red geysers” observed in more massive galaxies. Of the other 62 galaxies in the sample, we find 8 do appear to have some low-level, residual star formation, or emission from hot, evolved stars. The remaining galaxies in our sample have no detectable ionised gas emission throughout their structures, consistent with them being quenched. I will show that despite being the "simplest" galaxies in our current models of galaxy formation, these quenched dwarf galaxies are a diverse population.

  12. Constructing a WISE High Resolution Galaxy Atlas

    Science.gov (United States)

    Jarrett, T. H.; Masci, F.; Tsai, C. W.; Petty, S.; Cluver, M.; Assef, Roberto J.; Benford, D.; Blain, A.; Bridge, C.; Donoso, E.; hide

    2012-01-01

    After eight months of continuous observations, the Wide-field Infrared Survey Explorer (WISE) mapped the entire sky at 3.4 micron, 4.6 micron, 12 micron, and 22 micron. We have begun a dedicated WISE High Resolution Galaxy Atlas project to fully characterize large, nearby galaxies and produce a legacy image atlas and source catalog. Here we summarize the deconvolution techniques used to significantly improve the spatial resolution of WISE imaging, specifically designed to study the internal anatomy of nearby galaxies. As a case study, we present results for the galaxy NGC 1566, comparing the WISE enhanced-resolution image processing to that of Spitzer, Galaxy Evolution Explorer, and ground-based imaging. This is the first paper in a two-part series; results for a larger sample of nearby galaxies are presented in the second paper.

  13. Interactions of galaxies outside clusters and massive groups

    Science.gov (United States)

    Yadav, Jaswant K.; Chen, Xuelei

    2018-06-01

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

  14. COMPARISON OF IMPLICIT SCHEMES TO SOLVE EQUATIONS OF RADIATION HYDRODYNAMICS WITH A FLUX-LIMITED DIFFUSION APPROXIMATION: NEWTON–RAPHSON, OPERATOR SPLITTING, AND LINEARIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Tetsu, Hiroyuki; Nakamoto, Taishi, E-mail: h.tetsu@geo.titech.ac.jp [Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo 152-8551 (Japan)

    2016-03-15

    Radiation is an important process of energy transport, a force, and a basis for synthetic observations, so radiation hydrodynamics (RHD) calculations have occupied an important place in astrophysics. However, although the progress in computational technology is remarkable, their high numerical cost is still a persistent problem. In this work, we compare the following schemes used to solve the nonlinear simultaneous equations of an RHD algorithm with the flux-limited diffusion approximation: the Newton–Raphson (NR) method, operator splitting, and linearization (LIN), from the perspective of the computational cost involved. For operator splitting, in addition to the traditional simple operator splitting (SOS) scheme, we examined the scheme developed by Douglas and Rachford (DROS). We solve three test problems (the thermal relaxation mode, the relaxation and the propagation of linear waves, and radiating shock) using these schemes and then compare their dependence on the time step size. As a result, we find the conditions of the time step size necessary for adopting each scheme. The LIN scheme is superior to other schemes if the ratio of radiation pressure to gas pressure is sufficiently low. On the other hand, DROS can be the most efficient scheme if the ratio is high. Although the NR scheme can be adopted independently of the regime, especially in a problem that involves optically thin regions, the convergence tends to be worse. In all cases, SOS is not practical.

  15. An assessment of ion temperature measurements in the boundary of the Alcator C-Mod tokamak and implications for ion fluid heat flux limiters

    International Nuclear Information System (INIS)

    Brunner, D; LaBombard, B; Churchill, R M; Hughes, J; Lipschultz, B; Ochoukov, R; Theiler, C; Walk, J; Rognlien, T D; Umansky, M V; Whyte, D

    2013-01-01

    The ion temperature is not frequently measured in the boundary of magnetic fusion devices. Comparisons among different ion temperature techniques and simulations are even rarer. Here we present a comparison of ion temperature measurements in the boundary of the Alcator C-Mod tokamak from three different diagnostics: charge exchange recombination spectroscopy (CXRS), an ion sensitive probe (ISP), and a retarding field analyzer (RFA). Comparison between CXRS and the ISP along with close examination of the ISP measurements reveals that the ISP is space charge limited. It is thus unable to measure ion temperature in the high density (>10 19 m −3 ) boundary plasma of C-Mod with its present geometry. Comparison of ion temperatures measured by CXRS and the RFA shows fair agreement. Ion and electron parallel heat flow is analyzed with a simple 1D fluid code. The code takes divertor measurements as input and results are compared to the measured ratios of upstream ion to electron temperature, as inferred respectively by CXRS and a Langmuir probe. The analysis reveals the limits of the fluid model at high Knudsen number. The upstream temperature ratio is under predicted by a factor of 2. Heat flux limiters (kinetic corrections) to the fluid model are necessary to match experimental data. The values required are found to be close to those reported in kinetic simulations. The 1D code is benchmarked against the 2D plasma fluid code UEDGE with good agreement. (paper)

  16. An assessment of ion temperature measurements in the boundary of the Alcator C-Mod tokamak and implications for ion fluid heat flux limiters

    Science.gov (United States)

    Brunner, D.; LaBombard, B.; Churchill, R. M.; Hughes, J.; Lipschultz, B.; Ochoukov, R.; Rognlien, T. D.; Theiler, C.; Walk, J.; Umansky, M. V.; Whyte, D.

    2013-09-01

    The ion temperature is not frequently measured in the boundary of magnetic fusion devices. Comparisons among different ion temperature techniques and simulations are even rarer. Here we present a comparison of ion temperature measurements in the boundary of the Alcator C-Mod tokamak from three different diagnostics: charge exchange recombination spectroscopy (CXRS), an ion sensitive probe (ISP), and a retarding field analyzer (RFA). Comparison between CXRS and the ISP along with close examination of the ISP measurements reveals that the ISP is space charge limited. It is thus unable to measure ion temperature in the high density (>1019 m-3) boundary plasma of C-Mod with its present geometry. Comparison of ion temperatures measured by CXRS and the RFA shows fair agreement. Ion and electron parallel heat flow is analyzed with a simple 1D fluid code. The code takes divertor measurements as input and results are compared to the measured ratios of upstream ion to electron temperature, as inferred respectively by CXRS and a Langmuir probe. The analysis reveals the limits of the fluid model at high Knudsen number. The upstream temperature ratio is under predicted by a factor of 2. Heat flux limiters (kinetic corrections) to the fluid model are necessary to match experimental data. The values required are found to be close to those reported in kinetic simulations. The 1D code is benchmarked against the 2D plasma fluid code UEDGE with good agreement.

  17. Stellar chemical signatures and hierarchical galaxy formation

    NARCIS (Netherlands)

    Venn, KA; Irwin, M; Shetrone, MD; Tout, CA; Hill, [No Value; Tolstoy, E

    To compare the chemistries of stars in the Milky Way dwarf spheroidal (dSph) satellite galaxies with stars in the Galaxy, we have compiled a large sample of Galactic stellar abundances from the literature. When kinematic information is available, we have assigned the stars to standard Galactic

  18. Spectroscopy of superluminous supernova host galaxies

    DEFF Research Database (Denmark)

    Leloudas, G.; Kruehler, T.; Schulze, S

    2015-01-01

    -poor) often (~50% in our sample) occur in a class of galaxies that is known as Extreme Emission Line Galaxies (EELGs). The probability of this happening by chance is negligible and we therefore conclude that the extreme environmental conditions and the SLSN phenomenon are related. In contrast, SLSNe...

  19. Spectrophotometry of nearby field galaxies : The data

    NARCIS (Netherlands)

    Jansen, RA; Fabricant, D; Franx, M; Caldwell, N

    We have obtained integrated and nuclear spectra as well as U, B, R surface photometry for a representative sample of 196 nearby galaxies. These galaxies span the entire Hubble sequence in morphological type, as well as a wide range of luminosities (M(B) = -14 to -22). Here we present the

  20. ANGULAR-MOMENTUM IN BINARY SPIRAL GALAXIES

    NARCIS (Netherlands)

    OOSTERLOO, T

    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

  1. Predicting galaxy star formation rates via the co-evolution of galaxies and haloes

    Science.gov (United States)

    Watson, Douglas F.; Hearin, Andrew P.; Berlind, Andreas A.; Becker, Matthew R.; Behroozi, Peter S.; Skibba, Ramin A.; Reyes, Reinabelle; Zentner, Andrew R.; van den Bosch, Frank C.

    2015-01-01

    In this paper, we test the age matching hypothesis that the star formation rate (SFR) of a galaxy of fixed stellar mass is determined by its dark matter halo formation history, e.g. more quiescent galaxies reside in older haloes. We present new Sloan Digital Sky Survey measurements of the galaxy two-point correlation function and galaxy-galaxy lensing as a function of stellar mass and SFR, separated into quenched and star-forming galaxy samples to test this simple model. We find that our age matching model is in excellent agreement with these new measurements. We also find that our model is able to predict: (1) the relative SFRs of central and satellite galaxies, (2) the SFR dependence of the radial distribution of satellite galaxy populations within galaxy groups, rich groups, and clusters and their surrounding larger scale environments, and (3) the interesting feature that the satellite quenched fraction as a function of projected radial distance from the central galaxy exhibits an ˜r-.15 slope, independent of environment. These accurate predictions are intriguing given that we do not explicitly model satellite-specific processes after infall, and that in our model the virial radius does not mark a special transition region in the evolution of a satellite. The success of the model suggests that present-day galaxy SFR is strongly correlated with halo mass assembly history.

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

    Science.gov (United States)

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

    1997-10-01

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

  3. CORES AND THE KINEMATICS OF EARLY-TYPE GALAXIES

    International Nuclear Information System (INIS)

    Lauer, Tod R.

    2012-01-01

    I have combined the Emsellem et al. ATLAS 3D rotation measures of a large sample of early-type galaxies with Hubble Space Telescope based classifications of their central structure to characterize the rotation velocities of galaxies with cores. 'Core galaxies' rotate slowly, while 'power-law galaxies' (galaxies that lack cores) rotate rapidly, confirming the analysis of Faber et al. Significantly, the amplitude of rotation sharply discriminates between the two types in the –19 > M V > –22 domain over which the two types coexist. The slow rotation in the small set of core galaxies with M V > –20, in particular, brings them into concordance with the more massive core galaxies. The ATLAS 3D 'fast-rotating' and 'slow-rotating' early-type galaxies are essentially the same as power-law and core galaxies, respectively, or the Kormendy and Bender two families of elliptical galaxies based on rotation, isophote shape, and central structure. The ATLAS 3D fast rotators do include roughly half of the core galaxies, but their rotation amplitudes are always at the lower boundary of that subset. Essentially, all core galaxies have ATLAS 3D rotation amplitudes λ R e /2 ≤0.25, while all galaxies with λ R e /2 >0.25 and figure eccentricity >0.2 lack cores. Both figure rotation and the central structure of early-type galaxies should be used together to separate systems that appear to have formed from 'wet' versus 'dry' mergers.

  4. Quantifying the FIR interaction enhancement in paired galaxies

    International Nuclear Information System (INIS)

    Xu Cong; Sulentic, J.W.

    1990-01-01

    We studied the ''Catalogue of Isolated Pairs of Galaxies in the Northern Hemisphere'' by Karachentsev (1972) and a well matched comparison sample taken from the ''Catalogue of Isolated Galaxies'' by Karachentseva (1973) in order to quantify the enhanced FIR emission properties of interacting galaxies. 8 refs, 6 figs

  5. On the Nature and History of Blue Amorphous Galaxies

    Science.gov (United States)

    Marlowe, Amanda True

    1998-07-01

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

  6. The Far-Infrared Properties of the Most Isolated Galaxies

    Science.gov (United States)

    Lisenfeld, U.; Verdes-Montenegro, L.; Sulentic, J.; Leon, S.; Espada, D.; Bergond, G.; García, E.; Sabater, J.; Santander-Vela, J. D.; Verley, S.

    2007-05-01

    A long-standing question in galaxy evolution involves the role of nature (self-regulation) vs. nurture (environment) on the observed properties (and evolution) of galaxies. A collaboration centreed at the Instituto de Astrofisica de Andalucia (Granada, Spain) is trying to address this question by producing a observational database for a sample of 1050 isolated galaxies from the catalogue of Karachentseva (1973) with the overarching goal being the generation of a "zero-point" sample against which effects of environment on galaxies can be assessed. The AMIGA (Analysis of the Interstellar Medium of Isolated Galaxies) database (see www.iaa.es/AMIGA.html) will include optical, IR and radio line and continuum measures. The galaxies in the sample represent the most isolated galaxies in the local universe. In the present contribution, we will present the project, as well as the results of an analysis of the far-infrared (FIR) and molecular gas properties of this sample.

  7. Low surface brightness galaxies in the Fornax Cluster: automated galaxy surface photometry

    International Nuclear Information System (INIS)

    Davies, J.I.; Phillipps, S.; Disney, M.J.

    1988-01-01

    A sample is presented of low surface brightness galaxies (with extrapolated central surface brightness fainter than 22.0 Bμ) in the Fornax Cluster region which has been measured by the APM machine. Photometric parameters, namely profile shape, scale length, central brightness and total magnitude, are derived for the sample galaxies and correlations between the parameters of low surface brightness dwarf galaxies are discussed, with particular reference to the selection limits. Contrary to previous authors we find no evidence for a luminosity-surface brightness correlation in the sense of lower surface brightness galaxies having lower luminosities and scale sizes. In fact, the present data suggest that it is the galaxies with the largest scale lengths which are more likely to be of very low surface brightness. In addition, the larger scale length galaxies occur preferentially towards the centre of the Cluster. (author)

  8. The surface brightness of 1550 galaxies in Fornax: automated galaxy surface photometry: Pt. 2

    International Nuclear Information System (INIS)

    Phillipps, S.; Disney, M.J.; Kibblewhite, E.J.; Cawson, M.G.M.

    1987-01-01

    A survey of a complete sample of galaxies in the region of the Fornax cluster is presented. Measurements with the Automatic Plate Measuring machine are used to derive the observed distribution of galaxy surface brightness for 1550 objects. Corrections for surface brightness dependent selection effects are then made in order to estimate the true distribution. It is found that the sample (with 16.6 ≤ Msub(APM) ≤ 19.1) is divided into two distinct populations. The 'normal' galaxies with extrapolated central surface brightness Ssub(x) ≤ 22.5 Bμ form a uniformly distributed background of field galaxies. Low surface brightness galaxies (Ssub(x) ≥ 22.5 Bμ), on the other hand, are strongly clumped about the cluster centre. There appear to be few low surface brightness field galaxies. (author)

  9. Far-infrared luminosities of Markarian starburst galaxies

    International Nuclear Information System (INIS)

    Deutsch, L.K.; Willner, S.P.

    1986-01-01

    Total far-infrared luminosities have been calculated from measured IRAS fluxes for a sample of optically selected galaxies and for a comparison sample of spiral galaxies. The starburst galaxies are notably more luminous in the far-infrared and have higher dust color temperatures than the comparison galaxies. The far-infrared light dominates the total luminosity of the starburst galaxies, and a significant amount of dust must be present. The far-infrared emission correlates well with total blue luminosity, nuclear blue luminosity, and nuclear H-alpha luminosity. The dust that produces the far-infrared light is probably heated predominantly by B rather than by O stars. 30 references

  10. Observations of Superwinds in Dwarf Galaxies

    Science.gov (United States)

    Marlowe, A. T.; Heckman, T. M.; Wyse, R.; Schommer, R.

    1993-12-01

    Dwarf galaxies are important in developing our understanding of the formation and evolution of galaxies, and of the structure in the universe. The concept of supernova-driven mass outflows is a vital ingredient in theories of the structure and evolution of dwarfs galaxies. We have begun a detailed multi-waveband search for outflows in starbursting dwarf galaxies, and have obtained Fabry-Perot images and Echelle spectra of 20 nearby actively-star-forming dwarf galaxies. In about half the sample, the Fabry-Perot Hα images show loops and filaments with sizes of one to a few kpc. The Echelle spectra taken through the loops and filaments show kinematics consistent with expanding bubble-like structures. We describe these data, and present seven dwarfs in our sample that have the strongest evidence of outflows.

  11. A study of spiral galaxies

    International Nuclear Information System (INIS)

    Wevers, B.M.H.R.

    1984-01-01

    Attempts have been made to look for possible correlations between integral properties of spiral galaxies as a function of morphological type. To investigate this problem, one needs the detailed distribution of both the gaseous and the stellar components for a well-defined sample of spiral galaxies. A sample of about 20 spiral galaxies was therefore defined; these galaxies were observed in the 21 cm neutral hydrogen line with the Westerbork Synthesis Radio Telescope and in three broad-band optical colours with the 48-inch Palomar Smidt Telescope. First, an atlas of the combined radio and optical observations of 16 nearby northern-hemisphere spiral galaxies is presented. Luminosity profiles are discussed and the scale lengths of the exponential disks and extrapolated central surface brightnesses are derived, as well as radial color distributions; azimuthal surface brightness distributions and rotation curves. Possible correlations with optical features are investigated. It is found that 20 to 50 per cent of the total mass is in the disk. (Auth.)

  12. Genesis of dwarf galaxies in interacting system

    International Nuclear Information System (INIS)

    Duc, Pierre-Alain

    1995-01-01

    This research thesis addresses the study of interacting and merging galaxies, and more particularly the associated stellar formation episodes. The author first reports an analysis of the central regions of these objects by studying a specific class among them, i.e. galaxies discovered by the IRAS satellite which are ultra-luminous in the far infrared. The author presents results obtained by optical and infrared imagery and spectroscopy of a complete sample of objects located in the southern hemisphere. In the second part, the author focusses on outside regions of interacting galaxies, discusses the observation of filaments formed under the influence of tidal forces acting during galactic collisions, and of condensations which are as luminous as dwarf galaxies. Then a multi-wavelength study of several neighbouring systems revealed the existence of a specific class of objects, the tidal dwarf galaxies, which are formed from stellar and gaseous material snatched from the disk of interacting galaxies. Gas-rich tidal dwarf galaxies contain, like dwarf irregular galaxies or blue compact galaxies, newly formed stars. But, in opposition with these ones, they are richer in heavy elements: this is one of the consequences of a specific mode of galactic formation based on a cosmic recycling [fr

  13. Active Galactic Nuclei in Dwarf Galaxies

    Science.gov (United States)

    Hein, Megan; Secrest, N.; Satyapal, S.

    2014-01-01

    Supermassive black holes (SMBHs) one million to a few billion times the mass of our sun are thought to reside in the center of most, if not all, bulge-dominated galaxies. It has been observed that the mass of these SMBHs is strongly correlated with the mass of these bulges, leading to the popular view that these central black holes are formed by galaxy mergers, which induce the growth of the galaxy's bulge and provide matter with which to feed the black hole. Although these properties and their possible consequences have been studied extensively in high mass galaxies and galaxies with large bulges, there is very little research on the possible existence and subsequent properties of SMBHs in low mass galaxies or galaxies with small or no central bulges. This is a significant weakness in the research of these objects as the study of this population of galaxies would allow us to gain valuable insight into SMBH seeds, black holes thought to have formed in the early universe. Strong X-rays are a good indicator of an accreting black hole, because they require more energy to produce and SMBHs are highly energetic, as well as being easier to see due to their ability to penetrate matter more easily than other forms of radiation. In this poster, I will present the results from an X-ray investigation using data matched from the Chandra X-ray observatory to a sample of low mass galaxies (with a mass of log(M) < 9).

  14. Investigations of Galaxy Clusters Using Gravitational Lensing

    Energy Technology Data Exchange (ETDEWEB)

    Wiesner, Matthew P. [Northern Illinois Univ., DeKalb, IL (United States)

    2014-08-01

    In this dissertation, we discuss the properties of galaxy clusters that have been determined using strong and weak gravitational lensing. A galaxy cluster is a collection of galaxies that are bound together by the force of gravity, while gravitational lensing is the bending of light by gravity. Strong lensing is the formation of arcs or rings of light surrounding clusters and weak lensing is a change in the apparent shapes of many galaxies. In this work we examine the properties of several samples of galaxy clusters using gravitational lensing. In Chapter 1 we introduce astrophysical theory of galaxy clusters and gravitational lensing. In Chapter 2 we examine evidence from our data that galaxy clusters are more concentrated than cosmology would predict. In Chapter 3 we investigate whether our assumptions about the number of galaxies in our clusters was valid by examining new data. In Chapter 4 we describe a determination of a relationship between mass and number of galaxies in a cluster at higher redshift than has been found before. In Chapter 5 we describe a model of the mass distribution in one of the ten lensing systems discovered by our group at Fermilab. Finally in Chapter 6 we summarize our conclusions.

  15. Are star formation rates of galaxies bimodal?

    Science.gov (United States)

    Feldmann, Robert

    2017-09-01

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

  16. Redshifts of radio galaxies in Abell clusters of galaxies

    International Nuclear Information System (INIS)

    Owen, F.N.; White, R.A.; Thronson, H.A. Jr.

    1988-01-01

    The paper presents redshifts for 51 radio galaxies and companion systems which were obtained with the Steward 2.3-m and multiple mirror telescopes. The observations were performed over the course of six runs during 1980-1983. The sample includes eight multiple systems (or multiple nuclei) having internal velocity differences ranging from 150 to 2400 km/s. 17 references

  17. Selection bias in dynamically measured supermassive black hole samples: scaling relations and correlations between residuals in semi-analytic galaxy formation models

    Science.gov (United States)

    Barausse, Enrico; Shankar, Francesco; Bernardi, Mariangela; Dubois, Yohan; Sheth, Ravi K.

    2017-07-01

    Recent work has confirmed that the scaling relations between the masses of supermassive black holes and host-galaxy properties such as stellar masses and velocity dispersions may be biased high. Much of this may be caused by the requirement that the black hole sphere of influence must be resolved for the black hole mass to be reliably estimated. We revisit this issue with a comprehensive galaxy evolution semi-analytic model. Once tuned to reproduce the (mean) correlation of black hole mass with velocity dispersion, the model cannot account for the correlation with stellar mass. This is independent of the model's parameters, thus suggesting an internal inconsistency in the data. The predicted distributions, especially at the low-mass end, are also much broader than observed. However, if selection effects are included, the model's predictions tend to align with the observations. We also demonstrate that the correlations between the residuals of the scaling relations are more effective than the relations themselves at constraining models for the feedback of active galactic nuclei (AGNs). In fact, we find that our model, while in apparent broad agreement with the scaling relations when accounting for selection biases, yields very weak correlations between their residuals at fixed stellar mass, in stark contrast with observations. This problem persists when changing the AGN feedback strength, and is also present in the hydrodynamic cosmological simulation Horizon-AGN, which includes state-of-the-art treatments of AGN feedback. This suggests that current AGN feedback models are too weak or simply not capturing the effect of the black hole on the stellar velocity dispersion.

  18. HOT GAS HALOS IN EARLY-TYPE FIELD GALAXIES

    International Nuclear Information System (INIS)

    Mulchaey, John S.; Jeltema, Tesla E.

    2010-01-01

    We use Chandra and XMM-Newton to study the hot gas content in a sample of field early-type galaxies. We find that the L X -L K relationship is steeper for field galaxies than for comparable galaxies in groups and clusters. The low hot gas content of field galaxies with L K ∼ * suggests that internal processes such as supernovae-driven winds or active galactic nucleus feedback expel hot gas from low-mass galaxies. Such mechanisms may be less effective in groups and clusters where the presence of an intragroup or intracluster medium can confine outflowing material. In addition, galaxies in groups and clusters may be able to accrete gas from the ambient medium. While there is a population of L K ∼ * galaxies in groups and clusters that retain hot gas halos, some galaxies in these rich environments, including brighter galaxies, are largely devoid of hot gas. In these cases, the hot gas halos have likely been removed via ram pressure stripping. This suggests a very complex interplay between the intragroup/intracluster medium and hot gas halos of galaxies in rich environments, with the ambient medium helping to confine or even enhance the halos in some cases and acting to remove gas in others. In contrast, the hot gas content of more isolated galaxies is largely a function of the mass of the galaxy, with more massive galaxies able to maintain their halos, while in lower mass systems the hot gas escapes in outflowing winds.

  19. The AGN Luminosity Fraction in Galaxy Mergers

    Science.gov (United States)

    Dietrich, Jeremy; Weiner, Aaron; Ashby, Matthew; Martinez-Galarza, Juan Rafael; Smith, Howard Alan

    2017-01-01

    Galaxy mergers are key events in galaxy evolution, generally triggering massive starbursts and AGNs. However, in these chaotic systems, it is not yet known what fraction each of these two mechanisms contributes to the total luminosity. Here we measure and model spectral energy distributions (SEDs) using the Code for Investigating Galaxy Emission (CIGALE) in up to 33 broad bands from the UV to the far-IR for 23 IR-luminous galaxies to estimate the fraction of the bolometric IR luminosity that can be attributed to the AGN. The galaxies are split nearly evenly into two subsamples: late-stage mergers, found in the IRAS Revised Bright Galaxy Sample or Faint Source Catalog, and early-stage mergers found in the Spitzer Interacting Galaxy Sample. We find that the AGN contribution to the total IR luminosity varies greatly from system to system, from 0% up to ~90%, but is substantially greater in the later-stage and brighter mergers. This is consistent with what is known about galaxy evolution and the triggering of AGNs.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

  20. Global extinction in spiral galaxies

    NARCIS (Netherlands)

    Tully, RB; Pierce, MJ; Saunders, W; Verheijen, MAW; Witchalls, PL

    Magnitude-limited samples of spiral galaxies drawn from the Ursa Major and Pisces Clusters are used to determine their extinction properties as a function of inclination. Imaging photometry is available for 87 spirals in the B, R, I, and K' bands. Extinction causes systematic scatter in

  1. Do Galaxies Follow Darwinian Evolution?

    Science.gov (United States)

    2006-12-01

    , France, who coordinates the VIMOS VLT Deep Survey team that made the discovery. "They suggest that galaxies as we see them today are the product of their inherent genetic information, evolved over time, as well as complex interactions with their environments, such as mergers." Scientists have known for several decades that galaxies in the Universe's past look different to those in the present-day Universe, local to the Milky Way [3]. Today, galaxies can be roughly classified as red, when few or no new stars are being born, or blue, where star formation is still ongoing. Moreover, a strong correlation exists between a galaxy's colour and the environment it resides in: the more sociable types found in dense clusters are more likely to be red than the more isolated ones. By looking back at a wide range of galaxies of a variety of ages, the astronomers were aiming to study how this peculiar correlation has evolved over time. "Using VIMOS, we were able to use the largest sample of galaxies currently available for this type of study, and because of the instrument's ability to study many objects at a time we obtained many more measurements than previously possible," said Angela Iovino, from the Brera Astronomical Observatory, Italy, another member of the team. The team's discovery of a marked variation in the 'colour-density' relationship, depending on whether a galaxy is found in a cluster or alone, and on its luminosity, has many potential implications. The findings suggest for example that being located in a cluster quenches a galaxy's ability to form stars more quickly compared with those in isolation. Luminous galaxies also run out of star-forming material at an earlier time than fainter ones. They conclude that the connection between galaxies' colour, luminosity and their local environment is not merely a result of primordial conditions 'imprinted' during their formation - but just as for humans, galaxies' relationship and interactions can have a profound impact on their

  2. THE GALAXY OPTICAL LUMINOSITY FUNCTION FROM THE AGN AND GALAXY EVOLUTION SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Cool, Richard J. [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Eisenstein, Daniel J. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Kochanek, Christopher S. [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Brown, Michael J. I. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Caldwell, Nelson; Forman, William R.; Hickox, Ryan C.; Jones, Christine; Murray, Stephen S. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Dey, Arjun; Jannuzi, Buell T. [National Optical Astronomy Observatory, Tucson, AZ 85726 (United States); Moustakas, John [Center for Astrophysics and Space Science, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States)

    2012-03-20

    We present the galaxy optical luminosity function for the redshift range 0.05 < z < 0.75 from the AGN and Galaxy Evolution Survey, a spectroscopic survey of 7.6 deg{sup 2} in the Booetes field of the NOAO Deep Wide-Field Survey. Our statistical sample is composed of 12,473 galaxies with known redshifts down to I = 20.4 (AB). Our results at low redshift are consistent with those from Sloan Digital Sky Survey; at higher redshift, we find strong evidence for evolution in the luminosity function, including differential evolution between blue and red galaxies. We find that the luminosity density evolves as (1 + z){sup (0.54{+-}0.64)} for red galaxies and (1 + z){sup (1.64{+-}0.39)} for blue galaxies.

  3. Galaxy LIMS for next-generation sequencing

    NARCIS (Netherlands)

    Scholtalbers, J.; Rossler, J.; Sorn, P.; Graaf, J. de; Boisguerin, V.; Castle, J.; Sahin, U.

    2013-01-01

    SUMMARY: We have developed a laboratory information management system (LIMS) for a next-generation sequencing (NGS) laboratory within the existing Galaxy platform. The system provides lab technicians standard and customizable sample information forms, barcoded submission forms, tracking of input

  4. Demographics of Starbursts in Nearby Seyfert Galaxies

    Science.gov (United States)

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

    2002-12-01

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

  5. Multicolor photometry of the nearby galaxy cluster A119

    International Nuclear Information System (INIS)

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

    2012-01-01

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

  6. Polar ring galaxies in the Galaxy Zoo

    Science.gov (United States)

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

    2012-05-01

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

  7. 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)

  8. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-01

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

  9. Formation of galaxies

    International Nuclear Information System (INIS)

    Szalay, A.S.

    1984-12-01

    The present theories of galaxy formation are reviewed. The relation between peculiar velocities and the correlation function of galaxies points to the possibility that galaxies do not form uniformly everywhere. Scale invariant properties of the cluster-cluster correlations are discussed. Comparing the correlation functions in a dimensionless way, galaxies appear to be stronger clustered, in contrast with the comparison of the dimensional amplitudes of the correlation functions. Theoretical implications of several observations as Lyman-α clouds, correlations of faint galaxies are discussed. None of the present theories of galaxy formation can account for all facts in a natural way. 29 references

  10. Joint analysis of galaxy-galaxy lensing and galaxy clustering: Methodology and forecasts for Dark Energy Survey

    International Nuclear Information System (INIS)

    Park, Y.; Krause, E.; Dodelson, S.; Jain, B.; Amara, A.

    2016-01-01

    Here, the joint analysis of galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth function of large-scale structure. Anticipating a near future application of this analysis to Dark Energy Survey (DES) measurements of galaxy positions and shapes, we develop a practical approach to modeling the assumptions and systematic effects affecting the joint analysis of small-scale galaxy-galaxy lensing and large-scale galaxy clustering. Introducing parameters that characterize the halo occupation distribution (HOD), photometric redshift uncertainties, and shear measurement errors, we study how external priors on different subsets of these parameters affect our growth constraints. Degeneracies within the HOD model, as well as between the HOD and the growth function, are identified as the dominant source of complication, with other systematic effects being subdominant. The impact of HOD parameters and their degeneracies necessitate the detailed joint modeling of the galaxy sample that we employ. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the Universe, conservatively/optimistically constraining the growth function to 7.9%/4.8% with its first-year data that cover over 1000 square degrees, and to 3.9%/2.3% with its full five-year data that will survey 5000 square degrees, including both statistical and systematic uncertainties.

  11. GALAXY ENVIRONMENTS OVER COSMIC TIME: THE NON-EVOLVING RADIAL GALAXY DISTRIBUTIONS AROUND MASSIVE GALAXIES SINCE z = 1.6

    International Nuclear Information System (INIS)

    Tal, Tomer; Van Dokkum, Pieter G.; Leja, Joel; Franx, Marijn; Wake, David A.; Whitaker, Katherine E.

    2013-01-01

    We present a statistical study of the environments of massive galaxies in four redshift bins between z = 0.04 and z = 1.6, using data from the Sloan Digital Sky Survey and the NEWFIRM Medium Band Survey. We measure the projected radial distribution of galaxies in cylinders around a constant number density selected sample of massive galaxies and utilize a statistical subtraction of contaminating sources. Our analysis shows that massive primary galaxies typically live in group halos and are surrounded by 2-3 satellites with masses more than one-tenth of the primary galaxy mass. The cumulative stellar mass in these satellites roughly equals the mass of the primary galaxy itself. We further find that the radial number density profile of galaxies around massive primaries has not evolved significantly in either slope or overall normalization in the past 9.5 Gyr. A simplistic interpretation of this result can be taken as evidence for a lack of mergers in the studied groups and as support for a static evolution model of halos containing massive primaries. Alternatively, there exists a tight balance between mergers and accretion of new satellites such that the overall distribution of galaxies in and around the halo is preserved. The latter interpretation is supported by a comparison to a semi-analytic model, which shows a similar constant average satellite distribution over the same redshift range.

  12. Strong bimodality in the host halo mass of central galaxies from galaxy-galaxy lensing

    Science.gov (United States)

    Mandelbaum, Rachel; Wang, Wenting; Zu, Ying; White, Simon; Henriques, Bruno; More, Surhud

    2016-04-01

    We use galaxy-galaxy lensing to study the dark matter haloes surrounding a sample of locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey. We measure mean halo mass as a function of the stellar mass and colour of the central galaxy. Mock catalogues constructed from semi-analytic galaxy formation simulations demonstrate that most LBGs are the central objects of their haloes, greatly reducing interpretation uncertainties due to satellite contributions to the lensing signal. Over the full stellar mass range, 10.3 10.7. Tests using the mock catalogues and on the data themselves clarify the effects of LBG selection and show that it cannot artificially induce a systematic dependence of halo mass on LBG colour. The bimodality in halo mass at fixed stellar mass is reproduced by the astrophysical model underlying our mock catalogue, but the sign of the effect is inconsistent with recent, nearly parameter-free age-matching models. The sign and magnitude of the effect can, however, be reproduced by halo occupation distribution models with a simple (few-parameter) prescription for type dependence.

  13. AGES: THE AGN AND GALAXY EVOLUTION SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Kochanek, C. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Eisenstein, D. J.; Caldwell, N.; Jones, C.; Murray, S. S.; Forman, W. R.; Green, P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Cool, R. J. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States); Assef, R. J.; Eisenhardt, P.; Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Jannuzi, B. T.; Dey, A. [NOAO, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Brown, M. J. I. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Gonzalez, A. H. [Department of Astronomy, Bryant Space Science Center, University of Florida, Gainesville, FL 32611 (United States)

    2012-05-01

    The AGN and Galaxy Evolution Survey (AGES) is a redshift survey covering, in its standard fields, 7.7 deg{sup 2} of the Booetes field of the NOAO Deep Wide-Field Survey. The final sample consists of 23,745 redshifts. There are well-defined galaxy samples in 10 bands (the B{sub W} , R, I, J, K, IRAC 3.6, 4.5, 5.8, and 8.0 {mu}m, and MIPS 24 {mu}m bands) to a limiting magnitude of I < 20 mag for spectroscopy. For these galaxies, we obtained 18,163 redshifts from a sample of 35,200 galaxies, where random sparse sampling was used to define statistically complete sub-samples in all 10 photometric bands. The median galaxy redshift is 0.31, and 90% of the redshifts are in the range 0.085 < z < 0.66. Active galactic nuclei (AGNs) were selected as radio, X-ray, IRAC mid-IR, and MIPS 24 {mu}m sources to fainter limiting magnitudes (I < 22.5 mag for point sources). Redshifts were obtained for 4764 quasars and galaxies with AGN signatures, with 2926, 1718, 605, 119, and 13 above redshifts of 0.5, 1, 2, 3, and 4, respectively. We detail all the AGES selection procedures and present the complete spectroscopic redshift catalogs and spectral energy distribution decompositions. Photometric redshift estimates are provided for all sources in the AGES samples.

  14. Star Formation in low mass galaxies

    Science.gov (United States)

    Mehta, Vihang

    2018-01-01

    Our current hierarchical view of the universe asserts that the large galaxies we see today grew via mergers of numerous smaller galaxies. As evidenced by recent literature, the collective impact of these low mass galaxies on the universe is more substantial than previously thought. Studying the growth and evolution of these low mass galaxies is critical to our understanding of the universe as a whole. Star formation is one of the most important ongoing processes in galaxies. Forming stars is fundamental to the growth of a galaxy. One of the main goals of my thesis is to analyze the star formation in these low mass galaxies at different redshifts.Using the Hubble UltraViolet Ultra Deep Field (UVUDF), I investigate the star formation in galaxies at the peak of the cosmic star formation history using the ultraviolet (UV) light as a star formation indicator. Particularly, I measure the UV luminosity function (LF) to probe the volume-averaged star formation properties of galaxies at these redshifts. The depth of the UVUDF is ideal for a direct measurement of the faint end slope of the UV LF. This redshift range also provides a unique opportunity to directly compare UV to the "gold standard" of star formation indicators, namely the Hα nebular emission line. A joint analysis of the UV and Hα LFs suggests that, on average, the star formation histories in low mass galaxies (~109 M⊙) are more bursty compared to their higher mass counterparts at these redshifts.Complementary to the analysis of the average star formation properties of the bulk galaxy population, I investigate the details of star formation in some very bursty galaxies at lower redshifts selected from Spitzer Large Area Survey with Hyper-Suprime Cam (SPLASH). Using a broadband color-excess selection technique, I identify a sample of low redshift galaxies with bright nebular emission lines in the Subaru-XMM Deep Field (SXDF) from the SPLASH-SXDF catalog. These galaxies are highly star forming and have

  15. Star formation rates in isolated galaxies selected from the Two-Micron All-Sky Survey

    Science.gov (United States)

    Melnyk, O.; Karachentseva, V.; Karachentsev, I.

    2015-08-01

    We have considered the star formation properties of 1616 isolated galaxies from the 2MASS XSC (Extended Source Catalog) selected sample (2MIG) with the far-ultraviolet GALEX magnitudes. This sample was then compared with corresponding properties of isolated galaxies from the Local Orphan Galaxies (LOG) catalogue and paired galaxies. We found that different selection algorithms define different populations of isolated galaxies. The population of the LOG catalogue, selected from non-clustered galaxies in the Local Supercluster volume, mostly consists of low-mass spiral and late-type galaxies. The specific star formation rate (SSFR) upper limit in isolated and paired galaxies does not exceed the value of ˜dex(-9.4). This is probably common for galaxies of differing activity and environment (at least at z processes is the galaxy mass. However, the environmental influence is notable: paired massive galaxies with logM* > 11.5 have higher (S)SFR than isolated galaxies. Our results suggest that the environment helps to trigger the star formation in the highest mass galaxies. We found that the fraction of AGN in the paired sample is only a little higher than in our isolated galaxy sample. We assume that AGN phenomenon is probably defined by secular galaxy evolution.

  16. THE GROWTH OF COOL CORES AND EVOLUTION OF COOLING PROPERTIES IN A SAMPLE OF 83 GALAXY CLUSTERS AT 0.3 < z < 1.2 SELECTED FROM THE SPT-SZ SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, M.; Bautz, M. W. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Vikhlinin, A.; Stalder, B.; Ashby, M. L. N.; Bayliss, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); De Haan, T. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); Lin, H. W. [Caddo Parish Magnet High School, Shrevport, LA 71101 (United States); Aird, K. A. [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Bocquet, S.; Desai, S. [Department of Physics, Ludwig-Maximilians-Universitaet, Scheinerstr. 1, D-81679 Muenchen (Germany); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Cho, H. M. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); Clocchiatti, A., E-mail: mcdonald@space.mit.edu [Departamento de Astronomia y Astrosifica, Pontificia Universidad Catolica (Chile); and others

    2013-09-01

    We present first results on the cooling properties derived from Chandra X-ray observations of 83 high-redshift (0.3 < z < 1.2) massive galaxy clusters selected by their Sunyaev-Zel'dovich signature in the South Pole Telescope data. We measure each cluster's central cooling time, central entropy, and mass deposition rate, and compare these properties to those for local cluster samples. We find no significant evolution from z {approx} 0 to z {approx} 1 in the distribution of these properties, suggesting that cooling in cluster cores is stable over long periods of time. We also find that the average cool core entropy profile in the inner {approx}100 kpc has not changed dramatically since z {approx} 1, implying that feedback must be providing nearly constant energy injection to maintain the observed ''entropy floor'' at {approx}10 keV cm{sup 2}. While the cooling properties appear roughly constant over long periods of time, we observe strong evolution in the gas density profile, with the normalized central density ({rho}{sub g,0}/{rho}{sub crit}) increasing by an order of magnitude from z {approx} 1 to z {approx} 0. When using metrics defined by the inner surface brightness profile of clusters, we find an apparent lack of classical, cuspy, cool-core clusters at z > 0.75, consistent with earlier reports for clusters at z > 0.5 using similar definitions. Our measurements indicate that cool cores have been steadily growing over the 8 Gyr spanned by our sample, consistent with a constant, {approx}150 M{sub Sun} yr{sup -1} cooling flow that is unable to cool below entropies of 10 keV cm{sup 2} and, instead, accumulates in the cluster center. We estimate that cool cores began to assemble in these massive systems at z{sub cool}=1.0{sup +1.0}{sub -0.2}, which represents the first constraints on the onset of cooling in galaxy cluster cores. At high redshift (z {approx}> 0.75), galaxy clusters may be classified as ''cooling flows

  17. Halo models of HI selected galaxies

    Science.gov (United States)

    Paul, Niladri; Choudhury, Tirthankar Roy; Paranjape, Aseem

    2018-06-01

    Modelling the distribution of neutral hydrogen (HI) in dark matter halos is important for studying galaxy evolution in the cosmological context. We use a novel approach to infer the HI-dark matter connection at the massive end (m_H{I} > 10^{9.8} M_{⊙}) from radio HI emission surveys, using optical properties of low-redshift galaxies as an intermediary. In particular, we use a previously calibrated optical HOD describing the luminosity- and colour-dependent clustering of SDSS galaxies and describe the HI content using a statistical scaling relation between the optical properties and HI mass. This allows us to compute the abundance and clustering properties of HI-selected galaxies and compare with data from the ALFALFA survey. We apply an MCMC-based statistical analysis to constrain the free parameters related to the scaling relation. The resulting best-fit scaling relation identifies massive HI galaxies primarily with optically faint blue centrals, consistent with expectations from galaxy formation models. We compare the Hi-stellar mass relation predicted by our model with independent observations from matched Hi-optical galaxy samples, finding reasonable agreement. As a further application, we make some preliminary forecasts for future observations of HI and optical galaxies in the expected overlap volume of SKA and Euclid/LSST.

  18. Green valley galaxies as a transition population in different environments

    Science.gov (United States)

    Coenda, Valeria; Martínez, Héctor J.; Muriel, Hernán

    2018-02-01

    We present a comparative analysis of the properties of passive, star-forming and transition (green valley) galaxies in four discrete environments: field, groups, the outskirts and the core of X-ray clusters. We construct samples of galaxies from the Sloan Digital Sky Survey in these environments so that they are bound to have similar redshift distributions. The classification of galaxies into the three sequences is based on the UV-optical colour NUV - r. We study a number of galaxy properties: stellar mass, morphology, specific star formation rate and the history of star formation. The analysis of green valley (GV) galaxies reveals that the physical mechanisms responsible for external quenching become more efficient moving from the field to denser environments. We confirm previous findings that GV galaxies have intermediate morphologies; moreover, we find that this appears to be independent of the environment. Regarding the stellar mass of GV galaxies, we find that they tend to be more massive in the field than in denser environments. On average, GV galaxies account for ∼ 20 per cent of all galaxies in groups and X-ray clusters. We find evidence that the field environment is inefficient in transforming low-mass galaxies. GV galaxies have average star formation histories intermediate between passive and star-forming galaxies, and have a clear and consistent dependence on the environment: both, the quenching time and the amplitude of the star formation rate, decrease towards higher density environments.

  19. Alignments of galaxies within cosmic filaments from SDSS DR7

    International Nuclear Information System (INIS)

    Zhang, Youcai; Yang, Xiaohu; Wang, Huiyuan; Wang, Lei; Mo, H. J.; Van den Bosch, Frank C.

    2013-01-01

    Using a sample of galaxy groups selected from the Sloan Digital Sky Survey Data Release 7, we examine the alignment between the orientation of galaxies and their surrounding large-scale structure in the context of the cosmic web. The latter is quantified using the large-scale tidal field, reconstructed from the data using galaxy groups above a certain mass threshold. We find that the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, while galaxies in sheets have their major axes preferentially aligned parallel to the plane of the sheets. The strength of this alignment signal is strongest for red, central galaxies, and in good agreement with that of dark matter halos in N-body simulations. This suggests that red, central galaxies are well aligned with their host halos, in quantitative agreement with previous studies based on the spatial distribution of satellite galaxies. There is a luminosity and mass dependence that brighter and more massive galaxies in filaments and sheets have stronger alignment signals. We also find that the orientation of galaxies is aligned with the eigenvector associated with the smallest eigenvalue of the tidal tensor. These observational results indicate that galaxy formation is affected by large-scale environments and strongly suggest that galaxies are aligned with each other over scales comparable to those of sheets and filaments in the cosmic web.

  20. Alignments of galaxies within cosmic filaments from SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Youcai; Yang, Xiaohu [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)

    2013-12-20

    Using a sample of galaxy groups selected from the Sloan Digital Sky Survey Data Release 7, we examine the alignment between the orientation of galaxies and their surrounding large-scale structure in the context of the cosmic web. The latter is quantified using the large-scale tidal field, reconstructed from the data using galaxy groups above a certain mass threshold. We find that the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, while galaxies in sheets have their major axes preferentially aligned parallel to the plane of the sheets. The strength of this alignment signal is strongest for red, central galaxies, and in good agreement with that of dark matter halos in N-body simulations. This suggests that red, central galaxies are well aligned with their host halos, in quantitative agreement with previous studies based on the spatial distribution of satellite galaxies. There is a luminosity and mass dependence that brighter and more massive galaxies in filaments and sheets have stronger alignment signals. We also find that the orientation of galaxies is aligned with the eigenvector associated with the smallest eigenvalue of the tidal tensor. These observational results indicate that galaxy formation is affected by large-scale environments and strongly suggest that galaxies are aligned with each other over scales comparable to those of sheets and filaments in the cosmic web.

  1. Clusters of Galaxies

    Science.gov (United States)

    Huchtmeier, W. K.; Richter, O. G.; Materne, J.

    1981-09-01

    The large-scale structure of the universe is dominated by clustering. Most galaxies seem to be members of pairs, groups, clusters, and superclusters. To that degree we are able to recognize a hierarchical structure of the universe. Our local group of galaxies (LG) is centred on two large spiral galaxies: the Andromeda nebula and our own galaxy. Three sr:naller galaxies - like M 33 - and at least 23 dwarf galaxies (KraanKorteweg and Tammann, 1979, Astronomische Nachrichten, 300, 181) can be found in the evironment of these two large galaxies. Neighbouring groups have comparable sizes (about 1 Mpc in extent) and comparable numbers of bright members. Small dwarf galaxies cannot at present be observed at great distances.

  2. Cosmology and galaxy formation

    International Nuclear Information System (INIS)

    Rees, M.J.

    1977-01-01

    Implications of the massive halos and ''missing mass'' for galaxy formation are addressed; it is suggested that this mass consists of ''Population III'' stars that formed before the galaxies did. 19 references

  3. ON THE STAR FORMATION PROPERTIES OF VOID GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Moorman, Crystal M.; Moreno, Jackeline; White, Amanda; Vogeley, Michael S. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Hoyle, Fiona [Pontifica Universidad Catolica de Ecuador, 12 de Octubre 1076 y Roca, Quito (Ecuador); Giovanelli, Riccardo; Haynes, Martha P., E-mail: crystal.m.moorman@drexel.edu [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University Ithaca, NY 14853 (United States)

    2016-11-10

    We measure the star formation properties of two large samples of galaxies from the SDSS in large-scale cosmic voids on timescales of 10 and 100 Myr, using H α emission line strengths and GALEX FUV fluxes, respectively. The first sample consists of 109,818 optically selected galaxies. We find that void galaxies in this sample have higher specific star formation rates (SSFRs; star formation rates per unit stellar mass) than similar stellar mass galaxies in denser regions. The second sample is a subset of the optically selected sample containing 8070 galaxies with reliable H i detections from ALFALFA. For the full H i detected sample, SSFRs do not vary systematically with large-scale environment. However, investigating only the H i detected dwarf galaxies reveals a trend toward higher SSFRs in voids. Furthermore, we estimate the star formation rate per unit H i mass (known as the star formation efficiency; SFE) of a galaxy, as a function of environment. For the overall H i detected population, we notice no environmental dependence. Limiting the sample to dwarf galaxies still does not reveal a statistically significant difference between SFEs in voids versus walls. These results suggest that void environments, on average, provide a nurturing environment for dwarf galaxy evolution allowing for higher specific star formation rates while forming stars with similar efficiencies to those in walls.

  4. SPATIAL ANISOTROPY OF GALAXY KINEMATICS IN SLOAN DIGITAL SKY SURVEY GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Skielboe, Andreas; Wojtak, Radosław; Pedersen, Kristian; Rozo, Eduardo; Rykoff, Eli S.

    2012-01-01

    Measurements of galaxy cluster kinematics are important in understanding the dynamical state and evolution of clusters of galaxies, as well as constraining cosmological models. While it is well established that clusters exhibit non-spherical geometries, evident in the distribution of galaxies on the sky, azimuthal variations of galaxy kinematics within clusters have yet to be observed. Here we measure the azimuthal dependence of the line-of-sight velocity dispersion profile in a stacked sample of 1743 galaxy clusters from the Sloan Digital Sky Survey (SDSS). The clusters are drawn from the SDSS DR8 redMaPPer catalog. We find that the line-of-sight velocity dispersion of galaxies lying along the major axis of the central galaxy is larger than those that lie along the minor axis. This is the first observational detection of anisotropic kinematics of galaxies in clusters. We show that the result is consistent with predictions from numerical simulations. Furthermore, we find that the degree of projected anisotropy is strongly dependent on the line-of-sight orientation of the galaxy cluster, opening new possibilities for assessing systematics in optical cluster finding.

  5. Dwarf Galaxies in the Chandra COSMOS Legacy Survey

    Science.gov (United States)

    Civano, Francesca Maria; Mezcua, Mar; Fabbiano, Giuseppina; Marchesi, Stefano; Suh, Hyewon; Volonteri, Marta; cyrille

    2018-01-01

    The existence of intermediate mass black holes (100 7. While detecting these seed black holes in the young Universe is observationally challenging, the nuclei of local dwarf galaxies are among the best places where to look for them as these galaxies resemble in mass and metallicity the first galaxies and they have not significantly grown through merger and accretion processes. We present a sample of 40 AGN in dwarf galaxies (107 0.5, our sample constitutes the highest-redshift discovery of AGN in dwarf galaxies. One of the dwarf galaxies is the least massive galaxy (M* = 6.6x107 Msun) found so far to host an active BH. We also present for the first time the evolution of the AGN fraction with stellar mass, X-ray luminosity, and redshift in dwarf galaxies out to z = 0.7, finding that it decreases with X-ray luminosity and stellar mass. Unlike massive galaxies, the AGN fraction is found to decrease with redshift, suggesting that AGN in dwarf galaxies evolve differently than those in high-mass galaxies.

  6. Herschel HIFI GOT C+ Survey: CII, HI, and CO Emissions in a Sample of Transition Clouds and Star-Forming regions in the Inner Galaxy

    Science.gov (United States)

    Pineda, Jorge; Velusamy, Thangasamy; Langer, William D.; Goldsmith, Paul; Li, Di; Yorke, Harold

    The GOT C+ a HIFI Herschel Key Project, studies the diffuse ISM throughout the Galactic Plane, using C+ as cloud tracer. The C+ line at 1.9 THz traces a so-far poorly studied stage in ISM cloud evolution -the transitional clouds going from atomic HI to molecular H2. This transition cloud phase, which is difficult to observe in HI and CO alone, may be best characterized via CII emission or absorption. The C+ line is also an excellent tracer of the warm diffuse gas and the warm, dense gas in the Photon Dominated Regions (PDRs). We can, therefore, use the CII emission as a probe to understand the effects of star formation on their interstellar environment. We present our first results on the transition between dense and hot gas (traced by CII) and dense and cold gas (traced by 12CO and 13CO) along a few representative lines of sight in the inner Galaxy from longitude 325 degrees to 25 degrees, taken during the HIFI Priority Science Phase. Comparisons of the high spectral resolution ( 1 km/s) HIFI data on C+ with HI, 12CO, and 13CO spectra allow us to separate out the different ISM components along each line of sight. Our results provide detailed information about the transition of diffuse atomic to molecular gas clouds needed to understand star formation and the lifecycle of the interstellar gas. These observations are being carried out with the Herschel Space Observatory, which is an ESA cornerstone mission, with contributions from NASA. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. JLP was supported under the NASA Postdoctoral Program at JPL, Caltech, administered by Oak Ridge Associated Universities through a contract with NASA, and is currently supported as a Caltech-JPL Postdoctoral associate.

  7. Sagittarius Dwarf Galaxy

    Science.gov (United States)

    Ibata, R.; Murdin, P.

    2000-11-01

    The Sagittarius DWARF GALAXY is the closest member of the Milky Way's entourage of satellite galaxies. Discovered by chance in 1994, its presence had previously been overlooked because it is largely hidden by the most crowded regions of our own Galaxy with which it is merging....

  8. Tidal interaction of galaxies

    International Nuclear Information System (INIS)

    Kozlov, N.N.; Syunyaev, R.A.; Ehneev, T.M.

    1974-01-01

    One of the hypotheses explaining the occurrence of anomalous details in interacting galaxies has been investigated. Pairs of galaxies with 'tails' oppositely directed or neighbouring galaxies with cofferdams 'bridges', as if connecting the galaxies, are called interacting galaxies. The hypothesis connects the origin of cofferdams and 'tails' of interacting galaxies with tidal effects ; the action of power gravitational forces in the intergalactic space. A source of such forces may be neighbouring stellar systems or invisible bodies, for instance, 'dead' quasars after a gravitational collapse. The effect of large masses of matter on the galaxy evolution has been investigated in the Institute of Applied Mathematics of the Academy of Sciences of the USSSR in 1971-1972 by numerical simulation of the process on a digital computer with the subsequent data transmission on a display. Different versions of a massive body flight relative to a galaxy disk are considered. Photographs of a display screen at different moments of time are presented. As a result of mathematical simulation of galaxies gravitational interactions effects are discovered which resemble real structures in photographs of galaxies. It seems to be premature to state that namely these mechanisms cause the formation of 'tails' and cofferdams between galaxies. However, even now it is clear that the gravitational interaction strongly affects the dynamics of the stellar system evolution. Further studies should ascertain a true scale of this effect and its genuine role in galaxy evolution

  9. GALAXY INFALL BY INTERACTING WITH ITS ENVIRONMENT: A COMPREHENSIVE STUDY OF 340 GALAXY CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Liyi [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands); Wen, Zhonglue [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China); Gandhi, Poshak [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Inada, Naohisa [Department of Physics, Nara National College of Technology, Yamatokohriyama, Nara 639-1080 (Japan); Kawaharada, Madoka [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 229-8510 (Japan); Kodama, Tadayuki [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Konami, Saori [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Nakazawa, Kazuhiro; Makishima, Kazuo [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Xu, Haiguang [Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang, Shanghai 200240 (China)

    2016-07-20

    To study systematically the evolution of the angular extents of the galaxy, intracluster medium (ICM), and dark matter components in galaxy clusters, we compiled the optical and X-ray properties of a sample of 340 clusters with redshifts <0.5, based on all the available data from the Sloan Digital Sky Survey and Chandra / XMM-Newton . For each cluster, the member galaxies were determined primarily with photometric redshift measurements. The radial ICM mass distribution, as well as the total gravitational mass distribution, was derived from a spatially resolved spectral analysis of the X-ray data. When normalizing the radial profile of galaxy number to that of the ICM mass, the relative curve was found to depend significantly on the cluster redshift; it drops more steeply toward the outside in lower-redshift subsamples. The same evolution is found in the galaxy-to-total mass profile, while the ICM-to-total mass profile varies in an opposite way. The behavior of the galaxy-to-ICM distribution does not depend on the cluster mass, suggesting that the detected redshift dependence is not due to mass-related effects, such as sample selection bias. Also, it cannot be ascribed to various redshift-dependent systematic errors. We interpret that the galaxies, the ICM, and the dark matter components had similar angular distributions when a cluster was formed, while the galaxies traveling in the interior of the cluster have continuously fallen toward the center relative to the other components, and the ICM has slightly expanded relative to the dark matter although it suffers strong radiative loss. This cosmological galaxy infall, accompanied by an ICM expansion, can be explained by considering that the galaxies interact strongly with the ICM while they are moving through it. The interaction is considered to create a large energy flow of 10{sup 4445} erg s{sup 1} per cluster from the member galaxies to their environment, which is expected to continue over cosmological timescales.

  10. The cluster environments of powerful, high-redshift radio galaxies

    International Nuclear Information System (INIS)

    Yates, M.G.

    1989-01-01

    We present deep imaging of a sample of 25 powerful radio galaxies in the redshift range 0.15 gr ) about each source, a measure of the richness of environment. The powerful radio galaxies in this sample at z>0.3 occupy environments nearly as rich on average as Abell class 0 clusters of galaxies, about three times richer than the environments of the z<0.3 radio galaxies. This trend in cluster environment is consistent with that seen in radio-loud quasars over the same redshift range. Our previous work on the 3CR sample suggested that the fundamental parameter which correlates with the richness of environment might be the radio luminosity of the galaxy, rather than its redshift. Our direct imaging confirms that the most powerful radio galaxies do inhabit rich environments. (author)

  11. Star formation properties of galaxy cluster A1767

    International Nuclear Information System (INIS)

    Yan, Peng-Fei; Li, Feng; Yuan, Qi-Rong

    2015-01-01

    Abell 1767 is a dynamically relaxed, cD cluster of galaxies with a redshift of 0.0703. Among 250 spectroscopically confirmed member galaxies within a projected radius of 2.5r 200 , 243 galaxies (∼ 97%) are spectroscopically covered by the Sloan Digital Sky Survey. Based on this homogeneous spectral sample, the stellar evolutionary synthesis code STARLIGHT is applied to investigate the stellar populations and star formation histories of galaxies in this cluster. The star formation properties of galaxies, such as mean stellar ages, metallicities, stellar masses, and star formation rates, are presented as functions of local galaxy density. A strong environmental effect is found such that massive galaxies in the high-density core region of the cluster tend to have higher metallicities, older mean stellar ages, and lower specific star formation rates (SSFRs), and their recent star formation activities have been remarkably suppressed. In addition, the correlations of the metallicity and SSFR with stellar mass are confirmed. (paper)

  12. Multiple mechanisms quench passive spiral galaxies

    Science.gov (United States)

    Fraser-McKelvie, Amelia; Brown, Michael J. I.; Pimbblet, Kevin; Dolley, Tim; Bonne, Nicolas J.

    2018-02-01

    We examine the properties of a sample of 35 nearby passive spiral galaxies in order to determine their dominant quenching mechanism(s). All five low-mass (M⋆ environments. We postulate that cluster-scale gas stripping and heating mechanisms operating only in rich clusters are required to quench low-mass passive spirals, and ram-pressure stripping and strangulation are obvious candidates. For higher mass passive spirals, while trends are present, the story is less clear. The passive spiral bar fraction is high: 74 ± 15 per cent, compared with 36 ± 5 per cent for a mass, redshift and T-type matched comparison sample of star-forming spiral galaxies. The high mass passive spirals occur mostly, but not exclusively, in groups, and can be central or satellite galaxies. The passive spiral group fraction of 74 ± 15 per cent is similar to that of the comparison sample of star-forming galaxies at 61 ± 7 per cent. We find evidence for both quenching via internal structure and environment in our passive spiral sample, though some galaxies have evidence of neither. From this, we conclude no one mechanism is responsible for quenching star formation in passive spiral galaxies - rather, a mixture of mechanisms is required to produce the passive spiral distribution we see today.

  13. Redshift differences of galaxies in nearby groups

    Science.gov (United States)

    Harrison, E. R.

    1975-01-01

    It is reported that galaxies in nearby groups exhibit anomalous nonvelocity redshifts. In this discussion, (1) four classes of nearby groups of galacies are analyzed, and no significant nonvelocity redshift effect is found; and (2) it is pointed out that transverse velocities (i.e., velocities transverse to the line of sight of the main galaxy, or center of mass) contribute components to the redshift measurements of companion galaxies. The redshifts of galaxies in nearby groups of appreciable angular size are considerably affected by these velocity projection effects. The transverse velocity contributions average out in rich, isotropic groups, and also in large samples of irregular groups of low membership, as in the four classes referred to in (1), but can introduce apparent discrepancies in small samples (as studied by Arp) of nearby groups of low membership.

  14. Chemical evolution of galaxies

    CERN Document Server

    Matteucci, Francesca

    2012-01-01

    The term “chemical evolution of galaxies” refers to the evolution of abundances of chemical species in galaxies, which is due to nuclear processes occurring in stars and to gas flows into and out of galaxies. This book deals with the chemical evolution of galaxies of all morphological types (ellipticals, spirals and irregulars) and stresses the importance of the star formation histories in determining the properties of stellar populations in different galaxies. The topic is approached in a didactical and logical manner via galaxy evolution models which are compared with observational results obtained in the last two decades: The reader is given an introduction to the concept of chemical abundances and learns about the main stellar populations in our Galaxy as well as about the classification of galaxy types and their main observables. In the core of the book, the construction and solution of chemical evolution models are discussed in detail, followed by descriptions and interpretations of observations of ...

  15. Galaxy Zoo: Observing secular evolution through bars

    International Nuclear Information System (INIS)

    Cheung, Edmond; Faber, S. M.; Koo, David C.; Athanassoula, E.; Bosma, A.; Masters, Karen L.; Nichol, Robert C.; Melvin, Thomas; Bell, Eric F.; Lintott, Chris; Schawinski, Kevin; Skibba, Ramin A.; Willett, Kyle W.

    2013-01-01

    In this paper, we use the Galaxy Zoo 2 data set to study the behavior of bars in disk galaxies as a function of specific star formation rate (SSFR) and bulge prominence. Our sample consists of 13,295 disk galaxies, with an overall (strong) bar fraction of 23.6% ± 0.4%, of which 1154 barred galaxies also have bar length (BL) measurements. These samples are the largest ever used to study the role of bars in galaxy evolution. We find that the likelihood of a galaxy hosting a bar is anticorrelated with SSFR, regardless of stellar mass or bulge prominence. We find that the trends of bar likelihood and BL with bulge prominence are bimodal with SSFR. We interpret these observations using state-of-the-art simulations of bar evolution that include live halos and the effects of gas and star formation. We suggest our observed trends of bar likelihood with SSFR are driven by the gas fraction of the disks, a factor demonstrated to significantly retard both bar formation and evolution in models. We interpret the bimodal relationship between bulge prominence and bar properties as being due to the complicated effects of classical bulges and central mass concentrations on bar evolution and also to the growth of disky pseudobulges by bar evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

  16. Resolving Gas-Phase Metallicity In Galaxies

    Science.gov (United States)

    Carton, David

    2017-06-01

    Chapter 2: As part of the Bluedisk survey we analyse the radial gas-phase metallicity profiles of 50 late-type galaxies. We compare the metallicity profiles of a sample of HI-rich galaxies against a control sample of HI-'normal' galaxies. We find the metallicity gradient of a galaxy to be strongly correlated with its HI mass fraction {M}{HI}) / {M}_{\\ast}). We note that some galaxies exhibit a steeper metallicity profile in the outer disc than in the inner disc. These galaxies are found in both the HI-rich and control samples. This contradicts a previous indication that these outer drops are exclusive to HI-rich galaxies. These effects are not driven by bars, although we do find some indication that barred galaxies have flatter metallicity profiles. By applying a simple analytical model we are able to account for the variety of metallicity profiles that the two samples present. The success of this model implies that the metallicity in these isolated galaxies may be in a local equilibrium, regulated by star formation. This insight could provide an explanation of the observed local mass-metallicity relation. Chapter 3 We present a method to recover the gas-phase metallicity gradients from integral field spectroscopic (IFS) observations of barely resolved galaxies. We take a forward modelling approach and compare our models to the observed spatial distribution of emission line fluxes, accounting for the degrading effects of seeing and spatial binning. The method is flexible and is not limited to particular emission lines or instruments. We test the model through comparison to synthetic observations and use downgraded observations of nearby galaxies to validate this work. As a proof of concept we also apply the model to real IFS observations of high-redshift galaxies. From our testing we show that the inferred metallicity gradients and central metallicities are fairly insensitive to the assumptions made in the model and that they are reliably recovered for galaxies

  17. The statistics of galaxies: beyond correlation functions

    International Nuclear Information System (INIS)

    Lachieze-Rey, M.

    1988-01-01

    I mention some normalization problems encountered when estimating the 2-point correlation functions in samples of galaxies of different average densities. I present some aspects of the void probability function as a statistical indicator, free of such normalization problems. Finally I suggest a new statistical approach to give an account in a synthetic way of those aspects of the galaxy distribution that a conventional method is unable to characterize

  18. Statistical analysis of metallicity in spiral galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Galeotti, P [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Turin Univ. (Italy). Ist. di Fisica Generale)

    1981-04-01

    A principal component analysis of metallicity and other integral properties of 33 spiral galaxies is presented; the involved parameters are: morphological type, diameter, luminosity and metallicity. From the statistical analysis it is concluded that the sample has only two significant dimensions and additonal tests, involving different parameters, show similar results. Thus it seems that only type and luminosity are independent variables, being the other integral properties of spiral galaxies correlated with them.

  19. Flattening and radio emission among elliptical galaxies

    International Nuclear Information System (INIS)

    Disney, M.J.; Sparks, W.B.; Wall, J.V.

    1984-01-01

    In a sample of 132 bright elliptical galaxies it is shown that there is a strong correlation between radio activity and flattening in the sense that radio ellipticals are both apparently and inherently rounder than the average elliptical. Both extended and compact sources are subject to the same correlation. No galaxies with axial ratios below 0.65 are found to be radio emitters. (author)

  20. Do satellite galaxies trace matter in galaxy clusters?

    Science.gov (United States)

    Wang, Chunxiang; Li, Ran; Gao, Liang; Shan, Huanyuan; Kneib, Jean-Paul; Wang, Wenting; Chen, Gang; Makler, Martin; Pereira, Maria E. S.; Wang, Lin; Maia, Marcio A. G.; Erben, Thomas

    2018-04-01

    The spatial distribution of satellite galaxies encodes rich information of the structure and assembly history of galaxy clusters. In this paper, we select a red-sequence Matched-filter Probabilistic Percolation cluster sample in SDSS Stripe 82 region with 0.1 ≤ z ≤ 0.33, 20 0.7. Using the high-quality weak lensing data from CS82 Survey, we constrain the mass profile of this sample. Then we compare directly the mass density profile with the satellite number density profile. We find that the total mass and number density profiles have the same shape, both well fitted by an NFW profile. The scale radii agree with each other within a 1σ error (r_s,gal=0.34_{-0.03}^{+0.04} Mpc versus r_s=0.37_{-0.10}^{+0.15} Mpc).

  1. Motions of galaxies in the neighborhood of the local group

    International Nuclear Information System (INIS)

    Faber, S.M.; Burstein, D.

    1988-01-01

    Two samples of spiral galaxies, as well as elliptical galaxies, are presently used to investigate the velocity field of galaxies relative to the cosmic microwave background to a distance of 3000 km/sec. The velocity-field models optimized include motions due to a spherically-symmetric Great Attractor, a Virgocentric flow, and a Local Anomally of which the Local Group is a part. While the spiral samples are in good agreement with the Great-Attractor-Virgo model for the motion of elliptical galaxies, new observations indicate that the Great Attractor is not spherically symmetric in its inner regions and may require modification of the model. 27 refs

  2. Dual Active Galactic Nuclei in Nearby Galaxies

    Science.gov (United States)

    Das, Mousumi; Rubinur, Khatun; Karb, Preeti; Varghese, Ashlin; Novakkuni, Navyasree; James, Atul

    2018-04-01

    Galaxy mergers play a crucial role in the formation of massive galaxies and the buildup of their bulges. An important aspect of the merging process is the in-spiral of the supermassive black-holes (SMBHs) to the centre of the merger remnant and the eventual formation of a SMBH binary. If both the SMBHs are accreting they will form a dual or binary active galactic nucleus (DAGN). The final merger remnant is usually very bright and shows enhanced star formation. In this paper we summarise the current sample of DAGN from previous studies and describe methods that can be used to identify strong DAGN candidates from optical and spectroscopic surveys. These methods depend on the Doppler separation of the double peaked AGN emission lines, the nuclear velocity dispersion of the galaxies and their optical/UV colours. We describe two high resolution, radio observations of DAGN candidates that have been selected based on their double peaked optical emission lines (DPAGN). We also examine whether DAGN host galaxies have higher star formation rates (SFRs) compared to merging galaxies that do not appear to have DAGN. We find that the SFR is not higher for DAGN host galaxies. This suggests that the SFRs in DAGN host galaxies is due to the merging process itself and not related to the presence of two AGN in the system.

  3. The dark side of galaxy colour: evidence from new SDSS measurements of galaxy clustering and lensing

    Energy Technology Data Exchange (ETDEWEB)

    Hearin, Andrew P. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States). Fermilab Center for Particle Astrophysics; Watson, Douglas F. [Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP); Becker, Matthew R. [Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP); KICP, Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Reyes, Reinabelle [Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP); Berlind, Andreas A. [Vanderbilt Univ., Nashville, TN (United States). Dept. of Physics and Astronomy; Zentner, Andrew R. [Pittsburgh Particle Physics, Astrophysics, and Cosmology Center (PITT PACC), PA (United States)

    2014-08-12

    The age matching model has recently been shown to predict correctly the luminosity L and g-r color of galaxies residing within dark matter halos. The central tenet of the model is intuitive: older halos tend to host galaxies with older stellar populations. In this paper, we demonstrate that age matching also correctly predicts the g-r color trends exhibited in a wide variety of statistics of the galaxy distribution for stellar mass M* threshold samples. In particular, we present new measurements of the galaxy two-point correlation function and the galaxy-galaxy lensing signal as a function of M* and g-r color from the Sloan Digital Sky Survey, and show that age matching exhibits remarkable agreement with these and other statistics of low-redshift galaxies. In so doing, we also demonstrate good agreement between the galaxy-galaxy lensing observed by SDSS and the signal predicted by abundance matching, a new success of this model. We describe how age matching is a specific example of a larger class of Conditional Abundance Matching models (CAM), a theoretical framework we introduce here for the first time. CAM provides a general formalism to study correlations at fixed mass between any galaxy property and any halo property. The striking success of our simple implementation of CAM provides compelling evidence that this technique has the potential to describe the same set of data as alternative models, but with a dramatic reduction in the required number of parameters. CAM achieves this reduction by exploiting the capability of contemporary N-body simulations to determine dark matter halo properties other than mass alone, which distinguishes our model from conventional approaches to the galaxy-halo connection.

  4. The dark side of galaxy colour: evidence from new SDSS measurements of galaxy clustering and lensing

    Science.gov (United States)

    Hearin, Andrew P.; Watson, Douglas F.; Becker, Matthew R.; Reyes, Reinabelle; Berlind, Andreas A.; Zentner, Andrew R.

    2014-10-01

    The age-matching model has recently been shown to predict correctly the luminosity L and g - r colour of galaxies residing within dark matter haloes. The central tenet of the model is intuitive: older haloes tend to host galaxies with older stellar populations. In this paper, we demonstrate that age matching also correctly predicts the g - r colour trends exhibited in a wide variety of statistics of the galaxy distribution for stellar mass M* threshold samples. In particular, we present new Sloan Digital Sky Survey (SDSS) measurements of galaxy clustering and the galaxy-galaxy lensing signal ΔΣ as a function of M* and g - r colour, and show that age matching exhibits remarkable agreement with these and other statistics of low-redshift galaxies. In so doing, we also demonstrate good agreement between the galaxy-galaxy lensing observed by SDSS and the ΔΣ signal predicted by abundance matching, a new success of this model. We describe how age matching is a specific example of a larger class of conditional abundance matching models (CAM), a theoretical framework we introduce here for the first time. CAM provides a general formalism to study correlations at fixed mass between any galaxy property and any halo property. The striking success of our simple implementation of CAM suggests that this technique has the potential to describe the same set of data as alternative models, but with a dramatic reduction in the required number of parameters. CAM achieves this reduction by exploiting the capability of contemporary N-body simulations to determine dark matter halo properties other than mass alone, which distinguishes our model from conventional approaches to the galaxy-halo connection.

  5. LOW CO LUMINOSITIES IN DWARF GALAXIES

    International Nuclear Information System (INIS)

    Schruba, Andreas; Walter, Fabian; Sandstrom, Karin; Leroy, Adam K.; Bigiel, Frank; Brinks, Elias; De Blok, W. J. G.; Kramer, Carsten; Rosolowsky, Erik; Schuster, Karl; Usero, Antonio; Weiss, Axel; Wiesemeyer, Helmut

    2012-01-01

    We present maps of 12 COJ = 2-1 emission covering the entire star-forming disks of 16 nearby dwarf galaxies observed by the IRAM HERACLES survey. The data have 13'' angular resolution, ∼250 pc at our average distance of D = 4 Mpc, and sample the galaxies by 10-1000 resolution elements. We apply stacking techniques to perform the first sensitive search for CO emission in dwarf galaxies outside the Local Group ranging from individual lines of sight, stacking over IR-bright regions of embedded star formation, and stacking over the entire galaxy. We detect five galaxies in CO with total CO luminosities of L CO2-1 = (3-28) × 10 6 K km s –1 pc 2 . The other 11 galaxies remain undetected in CO even in the stacked images and have L CO2-1 ∼ 6 K km s –1 pc 2 . We combine our sample of dwarf galaxies with a large sample of spiral galaxies from the literature to study scaling relations of L CO with M B and metallicity. We find that dwarf galaxies with metallicities of Z ≈ 1/2-1/10 Z ☉ have L CO of 2-4 orders of magnitude smaller than massive spiral galaxies and that their L CO per unit L B is 1-2 orders of magnitude smaller. A comparison with tracers of star formation (FUV and 24 μm) shows that L CO per unit star formation rate (SFR) is 1-2 orders of magnitude smaller in dwarf galaxies. One possible interpretation is that dwarf galaxies form stars much more efficiently: we argue that the low L CO /SFR ratio is due to the fact that the CO-to-H 2 conversion factor, α CO , changes significantly in low-metallicity environments. Assuming that a constant H 2 depletion time of τ dep = 1.8 Gyr holds in dwarf galaxies (as found for a large sample of nearby spirals) implies α CO values for dwarf galaxies with Z ≈ 1/2-1/10 Z ☉ that are more than one order of magnitude higher than those found in solar metallicity spiral galaxies. Such a significant increase of α CO at low metallicity is consistent with previous studies, in particular those of Local Group dwarf

  6. INDIVIDUAL AND GROUP GALAXIES IN CNOC1 CLUSTERS

    International Nuclear Information System (INIS)

    Li, I. H.; Yee, H. K. C.; Ellingson, E.

    2009-01-01

    Using wide-field BVR c I imaging for a sample of 16 intermediate redshift (0.17 red ) to infer the evolutionary status of galaxies in clusters, using both individual galaxies and galaxies in groups. We apply the local galaxy density, Σ 5 , derived using the fifth nearest neighbor distance, as a measure of local environment, and the cluster-centric radius, r CL , as a proxy for global cluster environment. Our cluster sample exhibits a Butcher-Oemler effect in both luminosity-selected and stellar-mass-selected samples. We find that f red depends strongly on Σ 5 and r CL , and the Butcher-Oemler effect is observed in all Σ 5 and r CL bins. However, when the cluster galaxies are separated into r CL bins, or into group and nongroup subsamples, the dependence on local galaxy density becomes much weaker. This suggests that the properties of the dark matter halo in which the galaxy resides have a dominant effect on its galaxy population and evolutionary history. We find that our data are consistent with the scenario that cluster galaxies situated in successively richer groups (i.e., more massive dark matter halos) reach a high f red value at earlier redshifts. Associated with this, we observe a clear signature of 'preprocessing', in which cluster galaxies belonging to moderately massive infalling galaxy groups show a much stronger evolution in f red than those classified as nongroup galaxies, especially at the outskirts of the cluster. This result suggests that galaxies in groups infalling into clusters are significant contributors to the Butcher-Oemler effect.

  7. THE GALAXY OPTICAL LUMINOSITY FUNCTION FROM THE AGN AND GALAXY EVOLUTION SURVEY

    International Nuclear Information System (INIS)

    Cool, Richard J.; Eisenstein, Daniel J.; Kochanek, Christopher S.; Brown, Michael J. I.; Caldwell, Nelson; Forman, William R.; Hickox, Ryan C.; Jones, Christine; Murray, Stephen S.; Dey, Arjun; Jannuzi, Buell T.; Moustakas, John

    2012-01-01

    We present the galaxy optical luminosity function for the redshift range 0.05 2 in the Boötes field of the NOAO Deep Wide-Field Survey. Our statistical sample is composed of 12,473 galaxies with known redshifts down to I = 20.4 (AB). Our results at low redshift are consistent with those from Sloan Digital Sky Survey; at higher redshift, we find strong evidence for evolution in the luminosity function, including differential evolution between blue and red galaxies. We find that the luminosity density evolves as (1 + z) (0.54±0.64) for red galaxies and (1 + z) (1.64±0.39) for blue galaxies.

  8. Kinematic evidence of satellite galaxy populations in the potential wells of first-ranked cluster galaxies

    Science.gov (United States)

    Cowie, L. L.; Hu, E. M.

    1986-01-01

    The velocities of 38 centrally positioned galaxies (r much less than 100 kpc) were measured relative to the velocity of the first-ranked galaxy in 14 rich clusters. Analysis of the velocity distribution function of this sample and of previous data shows that the population cannot be fit by a single Gaussian. An adequate fit is obtained if 60 percent of the objects lie in a Gaussian with sigma = 250 km/s and the remainder in a population with sigma = 1400 km/s. All previous data sets are individually consistent with this conclusion. This suggests that there is a bound population of galaxies in the potential well of the central galaxy in addition to the normal population of the cluster core. This is taken as supporting evidence for the galactic cannibalism model of cD galaxy formation.

  9. Optical-to-virial velocity ratios of local disc galaxies from combined kinematics and galaxy-galaxy lensing

    Science.gov (United States)

    Reyes, R.; Mandelbaum, R.; Gunn, J. E.; Nakajima, R.; Seljak, U.; Hirata, C. M.

    2012-10-01

    In this paper, we measure the optical-to-virial velocity ratios Vopt/V200c of disc galaxies in the Sloan Digital Sky Survey (SDSS) at a mean redshift of = 0.07 and with stellar masses 109 < M* < 1011 M⊙. Vopt/V200c, the ratio of the circular velocity measured at the optical radius of the disc (˜10 kpc) to that at the virial radius of the dark matter halo (˜150 kpc), is a powerful observational constraint on disc galaxy formation. It links galaxies to their dark matter haloes dynamically and constrains the total mass profile of disc galaxies over an order of magnitude in length scale. For this measurement, we combine Vopt derived from the Tully-Fisher relation (TFR) from Reyes et al. with V200c derived from halo masses measured with galaxy-galaxy lensing. In anticipation of this combination, we use similarly selected galaxy samples for both the TFR and lensing analysis. For three M* bins with lensing-weighted mean stellar masses of 0.6, 2.7 and 6.5 × 1010 M⊙, we find halo-to-stellar mass ratios M200c/M* = 41, 23 and 26, with 1σ statistical uncertainties of around 0.1 dex, and Vopt/V200c = 1.27 ± 0.08, 1.39 ± 0.06 and 1.27 ± 0.08 (1σ), respectively. Our results suggest that the dark matter and baryonic contributions to the mass within the optical radius are comparable, if the dark matter halo profile has not been significantly modified by baryons. The results obtained in this work will serve as inputs to and constraints on disc galaxy formation models, which will be explored in future work. Finally, we note that this paper presents a new and improved galaxy shape catalogue for weak lensing that covers the full SDSS Data Release 7 footprint.

  10. Galactic rings revisited - I. CVRHS classifications of 3962 ringed galaxies from the Galaxy Zoo 2 Database

    Science.gov (United States)

    Buta, Ronald J.

    2017-11-01

    Rings are important and characteristic features of disc-shaped galaxies. This paper is the first in a series that re-visits galactic rings with the goals of further understanding the nature of the features and for examining their role in the secular evolution of galaxy structure. The series begins with a new sample of 3962 galaxies drawn from the Galaxy Zoo 2 citizen science data base, selected because zoo volunteers recognized a ring-shaped pattern in the morphology as seen in Sloan Digital Sky Survey colour images. The galaxies are classified within the framework of the Comprehensive de Vaucouleurs revised Hubble-Sandage system. It is found that zoo volunteers cued on the same kinds of ring-like features that were recognized in the 1995 Catalogue of Southern Ringed Galaxies. This paper presents the full catalogue of morphological classifications, comparisons with other sources of classifications and some histograms designed mainly to highlight the content of the catalogue. The advantages of the sample are its large size and the generally good quality of the images; the main disadvantage is the low physical resolution that limits the detectability of linearly small rings such as nuclear rings. The catalogue includes mainly inner and outer disc rings and lenses. Cataclysmic (`encounter-driven') rings (such as ring and polar ring galaxies) are recognized in less than 1 per cent of the sample.

  11. Galaxies Die in Groups: An IRAC Autopsy

    Science.gov (United States)

    Wilman, D. J.; Pierini, D.; Tyler, K.; McGee, S. L.; Oemler, A., Jr.; Morris, S. L.; Balogh, M. L.; Bower, R. G.; Mulchaey, J. S.

    2008-10-01

    The most massive galaxies in the Universe are also the oldest. To overturn this apparent contradiction with hierarchical growth models, we focus on the group-scale haloes which host most of these galaxies. Our z˜0.4 group sample is selected in redshift space from the CNOC2 redshift survey. A stellar mass selected M_{*} ≲ 2×10^{10}M_{⊙} sample is constructed using IRAC observations. A sensitive Mid InfraRed (MIR) IRAC colour is used to isolate passive galaxies. It produces a bimodal distribution, in which passive galaxies (highlighted by morphological early-types) define a tight MIR colour sequence (Infrared Passive Sequence, IPS). This is due to stellar atmospheric emission from old stellar populations. Significantly offset from the IPS are galaxies where reemission by dust boosts emission at λ_{obs}=8 micron. We term them InfraRed-Excess galaxies whether star formation and/or AGN activity are present. They include all known morphological late-types. The fraction of InfraRed Excess galaxies, f(IRE) drops with M_{*}, such that f(IRE)=0.5 at a ``crossover mass'' of M_{cr}˜ 1.3×10^{11}M_{⊙}. Within our optically-defined group sample there is a strong and consistent deficit in f(IRE) at all masses, but most clearly at M_{*} ≲ 10^{11}M_{⊙}. Suppression of star formation must mainly occur in groups, and the observed trend of f(IRE) with M_{*} can be explained if suppression of M_{*} ≲ 10^{11}M_{⊙} galaxies occurs primarily in the group environment.

  12. The Hunt for Missing Dwarf Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2015-11-01

    Theories of galaxy formation and evolution predict that there should be significantly more dwarf galaxies than have been observed. Are our theories wrong? Or are dwarf galaxies just difficult to detect? Recent results from a survey of a galaxy cluster 62 million light-years away suggest there may be lots of undiscovered dwarf galaxies hiding throughout the universe!Hiding in FaintnessThe missing dwarf problem has had hints of a resolution with the recent discovery of Ultra-Diffuse Galaxies (UDGs) in the Coma and Virgo galaxy clusters. UDGs have low masses and large radii, resulting in a very low surface brightness that makes them extremely difficult to detect. If many dwarfs are UDGs, this could well explain why weve been missing them!But the Coma and Virgo galaxy clusters are similar in that theyre both very massive. Are there UDGs in other galaxy clusters as well? To answer this question, an international team of scientists is running the Next Generation Fornax Survey (NGFS), a survey searching for faint dwarf galaxies in the central 30 square degrees of the Fornax galaxy cluster.The NGFS uses near-UV and optical observations from the Dark Energy Camera mounted on the 4m Blanco Telescope in Chile. The survey is still underway, but in a recent publication led by Roberto P. Muoz (Institute of Astrophysics at the Pontifical Catholic University of Chile), the team has released an overview of the first results from only the central 3 square degrees of the NGFS field.Surprising DetectionGalaxy radii vs. their absolute i-band magnitudes, for the dwarfs found in NGFS as well as other stellar systems in the nearby universe. The NGFS dwarfs are similar to the ultra-diffuse dwarfs found in the Virgo and Coma clusters, but are several orders of magnitude fainter. [Muoz et al. 2015]In just this small central field, the team has found an astounding 284 low-surface-brightness dwarf galaxy candidates 158 of them previously undetected. At the bright end of this sample are dwarf

  13. Statistical properties of Faraday rotation measure in external galaxies - I. Intervening disc galaxies

    Science.gov (United States)

    Basu, Aritra; Mao, S. A.; Fletcher, Andrew; Kanekar, Nissim; Shukurov, Anvar; Schnitzeler, Dominic; Vacca, Valentina; Junklewitz, Henrik

    2018-06-01

    Deriving the Faraday rotation measure (RM) of quasar absorption line systems, which are tracers of high-redshift galaxies intervening background quasars, is a powerful tool for probing magnetic fields in distant galaxies. Statistically comparing the RM distributions of two quasar samples, with and without absorption line systems, allows one to infer magnetic field properties of the intervening galaxy population. Here, we have derived the analytical form of the probability distribution function (PDF) of RM produced by a single galaxy with an axisymmetric large-scale magnetic field. We then further determine the PDF of RM for one random sight line traversing each galaxy in a population with a large-scale magnetic field prescription. We find that the resulting PDF of RM is dominated by a Lorentzian with a width that is directly related to the mean axisymmetric large-scale field strength of the galaxy population if the dispersion of B0 within the population is smaller than . Provided that RMs produced by the intervening galaxies have been successfully isolated from other RM contributions along the line of sight, our simple model suggests that in galaxies probed by quasar absorption line systems can be measured within ≈50 per cent accuracy without additional constraints on the magneto-ionic medium properties of the galaxies. Finally, we discuss quasar sample selection criteria that are crucial to reliably interpret observations, and argue that within the limitations of the current data base of absorption line systems, high-metallicity damped Lyman-α absorbers are best suited to study galactic dynamo action in distant disc galaxies.

  14. Statistical properties of Faraday rotation measure in external galaxies - I: intervening disc galaxies

    Science.gov (United States)

    Basu, Aritra; Mao, S. A.; Fletcher, Andrew; Kanekar, Nissim; Shukurov, Anvar; Schnitzeler, Dominic; Vacca, Valentina; Junklewitz, Henrik

    2018-03-01

    Deriving the Faraday rotation measure (RM) of quasar absorption line systems, which are tracers of high-redshift galaxies intervening background quasars, is a powerful tool for probing magnetic fields in distant galaxies. Statistically comparing the RM distributions of two quasar samples, with and without absorption line systems, allows one to infer magnetic field properties of the intervening galaxy population. Here, we have derived the analytical form of the probability distribution function (PDF) of RM produced by a single galaxy with an axisymmetric large-scale magnetic field. We then further determine the PDF of RM for one random sight line traversing each galaxy in a population with a large-scale magnetic field prescription. We find that the resulting PDF of RM is dominated by a Lorentzian with a width that is directly related to the mean axisymmetric large-scale field strength ⟨B0⟩ of the galaxy population if the dispersion of B0 within the population is smaller than ⟨B0⟩. Provided that RMs produced by the intervening galaxies have been successfully isolated from other RM contributions along the line of sight, our simple model suggests that ⟨B0⟩ in galaxies probed by quasar absorption line systems can be measured within ≈50 per cent accuracy without additional constraints on the magneto-ionic medium properties of the galaxies. Finally, we discuss quasar sample selection criteria that are crucial to reliably interpret observations, and argue that within the limitations of the current database of absorption line systems, high-metallicity damped Lyman-α absorbers are best suited to study galactic dynamo action in distant disc galaxies.

  15. Galaxy evolution in extreme environments: Molecular gas content star formation and AGN in isolated void galaxies

    Science.gov (United States)

    Das, Mousumi; Iono, Daisuke; Saito, Toshiki; Subramanian, Smitha

    Since the early redshift surveys of the large scale structure of our universe, it has become clear that galaxies cluster along walls, sheet and filaments leaving large, empty regions called voids between them. Although voids represent the most under dense parts of our universe, they do contain a sparse but significant population of isolated galaxies that are generally low luminosity, late type disk galaxies. Recent studies show that most void galaxies have ongoing star formation and are in an early stage of evolution. We present radio, optical studies of the molecular gas content and star formation in a sample of void galaxies. Using SDSS data, we find that AGN are rare in these systems and are found only in the Bootes void; their black hole masses and radio properties are similar to bright spirals galaxies. Our studies suggest that close galaxy interactions and gas accretion are the main drivers of galaxy evolution in these systems despite their location in the underdense environment of the voids.

  16. A Multiwavelength Study of a Sample of 70 μm Selected Galaxies in the COSMOS Field : I. Spectral Energy Distributions and Luminosities

    NARCIS (Netherlands)

    Kartaltepe, Jeyhan S.; Sanders, D. B.; Le Floc'h, E.; Frayer, D. T.; Aussel, H.; Arnouts, S.; Ilbert, O.; Salvato, M.; Scoville, N. Z.; Surace, J.; Yan, L.; Brusa, M.; Capak, P.; Caputi, K.; Carollo, C. M.; Civano, F.; Elvis, M.; Faure, C.; Hasinger, G.; Koekemoer, A. M.; Lee, N.; Lilly, S.; Liu, C. T.; McCracken, H. J.; Schinnerer, E.; Smolčić, V.; Taniguchi, Y.; Thompson, D. J.; Trump, J.

    We present a large robust sample of 1503 reliable and unconfused 70 μm selected sources from the multiwavelength data set of the Cosmic Evolution Survey. Using the Spitzer IRAC and MIPS photometry, we estimate the total infrared (IR) luminosity, L IR (8-1000 μm), by finding the best-fit template

  17. THE ORIGIN OF THE INFRARED EMISSION IN RADIO GALAXIES. II. ANALYSIS OF MID- TO FAR-INFRARED SPITZER OBSERVATIONS OF THE 2JY SAMPLE

    NARCIS (Netherlands)

    Dicken, D.; Tadhunter, C.; Axon, D.; Morganti, R.; Inskip, K. J.; Holt, J.; Delgado, R. Gonzalez; Groves, B.

    2009-01-01

    We present an analysis of deep mid- to far-infrared (MFIR) Spitzer photometric observations of the southern 2Jy sample of powerful radio sources (0.05

  18. Isolated galaxies, pairs, and groups of galaxies

    International Nuclear Information System (INIS)

    Kuneva, I.; Kalinkov, M.

    1990-01-01

    The authors searched for isolated galaxies, pairs and groups of galaxies in the CfA survey (Huchra et al. 1983). It was assumed that the distances to galaxies are given by R = V/H sub o, where H sub o = 100 km s(exp -1) Mpc(exp -1) and R greater than 6 Mpc. The searching procedure is close to those, applied to find superclusters of galaxies (Kalinkov and Kuneva 1985, 1986). A sphere with fixed radius r (asterisk) is described around each galaxy. The mean spatial density in the sphere is m. Let G 1 be any galaxy and G 2 be its nearest neighbor at a distance R 2 . If R sub 2 exceeds the 95 percent quintile in the distribution of the distances of the second neighbors, then G 1 is an isolated galaxy. Let the midpoint of G 1 and G 2 be O 2 and r 2 =R 2 2. For the volume V 2 , defined with the radius r 2 , the density D 2 less than k mu, the galaxy G 2 is a single one and the procedure for searching for pairs and groups, beginning with this object is over and we have to pass to another object. Here the authors present the groups - isolated and nonisolated - with n greater than 3, found in the CfA survey in the Northern galactic hemisphere. The parameters used are k = 10 and r (asterisk) = 5 Mpc. Table 1 contains: (1) the group number, (2) the galaxy, nearest to the multiplet center, (3) multiplicity n, (4) the brightest galaxy if it is not listed in (2); (5) and (6) are R.A. and Dec. (1950), (7) - mean distance D in Mpc. Further there are the mean density rho (8) of the multiplet (galaxies Mpc (exp -3)), (9) the density rho (asterisk) for r (asterisk) = 5 Mpc and (10) the density rho sub g for the group with its nearest neighbor. The parenthesized digits for densities in the last three columns are powers of ten

  19. X-Ray Temperatures, Luminosities, and Masses from XMM-Newton Follow-up of the First Shear-selected Galaxy Cluster Sample

    Energy Technology Data Exchange (ETDEWEB)

    Deshpande, Amruta J.; Hughes, John P. [Department of Physics and Astronomy, Rutgers the State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Wittman, David, E-mail: amrejd@physics.rutgers.edu, E-mail: jph@physics.rutgers.edu, E-mail: dwittman@physics.ucdavis.edu [Department of Physics, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States)

    2017-04-20

    We continue the study of the first sample of shear-selected clusters from the initial 8.6 square degrees of the Deep Lens Survey (DLS); a sample with well-defined selection criteria corresponding to the highest ranked shear peaks in the survey area. We aim to characterize the weak lensing selection by examining the sample’s X-ray properties. There are multiple X-ray clusters associated with nearly all the shear peaks: 14 X-ray clusters corresponding to seven DLS shear peaks. An additional three X-ray clusters cannot be definitively associated with shear peaks, mainly due to large positional offsets between the X-ray centroid and the shear peak. Here we report on the XMM-Newton properties of the 17 X-ray clusters. The X-ray clusters display a wide range of luminosities and temperatures; the L {sub X} − T {sub X} relation we determine for the shear-associated X-ray clusters is consistent with X-ray cluster samples selected without regard to dynamical state, while it is inconsistent with self-similarity. For a subset of the sample, we measure X-ray masses using temperature as a proxy, and compare to weak lensing masses determined by the DLS team. The resulting mass comparison is consistent with equality. The X-ray and weak lensing masses show considerable intrinsic scatter (∼48%), which is consistent with X-ray selected samples when their X-ray and weak lensing masses are independently determined.

  20. Correlations among Galaxy Properties from the Sloan Digital Sky Survey

    Science.gov (United States)

    Li, Zhongmu; Mao, Caiyan

    2013-07-01

    Galaxies are complex systems with many properties. Correlations among galaxy properties can supply important clues for studying the formation and evolution of galaxies. Using principal component analysis and least-squares fitting, this paper investigates the correlations among galactic parameters involving more properties (color, morphology, stellar population, and absolute magnitude) than previous studies. We use a volume-limited sample (whole sample) of 75,423 galaxies that was selected from the Sloan Digital Sky Survey Data Release 2 and divided into two subsamples (blue and red samples) using a critical color of (g - r) = 0.70 mag. In addition to recovering some previous results, we also obtain some new results. First, all separators for dividing galaxies into two groups can be related via good parameter-first principal component (PC1) correlations. A critical PC1 that indicates whether or not stellar age (or the evolution of a stellar population over time) is important can be used to separate galaxies. This suggests that a statistical parameter, PC1, is helpful in understanding the physical separators of galaxies. In addition, stellar age is shown to be unimportant for red galaxies, while both stellar age and mass are dominating parameters of blue galaxies. This suggests that the various numbers of dominating parameters of galaxies may result from the use of different samples. Finally, some parameters are shown to be correlated, and quantitative fits for a few correlations are obtained, e.g., log(t) = 8.57 + 1.65 (g - r) for the age (log t) and color (g - r) of blue galaxies and log (M *) = 4.31 - 0.30 M r for the stellar mass (log M *) and absolute magnitude (M r) of red galaxies. The median relationships between various parameter pairs are also presented for comparison.

  1. Diversity among galaxy clusters

    International Nuclear Information System (INIS)

    Struble, M.F.; Rood, H.J.

    1988-01-01

    The classification of galaxy clusters is discussed. Consideration is given to the classification scheme of Abell (1950's), Zwicky (1950's), Morgan, Matthews, and Schmidt (1964), and Morgan-Bautz (1970). Galaxies can be classified based on morphology, chemical composition, spatial distribution, and motion. The correlation between a galaxy's environment and morphology is examined. The classification scheme of Rood-Sastry (1971), which is based on clusters's morphology and galaxy population, is described. The six types of clusters they define include: (1) a cD-cluster dominated by a single large galaxy, (2) a cluster dominated by a binary, (3) a core-halo cluster, (4) a cluster dominated by several bright galaxies, (5) a cluster appearing flattened, and (6) an irregularly shaped cluster. Attention is also given to the evolution of cluster structures, which is related to initial density and cluster motion

  2. Galaxy formation and evolution

    CERN Document Server

    Mo, Houjun; White, Simon

    2010-01-01

    The rapidly expanding field of galaxy formation lies at the interface between astronomy, particle physics, and cosmology. Covering diverse topics from these disciplines, all of which are needed to understand how galaxies form and evolve, this book is ideal for researchers entering the field. Individual chapters explore the evolution of the Universe as a whole and its particle and radiation content; linear and nonlinear growth of cosmic structure; processes affecting the gaseous and dark matter components of galaxies and their stellar populations; the formation of spiral and elliptical galaxies; central supermassive black holes and the activity associated with them; galaxy interactions; and the intergalactic medium. Emphasizing both observational and theoretical aspects, this book provides a coherent introduction for astronomers, cosmologists, and astroparticle physicists to the broad range of science underlying the formation and evolution of galaxies.

  3. Suites of dwarfs around Nearby giant galaxies

    International Nuclear Information System (INIS)

    Karachentsev, Igor D.; Kaisina, Elena I.; Makarov, Dmitry I.

    2014-01-01

    The Updated Nearby Galaxy Catalog (UNGC) contains the most comprehensive summary of distances, radial velocities, and luminosities for 800 galaxies located within 11 Mpc from us. The high density of observables in the UNGC makes this sample indispensable for checking results of N-body simulations of cosmic structures on a ∼1 Mpc scale. The environment of each galaxy in the UNGC was characterized by a tidal index Θ 1 , depending on the separation and mass of the galaxy's main disturber (MD). We grouped UNGC galaxies with a common MD in suites, and ranked suite members according to their Θ 1 . All suite members with positive Θ 1 are assumed to be physical companions of the MD. About 58% of the sample are members of physical groups. The distribution of suites by the number of members, n, follows a relation N(n) ∼ n –2 . The 20 most populated suites contain 468 galaxies, i.e., 59% of the UNGC sample. The fraction of MDs among the brightest galaxies is almost 100% and drops to 50% at M B = –18 m . We discuss various properties of MDs, as well as galaxies belonging to their suites. The suite abundance practically does not depend on the morphological type, linear diameter, or hydrogen mass of the MD, the tightest correlation being with the MD dynamical mass. Dwarf galaxies around MDs exhibit well-known segregation effects: the population of the outskirts has later morphological types, richer H I contents, and higher rates of star formation activity. Nevertheless, there are some intriguing cases where dwarf spheroidal galaxies occur at the far periphery of the suites, as well as some late-type dwarfs residing close to MDs. Comparing simulation results with galaxy groups, most studies assume the Local Group is fairly typical. However, we recognize that the nearby groups significantly differ from each other and there is considerable variation in their properties. The suites of companions around the Milky Way and M31, consisting of the Local Group, do not

  4. Gradient pattern analysis applied to galaxy morphology

    Science.gov (United States)

    Rosa, R. R.; de Carvalho, R. R.; Sautter, R. A.; Barchi, P. H.; Stalder, D. H.; Moura, T. C.; Rembold, S. B.; Morell, D. R. F.; Ferreira, N. C.

    2018-06-01

    Gradient pattern analysis (GPA) is a well-established technique for measuring gradient bilateral asymmetries of a square numerical lattice. This paper introduces an improved version of GPA designed for galaxy morphometry. We show the performance of the new method on a selected sample of 54 896 objects from the SDSS-DR7 in common with Galaxy Zoo 1 catalogue. The results suggest that the second gradient moment, G2, has the potential to dramatically improve over more conventional morphometric parameters. It separates early- from late-type galaxies better (˜ 90 per cent) than the CAS system (C˜ 79 per cent, A˜ 50 per cent, S˜ 43 per cent) and a benchmark test shows that it is applicable to hundreds of thousands of galaxies using typical processing systems.

  5. The dependence of halo mass on galaxy size at fixed stellar mass using weak lensing

    Science.gov (United States)

    Charlton, Paul J. L.; Hudson, Michael J.; Balogh, Michael L.; Khatri, Sumeet

    2017-12-01

    Stellar mass has been shown to correlate with halo mass, with non-negligible scatter. The stellar mass-size and luminosity-size relationships of galaxies also show significant scatter in galaxy size at fixed stellar mass. It is possible that, at fixed stellar mass and galaxy colour, the halo mass is correlated with galaxy size. Galaxy-galaxy lensing allows us to measure the mean masses of dark matter haloes for stacked samples of galaxies. We extend the analysis of the galaxies in the CFHTLenS catalogue by fitting single Sérsic surface brightness profiles to the lens galaxies in order to recover half-light radius values, allowing us to determine halo masses for lenses according to their size. Comparing our halo masses and sizes to baselines for that stellar mass yields a differential measurement of the halo mass-galaxy size relationship at fixed stellar mass, defined as Mh(M_{*}) ∝ r_{eff}^{η }(M_{*}). We find that, on average, our lens galaxies have an η = 0.42 ± 0.12, i.e. larger galaxies live in more massive dark matter haloes. The η is strongest for high-mass luminous red galaxies. Investigation of this relationship in hydrodynamical simulations suggests that, at a fixed M*, satellite galaxies have a larger η and greater scatter in the Mh and reff relationship compared to central galaxies.

  6. The Dependence of galaxy colors on luminosity and environment at z~0.4

    Energy Technology Data Exchange (ETDEWEB)

    Yee, H.K.C.; /Toronto U., Astron. Dept.; Hsieh, B.C.; /Taiwan, Natl. Central U. /Taipei, Inst. Astron. Astrophys.; Lin, Huan; /Fermilab; Gladders, M.D.; /Carnegie Inst.

    2005-08-01

    The authors analyze the B-R{sub c} colors of galaxies as functions of luminosity and local galaxy density using a large photometric redshift catalog based on the Red-Sequence Cluster Survey. They select two samples of galaxies with a magnitude limit of M{sub R{sub e}} < -18.5 and redshift ranges of 0.2 {le} z < 0.4 and 0.4 {le} x < 0.6 containing 10{sup 5} galaxies each. they model the color distributions of subsamples of galaxies and derive the red galaxy fraction and peak colors of red and blue galaxies as functions of galaxy luminosity and environment. The evolution of these relationships over the redshift range of x {approx} 0.5 to z {approx} 0.05 is analyzed in combination with published results from the Sloan Digital Sky Survey. They find that there is a strong evolution in the restframe peak color of bright blue galaxies in that they become redder with decreasing redshift, while the colors of faint blue galaxies remain approximately constant. This effect supports the ''downsizing'' scenario of star formation in galaxies. While the general dependence of the galaxy color distributions on the environment is small, they find that the change of red galaxy fraction with epoch is a function of the local galaxy density, suggesting that the downsizing effect may operate with different timescales in regions of different galaxy densities.

  7. EVIDENCE FOR MORPHOLOGY AND LUMINOSITY TRANSFORMATION OF GALAXIES AT HIGH REDSHIFTS

    International Nuclear Information System (INIS)

    Hwang, Ho Seong; Park, Changbom

    2009-01-01

    We study the galaxy morphology-luminosity-environmental relation and its redshift evolution using a spectroscopic sample of galaxies in the Great Observatories Origins Deep Survey. In the redshift range of 0.4 ≤ z ≤ 1.0, we detect conformity in morphology between neighboring galaxies. The realm of conformity is confined within the virialized region associated with each galaxy plus dark matter halo system. When a galaxy is located within the virial radius of its nearest neighbor galaxy, its morphology strongly depends on the neighbor's distance and morphology: the probability for a galaxy to be an early type (f E ) increases as it approaches an early-type neighbor, but decreases as it approaches a late-type neighbor. We find that f E evolves much faster in high-density regions than in low-density regions, and that the morphology-density relation becomes significantly weaker at z ∼ 1. This may be because the rate of galaxy-galaxy interactions is higher in high-density regions, and a series of interactions and mergers over the course of galaxy life eventually transform late types into early types. We find more isolated galaxies are more luminous, which supports luminosity transformation through mergers at these redshifts. Our results are consistent with those from nearby galaxies, and demonstrate that galaxy-galaxy interactions have been strongly affecting the galaxy evolution over a long period of time.

  8. The origin of galaxies

    International Nuclear Information System (INIS)

    Carr, B.J.

    1982-01-01

    The existence of galaxies implies that the early Universe must have contained initial density fluctuations. Overdense regions would then expand more slowly than the background and eventually - providing the fluctuations were not damped out first - they would stop expanding altogether and collapse to form bound objects. To understand how galaxies form we therefore need to know: how the initial density fluctuations arise, under what circumstances they evolve into bound objects, and how the bound objects develop the observed characteristics of galaxies. (author)

  9. Galaxy correlations and cosmology

    International Nuclear Information System (INIS)

    Fall, S.M.

    1979-01-01

    Correlations in the distribution of galaxies provide some important clues about the structure and evolution of the Universe on scales larger than individual galaxies. In recent years much effort has been devoted to estimating and interpreting galaxy correlations. This is a review of these efforts. It is meant to provide both an introductory overview of the subject and a critical assessment of some recent developments

  10. Neighbours of our galaxy

    International Nuclear Information System (INIS)

    Wielebinski, R.

    1982-01-01

    Large telescope and radio-astronomy bring remote regions of the universe into view. Radio waves are emitted by all celestial objects. Precise examination of our own galaxy, the Milky Way, is useful for investigating more remote objects. Some of the remote galaxies are noteworthy, because they emit up to 1,000 times more radio waves than their neighbours. Centaurus A is an example of such an active galaxy. (orig.)

  11. Classifying the Optical Morphology of Shocked POststarburst Galaxies

    Science.gov (United States)

    Stewart, Tess; SPOGs Team

    2018-01-01

    The Shocked POststarburst Galaxy Survey (SPOGS) is a sample of galaxies in transition from blue, star forming spirals to red, inactive ellipticals. These galaxies are earlier in the transition than classical poststarburst samples. We have classified the physical characteristics of the full sample of 1067 SPOGs in 7 categories, covering (1) their shape; (2) the relative prominence of their nuclei; (3) the uniformity of their optical color; (4) whether the outskirts of the galaxy were indicative of on-going star formation; (5) whether they are engaged in interactions with other galaxies, and if so, (6) the kinds of galaxies with which they are interacting; and (7) the presence of asymmetrical features, possibly indicative of recent interactions. We determined that a plurality of SPOGs are in elliptical galaxies, indicating morphological transformations may tend to conclude before other indicators of transitions have faded. Further, early-type SPOGs also tend to have the brightest optical nuclei. Most galaxies do not show signs of current or recent interactions. We used these classifications to search for correlations between qualitative and quantitative characteristics of SPOGs using Sloan Digital Sky Survey and Wide-field Infrared Survey Explorer magnitudes. We find that relative optical nuclear brightness is not a good indicator of the presence of an active galactic nuclei and that galaxies with visible indications of active star formation also cluster in optical color and diagnostic line ratios.

  12. Galaxy-galaxy lensing estimators and their covariance properties

    Science.gov (United States)

    Singh, Sukhdeep; Mandelbaum, Rachel; Seljak, Uroš; Slosar, Anže; Vazquez Gonzalez, Jose

    2017-11-01

    We study the covariance properties of real space correlation function estimators - primarily galaxy-shear correlations, or galaxy-galaxy lensing - using SDSS data for both shear catalogues and lenses (specifically the BOSS LOWZ sample). Using mock catalogues of lenses and sources, we disentangle the various contributions to the covariance matrix and compare them with a simple analytical model. We show that not subtracting the lensing measurement around random points from the measurement around the lens sample is equivalent to performing the measurement using the lens density field instead of the lens overdensity field. While the measurement using the lens density field is unbiased (in the absence of systematics), its error is significantly larger due to an additional term in the covariance. Therefore, this subtraction should be performed regardless of its beneficial effects on systematics. Comparing the error estimates from data and mocks for estimators that involve the overdensity, we find that the errors are dominated by the shape noise and lens clustering, which empirically estimated covariances (jackknife and standard deviation across mocks) that are consistent with theoretical estimates, and that both the connected parts of the four-point function and the supersample covariance can be neglected for the current levels of noise. While the trade-off between different terms in the covariance depends on the survey configuration (area, source number density), the diagnostics that we use in this work should be useful for future works to test their empirically determined covariances.

  13. PHOTOMETRIC REDSHIFTS OF SUBMILLIMETER GALAXIES

    International Nuclear Information System (INIS)

    Chakrabarti, Sukanya; Magnelli, Benjamin; Lutz, Dieter; Berta, Stefano; Popesso, Paola; McKee, Christopher F.; Pozzi, Francesca

    2013-01-01

    We use the photometric redshift method of Chakrabarti and McKee to infer photometric redshifts of submillimeter galaxies with far-IR (FIR) Herschel data obtained as part of the PACS Evolutionary Probe program. For the sample with spectroscopic redshifts, we demonstrate the validity of this method over a large range of redshifts (4 ∼> z ∼> 0.3) and luminosities, finding an average accuracy in (1 + z phot )/(1 + z spec ) of 10%. Thus, this method is more accurate than other FIR photometric redshift methods. This method is different from typical FIR photometric methods in deriving redshifts from the light-to-gas mass (L/M) ratio of infrared-bright galaxies inferred from the FIR spectral energy distribution, rather than dust temperatures. To assess the dependence of our photometric redshift method on the data in this sample, we contrast the average accuracy of our method when we use PACS data, versus SPIRE data, versus both PACS and SPIRE data. We also discuss potential selection effects that may affect the Herschel sample. Once the redshift is derived, we can determine physical properties of infrared-bright galaxies, including the temperature variation within the dust envelope, luminosity, mass, and surface density. We use data from the GOODS-S field to calculate the star formation rate density (SFRD) of submillimeter bright sources detected by AzTEC and PACS. The AzTEC-PACS sources, which have a threshold 850 μm flux ∼> 5 mJy, contribute 15% of the SFRD from all ultraluminous infrared galaxies (L IR ∼> 10 12 L ☉ ), and 3% of the total SFRD at z ∼ 2

  14. Effects of the environment on galaxies in the Catalogue of Isolated Galaxies: physical satellites and large scale structure

    Science.gov (United States)

    Argudo-Fernández, M.; Verley, S.; Bergond, G.; Sulentic, J.; Sabater, J.; Fernández Lorenzo, M.; Espada, D.; Leon, S.; Sánchez-Expósito, S.; Santander-Vela, J. D.; Verdes-Montenegro, L.

    2014-04-01

    Context. We present a study of the 3D environment for a sample of 386 galaxies in the Catalogue of Isolated Galaxies (CIG, Karachentseva 1973) using the Ninth Data Release of the Sloan Digital Sky Survey (SDSS-DR9). Aims: We aim to identify and quantify the effects of the satellite distribution around a sample of galaxies in the CIG, as well as the effects of the large-scale structure (LSS). Methods: To recover the physically bound galaxies we first focused on the satellites that are within the escape speed of each CIG galaxy. We also propose a more conservative method using the stacked Gaussian distribution of the velocity difference of the neighbours. The tidal strengths affecting the primary galaxy were estimated to quantify the effects of the local and LSS environments. We also defined the projected number density parameter at the fifth nearest neighbour to characterise the LSS around the CIG galaxies. Results: Out of the 386 CIG galaxies considered in this study, at least 340 (88% of the sample) have no physically linked satellite. Following the more conservative Gaussian distribution of physical satellites around the CIG galaxies leads to upper limits. Out of the 386 CIG galaxies, 327 (85% of the sample) have no physical companion within a projected distance of 0.3 Mpc. The CIG galaxies are distributed following the LSS of the local Universe, although presenting a large heterogeneity in their degree of connection with it. When present around a CIG galaxy, the effect of physically bound galaxies largely dominates (typically by more than 90%) the tidal strengths generated by the LSS. Conclusions: The CIG samples a variety of environments, from galaxies with physical satellites to galaxies without neighbours within 3 Mpc. A clear segregation appears between early-type CIG galaxies with companions and isolated late-type CIG galaxies. Isolated galaxies are in general bluer, with probably younger stellar populations and very high star formation compared with older

  15. STRUCTURES OF LOCAL GALAXIES COMPARED TO HIGH-REDSHIFT STAR-FORMING GALAXIES

    International Nuclear Information System (INIS)

    Petty, Sara M.; De Mello, DuIlia F.; Gallagher, John S.; Gardner, Jonathan P.; Lotz, Jennifer M.; Matt Mountain, C.; Smith, Linda J.

    2009-01-01

    The rest-frame far-ultraviolet morphologies of eight nearby interacting and starburst galaxies (Arp 269, M 82, Mrk 8, NGC 520, NGC 1068, NGC 3079, NGC 3310, and NGC 7673) are compared with 54 galaxies at z ∼ 1.5 and 46 galaxies at z ∼ 4 observed in the Great Observatories Origins Deep Survey (GOODS) taken with the Advanced Camera for Surveys onboard the Hubble Space Telescope. The nearby sample is artificially redshifted to z ∼ 1.5 and 4 by applying luminosity and size scaling. We compare the simulated galaxy morphologies to real z ∼ 1.5 and 4 UV-bright galaxy morphologies. We calculate the Gini coefficient (G), the second-order moment of the brightest 20% of the galaxy's flux (M 20 ), and the Sersic index (n). We explore the use of nonparametric methods with two-dimensional profile fitting and find the combination of M 20 with n an efficient method to classify galaxies as having merger, exponential disk, or bulge-like morphologies. When classified according to G and M 20 20/30% of real/simulated galaxies at z ∼ 1.5 and 37/12% at z ∼ 4 have bulge-like morphologies. The rest have merger-like or intermediate distributions. Alternatively, when classified according to the Sersic index, 70% of the z ∼ 1.5 and z ∼ 4 real galaxies are exponential disks or bulge-like with n>0.8, and ∼ 30% of the real galaxies are classified as mergers. The artificially redshifted galaxies have n values with ∼ 35% bulge or exponential at z ∼ 1.5 and 4. Therefore, ∼ 20%-30% of Lyman-break galaxies have structures similar to local starburst mergers, and may be driven by similar processes. We assume merger-like or clumpy star-forming galaxies in the GOODS field have morphological structure with values n 20 > - 1.7. We conclude that Mrk 8, NGC 3079, and NGC 7673 have structures similar to those of merger-like and clumpy star-forming galaxies observed at z ∼ 1.5 and 4.

  16. Does the galaxy-halo connection vary with environment?

    Science.gov (United States)

    Dragomir, Radu; Rodríguez-Puebla, Aldo; Primack, Joel R.; Lee, Christoph T.

    2018-05-01

    (Sub)halo abundance matching (SHAM) assumes that one (sub) halo property, such as mass Mvir or peak circular velocity Vpeak, determines properties of the galaxy hosted in each (sub) halo such as its luminosity or stellar mass. This assumption implies that the dependence of galaxy luminosity functions (GLFs) and the galaxy stellar mass function (GSMF) on environmental density is determined by the corresponding halo density dependence. In this paper, we test this by determining from a Sloan Digital Sky Survey sample the observed dependence with environmental density of the ugriz GLFs and GSMF for all galaxies, and for central and satellite galaxies separately. We then show that the SHAM predictions are in remarkable agreement with these observations, even when the galaxy population is divided between central and satellite galaxies. However, we show that SHAM fails to reproduce the correct dependence between environmental density and g - r colour for all galaxies and central galaxies, although it better reproduces the colour dependence on environmental density of satellite galaxies.

  17. Powerful warm infrared sources in early-type galaxies

    International Nuclear Information System (INIS)

    Dressel, L.L.

    1988-01-01

    IRAS far-infrared sources have been identified with 129 S0, Sa, Sb, and Sc galaxies in a statistically complete sample of 738 galaxies brighter than 14.5 mag and smaller than 4.0 arcmin. In most cases, the far-IR colors and the ratios of far-IR flux to radio flux density are those of normal galactic disks and/or starbursts. The most powerful far-IR sources in S0 and Sa galaxies are just as powerful as the strongest far-IR sources in Sb and Sc galaxies. Bright-IR sources in S0 and Sa galaxies are warm; those in Sc galaxies are cool. Sb galaxies have both warm and cool IR sources. Bright warm IR sources occur much more frequently in barred galaxies than in galaxies without bars for types S0, Sa, and Sb. Bright, cool IR sources are found with increasing frequency along the Hubble sequence, regardless of the presence or absence of a bar. At least some S0 galaxies with warm, bright IR sources have peculiar morphologies and ambiguous classifications. 22 references

  18. The Dark Side of Galaxy Color: evidence from new SDSS measurements of galaxy clustering and lensing

    OpenAIRE

    Hearin, Andrew P.; Watson, Douglas F.; Becker, Matthew R.; Reyes, Reinabelle; Berlind, Andreas A.; Zentner, Andrew R.

    2013-01-01

    The age matching model has recently been shown to predict correctly the luminosity L and g-r color of galaxies residing within dark matter halos. The central tenet of the model is intuitive: older halos tend to host galaxies with older stellar populations. In this paper, we demonstrate that age matching also correctly predicts the g-r color trends exhibited in a wide variety of statistics of the galaxy distribution for stellar mass M* threshold samples. In particular, we present new measureme...

  19. Clustering of galaxies around AGNs in the HSC Wide survey

    Science.gov (United States)

    Shirasaki, Yuji; Akiyama, Masayuki; Nagao, Tohru; Toba, Yoshiki; He, Wanqiu; Ohishi, Masatoshi; Mizumoto, Yoshihiko; Miyazaki, Satoshi; Nishizawa, Atsushi J.; Usuda, Tomonori

    2018-01-01

    We have measured the clustering of galaxies around active galactic nuclei (AGNs) for which single-epoch virial masses of the super-massive black hole (SMBH) are available to investigate the relation between the large-scale environment of AGNs and the evolution of SMBHs. The AGN samples used in this work were derived from the Sloan Digital Sky Survey (SDSS) observations and the galaxy samples were from the 240 deg2 S15b data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). The investigated redshift range is 0.6-3.0, and the masses of the SMBHs lie in the range 107.5-1010 M⊙. The absolute magnitude of the galaxy samples reaches to Mλ310 ˜ -18 at rest-frame wavelength 310 nm for the low-redshift end of the samples. More than 70% of the galaxies in the analysis are blue. We found a significant dependence of the cross-correlation length on redshift, which primarily reflects the brightness-dependence of the galaxy clustering. At the lowest redshifts the cross-correlation length increases from 7 h-1 Mpc around Mλ310 = -19 mag to >10 h-1 Mpc beyond Mλ310 = -20 mag. No significant dependence of the cross-correlation length on BH mass was found for whole galaxy samples dominated by blue galaxies, while there was an indication of BH mass dependence in the cross-correlation with red galaxies. These results provides a picture of the environment of AGNs studied in this paper being enriched with blue star-forming galaxies, and a fraction of the galaxies are evolving into red galaxies along with the evolution of SMBHs in that system.

  20. The dark matter of galaxy voids

    Science.gov (United States)

    Sutter, P. M.; Lavaux, Guilhem; Wandelt, Benjamin D.; Weinberg, David H.; Warren, Michael S.

    2014-03-01

    How do observed voids relate to the underlying dark matter distribution? To examine the spatial distribution of dark matter contained within voids identified in galaxy surveys, we apply Halo Occupation Distribution models representing sparsely and densely sampled galaxy surveys to a high-resolution N-body simulation. We compare these galaxy voids to voids found in the halo distribution, low-resolution dark matter and high-resolution dark matter. We find that voids at all scales in densely sampled surveys - and medium- to large-scale voids in sparse surveys - trace the same underdensities as dark matter, but they are larger in radius by ˜20 per cent, they have somewhat shallower density profiles and they have centres offset by ˜ 0.4Rv rms. However, in void-to-void comparison we find that shape estimators are less robust to sampling, and the largest voids in sparsely sampled surveys suffer fragmentation at their edges. We find that voids in galaxy surveys always correspond to underdensities in the dark matter, though the centres may be offset. When this offset is taken into account, we recover almost identical radial density profiles between galaxies and dark matter. All mock catalogues used in this work are available at http://www.cosmicvoids.net.

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

    International Nuclear Information System (INIS)

    Gondhalekar, P.M.

    1982-08-01

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

  2. Young stellar populations in early-type galaxies in the Sloan Digital Sky Survey

    Science.gov (United States)

    Nolan, Louisa A.; Raychaudhury, Somak; Kabán, Ata

    2007-02-01

    We use a purely data-driven rectified factor analysis to identify early-type galaxies with recent star formation in Data Release 4 of the Sloan Digital Sky Survey Spectroscopic Catalogue. We compare the spectra and environment of these galaxies with those of `normal' early-type galaxies, and a sample of independently selected E+A galaxies. We calculate the projected local galaxy surface density from the nearest five and 10 neighbours (Σ5 and Σ10) for each galaxy in our sample, and find that the dependence on projected local density, of the properties of E+A galaxies, is not significantly different from that of early-type galaxies with young stellar populations, dropping off rapidly towards denser environments, and flattening off at densities ~10 per cent of the stellar mass in these galaxies. This, together with the similarity of the environments in which this `E+F' population and the E+A galaxy sample are found, suggests that E+F galaxies used to be E+A galaxies, but have evolved by a further ~ one to a few Gyr. Our rectified factor analysis is sensitive enough to identify this hidden population, which allows us to study the global and intrinsic properties of early-type galaxies created in major mergers or interactions, and compare them with those early-types which have had the bulk of their stars in place since a much earlier epoch.

  3. Galaxy-Wide Shocks in the H$\\alpha$ Emission of Nearby Galaxy Mergers

    Science.gov (United States)

    Mortazavi, S. Alireza; Lotz, Jennifer M.

    2018-01-01

    We examine the properties of shocked gas produced as a result of binary galaxy interactions, using H$\\alpha$ emission in a sample 22 mergers observed with SparsePak Integral Field Unit (IFU) at Kitt Peak National Observatory (KPNO). Our sample consists of major and minor tidally interacting galaxies (mass ratio $1text{f}_\\text{shocked}$, and examine the spatial distribution of shocks. We find that close galaxy pairs have, on average, a higher shock fraction than wide pairs, and our coalesced mergers have the highest average $\\text{f}_\\text{shocked}$. Additionally, we find for the first time, correlations between mass ratio, mass of the companion, and $\\text{f}_\\text{shocked}$ in tidally interacting galaxy pairs. Among the non-coalesced systems in our sample, the galaxy pairs with more equal light ratio (stellar mass ratio) tend to have a higher average $\\text{f}_\\text{shocked}$. Also, the primary (more massive) companions are on average slightly more shocked than the secondary (less massive) ones. Utilizing dynamical models in the literature and this work, we inspect trends between $\\text{f}_\\text{shocked}$ and the reconstructed encounter parameters. In this very limited sample, we find that the orbital pericentric separation is correlated with shock fraction, consistent with shocks being produced by the chain of events caused by the tidal impulse during the first passage. These results lay a basis for furture analysis using the higher statistics provided by the on-going and future IFU galaxy surveys.

  4. Environment effects on the flattening distribution of galaxies

    International Nuclear Information System (INIS)

    Freitas Pacheco, J.A. de; Souza, R.E. de; Arakaki, L.

    1983-01-01

    The results of a study of environment effects on the flattening distribution of galaxies are presented. Samples of different morphological types in regions of high and low projected galaxian density were prepared using the Uppsala General Catalogue of Galaxies. No significant differences were detected for the E and Spiral galaxies. However this study suggest that there is an excess of flat S phi systems in regions of high galaxian density with respect the field systems. These 'flat' S phi's are interpreted as being gas stripped Sa galaxies and the consequences of such a hypothesis are also discussed. (Author) [pt

  5. The Occurence of Nuclear Starbursts in Seyfert 1 Galaxies

    Science.gov (United States)

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

    2001-05-01

    Medium resolution H and K band spectra with high angular reesolution were obtained for a small sample of nearby Seyfert galaxies using NIRSPEC at the Keck telescope. Recent studies with medium resolution have found evidence for a lack of powerful starbursts in Seyfert1 galaxies. Differences between the two Seyfert types might provide a challenge for the unified scheme proposed for Seyfert galaxies. A preliminary analysis indicates that most of the Seyfert1 galaxies do indeed show signs of circumnuclar star formation. Detailed modelling using population synthesis in conjunction with NIR spectral synthesis will allow to estimate the age, star formation history and mass of these stellar population.

  6. Atomic hydrogen properties of active galactic nuclei host galaxies: H I in 16 nuclei of galaxies (NUGA) sources

    International Nuclear Information System (INIS)

    Haan, Sebastian; Schinnerer, Eva; Mundell, Carole G.; García-Burillo, Santiago; Combes, Francoise

    2008-01-01

    We present a comprehensive spectroscopic imaging survey of the distribution and kinematics of atomic hydrogen (H I) in 16 nearby spiral galaxies hosting low luminosity active galactic nuclei (AGN), observed with high spectral and spatial resolution (resolution: ∼20'', ∼5 km s –1 ) using the NRAO Very Large Array (VLA). The sample contains a range of nuclear types ranging from Seyfert to star-forming nuclei, and was originally selected for the NUclei of GAlaxies project (NUGA)—a spectrally and spatially resolved interferometric survey of gas dynamics in nearby galaxies designed to identify the fueling mechanisms of AGN and the relation to host galaxy evolution. Here we investigate the relationship between the H I properties of these galaxies, their environment, their stellar distribution, and their AGN type. The large-scale H I morphology of each galaxy is classified as ringed, spiral, or centrally concentrated; comparison of the resulting morphological classification with the AGN type reveals that ring structures are significantly more common in low-ionization narrow emission-line regions (LINER) than in Seyfert host galaxies, suggesting a time evolution of the AGN activity together with the redistribution of the neutral gas. Dynamically disturbed H I disks are also more prevalent in LINER host galaxies than in Seyfert host galaxies. While several galaxies are surrounded by companions (some with associated H I emission), there is no correlation between the presence of companions and the AGN type (Seyfert/LINER).

  7. The Swift BAT Perspective on Non-Thermal Emission in HIFLUGCS Galaxy Clusters

    Science.gov (United States)

    Wik, Daniel R.

    2011-01-01

    The search for diffuse non-thermal, inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been underway for many years, with most detections being either of low significance or controversial. Until recently, comprehensive surveys of hard X-ray emission from clusters were not possible; instead, individually proposed-for. long observations would be collated from the archive. With the advent of the Swift BAT all sky survey, any c1u,;ter's emission above 14 keV can be probed with nearly uniform sensitivity. which is comparable to that of RXTE, Beppo-SAX, and Suzaku with the 58-month version of the survey. In this work. we search for non-thermal excess emission above the exponentially decreasing, high energy thermal emission in the flux-limited HIFLUGCS sample. The BAT emission from many of the detected clusters is marginally extended; we are able to extract the total flux for these clusters using fiducial models for their spatial extent. To account for thermal emission at BAT energies, XMM-Newton EPIC spectra are extracted from coincident spatial regions so that both the thermal and non-thermal spectral components can be determined simultaneou,;ly in joint fits. We find marginally significant IC components in 6 clusters, though after closer inspection and consideration of systematic errors we are unable to claim a clear detection in any of them. The spectra of all clusters are also summed to enhance a cumulative non-thermal signal not quite detectable in individual clusters. After constructing a model based on single temperature

  8. Quark nugget dark matter: no contradiction with 511 keV line emission from dwarf galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, Kyle; Zhitnitsky, Ariel, E-mail: klawson@phas.ubc.ca, E-mail: arz@phas.ubc.ca [Department of Physics and Astronomy, University of British Columbia, Vancouver, B.C. V6T 1Z1 (Canada)

    2017-02-01

    The observed galactic 511 keV line has been interpreted in a number of papers as a possible signal of dark matter annihilation within the galactic bulge. If this is the case then it is possible that a similar spectral feature may be observed in association with nearby dwarf galaxies. These objects are believed to be strongly dark matter dominated and present a relatively clean observational target. Recently INTEGRAL observations have provided new constraints on the 511 keV flux from nearby dwarf galaxies [1] motivating further investigation into the mechanism by which this radiation may arise. In the model presented here dark matter in the form of heavy quark nuggets produces the galactic 511 keV emission line through interactions with the visible matter. It is argued that this type of interaction is not strongly constrained by the flux limits reported in [2].

  9. Radio emission in the Virgo cluster and in SO galaxies

    International Nuclear Information System (INIS)

    Kotanyi, C.

    1981-01-01

    A survey of the radio continuum emission from the galaxies in the Virgo Cluster is presented. The sample of 274 galaxies in total contains a subsample of 188 galaxies complete down to magntiude msub(p) = 14. The observations consisted mostly of short (10 minutes) observations providing one-dimensional (East-West) strip distributions of the radio brightness at 1.4 GHz, with an East-West resolution of 23'' allowing separation of central sources from extended emission, and an r.m.s. noise level of 2 mJy. The radio emission of SO galaxies is examined. A sample of 145 SO galaxies is obtained by combining the Virgo cluster SO's with the nearby non-cluster SO's. The radio data, mainly from short observations, are used to derive the RLF. The radio emission in SO galaxies is at least three times weaker than that in ellipticals and spirals. Flat-spectrum compact nuclear sources are found in SO galaxies but they are at least 10 times weaker than in elliptical galaxies, which is attributed to the small mass of the bulges in SO's as compared to the mass of elliptical galaxies. The absence of steep-spectrum, extended central sources and of disk radio emission in SO's is attributed to their low neutral hydrogen content. (Auth.)

  10. Properties of the Photometric Components of Lenticular Galaxies

    Directory of Open Access Journals (Sweden)

    J. Alfonso L. Aguerri

    2012-01-01

    their origin and evolution. I also explain the different properties of the lenticular galaxies that have evolved through each of these formation processes. A unique opportunity for understanding the origin of S0 galaxies will shortly be forthcoming. This is due to the morphological classifications of large galaxy samples that have recently been published. These classifications have given us our first ever opportunity to study large samples of lenticulars within a wide range of masses and located in a great variety of environments. These large samples will provide us with a real census of nearby lenticular galaxies and could be crucial in finally helping us to understand the origin and evolution of these galaxies.

  11. Selection effects in the bivariate brightness distribution for spiral galaxies

    International Nuclear Information System (INIS)

    Phillipps, S.; Disney, M.

    1986-01-01

    The joint distribution of total luminosity and characteristic surface brightness (the bivariate brightness distribution) is investigated for a complete sample of spiral galaxies in the Virgo cluster. The influence of selection and physical limits of various kinds on the apparent distribution are detailed. While the distribution of surface brightness for bright galaxies may be genuinely fairly narrow, faint galaxies exist right across the (quite small) range of accessible surface brightnesses so no statement can be made about the true extent of the distribution. The lack of high surface brightness bright galaxies in the Virgo sample relative to an overall RC2 sample (mostly field galaxies) supports the contention that the star-formation rate is reduced in the inner region of the cluster for environmental reasons. (author)

  12. The formation of galaxies

    International Nuclear Information System (INIS)

    Gunn, J.E.

    1983-01-01

    The presently fashionable ideas for galaxy formation are reviewed briefly, and it is concluded that the standard isothermal heirarchy fits the available data best. A simple infall picture is presented which explains many of the observed properties of disk galaxies. (orig.)

  13. The galaxy builders

    Science.gov (United States)

    Cho, Adrian

    2018-06-01

    Philip Hopkins, a theoretical astrophysicist at the California Institute of Technology in Pasadena, likes to prank his colleagues. An expert in simulating the formation of galaxies, Hopkins sometimes begins his talks by projecting images of his creations next to photos of real galaxies and defying his audience to tell them apart. "We can even trick astronomers," Hopkins says. For decades, scientists have tried to simulate how the trillions of galaxies in the observable universe arose from clouds of gas after the big bang. But only in the past few years have the simulations begun to reproduce both the details of individual galaxies and their distribution of masses and shapes. As the fake universes improve, their role is also changing. Previously, information flowed one way: from the astronomers studying real galaxies to the modelers trying to simulate them. Now, insight is flowing the other way, too, with the models helping guide astronomers and astrophysicists. The models suggest that the earliest galaxies were oddly pickle-shaped, that wafer-thin spiral galaxies are surprisingly rugged in the face of collisions, and, perhaps most important, that galaxies must form stars far more slowly than astrophysicists expected. Progress is coming so fast, says Tiziana Di Matteo, a numerical cosmologist at Carnegie Mellon University in Pittsburgh, Pennsylvania, that "the whole thing has reached this little golden age."

  14. The Evolution of Galaxies

    Czech Academy of Sciences Publication Activity Database

    Palouš, Jan

    2007-01-01

    Roč. 17, - (2007), s. 34-40 ISSN 1220-5168. [Heliospere and galaxy. Sinaia, 03.05.2007-05.05.2007] R&D Projects: GA MŠk(CZ) LC06014 Institutional research plan: CEZ:AV0Z10030501 Keywords : ISM structure * stars formation * evolution of galaxies Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  15. Dwarf Elliptical Galaxies

    Science.gov (United States)

    Caldwell, N.; Murdin, P.

    2000-11-01

    DWARF SPHEROIDAL GALAXIES were first identified by Shapley, who had noticed two very diffuse collections of stars on Harvard patrol plates. Although these systems had about as many stars as a GLOBULAR CLUSTER, they were of much lower density, and hence much larger radius, and thus were considered distinct galaxies. These two, named Fornax and Sculptor after the constellations in which they ap...

  16. Hubble's Menagerie of Galaxies

    Indian Academy of Sciences (India)

    Srimath

    astronom ers have even w ondered ifH ubble's galaxy typ es form an evolutionary sequence: does one type of galaxy evolve into another? 1. T he D iscovery of G alaxies. A stronom ers began to ponder these issues only after they discovered w hat ...

  17. Our galaxy is exploding

    International Nuclear Information System (INIS)

    Closets, Francois de.

    1977-01-01

    Improvements made in radioastronomy, and infrared, X and γ emission studies of the Galaxy have allowed to study the galactic nucleus, which is characterized by an intense activity. The most recent hypotheses made to explain this activity and replace it in the general context of the evolution of the galaxies are presented [fr

  18. Our aging galaxy

    International Nuclear Information System (INIS)

    Lyngaa, G.

    1980-01-01

    The origin and evolution of the galaxies is described, according to the presently prevailing theories. The various types of galaxy and their structures are described, and also the formation of stars from the gas clouds. The spiral structure and the evolution of the disc are discussed. Finally the future development on the time scale of thousands of millions of years is briefly discussed. (JIW)

  19. Visibility of galaxies

    International Nuclear Information System (INIS)

    Disney, M.J.

    1976-01-01

    It is stated that counts of galaxies could be seriously biased by selection effects, largely influenced by the brightness of the night sky. To illustrate this suppose the Earth were situated near the center of a giant elliptical galaxy. The mean surface brightness of the sky would then appear some 8 to 9 mag. brighter than is observed from our position in the Galaxy. Extragalactic space would then appear to be empty void; spiral and irregular galaxies would be invisible, and all that could be easily detected would be the core regions of galaxy ellipticals very similar to our own. Much of the Universe would be blinded by the surface brightness of the parent galaxy. This blinding, however, is a relative matter and the question arises as to what extent we are blinded by the spiral galaxy in which we exist. Strong indirect evidence exists that our knowledge of galaxies is heavily biased by the sky background, and the true population of extragalactic space may be very different from that seen. Other relevant work is also discussed, and further investigational work is indicated. (U.K.)

  20. Hunting for Dark Matter in Spheroidal Galaxies

    Science.gov (United States)

    Steele, Rebecca; Holwerda, Benne; Kielkopf, John F.

    2018-06-01

    Searches for blended spectra have been highly successful in identifying strongly lensing galaxies: these spectra show a low-redshift passive galaxy with much stronger emission lines from the source being lensed. We have recently identified 112 strong lensing candidates in the Galaxy and Mass Assembly Survey (GAMA). The improved sensitivity and redshift determination makes this a very clean sample of two-galaxy spectra, spanning both lower-mass galaxy strong lenses as well as a higher redshiftregime (z > 0.4). As a first step of a PhD project, we will vet the 112 candidate strong gravitational lenses using the new Kilo Degree Survey (KiDS), which is both deeper and sharper than existing Sloan images. Once confirmed, these lower mass gravitational lenses can be targeted with the soon-to-launch James Webb Space Telescope or the Hubble Space Telescope for follow-up observations. Models of the gravitational lenses give us direct measures of the dark matter content of these low-mass galaxies, thought to be dominated by dark matter.

  1. Galaxy pairs as a probe for mergers at z ~ 2

    DEFF Research Database (Denmark)

    Man, A.W.S.; Zirm, Andrew Wasmuth; Toft, Sune

    2011-01-01

    In this work I investigate the redshift evolution of pair fraction of a sample of 196 massive galaxies from z = 0 to 3, selected from the COSMOS field. We find that on average a massive galaxy undergoes ~ 1.1 \\pm 0.5 major merger since z = 3. I will review the current limitations of using the pair...

  2. Millimeter observations of radio-loud active galaxies

    NARCIS (Netherlands)

    van Bemmel, IM; Bertoldi, F

    In order to study the nature of the far-infrared emission observed in radio-loud active galaxies, we have obtained 1.2 mill observations with the IRAM 30 m telescope for a sample of eight radio-loud active galaxies. In all objects we find that the 1.2 mm emission is dominated by non-thermal

  3. Molecules as tracers of galaxy evolution: an EMIR survey

    DEFF Research Database (Denmark)

    Costagliola, F.; Aalto, S.; I. Rodriguez, M.

    2011-01-01

    We investigate the molecular gas properties of a sample of 23 galaxies in order to find and test chemical signatures of galaxy evolution and to compare them to IR evolutionary tracers. Observation at 3 mm wavelengths were obtained with the EMIR broadband receiver, mounted on the IRAM 30 m telesco...

  4. The Westerbork HI Survey of Irregular and Spiral Galaxies, WHISP

    NARCIS (Netherlands)

    van der Hulst, JM; van Albada, TS; Sancisi, R; Hibbard, JE; Rupen, MP; VanGorkom, JH

    2001-01-01

    This paper briefly describes WHISP, an ongoing project to image the H(I) in a large sample of nearby galaxies with the Westerbork Synthesis Radio Telescope (WSRT). The goal of the survey is to investigate the H(I) density distributions and velocity fields of galaxies as a function of Hubble type,

  5. The Westerbork HI survey of irregular and spiral galaxies, WHISP

    NARCIS (Netherlands)

    van der Hulst, JM; Taylor, AR; Landecker, TL; Willis, AG

    2002-01-01

    This paper briefly describes WHISP, an ongoing project to image the HI in a large sample of nearby galaxies with the Westerbork Synthesis Radio Telescope (WSRT). The goal of the survey is to investigate the HI density distributions and velocity fields of galaxies as a function of Hubble type,

  6. Seyfert Galaxies: Radio Continuum Emission Properties and the ...

    Indian Academy of Sciences (India)

    sample of Seyfert galaxies in the framework of the unification scheme. Key words. Galaxies: ... 25/49 sub-fields. Self-calibration is used iteratively to improve the image quality. 4. ... Antonucci, R. R. J., Miller, J. S. 1985, Astrophys. J., 297, 621.

  7. Structure analysis of edge-on spiral galaxies

    NARCIS (Netherlands)

    deGrijs, R; vanderKruit, PC

    The stellar distribution of a small sample of edge-on spiral galaxies is examined in B, V, R, and I by fitting model distributions to the light profiles, both perpendicular to the galaxy planes and along the major axes. We have developed a method to compare the fits for the models obtained for

  8. Emission-line galaxies toward the booetes void

    International Nuclear Information System (INIS)

    Moody, J.W.

    1986-01-01

    Galaxies with strong emission are potentially useful as probes of the large-scale galaxian distribution. However, to serve as probes, their relative frequency and clustering properties must be known. This dissertation presents a study of these properties for field galaxies having [OIII] λ5007 emission equivalent widths greater than 10 A and reports on a search for galaxies with [OIII] λ5007 emission in the direction of the Booetes void, a volume located at α = 4/sup h/48/sup m/, δ = 47 0 , and cz = 15,000 km/sec that has been demonstrated to be under-abundant in galaxies by a factor of at least four. The study of field emission-line galaxies was done in two magnitude limited surveys consisting of 341 galaxies from both the north and south galactic caps having previously published redshifts and photometry. The galaxy spectra used for redshifts were examined and supplemented by new observations for 56 objects, primarily those with confirmed or suspected emission. Emission-line galaxies were found to comprise 8.8% of galaxies in a Illa-J selected sample or 6.6% of galaxies in a Illa-F selected sample. A search for emission-line galaxies towards the Booetes void was undertaken using the Burrell Schmidt telescope and an objective prism giving a reciprocal dispersion of 900 A/mm at Hβ. Three galaxies were found to lie within it, a result consistent with distributions through the void ranging from uniform to under-abundant by a factor of three

  9. Distant Galaxy Clusters Hosting Extreme Central Galaxies

    Science.gov (United States)

    McDonald, Michael

    2014-09-01

    The recently-discovered Phoenix cluster harbors the most star-forming central cluster galaxy of any cluster in the known Universe, by nearly a factor of 10. This extreme system appears to be fulfilling early cooling flow predictions, although the lack of similar systems makes any interpretation difficult. In an attempt to find other "Phoenix-like" clusters, we have cross-correlated archival all-sky surveys (in which Phoenix was detected) and isolated 4 similarly-extreme systems which are also coincident in position and redshift with an overdensity of red galaxies. We propose here to obtain Chandra observations of these extreme, Phoenix-like systems, in order to confirm them as relaxed, rapidly-cooling galaxy clusters.

  10. Starbursts and IRAS galaxies

    International Nuclear Information System (INIS)

    Belfort, P.

    1987-01-01

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

  11. Gas accretion onto galaxies

    CERN Document Server

    Davé, Romeel

    2017-01-01

    This edited volume presents the current state of gas accretion studies from both observational and theoretical perspectives, and charts our progress towards answering the fundamental yet elusive question of how galaxies get their gas. Understanding how galaxies form and evolve has been a central focus in astronomy for over a century. These studies have accelerated in the new millennium, driven by two key advances: the establishment of a firm concordance cosmological model that provides the backbone on which galaxies form and grow, and the recognition that galaxies grow not in isolation but within a “cosmic ecosystem” that includes the vast reservoir of gas filling intergalactic space. This latter aspect in which galaxies continually exchange matter with the intergalactic medium via inflows and outflows has been dubbed the “baryon cycle”. The topic of this book is directly related to the baryon cycle, in particular its least well constrained aspect, namely gas accretion. Accretion is a rare area of ast...

  12. Spectral evolution of galaxies

    International Nuclear Information System (INIS)

    Rocca-Volmerange, B.

    1989-01-01

    A recent striking event in Observational Cosmology is the discovery of a large population of galaxies at extreme cosmological distances (extended from spectral redshifts ≅ 1 to ≥ 3) corresponding to a lookback time of 80% of the Universe's age. However when galaxies are observed at such remote epochs, their appearances are affected by at least two simultaneous effects which are respectively a cosmological effect and the intrinsic evolution of their stellar populations which appear younger than in our nearby galaxies. The fundamental problem is first to disentangle the respective contributions of these two effects to apparent magnitudes and colors of distant galaxies. Other effects which are likely to modify the appearance of galaxies are amplification by gravitational lensing and interaction with environment will also be considered. (author)

  13. Statistical Properties of Gamma-Ray Burst Host Galaxies Jie-Min ...

    Indian Academy of Sciences (India)

    Statistical Properties of Gamma-Ray Burst Host Galaxies. Jie-Min Chen1, Jin Zhang2,3, ... of GRB host galaxies and explore possible correlations between these properties. We also investigate possible cosmic ... hydrogen column density for the GRB host galaxies in our sample. 6.295. The stellar masses are mainly in the ...

  14. Stellar populations of elliptical galaxies in Virgo Cluster. I. The data and stellar population analysis

    NARCIS (Netherlands)

    Yamada, Y; Arimoto, N; Vazdekis, A; Peletier, RF

    2006-01-01

    We have determined spectroscopic ages of elliptical galaxies in the Virgo Cluster using spectra of very high signal-to-noise ratio (S/N > 100 angstrom(-1)). We observed eight galaxies with the Subaru Telescope and have combined this sample with six galaxies previously observed with the WHT. To

  15. 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

  16. Galaxies Gather at Great Distances

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] Distant Galaxy Cluster Infrared Survey Poster [figure removed for brevity, see original site] [figure removed for brevity, see original site] Bird's Eye View Mosaic Bird's Eye View Mosaic with Clusters [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] 9.1 Billion Light-Years 8.7 Billion Light-Years 8.6 Billion Light-Years Astronomers have discovered nearly 300 galaxy clusters and groups, including almost 100 located 8 to 10 billion light-years away, using the space-based Spitzer Space Telescope and the ground-based Mayall 4-meter telescope at Kitt Peak National Observatory in Tucson, Ariz. The new sample represents a six-fold increase in the number of known galaxy clusters and groups at such extreme distances, and will allow astronomers to systematically study massive galaxies two-thirds of the way back to the Big Bang. A mosaic portraying a bird's eye view of the field in which the distant clusters were found is shown at upper left. It spans a region of sky 40 times larger than that covered by the full moon as seen from Earth. Thousands of individual images from Spitzer's infrared array camera instrument were stitched together to create this mosaic. The distant clusters are marked with orange dots. Close-up images of three of the distant galaxy clusters are shown in the adjoining panels. The clusters appear as a concentration of red dots near the center of each image. These images reveal the galaxies as they were over 8 billion years ago, since that's how long their light took to reach Earth and Spitzer's infrared eyes. These pictures are false-color composites, combining ground-based optical images captured by the Mosaic-I camera on the Mayall 4-meter telescope at Kitt Peak, with infrared pictures taken by Spitzer's infrared array camera. Blue and green represent visible light at wavelengths of 0.4 microns and 0.8 microns

  17. Analysis of the star formation histories of galaxies in different environments: from low to high density

    Science.gov (United States)

    Ortega-Minakata, René A.

    2015-11-01

    In this thesis, a value-added cataloge of 403,372 SDSS-DR7 galaxies is presented. This catalogue incorporates information on their stellar populations, including their star formation histories, their dominant emission-line activity type, inferred morphology and a measurement of their environmental density. The sample that formed this catalogue was selected from the SDSS-DR7 (Legacy) spectroscopic catalogue of galaxies in the Northern Galactic Cap, selecting only galaxies with high-quality spectra and redshift determination, and photometric measurements with small errors. Also, galaxies near the edge of the photometric survey footprint were excluded to avoid errors in the determination of their environment. Only galaxies in the 0.03-0.30 redshift range were considered. Starlight fits of the spectra of these galaxies were used to obtain information on their star formation history and stellar mass, velocity dispersion and mean age. From the fit residuals, emission-line fluxes were measured and used to obtain the dominant activity type of these galaxies using the BPT diagnostic diagram. A neighbour search code was written and applied to the catalogue to measure the local environmental density of these galaxies. This code counts the number of neighbours within a fixed search radius and a radial velocity range centered at each galaxy's radial velocity. A projected radius of 1.5 Mpc and a range of ± 2,500 km/s, both centered at the redshift of the target galaxy, were used to search and count all the neighbours of each galaxy in the catalogue. The neighbours were counted from the photometric catalogue of the SDSS-DR7 using photometric redshifts, to avoid incompleteness of the spectroscopic catalogue. The morphology of the galaxies in the catalogue was inferred by inverting previously found relations between subsamples of galaxies with visual morphology classification and their optical colours and concentration of light. The galaxies in the catalogue were matched to six

  18. The galaxy ancestor problem

    Science.gov (United States)

    Disney, M. J.; Lang, R. H.

    2012-11-01

    The Hubble Space Telescope (HST) findsgalaxies whose Tolman dimming exceeds 10 mag. Could evolution alone explain these as our ancestor galaxies or could they be representatives of quite a different dynasty whose descendants are no longer prominent today? We explore the latter hypothesis and argue that surface brightness selection effects naturally bring into focus quite different dynasties from different redshifts. Thus, the HST z = 7 galaxies could be examples of galaxies whose descendants are both too small and too choked with dust to be recognizable in our neighbourhood easily today. Conversely, the ancestors of the Milky Way and its obvious neighbours would have completely sunk below the sky at z > 1.2, unless they were more luminous in the past, although their diffused light could account for the missing re-ionization flux. This Succeeding Prominent Dynasties Hypothesis (SPDH) fits the existing observations both naturally and well even without evolution, including the bizarre distributions of galaxy surface brightness found in deep fields, the angular size ˜(1 + z)-1 law, 'downsizing' which turns out to be an 'illusion' in the sense that it does not imply evolution, 'infant mortality', that is, the discrepancy between stars born and stars seen, the existence of 'red nuggets', and finally the recently discovered and unexpected excess of quasar absorption line damped Lyα systems at high redshift. If galaxies were not significantly brighter in the past and the SPDH were true, then a large proportion of galaxies could remain sunk from sight, possibly at all redshifts, and these sunken galaxies could supply the missing re-ionization flux. We show that fishing these sunken galaxies out of the sky by their optical emissions alone is practically impossible, even when they are nearby. More ingenious methods are needed to detect them. It follows that disentangling galaxy evolution through studying ever higher redshift galaxies may be a forlorn hope because one could

  19. Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

    International Nuclear Information System (INIS)

    Khosroshahi, Habib G.; Raouf, Mojtaba; Miraghaei, Halime; Brough, Sarah; Croton, Darren J.; Graham, Alister; Driver, Simon; Baldry, Ivan; Brown, Michael; Prescott, Matt; Wang, Lingyu

    2017-01-01

    We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and unrelaxed galaxy groups from the Galaxy and Mass Assembly survey. The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy (BGG), e.g., the luminosity gap between the two most luminous members, and the offset between the position of the BGG and the luminosity centroid of the group. We find that the radio luminosity of the largest galaxy in the group strongly depends on its environment, such that the BGGs in dynamically young (evolving) groups are an order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old (relaxed) groups. This observation has been successfully reproduced by a newly developed semi-analytic model that allows us to explore the various causes of these findings. We find that the fraction of radio-loud BGGs in the observed dynamically young groups is ∼2 times that of the dynamically old groups. We discuss the implications of this observational constraint on the central galaxy properties in the context of galaxy mergers and the super massive black hole accretion rate.

  20. Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

    Energy Technology Data Exchange (ETDEWEB)

    Khosroshahi, Habib G.; Raouf, Mojtaba; Miraghaei, Halime [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19395-5746 (Iran, Islamic Republic of); Brough, Sarah [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Croton, Darren J.; Graham, Alister [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122 (Australia); Driver, Simon [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Baldry, Ivan [Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom); Brown, Michael [School of Physics, Monash University, Clayton, VIC 3800 (Australia); Prescott, Matt [Astrophysics Group, The University of Western Cape, Robert Sobukwe Road, Bellville 7530 (South Africa); Wang, Lingyu, E-mail: habib@ipm.ir [SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD, Groningen (Netherlands)

    2017-06-20

    We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and unrelaxed galaxy groups from the Galaxy and Mass Assembly survey. The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy (BGG), e.g., the luminosity gap between the two most luminous members, and the offset between the position of the BGG and the luminosity centroid of the group. We find that the radio luminosity of the largest galaxy in the group strongly depends on its environment, such that the BGGs in dynamically young (evolving) groups are an order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old (relaxed) groups. This observation has been successfully reproduced by a newly developed semi-analytic model that allows us to explore the various causes of these findings. We find that the fraction of radio-loud BGGs in the observed dynamically young groups is ∼2 times that of the dynamically old groups. We discuss the implications of this observational constraint on the central galaxy properties in the context of galaxy mergers and the super massive black hole accretion rate.

  1. The Westerbork HI survey of spiral and irregular galaxies - I. HI imaging of late-type dwarf galaxies

    NARCIS (Netherlands)

    Swaters, RA; Van Albada, TS; van der Hulst, JM; Sancisi, R

    Neutral hydrogen observations with the Westerbork Synthesis Radio Telescope are presented for a sample of 73 late-type dwarf galaxies. These observations are part of the WHISP project (Westerbork Hi Survey of Spiral and Irregular Galaxies). Here we present Hi maps, velocity fields, global profiles

  2. EXPLORING THE z = 3-4 MASSIVE GALAXY POPULATION WITH ZFOURGE: THE PREVALENCE OF DUSTY AND QUIESCENT GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Spitler, Lee R.; Rees, Glen [Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia); Straatman, Caroline M. S.; Labbé, Ivo [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Glazebrook, Karl; Kacprzak, Glenn G.; Nanayakkara, Themiya [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Tran, Kim-Vy H.; Papovich, Casey; Kawinwanichakij, Lalitwadee; Mehrtens, Nicola; Tilvi, Vithal; Tomczak, Adam R. [George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Quadri, Ryan F.; Persson, S. Eric; Kelson, Daniel D.; McCarthy, Patrick J.; Monson, Andrew J. [Carnegie Observatories, Pasadena, CA 91101 (United States); Van Dokkum, Pieter [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Allen, Rebecca, E-mail: lee.spitler@mq.edu.au [Australian Astronomical Observatory, P.O. Box 296 Epping, NSW 1710 (Australia)

    2014-06-01

    Our understanding of the redshift z > 3 galaxy population relies largely on samples selected using the popular ''dropout'' technique, typically consisting of UV-bright galaxies with blue colors and prominent Lyman breaks. As it is currently unknown if these galaxies are representative of the massive galaxy population, we here use the FOURSTAR Galaxy Evolution (ZFOURGE) survey to create a stellar mass-limited sample at z = 3-4. Uniquely, ZFOURGE uses deep near-infrared medium-bandwidth filters to derive accurate photometric redshifts and stellar population properties. The mass-complete sample consists of 57 galaxies with log M >10.6, reaching below M {sup *} at z = 3-4. On average, the massive z = 3-4 galaxies are extremely faint in the observed optical with median R{sub tot}{sup AB}=27.48±0.41 (rest-frame M {sub 1700} = –18.05 ± 0.37). They lie far below the UV luminosity-stellar mass relation for Lyman break galaxies and are about ∼100 × fainter at the same mass. The massive galaxies are red (R – K {sub s} {sub AB} = 3.9 ± 0.2; rest-frame UV-slope β = –0.2 ± 0.3) likely from dust or old stellar ages. We classify the galaxy spectral energy distributions by their rest-frame U–V and V–J colors and find a diverse population: 46{sub −6−17}{sup +6+10}% of the massive galaxies are quiescent, 40{sub −6−5}{sup +6+7}% are dusty star-forming galaxies, and only 14{sub −3−4}{sup +3+10}% resemble luminous blue star-forming Lyman break galaxies. This study clearly demonstrates an inherent diversity among massive galaxies at higher redshift than previously known. Furthermore, we uncover a reservoir of dusty star-forming galaxies with 4 × lower specific star-formation rates compared to submillimeter-selected starbursts at z > 3. With 5 × higher numbers, the dusty galaxies may represent a more typical mode of star formation compared to submillimeter-bright starbursts.

  3. Distance determinations to shield galaxies from Hubble space telescope imaging

    Energy Technology Data Exchange (ETDEWEB)

    McQuinn, Kristen B. W.; Skillman, Evan D. [Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, 116 Church Street, S.E., Minneapolis, MN 55455 (United States); Cannon, John M.; Cave, Ian [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Salzer, John J. [Department of Astronomy, Indiana University, 727 East 3rd Street, Bloomington, IN 47405 (United States); Haynes, Martha P.; Adams, Elizabeth; Giovanelli, Riccardo [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Elson, Ed C. [Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Ott, Juërgen [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States); Saintonge, Amélie, E-mail: kmcquinn@astro.umn.edu [Max-Planck-Institute for Astrophysics, D-85741 Garching (Germany)

    2014-04-10

    The Survey of H I in Extremely Low-mass Dwarf (SHIELD) galaxies is an ongoing multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very low-mass galaxies. The galaxies were selected from the first ∼10% of the H I Arecibo Legacy Fast ALFA (ALFALFA) survey based on their inferred low H I mass and low baryonic mass, and all systems have recent star formation. Thus, the SHIELD sample probes the faint end of the galaxy luminosity function for star-forming galaxies. Here, we measure the distances to the 12 SHIELD galaxies to be between 5 and 12 Mpc by applying the tip of the red giant method to the resolved stellar populations imaged by the Hubble Space Telescope. Based on these distances, the H I masses in the sample range from 4 × 10{sup 6} to 6 × 10{sup 7} M {sub ☉}, with a median H I mass of 1 × 10{sup 7} M {sub ☉}. The tip of the red giant branch distances are up to 73% farther than flow-model estimates in the ALFALFA catalog. Because of the relatively large uncertainties of flow-model distances, we are biased toward selecting galaxies from the ALFALFA catalog where the flow model underestimates the true distances. The measured distances allow for an assessment of the native environments around the sample members. Five of the galaxies are part of the NGC 672 and NGC 784 groups, which together constitute a single structure. One galaxy is part of a larger linear ensemble of nine systems that stretches 1.6 Mpc from end to end. Three galaxies reside in regions with 1-9 neighbors, and four galaxies are truly isolated with no known system identified within a radius of 1 Mpc.

  4. Are spiral galaxies heavy smokers?

    International Nuclear Information System (INIS)

    Davies, J.; Disney, M.; Phillipps, S

    1990-01-01

    The dustiness of spiral galaxies is discussed. Starburst galaxies and the shortage of truly bright spiral galaxies is cited as evidence that spiral galaxies are far dustier than has been thought. The possibility is considered that the dust may be hiding missing mass

  5. JELLYFISH GALAXY CANDIDATES AT LOW REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Poggianti, B. M.; Fasano, G.; Omizzolo, A.; Gullieuszik, M.; Bettoni, D.; Paccagnella, A. [INAF-Astronomical Observatory of Padova (Italy); Moretti, A.; D’Onofrio, M. [Physics and Astronomy Department, University of Padova (Italy); Jaffé, Y. L. [Department of Astronomy, Universidad de Concepción, Concepción (Chile); Vulcani, B. [Kavli Institute for the Physics and Mathematics of the universe (WPI), The University of Tokyo Institutes for Advanced Study (UTIAS), the University of Tokyo, Kashiwa, 277-8582 (Japan); Fritz, J. [Centro de Radioastronomía y Astrofísica, CRyA, UNAM, Michoacán (Mexico); Couch, W. [Australian Astronomical Observatory, North Ryde, NSW 1670 (Australia)

    2016-03-15

    Galaxies that are being stripped of their gas can sometimes be recognized from their optical appearance. Extreme examples of stripped galaxies are the so-called “jellyfish galaxies” that exhibit tentacles of debris material with a characteristic jellyfish morphology. We have conducted the first systematic search for galaxies that are being stripped of their gas at low-z (z = 0.04−0.07) in different environments, selecting galaxies with varying degrees of morphological evidence for stripping. We have visually inspected B- and V-band images and identified 344 candidates in 71 galaxy clusters of the OMEGAWINGS+WINGS sample and 75 candidates in groups and lower mass structures in the PM2GC sample. We present the atlas of stripping candidates and a first analysis of their environment and their basic properties, such as morphologies, star formation rates and galaxy stellar masses. Candidates are found in all clusters and at all clustercentric radii, and their number does not correlate with the cluster velocity dispersion σ or X-ray luminosity L{sub X}. Interestingly, convincing cases of candidates are also found in groups and lower mass halos (10{sup 11}−10{sup 14}M{sub ⊙}), although the physical mechanism at work needs to be securely identified. All the candidates are disky, have stellar masses ranging from log M/M{sub ⊙} < 9 to > 11.5 and the majority of them form stars at a rate that is on average a factor of 2 higher (2.5σ) compared to non-stripped galaxies of similar mass. The few post-starburst and passive candidates have weak stripping evidence. We conclude that disturbed morphologies suggestive of stripping phenomena are ubiquitous in clusters and could be present even in groups and low mass halos. Further studies will reveal the physics of the gas stripping and clarify the mechanisms at work.

  6. Dynamics and configurations of galaxy triplets

    International Nuclear Information System (INIS)

    Anosova, J.P.; Orlov, V.V.; Chernin, A.D.; Ivanov, A.V.; Kiseleva, L.G.

    1990-01-01

    The purpose is to infer the probable dynamical states of galaxy triplets by the observed data on their configurations. Two methods are proposed for describing the distributions of the triplet configuration parameters characterizing a tendency to alignment and hierarchy: (1) obtaining a representative sample of configurations and determining its statistical parameters (moments and percentages); and (2) dividing the region of possible configurations of triple systems (Agekian and Anosova, 1967) into a set of segments and finding the probabilities for the configurations to find themselves in each of them. Both these methods allow representation of the data by numerical simulations as well as observations. The effect of projection was studied. It rather overestimates the alignment and hierarchy of the triple systems. Among the parameters of interest there are found some parameters that are least sensitive to projection effects. The samples consist of simulated galaxy triplets (with hidden mass) as well as of 46 probably physical triple galaxies (Karachentseva et al., 1979). The observed triples as well as numerical models show a tendency to alignment. The triple galaxies do not show any tendency to hierarchy (formation of the temporary binaries), but this tendency may be present for simulated triplets without significant dark matter. The significant hidden mass (of order ten times the total mass of a triplet) decreases the probability of forming a binary and so weakens the hierarchy. Small galaxy groups consisting of 3 to 7 members are probably the most prevalent types of galaxy aggregate (Gorbatsky, 1987). Galaxy triplets are the simplest groups, but dynamically nontrivial ones

  7. Photometric redshifts of galaxies from SDSS and 2MASS

    International Nuclear Information System (INIS)

    Wang Tao; Gu Qiusheng; Huang Jiasheng

    2009-01-01

    In order to find the physical parameters which determine the accuracy of photometric redshifts, we compare the spectroscopic and photometric redshifts (photo-z's) for a large sample of ∼ 80000 SDSS-2MASS galaxies. Photo-z's in this paper are estimated by using the artificial neural network photometric redshift method (ANNz). For a subset of ∼40000 randomly selected galaxies, we find that the photometric redshift recovers the spectroscopic redshift distribution very well with rms of 0.016. Our main results are as follows: (1) Using magnitudes directly as input parameters produces more accurate photo-z's than using colors; (2) The inclusion of 2MASS (J, H, K s ) bands does not improve photo-z's significantly, which indicates that near infrared data might not be important for the low-redshift sample; (3) Adding the concentration index (essentially the steepness of the galaxy brightness profile) as an extra input can improve the photo-z's estimation up to ∼ 10 percent; (4) Dividing the sample into early- and late-type galaxies by using the concentration index, normal and abnormal galaxies by using the emission line flux ratios, and red and blue galaxies by using color index (g - r), we can improve the accuracy of photo-z's significantly; (5) Our analysis shows that the outliers (where there is a big difference between the spectroscopic and photometric redshifts) are mainly correlated with galaxy types, e.g., most outliers are late-type (blue) galaxies.

  8. 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

  9. Dwarf galaxies : Important clues to galaxy formation

    NARCIS (Netherlands)

    Tolstoy, E

    2003-01-01

    The smallest dwarf galaxies are the most straight forward objects in which to study star formation processes on a galactic scale. They are typically single cell star forming entities, and as small potentials in orbit around a much larger one they are unlikely to accrete much (if any) extraneous

  10. THE CLUSTERING CHARACTERISTICS OF H I-SELECTED GALAXIES FROM THE 40% ALFALFA SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Ann M. [NASA Postdoctoral Program, NASA Langley Research Center, Hampton, VA 23618 (United States); Giovanelli, Riccardo; Haynes, Martha P. [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Guzzo, Luigi, E-mail: ann.m.martin@nasa.gov, E-mail: riccardo@astro.cornell.edu, E-mail: haynes@astro.cornell.edu, E-mail: luigi.guzzo@brera.inaf.it [INAF Osservatorio Astronomico di Brera, Milan (Italy)

    2012-05-01

    The 40% Arecibo Legacy Fast ALFA survey catalog ({alpha}.40) of {approx}10,150 H I-selected galaxies is used to analyze the clustering properties of gas-rich galaxies. By employing the Landy-Szalay estimator and a full covariance analysis for the two-point galaxy-galaxy correlation function, we obtain the real-space correlation function and model it as a power law, {xi}(r) = (r/r{sub 0}){sup -{gamma}}, on scales <10 h{sup -1} Mpc. As the largest sample of blindly H I-selected galaxies to date, {alpha}.40 provides detailed understanding of the clustering of this population. We find {gamma} = 1.51 {+-} 0.09 and r{sub 0} = 3.3 + 0.3, -0.2 h{sup -1} Mpc, reinforcing the understanding that gas-rich galaxies represent the most weakly clustered galaxy population known; we also observe a departure from a pure power-law shape at intermediate scales, as predicted in {Lambda}CDM halo occupation distribution models. Furthermore, we measure the bias parameter for the {alpha}.40 galaxy sample and find that H I galaxies are severely antibiased on small scales, but only weakly antibiased on large scales. The robust measurement of the correlation function for gas-rich galaxies obtained via the {alpha}.40 sample constrains models of the distribution of H I in simulated galaxies, and will be employed to better understand the role of gas in environmentally dependent galaxy evolution.

  11. Neutral hydrogen observations of binary galaxies

    International Nuclear Information System (INIS)

    Moorsel, G.A. van.

    1982-01-01

    The present investigation concerns a detailed neutral hydrogen study of a carefully selected sample of 16 double spiral galaxies with the Westerbork Synthesis Radio Telescope (WSRT). The observational data provide useful material for a number of questions concerning the dynamics of double galaxies, in particular the question of the mass distribution. In Chapter 2 the criteria used to select a sample of double galaxies for observation with the WSRT are discussed. Observing techniques and the reduction of the data using the GIPSY system are described in Chapter 3. Chapters 4 through 7 contain the observational results. In Chapter 8 the method of analysis is described. Masses for the individual galaxies derived from rotation curves are compared with the ''total'' masses estimated from the orbital motion. In this fashion a direct estimate of the amount of dark matter is obtained that avoids the use of mean M/L values. In Chapter 9 a mass estimator for groups is developed in a way analogous to the binary galaxy mass estimator described in Chapter 8. The question of selection effects and the bias of the mass estimator for the point mass model are discussed extensively in Chapter 10. The final results are discussed in Chapter 11. It is shown that the orbital mass exceeds the sum of the individual masses by a large factor for several pairs, indicating either that there is a large amount of dark matter or that something is amiss with the concept of a physical pair. (Auth.)

  12. Galaxy morphologies in the era of big-data surveys

    Science.gov (United States)

    Huertas-Company, M.

    Galaxy morphology is a first-order descriptor of a galaxy and a useful proxy to identify physical processes. The 100 years old Hubble fork describes the structural diversity of galaxies in the local universe. Unveiling the origins of this galaxy zoology is a key challenge in galaxy evolution. In this review talk, I first summarized some key advances in our understanding of the morphological evolution of galaxies from z ~ 0 to z ~ 3, thank you in particular to the SDSS and HST legacies. In the second part, I focused on the classification techniques. With the emergence in the last years of large surveys the samples of study have increased by several orders of magnitude going from a few tens to several millions of objects. This trend will clearly continue in the next decade with coming surveys/missions such as EUCLID and WFIRST. While galaxy classification is still a required step in any survey, visual inspection of galaxies is becoming prohibitively time-consuming. Under these circumstances, the techniques used to estimate galaxy morphologies need to be updated.

  13. Superclusters and galaxy formation

    Energy Technology Data Exchange (ETDEWEB)

    Einasto, J; Joeveer, M; Saar, E [Tartu Astrophysical Observatory, Toravere, Estonia (USSR)

    1980-01-03

    A study of the structure of superclusters in the Southern galactic hemisphere using Zwicky clusters as principal tracers of the large-scale structure of the Universe is reported. The data presented suggest that the formation of galaxies was a two stage process involving larger spatial dimensions than earlier workers have postulated. In the first stage proto-superclusters and big holes had to form from the non-dissipative dark matter while in the second hot gas, by cooling and settling down into the potential wells caused by dark matter, will form galaxies and clusters of galaxies.

  14. The galaxy-subhalo connection in low-redshift galaxy clusters from weak gravitational lensing

    Science.gov (United States)

    Sifón, Cristóbal; Herbonnet, Ricardo; Hoekstra, Henk; van der Burg, Remco F. J.; Viola, Massimo

    2018-07-01

    We measure the gravitational lensing signal around satellite galaxies in a sample of galaxy clusters at z measurements of faint, background sources in the vicinity of bright satellite galaxies. We find a small but significant bias, as light from the lenses makes the shapes of background galaxies appear radially aligned with the lens. We account for this bias by applying a correction that depends on both lens size and magnitude. We also correct for contamination of the source sample by cluster members. We use a physically motivated definition of subhalo mass, namely the mass bound to the subhalo, mbg, similar to definitions used by common subhalo finders in numerical simulations. Binning the satellites by stellar mass we provide a direct measurement of the subhalo-to-stellar-mass relation, log mbg/M⊙ = (11.54 ± 0.05) + (0.95 ± 0.10)log [m⋆/(2 × 1010 M⊙)]. This best-fitting relation implies that, at a stellar mass m⋆ ˜ 3 × 1010 M⊙, subhalo masses are roughly 50 per cent of those of central galaxies, and this fraction decreases at higher stellar masses. We find some evidence for a sharp change in the total-to-stellar mass ratio around the clusters' scale radius, which could be interpreted as galaxies within the scale radius having suffered more strongly from tidal stripping, but remain cautious regarding this interpretation.

  15. Galaxy Zoo: A Catalog of Overlapping Galaxy Pairs for Dust Studies

    Science.gov (United States)

    Keel, William C.; Manning, Anna M.; Holwerda, Benne W.; Mezzoprete, Massimo; Lintott, Chris J.; Schawinski, Kevin; Gay, Pamela; Masters, Karen L.

    2013-01-01

    Analysis of galaxies with overlapping images offers a direct way to probe the distribution of dust extinction and its effects on the background light. We present a catalog of 1990 such galaxy pairs selected from the Sloan Digital Sky Survey (SDSS) by volunteers of the Galaxy Zoo project. We highlight subsamples which are particularly useful for retrieving such properties of the dust distribution as UV extinction, the extent perpendicular to the disk plane, and extinction in the inner parts of disks. The sample spans wide ranges of morphology and surface brightness, opening up the possibility of using this technique to address systematic changes in dust extinction or distribution with galaxy type. This sample will form the basis for forthcoming work on the ranges of dust distributions in local disk galaxies, both for their astrophysical implications and as the low-redshift part of a study of the evolution of dust properties. Separate lists and figures show deep overlaps, where the inner regions of the foreground galaxy are backlit, and the relatively small number of previously-known overlapping pairs outside the SDSS DR7 sky coverage.

  16. STELLAR POPULATIONS AND RADIAL MIGRATIONS IN VIRGO DISK GALAXIES

    International Nuclear Information System (INIS)

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

    2012-01-01

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

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

    Science.gov (United States)

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

    2018-06-01

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

  18. The RSA survey of dwarf galaxies, 1: Optical photometry

    Science.gov (United States)

    Vader, J. Patricia; Chaboyer, Brian

    1994-01-01

    We present detailed surface photometry, based on broad B-band charge coupled device (CCD) images, of about 80 dwarf galaxies. Our sample represents approximately 10% of all dwarf galaxies identified in the vicinity of Revised Shapley-Ames (RSA) galaxies on high resolution blue photographic plates, referred to as the RSA survey of dwarf galaxies. We derive global properties and radial surface brightness profiles, and examine the morphologies. The radial surface brightness profiles of dwarf galaxies, whether early or late type, display the same varieties in shape and complexity as those of classical giant galaxies. Only a few are well described by a pure r(exp 1/4) law. Exponential profiles prevail. Features typical of giant disk galaxies, such as exponential profiles with a central depression, lenses, and even, in one case (IC 2041), a relatively prominent bulge are also found in dwarf galaxies. Our data suggest that the central region evolves from being bulge-like, with an r(exp 1/4) law profile, in bright galaxies to a lens-like structure in dwarf galaxies. We prove detailed surface photometry to be a helpful if not always sufficient tool in investigating the structure of dwarf galaxies. In many cases kinematic information is needed to complete the picture. We find the shapes of the surface brightness profiles to be loosely associated with morphological type. Our sample contains several new galaxies with properties intermediate between those of giant and dwarf ellipticals (but no M32-like objects). This shows that such intermediate galaxies exist so that at least a fraction of early-type dwarf ellipticals is structurally related to early-type giants instead of belonging to a totally unrelated, disjunct family. This supports an origin of early-type dwarf galaxies as originally more massive systems that acquired their current morphology as a result of substantial, presumable supernova-driven, mass loss. On the other hand, several early-type dwarfs in our sample are

  19. Lyα EMITTING GALAXIES AS EARLY STAGES IN GALAXY FORMATION

    International Nuclear Information System (INIS)

    Cowie, Lennox L.; Barger, Amy J.; Hu, Esther M.

    2011-01-01

    We present optical spectroscopy of two samples of Galaxy Evolution Explorer grism selected Lyα emitters (LAEs): one at z = 0.195-0.44 and the other at z = 0.65-1.25. We have also observed a comparison sample of galaxies in the same redshift intervals with the same UV magnitude distributions but with no detected Lyα. We use the optical spectroscopy to eliminate active galactic nuclei and to obtain the optical emission-line properties of the samples. We compare the luminosities of the LAEs in the two redshift intervals and show that there is dramatic evolution in the maximum Lyα luminosity over z = 0-1. Focusing on the z = 0.195-0.44 samples alone, we show that there are tightly defined relations between all of the galaxy parameters and the rest-frame equivalent width (EW) of Hα. The higher EW(Hα) sources all have lower metallicities, bluer colors, smaller sizes, and less extinction, consistent with their being in the early stages of the galaxy formation process. We find that 75% ± 12% of the LAEs have EW(Hα) >100 A and, conversely, that 31% ± 13% of galaxies with EW(Hα) >100 A are LAEs. We correct the broadband magnitudes for the emission-line contributions and use spectral synthesis fits to estimate the ages of the galaxies. We find a median age of 1.1 x 10 8 yr for the LAE sample and 1.4 x 10 9 yr for the UV-continuum sample without detected Lyα. The median metallicity of the LAE sample is 12 + log (O/H) = 8.24, or about 0.4 dex lower than the UV-continuum sample.

  20. Magnification bias corrections to galaxy-lensing cross-correlations

    International Nuclear Information System (INIS)

    Ziour, Riad; Hui, Lam

    2008-01-01

    Galaxy-galaxy or galaxy-quasar lensing can provide important information on the mass distribution in the Universe. It consists of correlating the lensing signal (either shear or magnification) of a background galaxy/quasar sample with the number density of a foreground galaxy sample. However, the foreground galaxy density is inevitably altered by the magnification bias due to the mass between the foreground and the observer, leading to a correction to the observed galaxy-lensing signal. The aim of this paper is to quantify this correction. The single most important determining factor is the foreground redshift z f : the correction is small if the foreground galaxies are at low redshifts but can become non-negligible for sufficiently high redshifts. For instance, we find that for the multipole l=1000, the correction is above 1%x(5s f -2)/b f for z f > or approx. 0.37, and above 5%x(5s f -2)/b f for z f > or approx. 0.67, where s f is the number count slope of the foreground sample and b f its galaxy bias. These considerations are particularly important for geometrical measures, such as the Jain and Taylor ratio or its generalization by Zhang et al. Assuming (5s f -2)/b f =1, we find that the foreground redshift should be limited to z f < or approx. 0.45 in order to avoid biasing the inferred dark energy equation of state w by more than 5%, and that even for a low foreground redshift (<0.45), the background samples must be well separated from the foreground to avoid incurring a bias of similar magnitude. Lastly, we briefly comment on the possibility of obtaining these geometrical measures without using galaxy shapes, using instead magnification bias itself.

  1. The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups

    Energy Technology Data Exchange (ETDEWEB)

    Gerke, Brian F.; /UC, Berkeley; Newman, Jeffrey A.; /LBNL, NSD; Davis, Marc; /UC, Berkeley /UC, Berkeley, Astron.Dept.; Marinoni, Christian; /Brera Observ.; Yan, Renbin; Coil, Alison L.; Conroy, Charlie; Cooper, Michael C.; /UC, Berkeley, Astron.Dept.; Faber, S.M.; /Lick Observ.; Finkbeiner, Douglas P.; /Princeton U. Observ.; Guhathakurta, Puragra; /Lick Observ.; Kaiser, Nick; /Hawaii U.; Koo, David C.; Phillips, Andrew C.; /Lick Observ.; Weiner, Benjamin J.; /Maryland U.

    2012-02-14

    We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts in the range 0.7 {<=} z {<=} 1.4, over one square degree on the sky. Groups are identified using an algorithm (the Voronoi-Delaunay Method) that has been shown to accurately reproduce the statistics of groups in simulated DEEP2-like samples. We optimize this algorithm for the DEEP2 survey by applying it to realistic mock galaxy catalogs and assessing the results using a stringent set of criteria for measuring group-finding success, which we develop and describe in detail here. We find in particular that the group-finder can successfully identify {approx}78% of real groups and that {approx}79% of the galaxies that are true members of groups can be identified as such. Conversely, we estimate that {approx}55% of the groups we find can be definitively identified with real groups and that {approx}46% of the galaxies we place into groups are interloper field galaxies. Most importantly, we find that it is possible to measure the distribution of groups in redshift and velocity dispersion, n({sigma}, z), to an accuracy limited by cosmic variance, for dispersions greater than 350 km s{sup -1}. We anticipate that such measurements will allow strong constraints to be placed on the equation of state of the dark energy in the future. Finally, we present the first DEEP2 group catalog, which assigns 32% of the galaxies to 899 distinct groups with two or more members, 153 of which have velocity dispersions above 350 km s{sup -1}. We provide locations, redshifts and properties for this high-dispersion subsample. This catalog represents the largest sample to date of spectroscopically detected groups at z {approx} 1.

  2. Galaxy Zoo: Comparing the visual morphology of synthetic galaxies from the Illustris simulation with those in the real Universe.

    Science.gov (United States)

    Dickinson, Hugh; Lintott, Chris; Scarlata, Claudia; Fortson, Lucy; Bamford, Steven; Cardamone, Carolin; Keel, William C.; Kruk, Sandor; Masters, Karen; Simmons, Brooke D.; Vogelsberger, Mark; Torrey, Paul; Snyder, Gregory; Galaxy Zoo Science Team

    2018-01-01

    We present a comparision between the Illustris simulations and classifications from Galaxy Zoo, aiming to test the ability of modern large-scale cosmological simulations to accurately reproduce the local galaxy population. This comparison is enabled by the increasingly high spatial and temporal resolution obtained by such surveys.Using classifications that were accumulated via the Galaxy Zoo citizen science interface, we compare the visual morphologies for simulated images of Illustris galaxies with a compatible sample of images drawn from the Sloan Digital Sky Survey (SDSS) Legacy Survey.For simulated galaxies with stellar masses less than 1011 M⊙, significant differences are identified, which are most likely due to the limited resolution of the simulation, but could be revealing real differences in the dynamical evolution of populations of galaxies in the real and model universes. Above 1011 M⊙, Illustris galaxy morphologies correspond better with those of their SDSS counterparts, although even in this mass range the simulation appears to underproduce obviously disk-like galaxies. Morphologies of Illustris galaxies less massive than 1011 M⊙ should be treated with care.

  3. MASSIVE GALAXIES ARE LARGER IN DENSE ENVIRONMENTS: ENVIRONMENTAL DEPENDENCE OF MASS–SIZE RELATION OF EARLY-TYPE GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Yongmin; Im, Myungshin; Kim, Jae-Woo, E-mail: yymx2@astro.snu.ac.kr, E-mail: mim@astro.snu.ac.kr [Center for the Exploration of the Origin of the Universe (CEOU), Astronomy Program, Department of Physics and Astronomy, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-742 (Korea, Republic of)

    2017-01-01

    Under the Λ cold dark matter (ΛCDM) cosmological models, massive galaxies are expected to be larger in denser environments through frequent hierarchical mergers with other galaxies. Yet, observational studies of low-redshift early-type galaxies have shown no such trend, standing as a puzzle to solve during the past decade. We analyzed 73,116 early-type galaxies at 0.1 ≤  z  < 0.15, adopting a robust nonparametric size measurement technique and extending the analysis to many massive galaxies. We find for the first time that local early-type galaxies heavier than 10{sup 11.2} M {sub ⊙} show a clear environmental dependence in mass–size relation, in such a way that galaxies are as much as 20%–40% larger in the densest environments than in underdense environments. Splitting the sample into the brightest cluster galaxies (BCGs) and non-BCGs does not affect the result. This result agrees with the ΛCDM cosmological simulations and suggests that mergers played a significant role in the growth of massive galaxies in dense environments as expected in theory.

  4. Growing Galaxies Gently

    Science.gov (United States)

    2010-10-01

    New observations from ESO's Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics. The results appear in the 14 October issue of the journal Nature. The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems - including the Milky Way - that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed. A European team of astronomers has used ESO's Very Large Telescope to test this very different idea - that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways - by merging with other galaxies or by accreting material. The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: "The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe." The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written. The group began by selecting three very distant galaxies to see if they could find evidence

  5. A History of H i Stripping in Virgo: A Phase-space View of VIVA Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Hyein; Chung, Aeree; Smith, Rory [Department of Astronomy, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Jaffé, Yara L., E-mail: hiyoon@galaxy.yonsei.ac.kr, E-mail: achung@yonsei.ac.kr [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago (Chile)

    2017-04-01

    We investigate the orbital histories of Virgo galaxies at various stages of H i gas stripping. In particular, we compare the location of galaxies with different H i morphology in phase space. This method is a great tool for tracing the gas stripping histories of galaxies as they fall into the cluster. Most galaxies at the early stage of H i stripping are found in the first infall region of Virgo, while galaxies undergoing active H i stripping mostly appear to be falling in or moving out near the cluster core for the first time. Galaxies with severely stripped, yet symmetric, H i disks are found in one of two locations. Some are deep inside the cluster, but others are found in the cluster outskirts with low orbital velocities. We suggest that the latter group of galaxies belong to a “backsplash” population. These present the clearest candidates for backsplashed galaxies observationally identified to date. We further investigate the distribution of a large sample of H i-detected galaxies toward Virgo in phase space, confirming that most galaxies are stripped of their gas as they settle into the gravitational potential of the cluster. In addition, we discuss the impact of tidal interactions between galaxies and group preprocessing on the H i properties of the cluster galaxies, and link the associated star formation evolution to the stripping sequence of cluster galaxies.

  6. Enviromental Effects on Internal Color Gradients of Early-Type Galaxies

    Science.gov (United States)

    La Barbera, F.; de Carvalho, R. R.; Gal, R. R.; Busarello, G.; Haines, C. P.; Mercurio, A.; Merluzzi, P.; Capaccioli, M.; Djorgovski, S. G.

    2007-05-01

    One of the most debated issues of observational and theoretical cosmology is that of how the environment affects the formation and evolution of galaxies. To gain new insight into this subject, we have derived surface photometry for a sample of 3,000 early-type galaxies belonging to 163 clusters with different richness, spanning a redshift range of 0.05 to 0.25. This large data-set is used to analyze how the color distribution inside galaxies depends on several parameters, such as cluster richness, local galaxy density, galaxy luminosity and redshift. We find that the internal color profile of galaxies strongly depends on the environment where galaxies reside. Galaxies in poor and rich clusters are found to follow two distinct trends in the color gradient vs. redshift diagram, with color gradients beeing less steep in rich rather than in poor clusters. No dependence of color gradients on galaxy luminosity is detected both for poor and rich clusters. We find that color gradients strongly depend on local galaxy density, with more shallow gradients in high density regions. Interestingly, this result holds only for low richness clusters, with color gradients of galaxies in rich clusters showing no dependence on local galaxy density. Our results support a reasonable picture whereby young early-type galaxies form in a dissipative collapse process, and then undergo increased (either major or minor) merging activity in richer rather than in poor clusters.

  7. Cosmology and galaxy formation

    International Nuclear Information System (INIS)

    Jones, B.J.T.; Gonzalez, E.M.

    1985-05-01

    The aim of the present series of lectures is to be unashamedly pedagogical and present, in simple terms, an overview of our current thinking about our universe and the way in which we believe galaxies have formed. (orig./WL)

  8. Massive stars in galaxies

    International Nuclear Information System (INIS)

    Humphreys, R.M.

    1987-01-01

    The relationship between the morphologic type of a galaxy and the evolution of its massive stars is explored, reviewing observational results for nearby galaxies. The data are presented in diagrams, and it is found that the massive-star populations of most Sc spiral galaxies and irregular galaxies are similar, while those of Sb spirals such as M 31 and M 81 may be affected by morphology (via differences in the initial mass function or star-formation rate). Consideration is also given to the stability-related upper luminosity limit in the H-R diagram of hypergiant stars (attributed to radiation pressure in hot stars and turbulence in cool stars) and the goals of future observation campaigns. 88 references

  9. Interpretation of galaxy counts

    International Nuclear Information System (INIS)

    Tinsely, B.M.

    1980-01-01

    New models are presented for the interpretation of recent counts of galaxies to 24th magnitude, and predictions are shown to 28th magnitude for future comparison with data from the Space Telescope. The results supersede earlier, more schematic models by the author. Tyson and Jarvis found in their counts a ''local'' density enhancement at 17th magnitude, on comparison with the earlier models; the excess is no longer significant when a more realistic mixture of galaxy colors is used. Bruzual and Kron's conclusion that Kron's counts show evidence for evolution at faint magnitudes is confirmed, and it is predicted that some 23d magnitude galaxies have redshifts greater than unity. These may include spheroidal systems, elliptical galaxies, and the bulges of early-type spirals and S0's, seen during their primeval rapid star formation

  10. The Effects of Galaxy Interactions on Star Formation

    Science.gov (United States)

    Beverage, Aliza; Weiner, Aaron; Ramos Padilla, Andres; Ashby, Matthew; Smith, Howard A.

    2018-01-01

    Galaxy interactions are key events in galaxy evolution, and are widely thought to trigger significant increases in star formation. However, the mechanisms and timescales for these increases are still not well understood. In order to probe the effects of mergers, we undertook an investigation based on the Spitzer Interacting Galaxies Survey (SIGS), a sample of 102 nearby galaxies in 48 systems ranging from weakly interacting to near coalescence. Our study is unique in that we use both broadband photometry and a large sample of objects chosen to be statistically meaningful. Our data come from 32 broad bands ranging from the UV to far-IR, and we model spectral energy distributions (SEDs) using the Code for Investigating Galaxy Emission (CIGALE) to estimate physical characteristics for each galaxy. We find marginal statistical correlations between galaxy interaction strength and dust luminosity and the distribution of dust mass as a function of heating intensity. The specific star formation rates, however, do not show any enhancement across the interaction stages. This result challenges conventional wisdom that mergers induce star formation throughout galaxy interaction.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

  11. Galaxy bias from the Dark Energy Survey Science Verification data: combining galaxy density maps and weak lensing maps

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.; Pujol, A.; Gaztañaga, E.; Amara, A.; Réfrégier, A.; Bacon, D.; Becker, M. R.; Bonnett, C.; Carretero, J.; Castander, F. J.; Crocce, M.; Fosalba, P.; Giannantonio, T.; Hartley, W.; Jarvis, M.; Kacprzak, T.; Ross, A. J.; Sheldon, E.; Troxel, M. A.; Vikram, V.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Rosell, A. Carnero; Kind, M. Carrasco; Cunha, C. E.; D' Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Estrada, J.; Evrard, A. E.; Flaugher, B.; Frieman, J.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Ogando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Walker, A. R.

    2016-04-15

    We measure the redshift evolution of galaxy bias from a magnitude-limited galaxy sample by combining the galaxy density maps and weak lensing shear maps for a $\\sim$116 deg$^{2}$ area of the Dark Energy Survey (DES) Science Verification data. This method was first developed in Amara et al. (2012) and later re-examined in a companion paper (Pujol et al., in prep) with rigorous simulation tests and analytical treatment of tomographic measurements. In this work we apply this method to the DES SV data and measure the galaxy bias for a magnitude-limited galaxy sample. We find the galaxy bias and 1$\\sigma$ error bars in 4 photometric redshift bins to be 1.33$\\pm$0.18 (z=0.2-0.4), 1.19$\\pm$0.23 (z=0.4-0.6), 0.99$\\pm$0.36 ( z=0.6-0.8), and 1.66$\\pm$0.56 (z=0.8-1.0). These measurements are consistent at the 1-2$\\sigma$ level with mea- surements on the same dataset using galaxy clustering and cross-correlation of galaxies with CMB lensing. In addition, our method provides the only $\\sigma_8$-independent constraint among the three. We forward-model the main observational effects using mock galaxy catalogs by including shape noise, photo-z errors and masking effects. We show that our bias measurement from the data is consistent with that expected from simulations. With the forthcoming full DES data set, we expect this method to provide additional constraints on the galaxy bias measurement from more traditional methods. Furthermore, in the process of our measurement, we build up a 3D mass map that allows further exploration of the dark matter distribution and its relation to galaxy evolution.

  12. Automated galaxy surface photometry

    International Nuclear Information System (INIS)

    Cawson, M.G.M.; Kibblewhite, E.J.; Disney, M.J.; Phillipps, S.

    1987-01-01

    Two-dimensional surface photometry of a very large number of galaxies on a deep Schmidt plate has been obtained using the Automatic Plate Measuring System (APM). A method of photometric calibration, suitable for APM measurements, via pixel-by-pixel comparison with CCD frames of a number of the brighter galaxies is described and its advantages are discussed. The same method is used to demonstrate the consistency of measurement of the APM machine when used for surface photometry. (author)

  13. The catalog of edge-on disk galaxies from SDSS. I. The catalog and the structural parameters of stellar disks

    Energy Technology Data Exchange (ETDEWEB)

    Bizyaev, D. V. [Apache Point Observatory and New Mexico State University, Sunspot, NM, 88349 (United States); Kautsch, S. J. [Nova Southeastern University, Fort Lauderdale, FL 33314 (United States); Mosenkov, A. V. [Central Astronomical Observatory of RAS (Russian Federation); Reshetnikov, V. P.; Sotnikova, N. Ya.; Yablokova, N. V. [St. Petersburg State University (Russian Federation); Hillyer, R. W. [Christopher Newport University, Newport News, VA 23606 (United States)

    2014-05-20

    We present a catalog of true edge-on disk galaxies automatically selected from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS). A visual inspection of the g, r, and i images of about 15,000 galaxies allowed us to split the initial sample of edge-on galaxy candidates into 4768 (31.8% of the initial sample) genuine edge-on galaxies, 8350 (55.7%) non-edge-on galaxies, and 1865 (12.5%) edge-on galaxies not suitable for simple automatic analysis because these objects either show signs of interaction and warps, or nearby bright stars project on it. We added more candidate galaxies from RFGC, EFIGI, RC3, and Galaxy Zoo catalogs found in the SDSS footprints. Our final sample consists of 5747 genuine edge-on galaxies. We estimate the structural parameters of the stellar disks (the stellar disk thickness, radial scale length, and central surface brightness) in the galaxies by analyzing photometric profiles in each of the g, r, and i images. We also perform simplified three-dimensional modeling of the light distribution in the stellar disks of edge-on galaxies from our sample. Our large sample is intended to be used for studying scaling relations in the stellar disks and bulges and for estimating parameters of the thick disks in different types of galaxies via the image stacking. In this paper, we present the sample selection procedure and general description of the sample.

  14. Parameters of the covariance function of galaxies

    International Nuclear Information System (INIS)

    Fesenko, B.I.; Onuchina, E.V.

    1988-01-01

    The two-point angular covariance functions for two samples of galaxies are considered using quick methods of analysis. It is concluded that in the previous investigations the amplitude of the covariance function in the Lick counts was overestimated and the rate of decrease of the function underestimated

  15. THE M bh-σ DIAGRAM AND THE OFFSET NATURE OF BARRED ACTIVE GALAXIES

    International Nuclear Information System (INIS)

    Graham, Alister W.; Li Ihui

    2009-01-01

    From a sample of 50 predominantly inactive galaxies with direct supermassive black hole mass measurements, it has recently been established that barred galaxies tend to reside rightward of the M bh -σ relation defined by nonbarred galaxies. Either black holes in barred galaxies tend to be anemic or the central velocity dispersions in these galaxies have a tendency to be elevated by the presence of the bar. The latter option is in accord with studies connecting larger velocity dispersions in galaxies with old bars, while the former scenario is at odds with the observation that barred galaxies do not deviate from the M bh -luminosity relation. Using a sample of 88 galaxies with active galactic nuclei, whose supermassive black hole masses have been estimated from their associated emission lines, we reveal for the first time that they also display this same general behavior in the M bh -σ diagram depending on the presence of a bar or not. A new symmetrical and nonsymmetrical 'barless' M bh -σ relation is derived using 82 nonbarred galaxies. The barred galaxies are shown to reside on or up to ∼1 dex below this relation. This may explain why narrow-line Seyfert 1 galaxies appear offset from the 'barless' M bh -σ relation, and has far-reaching implications given that over half of the disk galaxy population are barred.

  16. Spectrophotometric Properties of E+A Galaxies in SDSS-IV MaNGA

    Science.gov (United States)

    Marinelli, Mariarosa; Dudley, Raymond; Edwards, Kay; Gonzalez, Andrea; Johnson, Amalya; Kerrison, Nicole; Melchert, Nancy; Ojanen, Winonah; Weaver, Olivia; Liu, Charles; SDSS-IV MaNGA

    2018-01-01

    Quenched post-starburst galaxies, or E+A galaxies, represent a unique and informative phase in the evolution of galaxies. We used a qualitative rubric-based methodology, informed by the literature, to manually select galaxies from the SDSS-IV IFU survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) using the single-fiber spectra from the Sloan Digital Sky Survey Data Release 8. Of the 2,812 galaxies observed so far in MaNGA, we found 39 galaxies meeting our criteria for E+A classification. Spectral energy distributions of these 39 galaxies from the far-UV to the mid-infrared demonstrate a heterogeneity in our sample emerging in the infrared, indicating many distinct paths to visually similar optical spectra. We used SDSS-IV MaNGA Pipe3D data products to analyze stellar population ages, and found that 34 galaxies exhibited stellar populations that were older at 1 effective radius than at the center of the galaxy. Given that our sample was manually chosen based on E+A markers in the single-fiber spectra aimed at the center of each galaxy, our E+A galaxies may have only experienced their significant starbursts in the central region, with a disk of quenched or quenching material further outward. This work was supported by grants AST-1460860 from the National Science Foundation and SDSS FAST/SSP-483 from the Alfred P. Sloan Foundation to the CUNY College of Staten Island.

  17. Alignment between galaxies and large-scale structure

    International Nuclear Information System (INIS)

    Faltenbacher, A.; Li Cheng; White, Simon D. M.; Jing, Yi-Peng; Mao Shude; Wang Jie

    2009-01-01

    Based on the Sloan Digital Sky Survey DR6 (SDSS) and the Millennium Simulation (MS), we investigate the alignment between galaxies and large-scale structure. For this purpose, we develop two new statistical tools, namely the alignment correlation function and the cos(2θ)-statistic. The former is a two-dimensional extension of the traditional two-point correlation function and the latter is related to the ellipticity correlation function used for cosmic shear measurements. Both are based on the cross correlation between a sample of galaxies with orientations and a reference sample which represents the large-scale structure. We apply the new statistics to the SDSS galaxy catalog. The alignment correlation function reveals an overabundance of reference galaxies along the major axes of red, luminous (L ∼ * ) galaxies out to projected separations of 60 h- 1 Mpc. The signal increases with central galaxy luminosity. No alignment signal is detected for blue galaxies. The cos(2θ)-statistic yields very similar results. Starting from a MS semi-analytic galaxy catalog, we assign an orientation to each red, luminous and central galaxy, based on that of the central region of the host halo (with size similar to that of the stellar galaxy). As an alternative, we use the orientation of the host halo itself. We find a mean projected misalignment between a halo and its central region of ∼ 25 deg. The misalignment decreases slightly with increasing luminosity of the central galaxy. Using the orientations and luminosities of the semi-analytic galaxies, we repeat our alignment analysis on mock surveys of the MS. Agreement with the SDSS results is good if the central orientations are used. Predictions using the halo orientations as proxies for central galaxy orientations overestimate the observed alignment by more than a factor of 2. Finally, the large volume of the MS allows us to generate a two-dimensional map of the alignment correlation function, which shows the reference

  18. Evolution of galaxies

    International Nuclear Information System (INIS)

    Palous, J.

    1987-01-01

    The proceedings contain 87 papers divided into 8 chapters. The chapter Bipolar outflows and star formations contains papers on optical and infrared observations of young bipolar outflow objects and the theory thereof, and on observations of cometary nebulae. The chapter Masers and early stellar evolution discusses molecular masers and star forming regions. The following chapter contains papers on initial mass function and star formation rates in galaxies. The chapter Clusters and star formation contains data on OB associations and open star clusters, their development and observations, CO and H 2 in our galaxy, the four vector model of radio emission and an atlas of the wavelength dependence of ultraviolet extinction in the Galaxy. The most voluminous is the chapter Evolution of galaxies. It contains papers on the theories of the physical and chemodynamic development of galaxies of different types, rotation research and rotation velocities of galaxies and their arms, and on mathematical and laboratory models of morphological development. Chapter seven contains papers dealing with active extragalactic objects, quasars and active galactic nuclei. The last chapter discusses cosmological models, the theory of the inflationary universe, and presents an interpretation of the central void and X-ray background. (M.D.). 299 figs., 48 tabs., 1651 refs

  19. Coma cluster of galaxies

    Science.gov (United States)

    1999-01-01

    Atlas Image mosaic, covering 34' x 34' on the sky, of the Coma cluster, aka Abell 1656. This is a particularly rich cluster of individual galaxies (over 1000 members), most prominently the two giant ellipticals, NGC 4874 (right) and NGC 4889 (left). The remaining members are mostly smaller ellipticals, but spiral galaxies are also evident in the 2MASS image. The cluster is seen toward the constellation Coma Berenices, but is actually at a distance of about 100 Mpc (330 million light years, or a redshift of 0.023) from us. At this distance, the cluster is in what is known as the 'Hubble flow,' or the overall expansion of the Universe. As such, astronomers can measure the Hubble Constant, or the universal expansion rate, based on the distance to this cluster. Large, rich clusters, such as Coma, allow astronomers to measure the 'missing mass,' i.e., the matter in the cluster that we cannot see, since it gravitationally influences the motions of the member galaxies within the cluster. The near-infrared maps the overall luminous mass content of the member galaxies, since the light at these wavelengths is dominated by the more numerous older stellar populations. Galaxies, as seen by 2MASS, look fairly smooth and homogeneous, as can be seen from the Hubble 'tuning fork' diagram of near-infrared galaxy morphology. Image mosaic by S. Van Dyk (IPAC).

  20. PEARS Emission Line Galaxies

    Science.gov (United States)

    Pirzkal, Nor; Rothberg, Barry; Ly, Chun; Rhoads, James E.; Malhotra, Sangeeta; Grogin, Norman A.; Dahlen, Tomas; Meurer, Gerhardt R.; Walsh, Jeremy; Hathi, Nimish P.; hide

    2012-01-01

    We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitless grism spectroscopic data obtained vl'ith the Advanced Camera for Surveys on HST. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random surveY of galaxies, as well as the availability of a wide variety of ancillary observations to support the spectroscopic results. Using the PEARS data we are able to identify star forming galaxies within the redshift volume 0 galaxies down to a limiting flux of approx 10 - 18 erg/s/sq cm . The ELRs have also been compared to the properties of the host galaxy, including morphology, luminosity, and mass. From this analysis we find three key results: 1) The computed line luminosities show evidence of a flattening in the luminosity function with increasing redshift; 2) The star forming systems show evidence of disturbed morphologies, with star formation occurring predominantly within one effective (half-light) radius. However, the morphologies show no correlation with host stellar mass; and 3) The number density of star forming galaxies with M(*) >= 10(exp 9) Solar M decreases by an order of magnitude at z<=0.5 relative to the number at 0.5 < z < 0.9 in support of the argument for galaxy downsizing.

  1. The Milky Way galaxy

    International Nuclear Information System (INIS)

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

    1985-01-01

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

  2. Radio and optical studies of high luminosity Iras galaxies

    International Nuclear Information System (INIS)

    Wolstencroft, R.D.; Parker, Q.A.; Savage, A.; MacGillivray, H.T.; Leggett, S.K.; Clowes, R.G.; Unger, S.W.; Pedlar, A.; Heasley, J.N.; Menzies, J.W.

    1987-01-01

    Follow-up observations of a complete sample of 154 IRAS galaxies, optically identified down to B=21, indicate that between 3 and 9% of the sample are ultraluminous depending on the choice of H 0 . VLA observations at 20 cm of the complete sample indicate that 85% are detected above 1mJy and for the most part the radio emission is centrally concentrated. The tight linear relation between radio and infrared luminosities is valid at the highest luminosities. Of the 11 most luminous objects one is a quasar: it fits the radio infrared relation very well which suggests that the infrared and radio emission has the same origin as in the other IRAS galaxies, ie. it probably originates primarily in regions of star formation in the host galaxy. The other 10 very luminous galaxies are either close but resolved mergers or double galaxies, presumably interacting. Radio observations of the 10 original empty field sources in our sample with no optical counterpart (B ≤ 21) allow us to conclude that 4 of these are fainter galaxies just outside the IRAS error ellipse with high values of L IR /L B . One other object, with a radio source at the edge of the error ellipse but no optical counterpart brighter than B = 23, may prove to be a highly luminous galaxy with L IR /L B > ∼ 1250

  3. MID-INFRARED EVIDENCE FOR ACCELERATED EVOLUTION IN COMPACT GROUP GALAXIES

    International Nuclear Information System (INIS)

    Walker, Lisa May; Johnson, Kelsey E.; Gallagher, Sarah C.; Hibbard, John E.; Hornschemeier, Ann E.; Tzanavaris, Panayiotis; Charlton, Jane C.; Jarrett, Thomas H.

    2010-01-01

    Compact galaxy groups are at the extremes of the group environment, with high number densities and low velocity dispersions that likely affect member galaxy evolution. To explore the impact of this environment in detail, we examine the distribution in the mid-infrared (MIR) 3.6-8.0 μm color space of 42 galaxies from 12 Hickson compact groups (HCGs) in comparison with several control samples, including the LVL+SINGS galaxies, interacting galaxies, and galaxies from the Coma Cluster. We find that the HCG galaxies are strongly bimodal, with statistically significant evidence for a gap in their distribution. In contrast, none of the other samples show such a marked gap, and only galaxies in the Coma infall region have a distribution that is statistically consistent with the HCGs in this parameter space. To further investigate the cause of the HCG gap, we compare the galaxy morphologies of the HCG and LVL+SINGS galaxies, and also probe the specific star formation rate (SSFR) of the HCG galaxies. While galaxy morphology in HCG galaxies is strongly linked to position with MIR color space, the more fundamental property appears to be the SSFR, or star formation rate normalized by stellar mass. We conclude that the unusual MIR color distribution of HCG galaxies is a direct product of their environment, which is most similar to that of the Coma infall region. In both cases, galaxy densities are high, but gas has not been fully processed or stripped. We speculate that the compact group environment fosters accelerated evolution of galaxies from star-forming and neutral gas-rich to quiescent and neutral gas-poor, leaving few members in the MIR gap at any time.

  4. Abundance ratios in dwarf elliptical galaxies

    Science.gov (United States)

    Şen, Ş.; Peletier, R. F.; Boselli, A.; den Brok, M.; Falcón-Barroso, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Lisker, T.; Mentz, J. J.; Paudel, S.; Salo, H.; Sybilska, A.; Toloba, E.; van de Ven, G.; Vazdekis, A.; Yesilyaprak, C.

    2018-04-01

    We determine abundance ratios of 37 dwarf ellipticals (dEs) in the nearby Virgo cluster. This sample is representative of the early-type population of galaxies in the absolute magnitude range -19.0 originate from late-type dwarfs or small spirals. Na-yields appear to be very metal-dependent, in agreement with studies of giant ellipticals, probably due to the large dependence on the neutron-excess in stars. We conclude that dEs have undergone a considerable amount of chemical evolution, they are therefore not uniformly old, but have extended SFH, similar to many of the Local Group galaxies.

  5. SDSS-IV MaNGA: Stellar angular momentum of about 2300 galaxies: unveiling the bimodality of massive galaxy properties

    Science.gov (United States)

    Graham, Mark T.; Cappellari, Michele; Li, Hongyu; Mao, Shude; Bershady, Matthew; Bizyaev, Dmitry; Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Drory, Niv; Law, David R.; Pan, Kaike; Thomas, Daniel; Wake, David A.; Weijmans, Anne-Marie; Westfall, Kyle B.; Yan, Renbin

    2018-03-01

    We measure λ _{R_e}, a proxy for galaxy specific stellar angular momentum within one effective radius, and the ellipticity, ɛ, for about 2300 galaxies of all morphological types observed with integral field spectroscopy as part of the MaNGA survey, the largest such sample to date. We use the (λ _{R_e}, ɛ ) diagram to separate early-type galaxies into fast and slow rotators. We also visually classify each galaxy according to its optical morphology and two-dimensional stellar velocity field. Comparing these classifications to quantitative λ _{R_e} measurements reveals tight relationships between angular momentum and galaxy structure. In order to account for atmospheric seeing, we use realistic models of galaxy kinematics to derive a general approximate analytic correction for λ _{R_e}. Thanks to the size of the sample and the large number of massive galaxies, we unambiguously detect a clear bimodality in the (λ _{R_e}, ɛ ) diagram which may result from fundamental differences in galaxy assembly history. There is a sharp secondary density peak inside the region of the diagram with low λ _{R_e} and ɛ their distribution of the misalignments between the photometric and kinematic position angles. We confirm that genuine slow rotators start appearing above M ≥ 2 × 1011M⊙ where a significant number of high-mass fast rotators also exist.

  6. Galaxy Zoo: An Experiment in Public Science Participation

    Science.gov (United States)

    Raddick, Jordan; Lintott, C. J.; Schawinski, K.; Thomas, D.; Nichol, R. C.; Andreescu, D.; Bamford, S.; Land, K. R.; Murray, P.; Slosar, A.; Szalay, A. S.; Vandenberg, J.; Galaxy Zoo Team

    2007-12-01

    An interesting question in modern astrophysics research is the relationship between a galaxy's morphology (appearance) and its formation and evolutionary history. Research into this question is complicated by the fact that to get a study sample, researchers must first assign a shape to a large number of galaxies. Classifying a galaxy by shape is nearly impossible for a computer, but easy for a human - however, looking at one million galaxies, one at a time, would take an enormous amount of time. To create such a research sample, we turned to citizen science. We created a web site called Galaxy Zoo (www.galaxyzoo.org) that invites the public to classify the galaxies. New members see a short tutorial and take a short skill test where they classify galaxies of known types. Once they pass the test, they begin to work with the entire sample. The site's interface shows the user an image of a single galaxy from the Sloan Digital Sky Survey. The user clicks a button to classify it. Each classification is stored in a database, associated with the galaxy that it describes. The site has become enormously popular with amateur astronomers, teachers, and others interested in astronomy. So far, more than 110,000 users have joined. We have started a forum where users share images of their favorite galaxies, ask science questions of each other and the "zookeepers," and share classification advice. In a separate poster, we will share science results from the site's first six months of operation. In this poster, we will describe the site as an experiment in public science outreach. We will share user feedback, discuss our plans to study the user community more systematically, and share advice on how to work with citizen science projects to the mutual benefit of both professional and citizen scientists.

  7. Matching Supernovae to Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2016-12-01

    One of the major challenges for modern supernova surveys is identifying the galaxy that hosted each explosion. Is there an accurate and efficient way to do this that avoids investing significant human resources?Why Identify Hosts?One problem in host galaxy identification. Here, the supernova lies between two galaxies but though the centroid of the galaxy on the right is closer in angular separation, this may be a distant background galaxy that is not actually near the supernova. [Gupta et al. 2016]Supernovae are a critical tool for making cosmological predictions that help us to understand our universe. But supernova cosmology relies on accurately identifying the properties of the supernovae including their redshifts. Since spectroscopic followup of supernova detections often isnt possible, we rely on observations of the supernova host galaxies to obtain redshifts.But how do we identify which galaxy hosted a supernova? This seems like a simple problem, but there are many complicating factors a seemingly nearby galaxy could be a distant background galaxy, for instance, or a supernovas host could be too faint to spot.The authors algorithm takes into account confusion, a measure of how likely the supernova is to be mismatched. In these illustrations of low (left) and high (right) confusion, the supernova is represented by a blue star, and the green circles represent possible host galaxies. [Gupta et al. 2016]Turning to AutomationBefore the era of large supernovae surveys, searching for host galaxies was done primarily by visual inspection. But current projects like the Dark Energy Surveys Supernova Program is finding supernovae by the thousands, and the upcoming Large Synoptic Survey Telescope will likely discover hundreds of thousands. Visual inspection will not be possible in the face of this volume of data so an accurate and efficient automated method is clearly needed!To this end, a team of scientists led by Ravi Gupta (Argonne National Laboratory) has recently

  8. Inclination effects on the recognition of Seyfert galaxies

    International Nuclear Information System (INIS)

    Keel, W.C.

    1980-01-01

    Axial ratios have been measured from images of 91 Seyfert galaxies thought to be disk systems, and their distribution as a function of axial ratio compared to that of field spirals similarly distributed in distance. There is a deficiency of nearly edge-on Seyfert 1 galaxies relative to the comparison sample. Examination of the visibility of nuclei in a sample of nearby spirals indicates that the effect is too large to be caused by absorption in the disks of normal spiral galaxies, while no absorption other than that expected from such disks is found in non-Seyfert Markarian spirals with bright, condensed nuclei

  9. THE MASS-DEPENDENT CLUSTERING HISTORY OF K-SELECTED GALAXIES AT z < 4 IN THE SXDS/UDS FIELD

    International Nuclear Information System (INIS)

    Furusawa, Junko; Sekiguchi, Kazuhiro; Takata, Tadafumi; Furusawa, Hisanori; Shimasaku, Kazuhiro; Simpson, Chris; Akiyama, Masayuki

    2011-01-01

    We investigate mass-dependent galaxy evolution based on a large sample of (more than 50,000) K-band selected galaxies in a multi-wavelength catalog of the Subaru/XMM-Newton Deep Survey and the UKIRT Infrared Deep Sky Survey/Ultra Deep Survey. We employ optical to near-infrared photometry to determine photometric redshifts of these galaxies. Then, we estimate the stellar mass of our sample galaxies using a standard fitting procedure as we used for estimation of the photometric redshift. From the sample galaxies, we obtain the stellar mass function of galaxies and the cosmic stellar mass density up to z ∼ 4. Our results are consistent with previous studies and we find a considerable number of low-mass galaxies (M * ∼ 10 10.5 ) at the redshift range 3 14 M sun ) to low (10 13 M sun ) with decreasing redshift at around z ∼ 2. We also find some high-mass density regions of massive galaxies at 1.4 ≤ z < 2.5 in our sample. These concentrations of massive galaxies may be candidate progenitors of the present-day clusters of galaxies. At this redshift range, massive star-forming galaxies are the dominant population making up the structures and the passively evolving galaxies show stronger clustering and they may have formed earlier than those star-forming galaxies.

  10. THE ENVIRONMENTAL DEPENDENCE OF THE FRACTION OF 'UNCONVENTIONAL' GALAXIES: RED LATE TYPES AND BLUE EARLY TYPES

    International Nuclear Information System (INIS)

    Deng Xinfa; He Jizhou; Wu Ping; Ding Yingping

    2009-01-01

    From the Main galaxy sample of the Sloan Digital Sky Survey Data Release 6, we construct two volume-limited samples with the luminosity -20.0 ≤ M r ≤ -18.5 and -22.40 ≤ M r ≤ -20.16, respectively, to explore the environmental dependence of the fraction of 'unconventional' galaxies: red late types and blue early types. We use the density estimator within the distance to the fifth nearest neighbor, and construct two samples at both extremes of density and perform comparative studies between them for each volume-limited sample. Results of two volume-limited samples show the same conclusions: the fraction of red late-type galaxies rises considerably with increasing local density, and that one of the blue early-type galaxies declines substantially with increasing local density. In addition, we note that bluer galaxies preferentially are late types, but the red galaxies are not dominated by early types.

  11. Galaxy Zoo: Motivations of Citizen Scientists

    Science.gov (United States)

    Raddick, Jordan; Lintott, C.; Bamford, S.; Land, K.; Locksmith, D.; Murray, P.; Nichol, B.; Schawinski, K.; Slosar, A.; Szalay, A.; Thomas, D.; Vandenberg, J.; Andreescu, D.

    2008-05-01

    We have developed Galaxy Zoo, a citizen science project in which volunteers classify images of galaxies by shape. The site has been hugely successful in reaching large numbers of people - more than 125,000 people have signed up. As a result, each galaxy has been classified more than 30 times, resulting in high-quality science results. We are studying the motivations of these volunteers to determine what about our site made it so captivating. We have some ideas - people enjoy helping science, looking at beautiful galaxy images, and the "game" nature of the interface. But we want to study the motivations systematically, to learn who thinks what, and how this affects what they do. We have designed a methodology in which we begin with interviews, asking open-ended questions of volunteers about their motivation. Then, we design a survey to collect motivation data for a larger sample. Lastly, for volunteers who agreed to give us their site username, we examine how they classified galaxies to look for correlations between motivation and behavior. In this poster, we describe our methodology and present preliminary results of our research.

  12. Star formation and substructure in galaxy clusters

    International Nuclear Information System (INIS)

    Cohen, Seth A.; Hickox, Ryan C.; Wegner, Gary A.; Einasto, Maret; Vennik, Jaan

    2014-01-01

    We investigate the relationship between star formation (SF) and substructure in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky Survey. Several past studies of individual galaxy clusters have suggested that cluster mergers enhance cluster SF, while others find no such relationship. The SF fraction in multi-component clusters (0.228 ± 0.007) is higher than that in single-component clusters (0.175 ± 0.016) for galaxies with M r 0.1 <−20.5. In both single- and multi-component clusters, the fraction of star-forming galaxies increases with clustercentric distance and decreases with local galaxy number density, and multi-component clusters show a higher SF fraction than single-component clusters at almost all clustercentric distances and local densities. Comparing the SF fraction in individual clusters to several statistical measures of substructure, we find weak, but in most cases significant at greater than 2σ, correlations between substructure and SF fraction. These results could indicate that cluster mergers may cause weak but significant SF enhancement in clusters, or unrelaxed clusters exhibit slightly stronger SF due to their less evolved states relative to relaxed clusters.

  13. INTERACTIONS OF GALAXIES IN THE GALAXY CLUSTER ENVIRONMENT

    International Nuclear Information System (INIS)

    Park, Changbom; Hwang, Ho Seong

    2009-01-01

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

  14. INTERACTIONS OF GALAXIES IN THE GALAXY CLUSTER ENVIRONMENT

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-10

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

  15. The Galaxy Evolution Probe

    Science.gov (United States)

    Glenn, Jason; Galaxy Evolution Probe Team

    2018-01-01

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

  16. WINGS: WFIRST Infrared Nearby Galaxy Survey

    Science.gov (United States)

    Williams, Benjamin

    WFIRST's combination of wide field and high resolution will revolutionize the study of nearby galaxies. We propose to produce and analyze simulated WFIRST data of nearby galaxies and their halos to maximize the scientific yield in the limited observing time available, ensuring the legacy value of WFIRST's eventual archive. We will model both halo structure and resolved stellar populations to optimize WFIRST's constraints on both dark matter and galaxy formation models in the local universe. WFIRST can map galaxy structure down to ~35 mag/square arcsecond using individual stars. The resulting maps of stellar halos and accreting dwarf companions will provide stringent tests of galaxy formation and dark matter models on galactic (and even sub-galactic) scales, which is where the most theoretical tension exists with the Lambda-CDM model. With a careful, coordinated plan, WFIRST can be expected to improve current sample sizes by 2 orders of magnitude, down to surface brightness limits comparable to those currently reached only in the Local Group, and that are >4 magnitudes fainter than achievable from the ground due to limitations in star-galaxy separation. WFIRST's maps of galaxy halos will simultaneously produce photometry for billions of stars in the main bodies of galaxies within 10 Mpc. These data will transform studies of star formation histories that track stellar mass growth as a function of time and position within a galaxy. They also will constrain critical stellar evolution models of the near-infrared bright, rapidly evolving stars that can contribute significantly to the integrated light of galaxies in the near-infrared. Thus, with WFIRST we can derive the detailed evolution of individual galaxies, reconstruct the complete history of star formation in the nearby universe, and put crucial constraints on the theoretical models used to interpret near-infrared extragalactic observations. We propose a three-component work plan that will ensure these gains by

  17. Statistical measures of galaxy clustering

    International Nuclear Information System (INIS)

    Porter, D.H.

    1988-01-01

    Consideration is given to the large-scale distribution of galaxies and ways in which this distribution may be statistically measured. Galaxy clustering is hierarchical in nature, so that the positions of clusters of galaxies are themselves spatially clustered. A simple identification of groups of galaxies would be an inadequate description of the true richness of galaxy clustering. Current observations of the large-scale structure of the universe and modern theories of cosmology may be studied with a statistical description of the spatial and velocity distributions of galaxies. 8 refs

  18. The Co-evolution of QSOs and Galaxies

    Science.gov (United States)

    Coziol, R.; Torres-Papaqui, J. P.; Andernach, H.

    2015-07-01

    Using two large samples of QSOs detected in the mid-infrared (MIR) with WISE, we find that the change of W2-W3 colors with redshift suggests that star formation in their host galaxies increases by a factor of 3 from z = 0 to 2.7, then stays constant up to z = 4, and decreases above z=4. This behavior is slightly different from the best fits for the star formation history of field galaxies as deduced from the Optical-UV and IR, but is consistent with what is observed for sub-mm galaxies at high z. Our results constitute the clearest evidence, so far, that QSO host galaxies form their stars before field galaxies, and are in good agreement with the hierarchical biased structure formation paradigm.

  19. Glimpsing the imprint of local environment on the galaxy stellar mass function

    Science.gov (United States)

    Tomczak, Adam R.; Lemaux, Brian C.; Lubin, Lori M.; Gal, Roy R.; Wu, Po-Feng; Holden, Bradford; Kocevski, Dale D.; Mei, Simona; Pelliccia, Debora; Rumbaugh, Nicholas; Shen, Lu

    2017-12-01

    We investigate the impact of local environment on the galaxy stellar mass function (SMF) spanning a wide range of galaxy densities from the field up to dense cores of massive galaxy clusters. Data are drawn from a sample of eight fields from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey. Deep photometry allow us to select mass-complete samples of galaxies down to 109 M⊙. Taking advantage of >4000 secure spectroscopic redshifts from ORELSE and precise photometric redshifts, we construct three-dimensional density maps between 0.55 environmental dependence in the SMFs of star-forming and quiescent galaxies, although not quite as strongly for the quiescent subsample. To characterize the connection between the SMF of field galaxies and that of denser environments, we devise a simple semi-empirical model. The model begins with a sample of ≈106 galaxies at zstart = 5 with stellar masses distributed according to the field. Simulated galaxies then evolve down to zfinal = 0.8 following empirical prescriptions for star-formation, quenching and galaxy-galaxy merging. We run the simulation multiple times, testing a variety of scenarios with differing overall amounts of merging. Our model suggests that a large number of mergers are required to reproduce the SMF in dense environments. Additionally, a large majority of these mergers would have to occur in intermediate density environments (e.g. galaxy groups).

  20. The population of early-type galaxies: how it evolves with time and how it differs from passive and late-type galaxies

    Science.gov (United States)

    Tamburri, S.; Saracco, P.; Longhetti, M.; Gargiulo, A.; Lonoce, I.; Ciocca, F.

    2014-10-01

    Aims: There are two aims to our analysis. On the one hand we are interested in addressing whether a sample of morphologically selected early-type galaxies (ETGs) differs from a sample of passive galaxies in terms of galaxy statistics. On the other hand we study how the relative abundance of galaxies, the number density, and, the stellar mass density for different morphological types change over the redshift range 0.6 ≤ z ≤ 2.5. Methods: From the 1302 galaxies brighter than Ks(AB) = 22 selected from the GOODS-MUSIC catalogue, we classified the ETGs, i.e. elliptical (E) and spheroidal galaxies (E/S0), on the basis of their morphology and the passive galaxies on the basis of their specific star formation rate (sSFR ≤ 10-11 yr-1). Since the definition of a passive galaxy depends on the model parameters assumed to fit the spectral energy distribution of the galaxy, in addition to the assumed sSFR threshold, we probed the dependence of this definition and selection on the stellar initial mass function (IMF). Results: We find that spheroidal galaxies cannot be distinguished from the other morphological classes on the basis of their low star formation rate, irrespective of the IMF adopted in the models. In particular, we find that a large fraction of passive galaxies (>30%) are disc-shaped objects and that the passive selection misses a significant fraction (~26%) of morphologically classified ETGs. Using the sample of 1302 galaxies morphologically classified into spheroidal galaxies (ETGs) and non-spheroidal galaxies (LTGs), we find that the fraction of these two morphological classes is constant over the redshift range 0.6 ≤ z ≤ 2.5, being 20-30% the fraction of ETGs and 70-80% the fraction of LTGs. However, at z mass density of the whole population of massive galaxies increase by almost a factor of ~10 between 0.6 ≤ z ≤ 2.5, with a faster increase of these densities for the ETGs than for the LTGs. Finally, we find that the number density of the highest

  1. C+/CO Transitions in the Diffuse ISM: Transitional Cloud Sample from the GOT C+ Survey of [CII] in the inner Galaxy at l = -30deg to 30deg

    Science.gov (United States)

    Velusamy, T.; Pineda, J. L.; Langer, W. D.; Willacy, K.; Goldsmith, P. F.

    2011-05-01

    Our knowledge of interstellar gas has been limited primarily to the diffuse atomic phase traced by HI and the well-shielded molecular phase traced by CO. Recently, using the first results of the Herschel Key Project GOT C+, a HIFI C+ survey of the Galactic plane, Velusamy, Langer, Pineda et al. (A&A 521, L18, 2010) have shown that in the diffuse interstellar transition clouds a significant fraction of the carbon exists primarily as C^+ with little C^0 and CO in a warm 'dark gas' layer in which hydrogen is mostly H_2 with little atomic H, surrounding a modest 12CO-emitting core. The [CII] fine structure transition, at 1.9 THz (158 μm) is the best tracer of this component of the interstellar medium, which is critical to our understanding of the atomic to molecular cloud transitions. The Herschel Key Project GOT C+ is designed to study such clouds by observing with HIFI the [CII] line emission along 500 lines of sight (LOSs) throughout the Galactic disk. Here we present the identification and chemical status of a few hundred diffuse and transition clouds traced by [CII], along with auxiliary HI and CO data covering ~100 LOSs in the inner Galaxy between l= -30° and 30°. We identify transition clouds as [CII] components that are characterized by the presence of both HI and 12CO, but no 13CO emission. The intensities, I(CII) and I(HI), are used as measures of the visual extinction, AV, in the cloud up to the C^+/C^0/CO transition layer and a comparison with I(12CO) yields a more complete H_2 molecular inventory. Our results show that [CII] emission is an excellent tool to study transition clouds and their carbon chemistry in the ISM, in particular as a unique tracer of molecular H_2, which is not easily observed by other means. The large sample presented here will serve as a resource to study the chemical and physical status of diffuse transition clouds in a wide range of Galactic environments and constrain the physical parameters such as the FUV intensity and cosmic

  2. An Archival Search For Young Globular Clusters in Galaxies

    Science.gov (United States)

    Whitmore, Brad

    1995-07-01

    One of the most intriguing results from HST has been the discovery of ultraluminous star clusters in interacting and merging galaxies. These clusters have the luminosities, colors, and sizes that would be expected of young globular clusters produced by the interaction. We propose to use the data in the HST Archive to determine how prevalent this phenomena is, and to determine whether similar clusters are produced in other environments. Three samples will be extracted and studied in a systematic and consistent manner: 1} interacting and merging galaxies, 2} starburst galaxies, 3} a control sample of ``normal'' galaxies. A preliminary search of the archives shows that there are at least 20 galaxies in each of these samples, and the number will grow by about 50 observations become available. The data will be used to determine the luminosity function, color histogram , spatial distribution, and structural properties of the clusters using the same techniques employed in our study of NGC 7252 {``Atoms -for-Peace'' galaxy} and NGC 4038/4039 {``The Antennae''}. Our ultimate goals are: 1} to understand how globular clusters form, and 2} to use the clusters as evolutionary tracers to unravel the histories of interacting galaxies.

  3. PRECISE TULLY-FISHER RELATIONS WITHOUT GALAXY INCLINATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Obreschkow, D.; Meyer, M. [International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia)

    2013-11-10

    Power-law relations between tracers of baryonic mass and rotational velocities of disk galaxies, so-called Tully-Fisher relations (TFRs), offer a wealth of applications in galaxy evolution and cosmology. However, measurements of rotational velocities require galaxy inclinations, which are difficult to measure, thus limiting the range of TFR studies. This work introduces a maximum likelihood estimation (MLE) method for recovering the TFR in galaxy samples with limited or no information on inclinations. The robustness and accuracy of this method is demonstrated using virtual and real galaxy samples. Intriguingly, the MLE reliably recovers the TFR of all test samples, even without using any inclination measurements—that is, assuming a random sin i-distribution for galaxy inclinations. Explicitly, this 'inclination-free MLE' recovers the three TFR parameters (zero-point, slope, scatter) with statistical errors only about 1.5 times larger than the best estimates based on perfectly known galaxy inclinations with zero uncertainty. Thus, given realistic uncertainties, the inclination-free MLE is highly competitive. If inclination measurements have mean errors larger than 10°, it is better not to use any inclinations than to consider the inclination measurements to be exact. The inclination-free MLE opens interesting perspectives for future H I surveys by the Square Kilometer Array and its pathfinders.

  4. Simulated galaxy interactions as probes of merger spectral energy distributions

    Energy Technology Data Exchange (ETDEWEB)

    Lanz, Lauranne; Zezas, Andreas; Smith, Howard A.; Ashby, Matthew L. N.; Fazio, Giovanni G.; Hernquist, Lars [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Hayward, Christopher C. [Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany); Brassington, Nicola, E-mail: llanz@ipac.caltech.edu [School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield, AL10 9AB (United Kingdom)

    2014-04-10

    We present the first systematic comparison of ultraviolet-millimeter spectral energy distributions (SEDs) of observed and simulated interacting galaxies. Our sample is drawn from the Spitzer Interacting Galaxy Survey and probes a range of galaxy interaction parameters. We use 31 galaxies in 14 systems which have been observed with Herschel, Spitzer, GALEX, and 2MASS. We create a suite of GADGET-3 hydrodynamic simulations of isolated and interacting galaxies with stellar masses comparable to those in our sample of interacting galaxies. Photometry for the simulated systems is then calculated with the SUNRISE radiative transfer code for comparison with the observed systems. For most of the observed systems, one or more of the simulated SEDs match reasonably well. The best matches recover the infrared luminosity and the star formation rate of the observed systems, and the more massive systems preferentially match SEDs from simulations of more massive galaxies. The most morphologically distorted systems in our sample are best matched to the simulated SEDs that are close to coalescence, while less evolved systems match well with the SEDs over a wide range of interaction stages, suggesting that an SED alone is insufficient for identifying the interaction stage except during the most active phases in strongly interacting systems. This result is supported by our finding that the SEDs calculated for simulated systems vary little over the interaction sequence.

  5. Coma cluster ultradiffuse galaxies are not standard radio galaxies

    Science.gov (United States)

    Struble, Mitchell F.

    2018-02-01

    Matching members in the Coma cluster catalogue of ultradiffuse galaxies (UDGs) from SUBARU imaging with a very deep radio continuum survey source catalogue of the cluster using the Karl G. Jansky Very Large Array (VLA) within a rectangular region of ∼1.19 deg2 centred on the cluster core reveals matches consistent with random. An overlapping set of 470 UDGs and 696 VLA radio sources in this rectangular area finds 33 matches within a separation of 25 arcsec; dividing the sample into bins with separations bounded by 5, 10, 20 and 25 arcsec finds 1, 4, 17 and 11 matches. An analytical model estimate, based on the Poisson probability distribution, of the number of randomly expected matches within these same separation bounds is 1.7, 4.9, 19.4 and 14.2, each, respectively, consistent with the 95 per cent Poisson confidence intervals of the observed values. Dividing the data into five clustercentric annuli of 0.1° and into the four separation bins, finds the same result. This random match of UDGs with VLA sources implies that UDGs are not radio galaxies by the standard definition. Those VLA sources having integrated flux >1 mJy at 1.4 GHz in Miller, Hornschemeier and Mobasher without SDSS galaxy matches are consistent with the known surface density of background radio sources. We briefly explore the possibility that some unresolved VLA sources near UDGs could be young, compact, bright, supernova remnants of Type Ia events, possibly in the intracluster volume.

  6. Optical polarization position angle versus radio structure axis in Seyfert galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Antonucci, R R.J. [National Radio Astronomy Observatory, Charlottesville, VA (USA)

    1983-05-12

    The hypothesis that there are two polarization classes of Seyfert galaxies, analogous to the perpendicular and parallel radio galaxy groups, is investigated by examining optical polarimetry data. In the sample considered it is shown that all the Seyfert 1 galaxies have roughly parallel polarization while all the Seyfert 2 galaxies have roughly perpendicular polarizations. These alignment effects can be interpreted as being due to thin and thick scattering disks, respectively, surrounding the continuum sources. This would represent a fundamental difference between the two types of Seyfert galaxies.

  7. The structure of nearby clusters of galaxies Hierarchical clustering and an application to the Leo region

    CERN Document Server

    Materne, J

    1978-01-01

    A new method of classifying groups of galaxies, called hierarchical clustering, is presented as a tool for the investigation of nearby groups of galaxies. The method is free from model assumptions about the groups. The scaling of the different coordinates is necessary, and the level from which one accepts the groups as real has to be determined. Hierarchical clustering is applied to an unbiased sample of galaxies in the Leo region. Five distinct groups result which have reasonable physical properties, such as low crossing times and conservative mass-to-light ratios, and which follow a radial velocity- luminosity relation. Only 4 out of 39 galaxies were adopted as field galaxies. (27 refs).

  8. Supernovae - A new selection effect. [statistical distribution in and radial distance from center of parent galaxy

    Science.gov (United States)

    Shaw, R. L.

    1979-01-01

    A sample of 228 supernovae that occurred in galaxies with known redshifts is used to show that the mean projected linear supernova distance from the center of the parent galaxy increases with increasing redshift. This effect is interpreted as an observational bias: the discovery rate of supernovae is reduced in the inner parts of distant, poorly resolved galaxies. Even under the optimistic assumption that no selection effects work in galaxies closer than 33 Mpc, about 50% of all supernovae are lost in the inner regions of galaxies beyond 150 Mpc. This observational bias must be taken into account in the derivation of statistical properties of supernovae.

  9. The correlation functions for the clustering of galaxies and Abell clusters

    International Nuclear Information System (INIS)

    Jones, B.J.T.; Jones, J.E.; Copenhagen Univ.

    1985-01-01

    The difference in amplitudes between the galaxy-galaxy correlation function and the correlation function between Abell clusters is a consequence of two facts. Firstly, most Abell clusters with z<0.08 lie in a relatively small volume of the sampled space, and secondly, the fraction of galaxies lying in Abell clusters differs considerably inside and outside of this volume. (The Abell clusters are confined to a smaller volume of space than are the galaxies.) We discuss the implications of this interpretation of the clustering correlation functions and present a simple model showing how such a situation may arise quite naturally in standard theories for galaxy formation. (orig.)

  10. Recovering the Properties of High-redshift Galaxies with Different JWST Broadband Filters

    DEFF Research Database (Denmark)

    Bisigello, L.; Caputi, K. I.; Colina, L.

    2017-01-01

    Imaging with the James Webb Space Telescope (JWST) will allow observations of the bulk of distant galaxies at the epoch of reionization. The recovery of their properties, such as age, color excess , specific star formation rate (sSFR), and stellar mass, will mostly rely on spectral energy...... of these galaxy properties. We performed our tests on a sample of 1542 simulated galaxies, with known input properties, at z = 7–10. We found that, with only eight NIRCam broadbands, we can recover the galaxy age within 0.1 Gyr and the color excess within 0.06 mag for 70% of the galaxies. Additionally...

  11. A catalog of polychromatic bulge-disc decompositions of ˜17.600 galaxies in CANDELS

    Science.gov (United States)

    Dimauro, Paola; Huertas-Company, Marc; Daddi, Emanuele; Pérez-González, Pablo G.; Bernardi