WorldWideScience

Sample records for submillimeter-selected galaxies smgs

  1. THE STAR FORMATION HISTORIES OF z {approx} 2 DUST-OBSCURED GALAXIES AND SUBMILLIMETER-SELECTED GALAXIES

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    Bussmann, R. S. [Harvard-Smithsonian Center for Astrophysics, 160 Concord Avenue, Cambridge, MA 02138 (United States); Dey, Arjun; Jannuzi, B. T. [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Armus, L.; Desai, V.; Soifer, B. T. [Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125 (United States); Brown, M. J. I. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Gonzalez, A. H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Melbourne, J., E-mail: rbussmann@cfa.harvard.edu [Division of Physics, Math and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)

    2012-01-10

    The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z {approx} 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M{sub *}) of two populations of Spitzer-selected ULIRGs that have extremely red R - [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6 {mu}m associated with stellar emission ({sup b}ump DOGs{sup )}, while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ({sup p}ower-law DOGs{sup )}. We measure M{sub *} by applying Charlot and Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M{sub *} values for SMGs, bump DOGs, and power-law DOGs are log(M{sub *}/M{sub Sun }) = 10.42{sup +0.42}{sub -0.36}, 10.62{sup +0.36}{sub -0.32}, and 10.71{sup +0.40}{sub -0.34}, respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z {approx} 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5 dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z {approx} 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M{sub *}, a situation that arises more naturally in major mergers than in smooth accretion-powered systems.

  2. Submillimeter Galaxies as Progenitors of Compact Quiescent Galaxies

    Science.gov (United States)

    Toft, S.; Smolcic, V.; Magnelli, B.; Karim, A.; Zirm, A.; Michalowski, M.; Capak, P.; Sheth, K.; Schawinski, K.; Krogager, J.-K.; hide

    2014-01-01

    Three billion years after the big bang (at redshift z = 2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation and extremely compact with stellar mass densities at least an order of magnitude larger than in low-redshift ellipticals, their descendants. Little is known about how they formed, but their evolved, dense stellar populations suggest formation within intense, compact starbursts 1-2 Gyr earlier (at 3 < z < 6). Simulations show that gas-rich major mergers can give rise to such starbursts, which produce dense remnants. Submillimeter-selected galaxies (SMGs) are prime examples of intense, gas-rich starbursts.With a new, representative spectroscopic sample of compact, quiescent galaxies at z = 2 and a statistically well-understood sample of SMGs, we show that z = 3-6 SMGs are consistent with being the progenitors of z = 2 quiescent galaxies, matching their formation redshifts and their distributions of sizes, stellar masses, and internal velocities. Assuming an evolutionary connection, their space densities also match if the mean duty cycle of SMG starbursts is 42(sup+40) -29 Myr (consistent with independent estimates), which indicates that the bulk of stars in these massive galaxies were formed in a major, early surge of star formation. These results suggest a coherent picture of the formation history of the most massive galaxies in the universe, from their initial burst of violent star formation through their appearance as high stellar-density galaxy cores and to their ultimate fate as giant ellipticals.

  3. Submillimeter galaxies as progenitors of compact quiescent galaxies

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    Toft, S.; Zirm, A.; Krogager, J.-K.; Man, A. W. S. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Mariesvej 30, DK-2100 Copenhagen (Denmark); Smolčić, V.; Krpan, J. [Physics Department, University of Zagreb, Bijenička cesta 32, 10002 Zagreb (Croatia); Magnelli, B.; Karim, A. [Argelander Institute for Astronomy, Auf dem Hügel 71, Bonn, D-53121 (Germany); Michalowski, M. [Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ (United Kingdom); Capak, P. [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States); Sheth, K. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Schawinski, K. [ETH Zurich, Institute for Astronomy, Department of Physics, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); Wuyts, S.; Lutz, D.; Staguhn, J.; Berta, S. [MPE, Postfach 1312, D-85741 Garching (Germany); Sanders, D. [Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii, Honolulu, HI 96822 (United States); Mccracken, H. [Institut dAstrophysique de Paris, UMR7095 CNRS, Universite Pierre et Marie Curie, 98 bis Boulevard Arago, F-75014 Paris (France); Riechers, D., E-mail: sune@dark-cosmology.dk [Department of Astronomy, Cornell University, 220 Space Sciences Building, Ithaca, NY 14853 (United States)

    2014-02-20

    Three billion years after the big bang (at redshift z = 2), half of the most massive galaxies were already old, quiescent systems with little to no residual star formation and extremely compact with stellar mass densities at least an order of magnitude larger than in low-redshift ellipticals, their descendants. Little is known about how they formed, but their evolved, dense stellar populations suggest formation within intense, compact starbursts 1-2 Gyr earlier (at 3 < z < 6). Simulations show that gas-rich major mergers can give rise to such starbursts, which produce dense remnants. Submillimeter-selected galaxies (SMGs) are prime examples of intense, gas-rich starbursts. With a new, representative spectroscopic sample of compact, quiescent galaxies at z = 2 and a statistically well-understood sample of SMGs, we show that z = 3-6 SMGs are consistent with being the progenitors of z = 2 quiescent galaxies, matching their formation redshifts and their distributions of sizes, stellar masses, and internal velocities. Assuming an evolutionary connection, their space densities also match if the mean duty cycle of SMG starbursts is 42{sub −29}{sup +40} Myr (consistent with independent estimates), which indicates that the bulk of stars in these massive galaxies were formed in a major, early surge of star formation. These results suggest a coherent picture of the formation history of the most massive galaxies in the universe, from their initial burst of violent star formation through their appearance as high stellar-density galaxy cores and to their ultimate fate as giant ellipticals.

  4. Overdensities of SMGs around WISE-selected, ultraluminous, high-redshift AGNs

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    Jones, Suzy F.; Blain, Andrew W.; Assef, Roberto J.; Eisenhardt, Peter; Lonsdale, Carol; Condon, James; Farrah, Duncan; Tsai, Chao-Wei; Bridge, Carrie; Wu, Jingwen; Wright, Edward L.; Jarrett, Tom

    2017-08-01

    We investigate extremely luminous dusty galaxies in the environments around Wide-field Infrared Survey Explorer (WISE)-selected hot dust-obscured galaxies (Hot DOGs) and WISE/radio-selected active galactic nuclei (AGNs) at average redshifts of z = 2.7 and 1.7, respectively. Previous observations have detected overdensities of companion submillimetre-selected sources around 10 Hot DOGs and 30 WISE/radio AGNs, with overdensities of ˜2-3 and ˜5-6, respectively. We find that the space densities in both samples to be overdense compared to normal star-forming galaxies and submillimetre galaxies (SMGs) in the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) Cosmology Legacy Survey (S2CLS). Both samples of companion sources have consistent mid-infrared (mid-IR) colours and mid-IR to submm ratios as SMGs. The brighter population around WISE/radio AGNs could be responsible for the higher overdensity reported. We also find that the star formation rate densities are higher than the field, but consistent with clusters of dusty galaxies. WISE-selected AGNs appear to be good signposts for protoclusters at high redshift on arcmin scales. The results reported here provide an upper limit to the strength of angular clustering using the two-point correlation function. Monte Carlo simulations show no angular correlation, which could indicate protoclusters on scales larger than the SCUBA-2 1.5-arcmin scale maps.

  5. VizieR Online Data Catalog: Redshift survey of ALMA-identified SMGs in ECDFS (Danielson+, 2017)

    Science.gov (United States)

    Danielson, A. L. R.; Swinbank, A. M.; Smail, I.; Simpson, J. M.; Casey, C. M.; Chapman, S. C.; da Cunha, E.; Hodge, J. A.; Walter, F.; Wardlow, J. L.; Alexander, D. M.; Brandt, W. N.; De Breuck, C.; Coppin, K. E. K.; Dannerbauer, H.; Dickinson, M.; Edge, A. C.; Gawiser, E.; Ivison, R. J.; Karim, A.; Kovacs, A.; Lutz, D.; Menten, K.; Schinnerer, E.; Weiss, A.; van der Werf, P.

    2017-11-01

    The 870um LESS survey (Weiss+ 2009, J/ApJ/707/1201) was undertaken using the LABOCA camera on APEX, covering an area of 0.5°x0.5° centered on the ECDFS. Follow-up observations of the LESS sources were carried out with ALMA (Hodge+ 2013, J/ApJ/768/91). In summary, observations for each source were taken between 2011 October and November in the Cycle 0 Project #2011.1.00294.S. To search for spectroscopic redshifts, we initiated an observing campaign using the the FOcal Reducer and low dispersion Spectrograph (FORS2) and VIsible MultiObject Spectrograph (VIMOS) on VLT (program 183.A-0666), but to supplement these observations, we also obtained observations with XSHOOTER on VLT (program 090.A-0927(A) from 2012 December 7-10), the Gemini Near-Infrared Spectrograph (GNIRS; program GN-2012B-Q-90) and the Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE) on the Keck I telescope (2012B_H251M, 2013BU039M, and 2013BN114M), all of which cover the near-infrared. As part of a spectroscopic campaign targeting Herschel-selected galaxies in the ECDFS, ALESS submillimeter galaxies (SMGs) were included on DEep Imaging Multi-Object Spectrograph (DEIMOS) slit masks on Keck II (program 2012B_H251). In total, we observed 109 out of the 131 ALESS SMGs in the combined main and supp samples. Spectroscopic redshifts for two of our SMGs, ALESS61.1 and ALESS65.1, were determined from serendipitous detections of the [CII]λ158um line in the ALMA band. See section 2.7. (2 data files).

  6. An ALMA survey of submillimeter galaxies in the extended Chandra deep field south: The redshift distribution and evolution of submillimeter galaxies

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    Simpson, J. M.; Swinbank, A. M.; Smail, Ian; Alexander, D. M.; Danielson, A. L. R.; Thomson, A. P. [Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Bertoldi, F.; Karim, A. [Argelander-Institute for Astronomy, Bonn University, Auf dem Hügel 71, D-53121 Bonn (Germany); De Breuck, C. [European Southern Observatory, Karl-Schwarzschild Straße, D-85748 Garching bei München (Germany); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 (Canada); Coppin, K. E. K. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Da Cunha, E.; Hodge, J. A.; Schinnerer, E. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Dannerbauer, H. [Universität Wien, Institut für Astrophysik, Türkenschanzstraße 17, A-1180 Wien (Austria); Greve, T. R. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Ivison, R. J. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Knudsen, K. K. [Department of Earth and Space Science, Onsala Space Observatory, Chalmers University of Technology, SE-43992 Onsala (Sweden); Poggianti, B. M., E-mail: j.m.simpson@dur.ac.uk [INAF-Astronomical Observatory of Padova, I-35122 Padova (Italy); and others

    2014-06-20

    We present the first photometric redshift distribution for a large sample of 870 μm submillimeter galaxies (SMGs) with robust identifications based on observations with ALMA. In our analysis we consider 96 SMGs in the Extended Chandra Deep Field South, 77 of which have 4-19 band photometry. We model the SEDs for these 77 SMGs, deriving a median photometric redshift of z {sub phot} = 2.3 ± 0.1. The remaining 19 SMGs have insufficient photometry to derive photometric redshifts, but a stacking analysis of Herschel observations confirms they are not spurious. Assuming that these SMGs have an absolute H-band magnitude distribution comparable to that of a complete sample of z ∼ 1-2 SMGs, we demonstrate that they lie at slightly higher redshifts, raising the median redshift for SMGs to z {sub phot} = 2.5 ± 0.2. Critically we show that the proportion of galaxies undergoing an SMG-like phase at z ≥ 3 is at most 35% ± 5% of the total population. We derive a median stellar mass of M {sub *} = (8 ± 1) × 10{sup 10} M {sub ☉}, although there are systematic uncertainties of up to 5 × for individual sources. Assuming that the star formation activity in SMGs has a timescale of ∼100 Myr, we show that their descendants at z ∼ 0 would have a space density and M{sub H} distribution that are in good agreement with those of local ellipticals. In addition, the inferred mass-weighted ages of the local ellipticals broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events that form most of the stars seen in the majority of luminous elliptical galaxies at the present day.

  7. An alma survey of submillimeter galaxies in the extended Chandra deep field-south: The agn fraction and X-ray properties of submillimeter galaxies

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    Wang, S. X.; Brandt, W. N.; Luo, B. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Smail, I.; Alexander, D. M.; Danielson, A. L. R.; Karim, A.; Simpson, J. M.; Swinbank, A. M. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Hodge, J. A.; Walter, F. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Lehmer, B. D. [The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Wardlow, J. L. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Xue, Y. Q. [Key Laboratory for Research in Galaxies and Cosmology, Center for Astrophysics, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Chapman, S. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Coppin, K. E. K. [Centre for Astrophysics, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Dannerbauer, H. [Universität Wien, Institute für Astrophysik, Türkenschanzstraße 17, 1180 Wien (Austria); De Breuck, C. [European Southern Observatory, Karl-Schwarzschild Straße 2, D-85748 Garching (Germany); Menten, K. M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Van der Werf, P., E-mail: xxw131@psu.edu, E-mail: niel@astro.psu.edu [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)

    2013-12-01

    The large gas and dust reservoirs of submillimeter galaxies (SMGs) could potentially provide ample fuel to trigger an active galactic nucleus (AGN), but previous studies of the AGN fraction in SMGs have been controversial largely due to the inhomogeneity and limited angular resolution of the available submillimeter surveys. Here we set improved constraints on the AGN fraction and X-ray properties of the SMGs with Atacama Large Millimeter/submillimeter Array (ALMA) and Chandra observations in the Extended Chandra Deep Field-South (E-CDF-S). This study is the first among similar works to have unambiguously identified the X-ray counterparts of SMGs; this is accomplished using the fully submillimeter-identified, statistically reliable SMG catalog with 99 SMGs from the ALMA LABOCA E-CDF-S Submillimeter Survey. We found 10 X-ray sources associated with SMGs (median redshift z = 2.3), of which eight were identified as AGNs using several techniques that enable cross-checking. The other two X-ray detected SMGs have levels of X-ray emission that can be plausibly explained by their star formation activity. Six of the eight SMG-AGNs are moderately/highly absorbed, with N {sub H} > 10{sup 23} cm{sup –2}. An analysis of the AGN fraction, taking into account the spatial variation of X-ray sensitivity, yields an AGN fraction of 17{sub −6}{sup +16}% for AGNs with rest-frame 0.5-8 keV absorption-corrected luminosity ≥7.8 × 10{sup 42} erg s{sup –1}; we provide estimated AGN fractions as a function of X-ray flux and luminosity. ALMA's high angular resolution also enables direct X-ray stacking at the precise positions of SMGs for the first time, and we found four potential SMG-AGNs in our stacking sample.

  8. An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: Spectroscopic Redshifts

    Science.gov (United States)

    Danielson, A. L. R.; Swinbank, A. M.; Smail, Ian; Simpson, J. M.; Casey, C. M.; Chapman, S. C.; da Cunha, E.; Hodge, J. A.; Walter, F.; Wardlow, J. L.; Alexander, D. M.; Brandt, W. N.; de Breuck, C.; Coppin, K. E. K.; Dannerbauer, H.; Dickinson, M.; Edge, A. C.; Gawiser, E.; Ivison, R. J.; Karim, A.; Kovacs, A.; Lutz, D.; Menten, K.; Schinnerer, E.; Weiß, A.; van der Werf, P.

    2017-05-01

    We present spectroscopic redshifts of {\\text{}}{S}870μ {{m}} ≳ 2 mJy submillimeter galaxies (SMGs), which have been identified from the ALMA follow-up observations of 870 μm detected sources in the Extended Chandra Deep Field South (the ALMA-LESS survey). We derive spectroscopic redshifts for 52 SMGs, with a median of z = 2.4 ± 0.1. However, the distribution features a high-redshift tail, with ˜23% of the SMGs at z≥slant 3. Spectral diagnostics suggest that the SMGs are young starbursts, and the velocity offsets between the nebular emission and UV ISM absorption lines suggest that many are driving winds, with velocity offsets of up to 2000 km s-1. Using the spectroscopic redshifts and the extensive UV-to-radio photometry in this field, we produce optimized spectral energy distributions (SEDs) using Magphys, and use the SEDs to infer a median stellar mass of {M}\\star = (6 ± 1)× 1010 M {}⊙ for our SMGs with spectroscopic redshift. By combining these stellar masses with the star formation rates (measured from the far-infrared SEDs), we show that SMGs (on average) lie a factor of ˜5 above the so-called “main sequence” at z˜ 2. We provide this library of 52 template fits with robust and uniquely well-sampled SEDs as a resource for future studies of SMGs, and also release the spectroscopic catalog of ˜2000 (mostly infrared-selected) galaxies targeted as part of the spectroscopic campaign.

  9. COMPACT STARBURSTS IN z similar to 3-6 SUBMILLIMETER GALAXIES REVEALED BY ALMA

    NARCIS (Netherlands)

    Ikarashi, Soh; Ivison, R. J.; Caputi, Karina I.; Aretxaga, Itziar; Dunlop, James S.; Hatsukade, Bunyo; Hughes, David H.; Iono, Daisuke; Izumi, Takuma; Kawabe, Ryohei; Kohno, Kotaro; Lagos, Claudia D. P.; Motohara, Kentaro; Nakanishi, Kouichiro; Ohta, Kouji; Tamura, Yoichi; Umehata, Hideki; Wilson, Grant W.; Yabe, Kiyoto; Yun, Min S.

    2015-01-01

    We report the source size distribution, as measured by ALMA millimetric continuum imaging, of a sample of 13 AzTEC-selected submillimeter galaxies (SMGs) at z(phot) similar to 3-6. Their infrared luminosities and star formation rates (SFRs) are L-IR similar to, 2-6 x 10(12) L-circle dot and similar

  10. A complete distribution of redshifts for submillimetre galaxies in the SCUBA-2 Cosmology Legacy Survey UDS field

    Science.gov (United States)

    Smith, D. J. B.; Hayward, C. C.; Jarvis, M. J.; Simpson, C.

    2017-10-01

    Submillimetre galaxies (SMGs) are some of the most luminous star-forming galaxies in the Universe; however, their properties remain hard to determine due to the difficulty of identifying their optical/near-infrared counterparts. One of the key steps to determining the nature of SMGs is measuring a redshift distribution representative of the whole population. We do this by applying statistical techniques to a sample of 761 850 μm sources from the Submillimetre Common User Bolometer Array 2 Cosmology Legacy Survey observations of the UKIDSS Ultra-Deep Survey (UDS) field. We detect excess galaxies around >98.4 per cent of the 850 μm positions in the deep UDS catalogue, giving us the first 850 μm selected sample to have virtually complete optical/near-infrared redshift information. Under the reasonable assumption that the redshifts of the excess galaxies are representative of the SMGs themselves, we derive a median SMG redshift of z = 2.05 ± 0.03, with 68 per cent of SMGs residing between 1.07 star forming, 8.0 ± 2.1 per cent have passive rest-frame colours and are therefore unlikely to be detected at submillimetre wavelengths even in deep interferometry. We show that brighter SMGs lie at higher redshifts, and use our SMG redshift distribution - along with the assumption of a universal far-infrared Spectral Energy Distribution (SED) - to estimate that SMGs contribute around 30 per cent of the cosmic star formation rate density between 0.5 < z < 5.0.

  11. AN ALMA SURVEY OF SUBMILLIMETER GALAXIES IN THE EXTENDED CHANDRA DEEP FIELD SOUTH: NEAR-INFRARED MORPHOLOGIES AND STELLAR SIZES

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    Chen, Chian-Chou; Smail, Ian; Swinbank, A. M.; Simpson, J. M.; Ma, Cheng-Jiun; Alexander, D. M.; Danielson, A. L. R.; Edge, A. C. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Biggs, A. D.; Ivison, R. J. [European Southern Observatory, Karl Schwarzschild Strasse 2, D-85748 Garching (Germany); Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 (Canada); Coppin, K. E. K. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Dannerbauer, H. [Institut für Astrophysik, Universität Wien, Türkenschanzstraße 17, A-1180 Wien (Austria); Greve, T. R. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Karim, A. [Argelander-Institute for Astronomy, Bonn University, Auf dem Hügel 71, D-53121 Bonn (Germany); Menten, Karl M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Schinnerer, E.; Walter, F. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Wardlow, J. L. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); and others

    2015-02-01

    We analyze Hubble Space Telescope WFC3/H {sub 160}-band observations of a sample of 48 Atacama Large Millimeter/submillimeter Array detected submillimeter galaxies (SMGs) in the Extended Chandra Deep Field South field, to study their stellar morphologies and sizes. We detect 79% ± 17% of the SMGs in the H {sub 160}-band imaging with a median sensitivity of 27.8 mag, and most (80%) of the nondetections are SMGs with 870 μm fluxes of S {sub 870} < 3 mJy. With a surface brightness limit of μ {sub H} ∼ 26 mag arcsec{sup –2}, we find that 82% ± 9% of the H {sub 160}-band-detected SMGs at z = 1-3 appear to have disturbed morphologies, meaning they are visually classified as either irregulars or interacting systems, or both. By determining a Sérsic fit to the H {sub 160} surface brightness profiles, we derive a median Sérsic index of n = 1.2 ± 0.3 and a median half-light radius of r{sub e} = 4.4{sub −0.5}{sup +1.1} kpc for our SMGs at z = 1-3. We also find significant displacements between the positions of the H {sub 160} component and 870 μm emission in these systems, suggesting that the dusty starburst regions and less-obscured stellar distribution are not colocated. We find significant differences in the sizes and the Sérsic index between our z = 2-3 SMGs and z ∼ 2 quiescent galaxies, suggesting that a major transformation of the stellar light profile is needed in the quenching processes if SMGs are progenitors of the red-and-dead z ∼ 2 galaxies. Given the short-lived nature of SMGs, we postulate that the majority of the z = 2-3 SMGs with S {sub 870} ≳ 2 mJy are early/mid-stage major mergers.

  12. The SCUBA-2 Cosmology Legacy Survey: Multi-wavelength Properties of ALMA-identified Submillimeter Galaxies in UKIDSS UDS

    NARCIS (Netherlands)

    Simpson, J. M.; Smail, Ian; Swinbank, A. M.; Ivison, R. J.; Dunlop, J. S.; Geach, J. E.; Almaini, O.; Arumugam, V.; Bremer, M. N.; Chen, Chian-Chou; Conselice, C.; Coppin, K. E. K.; Farrah, D.; Ibar, E.; Hartley, W. G.; Ma, C. J.; Michałowski, M. J.; Scott, D.; Spaans, M.; Thomson, A. P.; van der Werf, P. P.

    2017-01-01

    We present a multi-wavelength analysis of 52 submillimeter galaxies (SMGs), identified using ALMA 870 μm continuum imaging in a pilot program to precisely locate bright SCUBA-2-selected submillimeter sources in the UKIDSS Ultra Deep Survey (UDS) field. Using the available deep (especially

  13. An ALMA survey of submillimetre galaxies in the COSMOS field: Physical properties derived from energy balance spectral energy distribution modelling

    Science.gov (United States)

    Miettinen, O.; Delvecchio, I.; Smolčić, V.; Aravena, M.; Brisbin, D.; Karim, A.; Magnelli, B.; Novak, M.; Schinnerer, E.; Albrecht, M.; Aussel, H.; Bertoldi, F.; Capak, P. L.; Casey, C. M.; Hayward, C. C.; Ilbert, O.; Intema, H. T.; Jiang, C.; Le Fèvre, O.; McCracken, H. J.; Muñoz Arancibia, A. M.; Navarrete, F.; Padilla, N. D.; Riechers, D. A.; Salvato, M.; Scott, K. S.; Sheth, K.; Tasca, L. A. M.

    2017-09-01

    Context. Submillimetre galaxies (SMGs) represent an important source population in the origin and cosmic evolution of the most massive galaxies. Hence, it is imperative to place firm constraints on the fundamental physical properties of large samples of SMGs. Aims: We determine the physical properties of a sample of SMGs in the COSMOS field that were pre-selected at the observed-frame wavelength of λobs = 1.1 mm, and followed up at λobs = 1.3 mm with the Atacama Large Millimetre/submillimetre Array (ALMA). Methods: We used the MAGPHYS model package to fit the panchromatic (ultraviolet to radio) spectral energy distributions (SEDs) of 124 of the target SMGs, which lie at a median redshift of z = 2.30 (19.4% are spectroscopically confirmed). The SED analysis was complemented by estimating the gas masses of the SMGs by using the λobs = 1.3 mm dust emission as a tracer of the molecular gas component. Results: The sample median and 16th-84th percentile ranges of the stellar masses, obscured star formation rates, dust temperatures, and dust and gas masses were derived to be log(M⋆/M⊙) = 11.09+0.41-0.53, SFR = 402+661-233 M⊙ yr-1, Tdust = 39.7+9.7-7.4 K, log(Mdust/M⊙) = 9.01+0.20-0.31, and log(Mgas/M⊙ = 11.34+0.20-0.23, respectively. The Mdust/M⋆ ratio was found to decrease as a function of redshift, while the Mgas/Mdust ratio shows the opposite, positive correlation with redshift. The derived median gas-to-dust ratio of 120+73-30 agrees well with the canonical expectation. The gas fraction (Mgas/ (Mgas + M⋆)) was found to range from 0.10 to 0.98 with a median of 0.62+0.27-0.23. We found that 57.3% of our SMGs populate the main sequence (MS) of star-forming galaxies, while 41.9% of the sources lie above the MS by a factor of greater than three (one source lies below the MS). These super-MS objects, or starbursts, are preferentially found at z ≳ 3, which likely reflects the sensitivity limit of our source selection. We estimated that the median gas

  14. Characterizing elusive, faint dusty star-forming galaxies: a lensed, optically undetected ALMA galaxy at z 3.3

    Science.gov (United States)

    Santini, P.; Castellano, M.; Fontana, A.; Merlin, E.; Maiolino, R.; Mason, C.; Mignano, A.; Pilo, S.; Amorin, R.; Berta, S.; Bourne, N.; Calura, F.; Daddi, E.; Elbaz, D.; Grazian, A.; Magliocchetti, M.; Michałowski, M. J.; Pentericci, L.; Pozzi, F.; Rodighiero, G.; Schreiber, C.; Valiante, R.

    2016-12-01

    We present the serendipitous ALMA detection of a faint submillimeter galaxy (SMG) lensed by a foreground z 1 galaxy. By optimizing the source detection to deblend the system, we accurately build the full spectral energy distribution of the distant galaxy from the I814 band to radio wavelengths. It is extremely red, with a I-K colour larger than 2.5. We estimate a photometric redshift of 3.28 and determine the physical parameters. The distant galaxy turns out to be magnified by the foreground lens by a factor of 1.5, which implies an intrinsic Ks-band magnitude of 24.5, a submillimeter flux at 870 μm of 2.5 mJy and a SFR of 150-300 M⊙/ yr, depending on the adopted tracer. These values place our source towards the faint end of the distribution of observed SMGs, and in particular among the still few faint SMGs with a fully characterized spectral energy distribution, which allows us not only to accurately estimate its redshift, but also to measure its stellar mass and other physical properties. The galaxy studied in this work is a representative of the population of faint SMGs, of which only few objects are known to date, that are undetected in optical and therefore are not typically accounted for when measuring the cosmic star formation history (SFH). This faint galaxy population thus likely represents an important and missing piece in our understanding of the cosmic SFH. Its observation and characterization is of major importance to achieve a solid picture of galaxy evolution.

  15. THE SCUBA-2 COSMOLOGY LEGACY SURVEY: ALMA RESOLVES THE REST-FRAME FAR-INFRARED EMISSION OF SUB-MILLIMETER GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, J. M.; Smail, Ian; Swinbank, A. M.; Chen, Chian-Chou; Danielson, A. L. R.; Edge, A. C.; Ma, C.-J. [Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Almaini, O.; Conselice, C.; Hartley, W. G.; Lani, C. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Blain, A. W. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Bremer, M. N.; Coppin, K. E. K. [School of Physics, HH Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 (Canada); Dunlop, J. S.; Ivison, R. J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford HIll, Edinburgh EH9 3HJ (United Kingdom); Farrah, D. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Geach, J. E. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Karim, A., E-mail: j.m.simpson@dur.ac.uk [Argelander-Institute for Astronomy, Bonn University, Auf dem Hügel 71, D-53121 Bonn (Germany); and others

    2015-01-20

    We present high-resolution (0.''3) Atacama Large Millimeter Array 870 μm imaging of 52 sub-millimeter galaxies (SMGs) in the Ultra Deep Survey field to investigate the size and morphology of the sub-millimeter (sub-mm) emission on 2-10 kpc scales. We derive a median intrinsic angular size of FWHM = 0.''30 ± 0.''04 for the 23 SMGs in the sample detected at a signal-to-noise ratio (S/N) >10. Using the photometric redshifts of the SMGs we show that this corresponds to a median physical half-light diameter of 2.4 ± 0.2 kpc. A stacking analysis of the SMGs detected at S/N <10 shows they have sizes consistent with the 870 μm bright SMGs in the sample. We compare our results to the sizes of SMGs derived from other multi-wavelength studies, and show that the rest-frame ∼250 μm sizes of SMGs are consistent with studies of resolved {sup 12}CO (J = 3-2 to 7-6) emission lines, but that sizes derived from 1.4 GHz imaging appear to be approximately two times larger on average, which we attribute to cosmic ray diffusion. The rest-frame optical sizes of SMGs are around four times larger than the sub-millimeter sizes, indicating that the star formation in these galaxies is compact relative to the pre-existing stellar distribution. The size of the starburst region in SMGs is consistent with the majority of the star formation occurring in a central region, a few kiloparsecs in extent, with a median star formation rate surface density of 90 ± 30 M {sub ☉} yr{sup –1} kpc{sup –2}, which may suggest that we are witnessing an intense period of bulge growth in these galaxies.

  16. The Hawaii SCUBA-2 Lensing Cluster Survey: Are Low-luminosity Submillimeter Galaxies Detected in the Rest-frame UV?

    Science.gov (United States)

    Hsu, Li-Yen; Cowie, Lennox L.; Barger, Amy J.; Wang, Wei-Hao

    2017-12-01

    In this third paper of the Hawaii SCUBA-2 Lensing Cluster Survey series, we present Submillimeter Array (SMA) detections of six intrinsically faint 850 μm sources detected in SCUBA-2 images of the lensing cluster fields, A1689, A2390, A370, MACS J0717.5+3745, and MACS J1423.8+2404. Two of the SCUBA-2 sources split into doublets, yielding a total of eight SMA detections. The intrinsic 870 μm flux densities of these submillimeter galaxies (SMGs) are ∼1 mJy. Five of the eight SMGs are not detected in optical or near-infrared (NIR) images. The NIR-to-submillimeter flux ratios of these faint SMGs suggest that most of them are extremely dusty and/or are at very high redshifts. By combining these SMGs and several other samples from the literature, we find a bimodal distribution for the faint sources in the space of submillimeter flux versus NIR-to-submillimeter flux ratio. While most of the SMA-detected lensed sources are very obscured, the other SMGs with similar flux densities are mostly bright in the NIR. Future Atacama Large Millimeter/submillimeter Array observations of a large sample of SCUBA-2 sources in cluster fields will allow us to decide whether or not the bimodality we observe here really exists.

  17. The Interstellar Medium in High-redshift Submillimeter Galaxies as Probed by Infrared Spectroscopy*

    Science.gov (United States)

    Wardlow, Julie L.; Cooray, Asantha; Osage, Willow; Bourne, Nathan; Clements, David; Dannerbauer, Helmut; Dunne, Loretta; Dye, Simon; Eales, Steve; Farrah, Duncan; Furlanetto, Cristina; Ibar, Edo; Ivison, Rob; Maddox, Steve; Michałowski, Michał M.; Riechers, Dominik; Rigopoulou, Dimitra; Scott, Douglas; Smith, Matthew W. L.; Wang, Lingyu; van der Werf, Paul; Valiante, Elisabetta; Valtchanov, Ivan; Verma, Aprajita

    2017-03-01

    Submillimeter galaxies (SMGs) at z≳ 1 are luminous in the far-infrared, and have star formation rates, SFR, of hundreds to thousands of solar masses per year. However, it is unclear whether they are true analogs of local ULIRGs or whether the mode of their star formation is more similar to that in local disk galaxies. We target these questions by using Herschel-PACS to examine the conditions in the interstellar medium (ISM) in far-infrared luminous SMGs at z˜ 1-4. We present 70-160 μm photometry and spectroscopy of the [O IV]26 μm, [Fe II]26 μm, [S III]33 μm, [Si II]34 μm, [O III]52 μm, [N III]57 μm, and [O I]63 μm fine-structure lines and the S(0) and S(1) hydrogen rotational lines in 13 lensed SMGs identified by their brightness in early Herschel data. Most of the 13 targets are not individually spectroscopically detected; we instead focus on stacking these spectra with observations of an additional 32 SMGs from the Herschel archive—representing a complete compilation of PACS spectroscopy of SMGs. We detect [O I]63 μm, [Si II]34 μm, and [N III]57 μm at ≥slant 3σ in the stacked spectra, determining that the average strengths of these lines relative to the far-IR continuum are (0.36+/- 0.12)× {10}-3, (0.84+/- 0.17)× {10}-3, and (0.27+/- 0.10)× {10}-3, respectively. Using the [O III]52 μm/[N III]57 μm emission line ratio, we show that SMGs have average gas-phase metallicities ≳ {Z}⊙ . By using PDR modeling and combining the new spectral measurements with integrated far-infrared fluxes and existing [C II]158 μm data, we show that SMGs have average gas densities, n, of ˜ {10}1-3 {{cm}}-3 and FUV field strengths, {G}0˜ {10}2.2-4.5 (in Habing units: 1.6× {10}-3 {erg} {{cm}}-2 {{{s}}}-1), consistent with both local ULIRGs and lower luminosity star-forming galaxies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia, and important participation from NASA.

  18. Power-law Temperature Distribution SED Modeling To Reveal Properties of High-z Starburst Galaxies

    Science.gov (United States)

    Su, Ting; Staguhn, J.; Dwek, E.; Kovacs, A.

    2014-01-01

    Sub-millimeter galaxies (SMGs), selected as the most luminous sources in submm/mm surveys in recent decades, are a group of highly dust-obscured massive galaxies at high redshifts energized by starbursts. SMG surveys enable us to study the nature of those sources in detail. Previous samples of SMGs are typically distributed at z ˜ 0.5-3. In order to explore the evolutionary properties of SMGs up to an earlier epoch, we present a sample of 12 sources at average z ˜ 4. Five of our sources are from the GISMO 2mm Deep Field survey-the very first 2mm deep field survey, which favors higher redshift sources with its superior sensitivity and relatively longer wavelength. The other seven are extremely high redshift SMGs (z > 4) including six from Michalowski et al. 2010b and one at z=5.3 from Dwek et al. 2011. Since rest frame far-infrared continuum dust emission is the best tracer of star-formation activities to date, we employ a power-law temperature distribution SED model to analyze the data. This model which fits for dust grains embedded in a radiation field, allows for different dust compositions, size distribution, and emission region geometry. Our fit results represent the data very accurately even in the Wien part of the SED. Our analysis shows that the SED is not optically thin around the SED peak, as is often assumed. In my talk I will present source fitting results of dust mass, dust temperature, index of temperature power-law distribution, and emission region size. Furthermore, I will analyze the evolutionary trends of SMGs properties with redshift and discuss astrophysical implications for those results.

  19. Blending bias impacts the host halo masses derived from a cross-correlation analysis of bright submillimetre galaxies

    Science.gov (United States)

    Cowley, William I.; Lacey, Cedric G.; Baugh, Carlton M.; Cole, Shaun; Wilkinson, Aaron

    2017-08-01

    Placing bright submillimetre galaxies (SMGs) within the broader context of galaxy formation and evolution requires accurate measurements of their clustering, which can constrain the masses of their host dark matter haloes. Recent work has shown that the clustering measurements of these galaxies may be affected by a 'blending bias', which results in the angular correlation function of the sources extracted from single-dish imaging surveys being boosted relative to that of the underlying galaxies. This is due to confusion introduced by the coarse angular resolution of the single-dish telescope and could lead to the inferred halo masses being significantly overestimated. We investigate the extent to which this bias affects the measurement of the correlation function of SMGs when it is derived via a cross-correlation with a more abundant galaxy population. We find that the blending bias is essentially the same as in the autocorrelation case and conclude that the best way to reduce its effects is to calculate the angular correlation function using SMGs in narrow redshift bins. Blending bias causes the inferred host halo masses of the SMGs to be overestimated by a factor of ∼6 when a redshift interval of δz = 3 is used. However, this reduces to a factor of ∼2 for δz = 0.5. The broadening of photometric redshift probability distributions with increasing redshift can therefore impart a mild halo 'downsizing' effect on to the inferred host halo masses, though this trend is not as strong as seen in recent observational studies.

  20. Faint submillimeter galaxies revealed by multifield deep ALMA observations: number counts, spatial clustering, and a dark submillimeter line emitter

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Yoshiaki; Ouchi, Masami; Momose, Rieko [Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Kurono, Yasutaka, E-mail: ono@icrr.u-tokyo.ac.jp [Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago 763-0355 (Chile)

    2014-11-01

    We present the statistics of faint submillimeter/millimeter galaxies (SMGs) and serendipitous detections of a submillimeter/millimeter line emitter (SLE) with no multi-wavelength continuum counterpart revealed by the deep ALMA observations. We identify faint SMGs with flux densities of 0.1-1.0 mJy in the deep Band-6 and Band-7 maps of 10 independent fields that reduce cosmic variance effects. The differential number counts at 1.2 mm are found to increase with decreasing flux density down to 0.1 mJy. Our number counts indicate that the faint (0.1-1.0 mJy, or SFR{sub IR} ∼ 30-300 M {sub ☉} yr{sup –1}) SMGs contribute nearly a half of the extragalactic background light (EBL), while the remaining half of the EBL is mostly contributed by very faint sources with flux densities of <0.1 mJy (SFR{sub IR} ≲ 30 M {sub ☉} yr{sup –1}). We conduct counts-in-cells analysis with multifield ALMA data for the faint SMGs, and obtain a coarse estimate of galaxy bias, b {sub g} < 4. The galaxy bias suggests that the dark halo masses of the faint SMGs are ≲ 7 × 10{sup 12} M {sub ☉}, which is smaller than those of bright (>1 mJy) SMGs, but consistent with abundant high-z star-forming populations, such as sBzKs, LBGs, and LAEs. Finally, we report the serendipitous detection of SLE-1, which has no continuum counterparts in our 1.2 mm-band or multi-wavelength images, including ultra deep HST/WFC3 and Spitzer data. The SLE has a significant line at 249.9 GHz with a signal-to-noise ratio of 7.1. If the SLE is not a spurious source made by the unknown systematic noise of ALMA, the strong upper limits of our multi-wavelength data suggest that the SLE would be a faint galaxy at z ≳ 6.

  1. Physical conditions of the interstellar medium in high-redshift submillimetre bright galaxies

    Science.gov (United States)

    Yang, Chentao

    2017-12-01

    The discovery of a population of high- redshift dust-obscured submillimeter galaxies (SMGs) from ground-based submm cameras has revolutionised our understanding of galaxy evolution and star formation in extreme conditions. They are the strongest starbursts in the Universe approaching the Eddington limit and are believed to be the progenitors of the most massive galaxies today. However, theoretical models of galaxy evolution have even been challenged by a large number of detections of high-redshift SMGs. A very few among them are gravitationally lensed by an intervening galaxy. Recent wide-area extragalactic surveys have discovered hundreds of such strongly lensed SMGs, opening new exciting opportunities for observing the interstellar medium in these exceptional objects. We have thus carefully selected a sample of strongly gravitational lensed SMGs based on the submillimeter flux limit from the Herschel-ATLAS sample. Using IRAM telescopes, we have built a rich H2O-line-detected sample of 16 SMGs. We found a close-to-linear tight correlation between the H2O line and total infrared luminosity. This indicates the importance of far-IR pumping to the excitation of the H2O lines. Using a far-IR pumping model, we have derived the physical properties of the H2O gas and the dust. We showed that H2O lines trace a warm dense gas that may be closely related to the active star formation. Along with the H2O lines, several H2O+ lines have also been detected in three of our SMGs. We also find a tight correlation between the luminosity of the lines of H2O and H2O+ from local ULIRGs to high-redshift SMGs. The flux ratio between H2O+ and H2O suggests that cosmic rays from strong star forming activities are possibly driving the related oxygen chemistry. Another important common molecular gas tracer is the CO line. We have observed multiple transitions of the CO lines in each of our SMGs with IRAM 30m telescope. By analysing the CO line profile, we discovered a significant differential

  2. LENS MODELS OF HERSCHEL-SELECTED GALAXIES FROM HIGH-RESOLUTION NEAR-IR OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Calanog, J. A.; Cooray, A.; Ma, B.; Casey, C. M. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Fu, Hai [Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242 (United States); Wardlow, J. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Amber, S. [Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA (United Kingdom); Baker, A. J. [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Baes, M. [1 Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent (Belgium); Bock, J. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Bourne, N.; Dye, S. [School of Physics and Astronomy, University of Nottingham, NG7 2RD (United Kingdom); Bussmann, R. S. [Department of Astronomy, Space Science Building, Cornell University, Ithaca, NY 14853-6801 (United States); Chapman, S. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Clements, D. L. [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Conley, A. [Center for Astrophysics and Space Astronomy 389-UCB, University of Colorado, Boulder, CO 80309 (United States); Dannerbauer, H. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu-CNRS-Université Paris Diderot, CE-Saclay, pt courrier 131, F-91191 Gif-sur-Yvette (France); De Zotti, G. [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Dunne, L.; Eales, S. [School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); and others

    2014-12-20

    We present Keck-Adaptive Optics and Hubble Space Telescope high resolution near-infrared (IR) imaging for 500 μm bright candidate lensing systems identified by the Herschel Multi-tiered Extragalactic Survey and Herschel Astrophysical Terahertz Large Area Survey. Out of 87 candidates with near-IR imaging, 15 (∼17%) display clear near-IR lensing morphologies. We present near-IR lens models to reconstruct and recover basic rest-frame optical morphological properties of the background galaxies from 12 new systems. Sources with the largest near-IR magnification factors also tend to be the most compact, consistent with the size bias predicted from simulations and previous lensing models for submillimeter galaxies (SMGs). For four new sources that also have high-resolution submillimeter maps, we test for differential lensing between the stellar and dust components and find that the 880 μm magnification factor (μ{sub 880}) is ∼1.5 times higher than the near-IR magnification factor (μ{sub NIR}), on average. We also find that the stellar emission is ∼2 times more extended in size than dust. The rest-frame optical properties of our sample of Herschel-selected lensed SMGs are consistent with those of unlensed SMGs, which suggests that the two populations are similar.

  3. (Sub)millimetre interferometric imaging of a sample of COSMOS/AzTEC submillimetre galaxies. III. Environments

    Science.gov (United States)

    Smolčić, V.; Miettinen, O.; Tomičić, N.; Zamorani, G.; Finoguenov, A.; Lemaux, B. C.; Aravena, M.; Capak, P.; Chiang, Y.-K.; Civano, F.; Delvecchio, I.; Ilbert, O.; Jurlin, N.; Karim, A.; Laigle, C.; Le Fèvre, O.; Marchesi, S.; McCracken, H. J.; Riechers, D. A.; Salvato, M.; Schinnerer, E.; Tasca, L.; Toft, S.

    2017-01-01

    We investigate the environment of 23 submillimetre galaxies (SMGs) drawn from a signal-to-noise (S/N)-limited sample of SMGs originally discovered in the James Clerk Maxwell Telescope (JCMT)/AzTEC 1.1 mm continuum survey of a Cosmic Evolution Survey (COSMOS) subfield and then followed up with the Submillimetre Array and Plateau de Bure Interferometer at 890 μm and 1.3 mm, respectively. These SMGs already have well-defined multiwavelength counterparts and redshifts. We also analyse the environments of four COSMOS SMGs spectroscopically confirmed to lie at redshifts zspec > 4.5, and one at zspec = 2.49 resulting in a total SMG sample size of 28. We search for overdensities using the COSMOS photometric redshifts based on over 30 UV-NIR photometric measurements including the new UltraVISTA data release 2 and Spitzer/SPLASH data, and reaching an accuracy of σΔz/ (1 + z) = 0.0067 (0.0155) at z 3.5). To identify overdensities we apply the Voronoi tessellation analysis, and estimate the redshift-space overdensity estimator δg as a function of distance from the SMG and/or overdensity centre. We test and validate our approach via simulations, X-ray detected groups or clusters, and spectroscopic verifications using VUDS and zCOSMOS catalogues which show that even with photometric redshifts in the COSMOS field we can efficiently retrieve overdensities out to z ≈ 5. Our results yield that 11 out of 23 (48%) JCMT/AzTEC 1.1 mm SMGs occupy overdense environments. Considering the entire JCMT/AzTEC 1.1 mm S/N ≥ 4 sample and taking the expected fraction of spurious detections into account, this means that 35-61% of the SMGs in the S/N-limited sample occupy overdense environments. We perform an X-ray stacking analysis in the 0.5-2 keV band using a 32″ aperture and our SMG positions, and find statistically significant detections. For our z 2 subsample yields an average flux of (1.3 ± 0.5) × 10-16 erg s-1 cm-2 and a corresponding total massof M200 = 2 × 1013M⊙. Our

  4. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

    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......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...... 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...

  5. Active Galaxies

    DEFF Research Database (Denmark)

    Kilerci Eser, Ece

    one is related to the mass estimates of supermassive black holes (SMBHs). Mass estimates of SMBHs are important to understand the formation and evolution of SMBHs and their host galaxies. Black hole masses in Type 1 AGN are measured with the reverberation mapping (RM) technique. Reverberation mapping......Galaxy formation and evolution is one of the main research themes of modern astronomy. Active galaxies such as Active Galactic Nuclei (AGN) and Ultraluminous Infrared Galaxies (ULIRGs) are important evolutionary stages of galaxies. The ULIRG stage is mostly associated with galaxy mergers...... and interactions. During the interactions of gas-rich galaxies, the gas inflows towards the centers of the galaxies and can trigger both star formation and AGN activity. The ULIRG stage includes rapid star formation activity and fast black hole growth that is enshrouded by dust. Once the AGN emission...

  6. The multi-wavelength properties of faint submillimeter galaxies at 450 and 850um

    Science.gov (United States)

    Zavala, Jorge; Aretxaga, Itziar; Hughes, David; Dunlop, James; Michalowski, Michal; SCUBA-2 Cosmology Legacy Survey

    2017-01-01

    We present a multi-wavelength analysis for galaxies selected at 450 and 850um from the deepest SCUBA-2 observations in the EGS field. The median redshifts for the 450 and 850um samples are z~1.6 and z~2.2, respectively. However, the two populations have similar IR luminosities, SFR, and stellar masses, with mean values of ~1.5x10^12 L_sun, 150 M_sun/yr, and 9x10^10 M_sun, respectively. We find that most of our sources (>80%) lie in the high-mass end of the `main sequence' of star-forming galaxies. Exploring the IRX-beta relation we find that the most luminous galaxies are consistent with the Muerer law, while the less luminous galaxies are in better agreement with the SMC relation. Using the results of a two-dimensinal modelling of the HST H_160-band, we derive a median Sersic index of n=1.4 and a median half-light radius of ~4.8kpc for the whole sample. Based on a visual-like classification in the same band we find that the dominant component for most of the galaxies at all redshift is a disk, although there is a transition from irregular disks to disks with a spheroidal component from high to low redshift, which supports the scenario of SMGs as progenitors of present-day massive elliptical galaxies.

  7. A physical model for z ~ 2 dust-obscured galaxies

    Science.gov (United States)

    Narayanan, Desika; Dey, Arjun; Hayward, Christopher C.; Cox, Thomas J.; Bussmann, R. Shane; Brodwin, Mark; Jonsson, Patrik; Hopkins, Philip F.; Groves, Brent; Younger, Joshua D.; Hernquist, Lars

    2010-09-01

    We present a physical model for the origin of z ~ 2 dust-obscured galaxies (DOGs), a class of high-redshift ultraluminous infrared galaxies (ULIRGs) selected at 24μm which are particularly optically faint (F24μm/FR > 1000). By combining N-body/smoothed particle hydrodynamic simulations of high-redshift galaxy evolution with 3D polychromatic dust radiative transfer models, we find that luminous DOGs (with F24 >~ 0.3mJy at z ~ 2) are well modelled as extreme gas-rich mergers in massive (~5 × 1012-1013Msolar) haloes, with elevated star formation rates (SFR; ~500-1000Msolaryr-1) and/or significant active galactic nuclei (AGN) growth , whereas less luminous DOGs are more diverse in nature. At final coalescence, merger-driven DOGs transition from being starburst dominated to AGN dominated, evolving from a `bump' to a power-law (PL) shaped mid-IR (Infrared Array Camera, IRAC) spectral energy distribution (SED). After the DOG phase, the galaxy settles back to exhibiting a `bump' SED with bluer colours and lower SFRs. While canonically PL galaxies are associated with being AGN dominated, we find that the PL mid-IR SED can owe both to direct AGN contribution and to a heavily dust obscured stellar bump at times that the galaxy is starburst dominated. Thus, PL galaxies can be either starburst or AGN dominated. Less luminous DOGs can be well-represented either by mergers or by massive (Mbaryon ~ 5 × 1011Msolar) secularly evolving gas-rich disc galaxies (with SFR >~ 50Msolaryr-1). By utilizing similar models as those employed in the submillimetre galaxy (SMG) formation study of Narayanan et al., we investigate the connection between DOGs and SMGs. We find that the most heavily star-forming merger-driven DOGs can be selected as submillimetre galaxies, while both merger-driven and secularly evolving DOGs typically satisfy the BzK selection criteria. The model SEDs from the simulated galaxies match observed data reasonably well, though Mrk 231 and Arp 220 templates provide

  8. Galaxy Disks

    NARCIS (Netherlands)

    van der Kruit, P. C.; Freeman, K. C.

    The disks of disk galaxies contain a substantial fraction of their baryonic matter and angular momentum, and much of the evolutionary activity in these galaxies, such as the formation of stars, spiral arms, bars and rings, and the various forms of secular evolution, takes place in their disks. The

  9. Gravitational lens models based on submillimeter array imaging of Herschel -selected strongly lensed sub-millimeter galaxies at z > 1.5

    Energy Technology Data Exchange (ETDEWEB)

    Bussmann, R. S.; Gurwell, M. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Pérez-Fournon, I. [Instituto de Astrofísica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain); Amber, S. [Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA (United Kingdom); Calanog, J.; De Bernardis, F.; Wardlow, J. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Dannerbauer, H. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu-CNRS-Université Paris Diderot, CE-Saclay, pt courrier 131, F-91191 Gif-sur-Yvette (France); Fu, Hai [Department of Physics and Astronomy, The University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242 (United States); Harris, A. I. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Krips, M. [Institut de RadioAstronomie Millimétrique, 300 Rue de la Piscine, Domaine Universitaire, 38406 Saint Martin d' Hères (France); Lapi, A. [Department Fisica, Univ. Tor Vergata, Via Ricerca Scientifica 1, 00133 Rome, Italy and SISSA, Via Bonomea 265, 34136 Trieste (Italy); Maiolino, R. [Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Ave., Cambridge CB3 OHE (United Kingdom); Omont, A. [Institut d' Astrophysique de Paris, UMR 7095, CNRS, UPMC Univ. Paris 06, 98bis boulevard Arago, F-75014 Paris (France); Riechers, D. [Department of Astronomy, Space Science Building, Cornell University, Ithaca, NY 14853-6801 (United States); Baker, A. J. [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Rd, Piscataway, NJ 08854 (United States); Birkinshaw, M. [HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Bock, J. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); and others

    2013-12-10

    Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S {sub 500} > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r {sub half}) and far-infrared luminosities (L {sub FIR}) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z {sub lens} > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 μm flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L {sub FIR} (median L {sub FIR} = 7.9 × 10{sup 12} L {sub ☉}) and two decades in FIR luminosity surface density (median Σ{sub FIR} = 6.0 × 10{sup 11} L {sub ☉} kpc{sup –2}). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift.

  10. CONNECTING GRBs AND ULIRGs: A SENSITIVE, UNBIASED SURVEY FOR RADIO EMISSION FROM GAMMA-RAY BURST HOST GALAXIES AT 0 < z < 2.5

    Energy Technology Data Exchange (ETDEWEB)

    Perley, D. A. [Department of Astronomy, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Perley, R. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Hjorth, J.; Malesani, D. [Dark Cosmology Centre, Niels Bohr Institute, DK-2100 Copenhagen (Denmark); Michałowski, M. J. [Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ (United Kingdom); Cenko, S. B. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Jakobsson, P. [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavík (Iceland); Krühler, T. [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19 (Chile); Levan, A. J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Tanvir, N. R., E-mail: dperley@astro.caltech.edu [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom)

    2015-03-10

    Luminous infrared galaxies and submillimeter galaxies contribute significantly to stellar mass assembly and provide an important test of the connection between the gamma-ray burst (GRB) rate and that of overall cosmic star formation. We present sensitive 3 GHz radio observations using the Karl G. Jansky Very Large Array of 32 uniformly selected GRB host galaxies spanning a redshift range from 0 < z < 2.5, providing the first fully dust- and sample-unbiased measurement of the fraction of GRBs originating from the universe's most bolometrically luminous galaxies. Four galaxies are detected, with inferred radio star formation rates (SFRs) ranging between 50 and 300 M {sub ☉} yr{sup –1}. Three of the four detections correspond to events consistent with being optically obscured 'dark' bursts. Our overall detection fraction implies that between 9% and 23% of GRBs between 0.5 < z < 2.5 occur in galaxies with S {sub 3GHz} > 10 μJy, corresponding to SFR > 50 M {sub ☉} yr{sup –1} at z ∼ 1 or >250 M {sub ☉} yr{sup –1} at z ∼ 2. Similar galaxies contribute approximately 10%-30% of all cosmic star formation, so our results are consistent with a GRB rate that is not strongly biased with respect to the total SFR of a galaxy. However, all four radio-detected hosts have stellar masses significantly lower than IR/submillimeter-selected field galaxies of similar luminosities. We suggest that the GRB rate may be suppressed in metal-rich environments but independently enhanced in intense starbursts, producing a strong efficiency dependence on mass but little net dependence on bulk galaxy SFR.

  11. An ALMA survey of submillimetre galaxies in the COSMOS field: The extent of the radio-emitting region revealed by 3 GHz imaging with the Very Large Array

    Science.gov (United States)

    Miettinen, O.; Novak, M.; Smolčić, V.; Delvecchio, I.; Aravena, M.; Brisbin, D.; Karim, A.; Murphy, E. J.; Schinnerer, E.; Albrecht, M.; Aussel, H.; Bertoldi, F.; Capak, P. L.; Casey, C. M.; Civano, F.; Hayward, C. C.; Herrera Ruiz, N.; Ilbert, O.; Jiang, C.; Laigle, C.; Le Fèvre, O.; Magnelli, B.; Marchesi, S.; McCracken, H. J.; Middelberg, E.; Muñoz Arancibia, A. M.; Navarrete, F.; Padilla, N. D.; Riechers, D. A.; Salvato, M.; Scott, K. S.; Sheth, K.; Tasca, L. A. M.; Bondi, M.; Zamorani, G.

    2017-06-01

    Context. The observed spatial scale of the radio continuum emission from star-forming galaxies can be used to investigate the spatial extent of active star formation, constrain the importance of cosmic-ray transport, and examine the effects of galaxy interactions. Aims: We determine the radio size distribution of a large sample of 152 submillimetre galaxies (SMGs) in the COSMOS field that were pre-selected at 1.1 mm, and later detected with the Atacama Large Millimetre/submillimetre Array (ALMA) in the observed-frame 1.3 mm dust continuum emission at a signal-to-noise ratio (S/N) of ≥5. Methods: We used the deep, subarcsecond-resolution (1σ = 2.3μJy beam-1;.̋75) centimetre radio continuum observations taken by the Karl G. Jansky Very Large Array (VLA)-COSMOS 3 GHz Large Project. Results: One hundred and fifteen of the 152 target SMGs (76% ± 7%) were found to have a 3 GHz counterpart (≥ 4.2σ), which renders the radio detection rate notably high. The median value of the deconvolved major axis full width at half maximum (FWHM) size at 3 GHz is derived to be 0.̋59 ± 0.̋05 , or 4.6 ± 0.4 kpc in physical units, where the median redshift of the sources is z = 2.23 ± 0.13 (23% are spectroscopic and 77% are photometric values). The radio sizes are roughly log-normally distributed, and they show no evolutionary trend with redshift, or difference between different galaxy morphologies. We also derived the spectral indices between 1.4 and 3 GHz, and 3 GHz brightness temperatures for the sources, and the median values were found to be α1.4 GHz3 GHz = -0.67 (Sν ∝ να) and TB = 12.6 ± 2 K. Three of the target SMGs, which are also detected with the Very Long Baseline Array (VLBA) at 1.4 GHz (AzTEC/C24b, 61, and 77a), show clearly higher brightness temperatures than the typical values, reaching TB(3 GHz) > 104.03 K for AzTEC/C61. Conclusions: The derived median radio spectral index agrees with a value expected for optically thin non-thermal synchrotron radiation

  12. 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.

  13. Molecular gas in the Herschel-selected strongly lensed submillimeter galaxies at z 2-4 as probed by multi-J CO lines

    Science.gov (United States)

    Yang, C.; Omont, A.; Beelen, A.; Gao, Y.; van der Werf, P.; Gavazzi, R.; Zhang, Z.-Y.; Ivison, R.; Lehnert, M.; Liu, D.; Oteo, I.; González-Alfonso, E.; Dannerbauer, H.; Cox, P.; Krips, M.; Neri, R.; Riechers, D.; Baker, A. J.; Michałowski, M. J.; Cooray, A.; Smail, I.

    2017-12-01

    We present the IRAM-30 m observations of multiple-J CO (Jup mostly from 3 up to 8) and [C I](3P2 → 3P1) ([C I](2-1) hereafter) line emission in a sample of redshift 2-4 submillimeter galaxies (SMGs). These SMGs are selected among the brightest-lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Forty-seven CO lines and 7 [C I](2-1) lines have been detected in 15 lensed SMGs. A non-negligible effect of differential lensing is found for the CO emission lines, which could have caused significant underestimations of the linewidths, and hence of the dynamical masses. The CO spectral line energy distributions (SLEDs), peaking around Jup 5-7, are found to be similar to those of the local starburst-dominated ultra-luminous infrared galaxies and of the previously studied SMGs. After correcting for lensing amplification, we derived the global properties of the bulk of molecular gas in the SMGs using non-LTE radiative transfer modelling, such as the molecular gas density nH2 102.5-104.1 cm-3 and the kinetic temperature Tk 20-750 K. The gas thermal pressure Pth ranging from 105 K cm-3 to 106 K cm-3 is found to be correlated with star formation efficiency. Further decomposing the CO SLEDs into two excitation components, we find a low-excitation component with nH2 102.8-104.6 cm-3 and Tk 20-30 K, which is less correlated with star formation, and a high-excitation one (nH2 102.7-104.2 cm-3, Tk 60-400 K) which is tightly related to the on-going star-forming activity. Additionally, tight linear correlations between the far-infrared and CO line luminosities have been confirmed for the Jup ≥ 5 CO lines of these SMGs, implying that these CO lines are good tracers of star formation. The [C I](2-1) lines follow the tight linear correlation between the luminosities of the [C I](2-1) and the CO(1-0) line found in local starbursts, indicating that [C I] lines could serve as good total molecular gas mass tracers for high-redshift SMGs as well

  14. The formation and evolution of high-redshift dusty galaxies

    Science.gov (United States)

    Ma, Jingzhe; Gonzalez, Anthony H.; Ge, Jian; Vieira, Joaquin D.; Prochaska, Jason X.; Spilker, Justin; Strandet, Maria; Ashby, Matthew; Noterdaeme, Pasquier; Lundgren, Britt; Zhao, Yinan; Ji, Tuo; Zhang, Shaohua; Caucal, Paul; SPT SMG Collaboration

    2017-01-01

    Star formation and chemical evolution are among the biggest questions in galaxy formation and evolution. High-redshift dusty galaxies are the best sites to investigate mass assembly and growth, star formation rates, star formation history, chemical enrichment, and physical conditions. My thesis is based on two populations of high-redshift dusty galaxies, submillimeter galaxies (SMGs) and quasar 2175 Å dust absorbers, which are selected by dust emission and dust absorption, respectively.For the SMG sample, I have worked on the gravitationally lensed dusty, star-forming galaxies (DSFGs) at 2.8 thesis is focused on the stellar masses and star formation rates of these objects by means of multi-wavelength spectral energy distribution (SED) modelling. The data include HST/WFC3, Spitzer/IRAC, Herschel/PACS, Herschel/SPIRE, APEX/Laboca and SPT. Compared to the star-forming main sequence (MS), these DSFGs have specific SFRs that lie above the MS, suggesting that we are witnessing ongoing strong starburst events that may be driven by major mergers. SPT0346-52 at z = 5.7, the most extraordinary source in the SPT survey for which we obtained Chandra X-ray and ATCA radio data, was confirmed to have the highest star formation surface density of any known galaxy at high-z.The other half of my thesis is focused on a new population of quasar absorption line systems, 2175 Å dust absorbers, which are excellent probes of gas and dust properties, chemical evolution and physical conditions in the absorbing galaxies. This sample was selected from the SDSS and BOSS surveys and followed up with the Echelle Spectrographs and Imager on the Keck-II telescope, the Red & Blue Channel Spectrograph on the Multiple Mirror Telescope, and the Ultraviolet and Visible Echelle Spectrograph onboard the Very Large Telescope. We found a correlation between the presence of the 2175 Å bump and other ingredients including high metallicity, high depletion level, overall low ionization state of gas, neutral

  15. THE SCUBA-2 COSMOLOGY LEGACY SURVEY: MULTIWAVELENGTH COUNTERPARTS TO 10{sup 3} SUBMILLIMETER GALAXIES IN THE UKIDSS-UDS FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chian-Chou; Smail, Ian; Ma, Cheng-Jiun; Simpson, James M.; Swinbank, A. Mark [Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Ivison, Rob J.; Arumugam, Vinodiran; Mortlock, Alice; Dunlop, James S.; Michałowski, Michał J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Almaini, Omar; Conselice, Christopher J.; Hartley, Will G. [University of Nottingham, School of Physics and Astronomy, Nottingham, NG7 2RD (United Kingdom); Geach, James E. [Center for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Simpson, Chris [Astrophysics Research Institute, Liverpool John Moores University, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom); Aretxaga, Itziar [Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Luis Enrique Erro 1, Sta. Ma. Tonantzintla, Puebla (Mexico); Blain, Andrew [Physics and Astronomy, University of Leicester, Leicester, LE1 7RH (United Kingdom); Chapman, Scott C. [Department of Physics and Atmospheric Science, Dalhousie University, 6310 Coburg Road, Halifax, NS B3H 4R2 (Canada); Farrah, Duncan [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Halpern, Mark [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); and others

    2016-04-01

    We present multiwavelength identifications for the counterparts of 1088 submillimeter sources detected at 850 μm in the SCUBA-2 Cosmology Legacy Survey study of the UKIRT Infrared Deep Sky Survey-Ultra-Deep Survey (UDS) field. By utilizing an Atacama Large Millimeter Array (ALMA) pilot study on a subset of our bright SCUBA-2 sample as a training set, along with the deep optical–near-infrared (OIR) data available in this field, we develop a novel technique, Optical–IR Triple Color (OIRTC), using z − K, K − [3.6], [3.6] − [4.5] colors to select the candidate submillimeter galaxy (SMG) counterparts. By combining radio identification and the OIRTC technique, we find counterpart candidates for 80% of the Class = 1 ≥ 4σ SCUBA-2 sample, defined as those that are covered by both radio and OIR imaging and the base sample for our scientific analyses. Based on the ALMA training set, we expect the accuracy of these identifications to be 82% ± 20%, with a completeness of 69% ± 16%, essentially as accurate as the traditional p-value technique but with higher completeness. We find that the fraction of SCUBA-2 sources having candidate counterparts is lower for fainter 850 μm sources, and we argue that for follow-up observations sensitive to SMGs with S{sub 850} ≳ 1 mJy across the whole ALMA beam, the fraction with multiple counterparts is likely to be >40% for SCUBA-2 sources at S{sub 850} ≳ 4 mJy. We find that the photometric redshift distribution for the SMGs is well fit by a lognormal distribution, with a median redshift of z = 2.3 ± 0.1. After accounting for the sources without any radio and/or OIRTC counterpart, we estimate the median redshift to be z = 2.6 ± 0.1 for SMGs with S{sub 850} > 1 mJy. We also use this new large sample to study the clustering of SMGs and the far-infrared properties of the unidentified submillimeter sources by stacking their Herschel SPIRE far-infrared emission.

  16. The Hawaii SCUBA-2 Lensing Cluster Survey: Radio-detected Submillimeter Galaxies in the HST Frontier Fields

    Science.gov (United States)

    Hsu, Li-Yen; Desai, Vandana; Murphy, Eric J.; Cowie, Lennox L.; Heywood, Ian; Momjian, Emmanuel; Barger, Amy J.; Smail, Ian

    2017-05-01

    In this second paper of the Hawaii SCUBA-2 Lensing Cluster Survey series, we cross-match SCUBA-2 maps with 3 and 6 GHz images from the Janksy-VLA Frontier Fields Legacy Survey for three cluster fields, MACS J0416.1-2403, MACS J0717.5+3745, and MACS J1149.5+2223. Within the HST coverage, 14 out of 44 850 μm sources have 3 GHz counterparts, five of which are also detected at 6 GHz. The 850 μm flux densities of these detected sources span from 0.7 to 4.4 mJy after correcting for lensing amplification. The median redshift of the sample is z={1.28}-0.09+0.07, much lower than the typical redshifts (z = 2-3) of brighter submillimeter galaxies (SMGs) in the literature. In addition, we find that our sources have lower dust temperatures than those of the brighter SMGs. This is also confirmed by an analysis of the ratio between infrared star-formation rate and 850 μm flux density. However, these 14 sources may not represent the general submillimeter population at the same flux range, given that the SCUBA-2 sources without radio counterparts are likely at higher redshifts. Detection of these sources would require deeper radio images or submillimeter interferometry.

  17. 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...

  18. CO(J = 3-2) on-the-fly mapping of the nearby spiral galaxies NGC 628 and NGC 7793: Spatially resolved CO(J = 3-2) star-formation law

    Science.gov (United States)

    Muraoka, Kazuyuki; Takeda, Miho; Yanagitani, Kazuki; Kaneko, Hiroyuki; Nakanishi, Kouichiro; Kuno, Nario; Sorai, Kazuo; Tosaki, Tomoka; Kohno, Kotaro

    2016-04-01

    We present the results of CO(J = 3-2) on-the-fly mappings of two nearby non-barred spiral galaxies, NGC 628 and NGC 7793, with the Atacama Submillimeter Telescope Experiment at an effective angular resolution of 25″. We successfully obtained global distributions of CO(J = 3-2) emission over the entire disks at a sub-kpc resolution for both galaxies. We examined the spatially resolved (sub-kpc) relationship between CO(J = 3-2) luminosities (L^' }_CO(3-2)) and infrared (IR) luminosities (LIR) for NGC 628, NGC 7793, and M 83, and compared it with global luminosities of a JCMT (James Clerk Maxwell Telescope) Nearby Galaxy Legacy Survey sample. We found a striking linear L^' }_CO(3-2)-LIR correlation over the four orders of magnitude, and the correlation is consistent even with that for ultraluminous IR galaxies and submillimeter-selected galaxies. In addition, we examined the spatially resolved relationship between CO(J = 3-2) intensities (ICO(3-2)) and extinction-corrected star formation rates (SFRs) for NGC 628, NGC 7793, and M 83, and compared it with that for Giant Molecular Clouds in M 33 and 14 nearby galaxy centers. We found a linear ICO(3-2)-SFR correlation with ˜1 dex scatter. We conclude that the CO(J = 3-2) star-formation law (i.e., linear L^' }_CO(3-2)-LIR and ICO(3-2)-SFR correlations) is universally applicable to various types and spatial scales of galaxies; from spatially resolved nearby galaxy disks to distant IR-luminous galaxies, within ˜1 dex scatter.

  19. 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.

  20. Fast-Growing SMBHs in Fast-Growing Galaxies, at High Redshifts: The Role of Major Mergers As Revealed by ALMA

    Directory of Open Access Journals (Sweden)

    Benny Trakhtenbrot

    2017-11-01

    Full Text Available We present a long-term, multi-wavelength project to understand the epoch of fastest growth of the most massive black holes by using a sample of 40 luminous quasars at z ≃ 4.8. These quasars have rather uniform properties, with typical accretion rates and black hole masses of L/LEdd ≃ 0.7 and MBH ≃ 109M⊙. The sample consists of “FIR-bright” sources with a previous Herschel/SPIRE detection, suggesting SFR > 1,000 M⊙ yr−1, as well as of “FIR-faint” sources for which Herschel stacking analysis implies a typical SFR of ~400 M⊙ yr−1. Six of the quasars have been observed by ALMA in [C ii] λ157.74μm line emission and adjacent rest-frame 150μm continuum, to study the dusty cold ISM. ALMA detected companion, spectroscopically confirmed sub-mm galaxies (SMGs for three sources—one FIR-bright and two FIR-faint. The companions are separated by ~14–45 kpc from the quasar hosts, and we interpret them as major galaxy interactions. Our ALMA data therefore clearly support the idea that major mergers may be important drivers for rapid, early SMBH growth. However, the fact that not all high-SFR quasar hosts are accompanied by interacting SMGs, and their ordered gas kinematics observed by ALMA, suggest that other processes may be fueling these systems. Our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid SMBH growth.

  1. 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.

  2. Morphology of Seyfert Galaxies

    OpenAIRE

    Chen, Yen-Chen; Hwang, Chorng-Yuan

    2017-01-01

    We probed the relation between properties of Seyfert nuclei and morphology of their host galaxies. We selected Seyfert galaxies from the Sloan Digital Sky Survey with redshifts less 0.2 identified by the V\\'{e}ron Catalog (13th). We used the "{\\it{FracDev}}" parameter from SDSS galaxy fitting models to represent the bulge fractions of the Seyfert host galaxies. We found that the host galaxies of Seyfert 1 and Seyfert 2 are dominated by large bulge fractions, and Seyfert 2 galaxies are more li...

  3. MID-INFRARED PROPERTIES OF NEARBY LUMINOUS INFRARED GALAXIES. I. SPITZER INFRARED SPECTROGRAPH SPECTRA FOR THE GOALS SAMPLE

    Energy Technology Data Exchange (ETDEWEB)

    Stierwalt, S.; Armus, L.; Surace, J. A.; Inami, H.; Petric, A. O.; Diaz-Santos, T.; Haan, S.; Howell, J.; Marshall, J. [Spitzer Science Center, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Charmandaris, V. [Department of Physics and ITCP, University of Crete, GR-71003 Heraklion (Greece); Kim, D. C. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Mazzarella, J. M.; Chan, B. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Spoon, H. W. W. [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Veilleux, S. [Astronomy Department, University of Maryland, College Park, MD 20742 (United States); Evans, A. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States); Sanders, D. B. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96825 (United States); Appleton, P. [NASA Herschel Science Center, 770 S. Wilson Ave., Pasadena, CA 91125 (United States); Bothun, G. [Physics Department, University of Oregon, Eugene, OR 97402 (United States); Bridge, C. R., E-mail: sabrinas@virginia.edu [Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); and others

    2013-05-01

    emission, suggesting that the obscuring (cool) dust is associated with the outer regions of the starburst and not simply a measure of the dust along the line of sight through a large, dusty disk. A marked decline is seen for the fraction of high EQW (star formation dominated) sources as the merger progresses. The decline is accompanied by an increase in the fraction of composite sources while the fraction of sources where an AGN dominates the MIR emission remains low. When compared to the MIR spectra of submillimeter galaxies (SMGs) at z {approx} 2, both the average GOALS LIRG and ULIRG spectra are more absorbed at 9.7 {mu}m and the average GOALS LIRG has more PAH emission. However, when the AGN contributions to both the local GOALS LIRGs and the high-z SMGs are removed, the average local starbursting LIRG closely resembles the starburst-dominated SMGs.

  4. A Zoo of Galaxies

    Science.gov (United States)

    Masters, Karen L.

    2015-03-01

    We live in a universe filled with galaxies with an amazing variety of sizes and shapes. One of the biggest challenges for astronomers working in this field is to understand how all these types relate to each other in the background of an expanding universe. Modern astronomical surveys (like the Sloan Digital Sky Survey) have revolutionised this field of astronomy, by providing vast numbers of galaxies to study. The sheer size of the these databases made traditional visual classification of the types galaxies impossible and in 2007 inspired the Galaxy Zoo project (www.galaxyzoo.org); starting the largest ever scientific collaboration by asking members of the public to help classify galaxies by type and shape. Galaxy Zoo has since shown itself, in a series of now more than 30 scientific papers, to be a fantastic database for the study of galaxy evolution. In this Invited Discourse I spoke a little about the historical background of our understanding of what galaxies are, of galaxy classification, about our modern view of galaxies in the era of large surveys. I finish with showcasing some of the contributions galaxy classifications from the Galaxy Zoo project are making to our understanding of galaxy evolution.

  5. Hubble's Menagerie of Galaxies

    Indian Academy of Sciences (India)

    Srimath

    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 w as m eant by a galaxy. It w as in the 1920s that astronom ers realised that w e live in a separate galaxy, and that other galaxies w ...

  6. Accretion by the Galaxy

    NARCIS (Netherlands)

    Binney, J.; Fraternali, F.; Reylé, C.; Robin, A.; Schultheis, M.

    Cosmology requires at least half of the baryons in the Universe to be in the intergalactic medium, much of which is believed to form hot coronae around galaxies. Star-forming galaxies must be accreting from their coronae. Hi observations of external galaxies show that they have Hi halos associated

  7. 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 ...

  8. Companions of Bright Barred Shapley Ames Galaxies

    OpenAIRE

    Garcia-Barreto, J. Antonio; Carrillo, Rene; Vera-Villamizar, Nelson

    2003-01-01

    Companion galaxy environment for a subset of 78 bright and nearby barred galaxies from the Shapley Ames Catalog is presented. Among spiral barred galaxies there are Seyfert galaxies, galaxies with circumnuclear structures, galaxies not associated with any large scale galaxy cloud structure, galaxies with peculiar disk morphology (crooked arms) and galaxies with normal disk morphology; the list includes all Hubble types. The companion galaxy list includes number of companion galaxies within 20...

  9. 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.

  10. Classic Galaxy with Glamour

    Science.gov (United States)

    2005-01-01

    This color composite image of nearby NGC 300 combines the visible-light pictures from Carnegie Institution of Washington's 100-inch telescope at Las Campanas Observatory (colored red and yellow), with ultraviolet views from NASA's Galaxy Evolution Explorer. Galaxy Evolution Explorer detectors image far ultraviolet light (colored blue). This composite image traces star formation in progress. Young hot blue stars dominate the outer spiral arms of the galaxy, while the older stars congregate in the nuclear regions which appear yellow-green. Gases heated by hot young stars and shocks due to winds from massive stars and supernova explosions appear in pink, as revealed by the visible-light image of the galaxy. Located nearly 7 million light years away, NGC 300 is a member of a nearby group of galaxies known as the Sculptor Group. It is a spiral galaxy like our own Milky Way.

  11. Galaxy evolution. Galactic paleontology.

    Science.gov (United States)

    Tolstoy, Eline

    2011-07-08

    Individual low-mass stars have very long lives, comparable to the age of the universe, and can thus be used to probe ancient star formation. At present, such stars can be identified and studied only in the Milky Way and in the very closest of our neighboring galaxies, which are predominantly small dwarf galaxies. These nearby ancient stars are a fossil record that can provide detailed information about the physical processes that dominated the epoch of galaxy formation and subsequent evolution.

  12. Galaxies: The Long Wavelength View

    National Research Council Canada - National Science Library

    Fischer, J

    2000-01-01

    ... (more than 2 orders of magnitude) in the [C II]/FIR ratios in galaxies extending from blue compact dwarfs, to normal and starburst galaxies, down to elliptical and ultraluminous galaxies (ULICs...

  13. Lopsided spiral galaxies

    Indian Academy of Sciences (India)

    Lopsided spiral galaxies · Outline of the talk: · Collaborators · Background : · Lopsided distribution highlighted first: Baldwin, Lynden-Bell, & Sancisi (1980) · Lopsidedness also seen in an edge-on galaxy : NGC 891 · Slide 7 · Origin of m=1 disk distribution? Early Theoretical models: · Disk response to a lopsided halo ...

  14. Galaxies in Fligh t

    Indian Academy of Sciences (India)

    In the constellation of Corona Borealis, for example, there is a cluster containing some 400 galaxies. Our Milky Way is a member of a small cluster which embraces among others, the Andromeda Nebula and the two galaxies known as the Magellanic Clouds, which are of a relatively rare type that has no well- defined shape.

  15. 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.)

  16. 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...

  17. 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

  18. The gravitational dynamics of galaxies

    Indian Academy of Sciences (India)

    one could arrive at the number of galaxies of this size in the observable Universe – again around 1011. A few galaxies are bigger and brighter than our own, but many more are smaller, going down to dwarf galaxies which could be ten thousand times less luminous. Nevertheless, galaxies do form a distinct and unique unit ...

  19. Mysterious Blob Galaxies Revealed

    Science.gov (United States)

    2005-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 1Figure 2Figure 3 This image composite shows a giant galactic blob (red, figure 2) and the three merging galaxies NASA's Spitzer Space Telescope discovered within it (yellow, figure 3). Blobs are intensely glowing clouds of hot hydrogen gas that envelop faraway galaxies. They are about 10 times as large as the galaxies they surround. Visible-light images like the one shown in figure 2, reveal the vast extent of blobs, but don't provide much information about their host galaxies. Using its heat-seeking infrared eyes, Spitzer was able to see the dusty galaxies tucked inside one well-known blob located 11 billion light-years away. The findings reveal three monstrously bright galaxies, trillions of times brighter than the Sun, in the process of merging together (figure 3). Spitzer also observed three other blobs located in the same cosmic neighborhood, all of which were found to be glaringly bright. One of these blobs is also known to be a galactic merger, only between two galaxies instead of three. It remains to be seen whether the final two blobs studied also contain mergers. The Spitzer data were acquired by its multiband imaging photometer. The visible-light image was taken by the Blanco Telescope at the Cerro Tololo Inter-American Observatory, Chile.

  20. 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

  1. ACS Nearby Galaxy Survey

    Science.gov (United States)

    Dalcanton, Julianne

    2006-07-01

    Existing HST observations of nearby galaxies comprise a sparse and highly non-uniform archive, making comprehensive comparative studies among galaxies essentially impossible. We propose to secure HST's lasting impact on the study of nearby galaxies by undertaking a systematic, complete, and carefully crafted imaging survey of ALL galaxies in the Local Universe outside the Local Group. The resulting images will allow unprecedented measurements of: {1} the star formation history {SFH} of a >100 Mpc^3 volume of the Universe with a time resolution of Delta[log{t}]=0.25; {2} correlations between spatially resolved SFHs and environment; {3} the structure and properties of thick disks and stellar halos; and {4} the color distributions, sizes, and specific frequencies of globular and disk clusters as a function of galaxy mass and environment. To reach these goals, we will use a combination of wide-field tiling and pointed deep imaging to obtain uniform data on all 72 galaxies within a volume-limited sample extending to 3.5 Mpc, with an extension to the M81 group. For each galaxy, the wide-field imaging will cover out to 1.5 times the optical radius and will reach photometric depths of at least 2 magnitudes below the tip of the red giant branch throughout the limits of the survey volume. One additional deep pointing per galaxy will reach SNR 10 for red clump stars, sufficient to recover the ancient SFH from the color-magnitude diagram. This proposal will produce photometric information for 100 million stars {comparable to the number in the SDSS survey} and uniform multi-color images of half a square degree of sky. The resulting archive will establish the fundamental optical database for nearby galaxies, in preparation for the shift of high-resolution imaging to the near-infrared.

  2. Accretion by the Galaxy

    Directory of Open Access Journals (Sweden)

    Binney J.

    2012-02-01

    Full Text Available Cosmology requires at least half of the baryons in the Universe to be in the intergalactic medium, much of which is believed to form hot coronae around galaxies. Star-forming galaxies must be accreting from their coronae. Hi observations of external galaxies show that they have Hi halos associated with star formation. These halos are naturally modelled as ensembles of clouds driven up by supernova bubbles. These models can fit the data successfully only if clouds exchange mass and momentum with the corona. As a cloud orbits, it is ablated and forms a turbulent wake where cold high-metallicity gas mixes with hot coronal gas causing the prompt cooling of the latter. As a consequence the total mass of Hi increases. This model has recently been used to model the Leiden-Argentina-Bonn survey of Galactic Hi. The values of the model’s parameters that are required to model NGC 891, NGC 2403 and our Galaxy show a remarkable degree of consistency, despite the very different natures of the two external galaxies and the dramatic difference in the nature of the data for our Galaxy and the external galaxies. The parameter values are also consistent with hydrodynamical simulations of the ablation of individual clouds. The model predicts that a galaxy that loses its cool-gas disc for instance through a major merger cannot reform it from its corona; it can return to steady star formation only if it can capture a large body of cool gas, for example by accreting a gas-rich dwarf. Thus the model explains how major mergers can make galaxies “red and dead.”

  3. Updated Nearby Galaxy Catalog

    OpenAIRE

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

    2013-01-01

    We present an all-sky catalog of 869 nearby galaxies, having individual distance estimates within 11 Mpc or corrected radial velocities V_{LG} < 600 km/s. The catalog is a renewed and expanded version of the "Catalog of Neighboring Galaxies" by Karachentsev et al. (2004). It collects data on the following observables for the galaxies: angular diameters, apparent magnitudes in FUV-, B-, and K_s- bands, H_alpha and HI fluxes, morphological types, HI-line widths, radial velocities and distance e...

  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 Catalog of Edge-on Disk Galaxies: From Galaxies with a Bulge to Superthin Galaxies

    OpenAIRE

    Kautsch, S. J.; Grebel, E. K.; Barazza, F. D.; Gallagher, J. S.

    2005-01-01

    The formation and evolution of disk-dominated galaxies is difficult to explain, yet these objects exist. We therefore embarked on a study aimed at a better understanding of these enigmatic objects. We used data from the SDSS DR1 in order to identify edge-on galaxies with disks in a uniform, reproducible, automated fashion. We identified 3169 edge-on disk galaxies, which we subdivided into disk galaxies with bulge, intermediate types, and simple disk galaxies without any obvious bulge componen...

  6. 'Nomadic' nuclei of galaxies

    Science.gov (United States)

    Silchenko, O. K.; Lipunov, V. M.

    1985-12-01

    In this paper the authors discuss observational and theoretical arguments in favour of hypothesis on "nomad life" of active nuclei inside and outside galaxies as well as its consequences. It may be the anisotropic collapse of a supermassive star, or the disruption of a supermassive binary system after the collapse of one companion that would give birth to such nuclei. The authors predict the existence of veritable quasi-stellar active objects without any ghost galaxies.

  7. Dark matter in galaxies

    OpenAIRE

    Zasov, A. V.; Saburova, A. S.; Khoperskov, A. V.; Khoperskov, S. A.

    2017-01-01

    Dark matter in galaxies, its abundance, and its distribution remain a subject of long-standing discussion, especially in view of the fact that neither dark matter particles nor dark matter bodies have yet been found. Experts' opinions range from a very large number of completely dark galaxies exist to nonbaryonic dark matter does not exist at all in any significant amounts. We discuss astronomical evidence for the existence of dark matter and its connection with visible matter and examine att...

  8. Galaxies at High Redshift

    Science.gov (United States)

    Bauer, F. E.

    2014-10-01

    Recent years have seen tremendous progress in finding and charactering star-forming galaxies at high redshifts across the electromagnetic spectrum, giving us a more complete picture of how galaxies evolve, both in terms of their stellar and gas content, as well as the growth of their central supermassive black holes. A wealth of studies now demonstrate that star formation peaked at roughly half the age of the Universe and drops precariously as we look back to very early times, and that their central monsters apparently growth with them. At the highest-redshifts, we are pushing the boundaries via deep surveys at optical, X-ray, radio wavelengths, and more recently using gamma-ray bursts. I will review some of our accomplishments and failures. Telescope have enabled Lyman break galaxies to be robustly identified, but the UV luminosity function and star formation rate density of this population at z = 6 - 8 seems to be much lower than at z = 2 - 4. High escape fractions and a large contribution from faint galaxies below our current detection limits would be required for star-forming galaxies to reionize the Universe. We have also found that these galaxies have blue rest-frame UV colours, which might indicate lower dust extinction at z > 5. There has been some spectroscopic confirmation of these Lyman break galaxies through Lyman-α emission, but the fraction of galaxies where we see this line drops at z > 7, perhaps due to the onset of the Gunn-Peterson effect (where the IGM is opaque to Lyman-α).

  9. Dwarf elliptical galaxies

    Science.gov (United States)

    Ferguson, Henry C.; Binggeli, Bruno

    1994-01-01

    Dwarf elliptical (dE) galaxies, with blue absolute magnitudes typically fainter than M(sub B) = -16, are the most numerous type of galaxy in the nearby universe. Tremendous advances have been made over the past several years in delineating the properties of both Local Group satellite dE's and the large dE populations of nearby clusters. We review some of these advances, with particular attention to how well currently availiable data can constrain (a) models for the formation of dE's, (b) the physical and evolutionary connections between different types of galaxies that overlap in the same portion of the mass-spectrum of galaxies, (c) the contribution of dE's to the galaxy luminosity functions in clusters and the field, (d) the star-forming histories of dE's and their possible contribution to faint galaxy counts, and (e) the clustering properties of dE's. In addressing these issues, we highlight the extent to which selection effects temper these constraints, and outline areas where new data would be particularly valuable.

  10. 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

  11. 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

  12. 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.

  13. Using CO as a Physical Probe of the SF Activity in the Planck-Herschel Selected Hyper Luminous Infrared Galaxies

    Science.gov (United States)

    Harrington, Kevin

    2018-01-01

    Multi-J CO line studies are essential for quantifying the physical properties of the star-forming ISM, yet it is observationally expensive to detect those faint CO emission lines at high redshift. Our eight Planck-Herschel selected galaxies, with apparent LIR > 1013‑14 L⊙, serve as the best laboratories to conduct such a CO spectral line energy distribution analysis at high-z. Using our GBT and LMT (Jup = 1-3) measurements, we trace the bulk molecular gas mass, finding relatively large star formation efficiencies (as traced by the LIR-to-L’CO(1‑0) ratio) consistent with a starburst mode of activity. With our mid-J (Jup = 4-8) CO line measurements, obtained with the IRAM 30m telescope, we find gas excitation conditions ranging from sub-thermal SMGs to highly excited local starbursts out to Jup = 5-8. The consistently high velocity-integrated line intensities at Jup = 5-8 indicates the presence a warm/dense component responsible for exciting the higher-J CO lines, therefore we use coupled non-LTE large velocity gradient and dust radiative transfer models to begin characterising the two-component molecular ISM in these strongly lensed systems.

  14. Seeing Baby Dwarf Galaxies

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Visible/DSS Click on image for larger version Ultraviolet/GALEX Click on image for larger version Poster Version Click on image for larger version The unique ultraviolet vision of NASA's Galaxy Evolution Explorer reveals, for the first time, dwarf galaxies forming out of nothing more than pristine gas likely leftover from the early universe. Dwarf galaxies are relatively small collections of stars that often orbit around larger galaxies like our Milky Way. The forming dwarf galaxies shine in the far ultraviolet spectrum, rendered as blue in the call-out on the right hand side of this image. Near ultraviolet light, also obtained by the Galaxy Evolution Explorer, is displayed in green, and visible light from the blue part of the spectrum here is represented by red. The clumps (in circles) are distinctively blue, indicating they are primarily detected in far ultraviolet light. The faint blue overlay traces the outline of the Leo Ring, a huge cloud of hydrogen and helium that orbits around two massive galaxies in the constellation Leo (left panel). The cloud is thought likely to be a primordial object, an ancient remnant of material that has remained relatively unchanged since the very earliest days of the universe. Identified about 25 years ago by radio waves, the ring cannot be seen in visible light. Only a portion of the Leo Ring has been imaged in the ultraviolet, but this section contains the telltale ultraviolet signature of recent massive star formation within this ring of pristine gas. Astronomers have previously only seen dwarf galaxies form out of gas that has already been cycled through a galaxy and enriched with metals elements heavier than helium produced as stars evolve. The visible data come from the Digitized Sky Survey of the Space Telescope Science Institute in Baltimore, Md. The Leo Ring visible image (left

  15. Tidal alignment of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  16. Galaxy clusters: Falling into line

    Science.gov (United States)

    Sifón, Cristóbal

    2017-07-01

    Analysis of Hubble Space Telescope observations shows that the well-known alignment between the central galaxy of a galaxy cluster and its host cluster has been in place for at least ten billion years.

  17. Velocity-metallicity correlation for high-z DLA galaxies

    DEFF Research Database (Denmark)

    Ledoux, C.; Petitjean, P.; Fynbo, J.P.U.

    2006-01-01

    Galaxies: halos, galaxies: high-redshift, galaxies: ISM, quasars: absorption lines, cosmology: observations Udgivelsesdato: Oct.......Galaxies: halos, galaxies: high-redshift, galaxies: ISM, quasars: absorption lines, cosmology: observations Udgivelsesdato: Oct....

  18. Detection of Lyman/alpha emission from a DLA galaxy

    DEFF Research Database (Denmark)

    Moller, P.; Fynbo, Johan Peter Uldall; Fall, S.M

    2004-01-01

    HIGH-REDSHIFT; BREAK GALAXIES; STARFORMATION; DISK GALAXIES; METAL ENRICHMENT; HOST GALAXY; ABSORPTION; ABSORBER; SYSTEMS; SPECTROSCOPY......HIGH-REDSHIFT; BREAK GALAXIES; STARFORMATION; DISK GALAXIES; METAL ENRICHMENT; HOST GALAXY; ABSORPTION; ABSORBER; SYSTEMS; SPECTROSCOPY...

  19. 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 = 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.

  20. Double-Barred Galaxies

    OpenAIRE

    Erwin, Peter

    2009-01-01

    I present a brief review of what is known about double-barred galaxies, where a small ("inner") bar is nested inside a larger ("outer") bar; the review is focused primarily on their demographics and photometric properties. Roughly 20% of S0--Sb galaxies are double-barred; they may be rarer in later Hubble types. Inner bars are typically ~ 500 pc in radius (~ 12% the size of outer bars), but sizes range from ~ 100 pc to > 1 kpc. The structure of at least some inner bars appears very similar to...

  1. Galaxy S II

    CERN Document Server

    Gralla, Preston

    2011-01-01

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

  2. A DETAILED GRAVITATIONAL LENS MODEL BASED ON SUBMILLIMETER ARRAY AND KECK ADAPTIVE OPTICS IMAGING OF A HERSCHEL-ATLAS SUBMILLIMETER GALAXY AT z = 4.243 {sup ,} {sup ,}

    Energy Technology Data Exchange (ETDEWEB)

    Bussmann, R. S.; Gurwell, M. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Fu Hai; Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Smith, D. J. B.; Bonfield, D.; Dunne, L. [Centre for Astrophysics, Science and Technology Research Institute, University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Dye, S.; Eales, S. [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Auld, R. [Cardiff University, School of Physics and Astronomy, Queens Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Baes, M.; Fritz, J. [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); Cava, A. [Departamento de Astrofisica, Facultad de CC. Fisicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Clements, D. L.; Dariush, A. [Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Coppin, K. [Department of Physics, McGill University, Ernest Rutherford Building, 3600 Rue University, Montreal, Quebec, H3A 2T8 (Canada); Dannerbauer, H. [Universitaet Wien, Institut fuer Astronomie, Tuerkenschanzstrasse 17, 1180 Wien, Oesterreich (Austria); De Zotti, G. [Universita di Padova, Dipto di Astronomia, Vicolo dell' Osservatorio 2, IT 35122, Padova (Italy); Hopwood, R., E-mail: rbussmann@cfa.harvard.edu [Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); and others

    2012-09-10

    We present high-spatial resolution imaging obtained with the Submillimeter Array (SMA) at 880 {mu}m and the Keck adaptive optics (AO) system at the K{sub S}-band of a gravitationally lensed submillimeter galaxy (SMG) at z = 4.243 discovered in the Herschel Astrophysical Terahertz Large Area Survey. The SMA data (angular resolution Almost-Equal-To 0.''6) resolve the dust emission into multiple lensed images, while the Keck AO K{sub S}-band data (angular resolution Almost-Equal-To 0.''1) resolve the lens into a pair of galaxies separated by 0.''3. We present an optical spectrum of the foreground lens obtained with the Gemini-South telescope that provides a lens redshift of z{sub lens} = 0.595 {+-} 0.005. We develop and apply a new lens modeling technique in the visibility plane that shows that the SMG is magnified by a factor of {mu} = 4.1 {+-} 0.2 and has an intrinsic infrared (IR) luminosity of L{sub IR} = (2.1 {+-} 0.2) Multiplication-Sign 10{sup 13} L{sub Sun }. We measure a half-light radius of the background source of r{sub s} = 4.4 {+-} 0.5 kpc which implies an IR luminosity surface density of {Sigma}{sub IR} (3.4 {+-} 0.9) Multiplication-Sign 10{sup 11} L{sub Sun} kpc{sup -2}, a value that is typical of z > 2 SMGs but significantly lower than IR luminous galaxies at z {approx} 0. The two lens galaxies are compact (r{sub lens} Almost-Equal-To 0.9 kpc) early-types with Einstein radii of {theta}{sub E1} 0.57 {+-} 0.01 and {theta}{sub E2} = 0.40 {+-} 0.01 that imply masses of M{sub lens1} = (7.4 {+-} 0.5) Multiplication-Sign 10{sup 10} M{sub Sun} and M{sub lens2} = (3.7 {+-} 0.3) Multiplication-Sign 10{sup 10} M{sub Sun }. The two lensing galaxies are likely about to undergo a dissipationless merger, and the mass and size of the resultant system should be similar to other early-type galaxies at z {approx} 0.6. This work highlights the importance of high spatial resolution imaging in developing models of strongly lensed galaxies

  3. What Are S0 Galaxies?

    OpenAIRE

    Bergh, Sidney van den

    2009-01-01

    The data collected in the Shapley-Ames catalog of bright galaxies show that lenticular (S0) galaxies are typically about a magnitude fainter than both elliptical (E) and early spiral (Sa) galaxies. Hubble (1936) was therefore wrong to regard S0 galaxies as being intermediate between morphological types E and Sa. The observation that E5-E7 galaxies are significantly fainter than objects of sub-types E0-E5 suggests that many of the flattest 'ellipticals' may actually be misclassified lenticular...

  4. Featured Image: Identifying Weird Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-08-01

    Hoags Object, an example of a ring galaxy. [NASA/Hubble Heritage Team/Ray A. Lucas (STScI/AURA)]The above image (click for the full view) shows PanSTARRSobservationsof some of the 185 galaxies identified in a recent study as ring galaxies bizarre and rare irregular galaxies that exhibit stars and gas in a ring around a central nucleus. Ring galaxies could be formed in a number of ways; one theory is that some might form in a galaxy collision when a smaller galaxy punches through the center of a larger one, triggering star formation around the center. In a recent study, Ian Timmis and Lior Shamir of Lawrence Technological University in Michigan explore ways that we may be able to identify ring galaxies in the overwhelming number of images expected from large upcoming surveys. They develop a computer analysis method that automatically finds ring galaxy candidates based on their visual appearance, and they test their approach on the 3 million galaxy images from the first PanSTARRS data release. To see more of the remarkable galaxies the authors found and to learn more about their identification method, check out the paper below.CitationIan Timmis and Lior Shamir 2017 ApJS 231 2. doi:10.3847/1538-4365/aa78a3

  5. The Hooked Galaxy

    Science.gov (United States)

    2006-06-01

    Life is not easy, even for galaxies. Some indeed get so close to their neighbours that they get rather distorted. But such encounters between galaxies have another effect: they spawn new generations of stars, some of which explode. ESO's VLT has obtained a unique vista of a pair of entangled galaxies, in which a star exploded. Because of the importance of exploding stars, and particularly of supernovae of Type Ia [1], for cosmological studies (e.g. relating to claims of an accelerated cosmic expansion and the existence of a new, unknown, constituent of the universe - the so called 'Dark Energy'), they are a preferred target of study for astronomers. Thus, on several occasions, they pointed ESO's Very Large Telescope (VLT) towards a region of the sky that portrays a trio of amazing galaxies. MCG-01-39-003 (bottom right) is a peculiar spiral galaxy, with a telephone number name, that presents a hook at one side, most probably due to the interaction with its neighbour, the spiral galaxy NGC 5917 (upper right). In fact, further enhancement of the image reveals that matter is pulled off MCG-01-39-003 by NGC 5917. Both these galaxies are located at similar distances, about 87 million light-years away, towards the constellation of Libra (The Balance). ESO PR Photo 22/06 ESO PR Photo 22/06 The Hooked Galaxy and its Companion NGC 5917 (also known as Arp 254 and MCG-01-39-002) is about 750 times fainter than can be seen by the unaided eye and is about 40,000 light-years across. It was discovered in 1835 by William Herschel, who strangely enough, seems to have missed its hooked companion, only 2.5 times fainter. As seen at the bottom left of this exceptional VLT image, a still fainter and nameless, but intricately beautiful, barred spiral galaxy looks from a distance the entangled pair, while many 'island universes' perform a cosmic dance in the background. But this is not the reason why astronomers look at this region. Last year, a star exploded in the vicinity of the hook

  6. Jets in Active Galaxies

    Indian Academy of Sciences (India)

    tended regions of emission. These jets, which occur across the electromagnetic spectrum, are powered by supermassive black holes in the centres of the host galaxies. Jets are seen on the scale of parsecs in the nuclear regions to those which power the giant radio sources extending over several mega- parsecs. These jets ...

  7. Formation of Triaxial Galaxy

    Directory of Open Access Journals (Sweden)

    Jang-Hyeon Park

    1987-06-01

    Full Text Available Results of N-body simulation of dissipationless cold collapse of spherical gravitating system are presented. We compared the results with properties of elliptical galaxies. The system gradually evolved to triaxial system. The projected density profile is in good agreement with observations. In addition to triaxial instability, it seems that there is another instability.

  8. Outskirts of galaxies

    CERN Document Server

    Lee, Janice; Paz, Armando

    2017-01-01

    This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and a...

  9. The Mutable Galaxies -10 ...

    Indian Academy of Sciences (India)

    Perhaps one could then compare this with what is observed in galaxies. Let us find out how this can be quantified in order to be able to compare with observations. The second type of stars tend to 'lock up' a fraction of mass since they do not recycle their processed material. Let us call this fraction the 'lock-up fraction', 0:. Let.

  10. Green valley galaxies

    Directory of Open Access Journals (Sweden)

    Salim S.

    2014-01-01

    Full Text Available The “green valley” is a wide region separating the blue and the red peaks in the ultraviolet-optical color magnitude diagram, first revealed using GALEX UV photometry. The term was coined by Christopher Martin (Caltech, in 2005. Green valley highlights the discriminating power of UV to very low relative levels of ongoing star formation, to which the optical colors, including u−r, are insensitive. It corresponds to massive galaxies below the star-forming, “main” sequence, and therefore represents a critical tool for the study of the quenching of star formation and its possible resurgence in otherwise quiescent galaxies. This article reviews the results pertaining to (predominantly disk morphology, structure, environment, dust content and gas properties of green valley galaxies in the local universe. Their relationship to AGN is also discussed. Attention is given to biases emerging from defining the “green valley” using optical colors. We review various evolutionary scenarios and we present evidence for a new one, the quasi-static view of the green valley, in which the majority (but not all of galaxies currently in the green valley were only partially quenched in the distant past and now participate in a slow cosmic decline of star formation, which also drives down the activity on the main sequence, presumably as a result of the dwindling accretion/cooling onto galaxy disks. This emerging synthetic picture is based on the findings from Fang et al. (2012, Salim et al. (2012 and Martin et al. (2007, as well as other results.

  11. wft4galaxy: a workflow testing tool for galaxy.

    Science.gov (United States)

    Piras, Marco Enrico; Pireddu, Luca; Zanetti, Gianluigi

    2017-12-01

    Workflow managers for scientific analysis provide a high-level programming platform facilitating standardization, automation, collaboration and access to sophisticated computing resources. The Galaxy workflow manager provides a prime example of this type of platform. As compositions of simpler tools, workflows effectively comprise specialized computer programs implementing often very complex analysis procedures. To date, no simple way to automatically test Galaxy workflows and ensure their correctness has appeared in the literature. With wft4galaxy we offer a tool to bring automated testing to Galaxy workflows, making it feasible to bring continuous integration to their development and ensuring that defects are detected promptly. wft4galaxy can be easily installed as a regular Python program or launched directly as a Docker container-the latter reducing installation effort to a minimum. Available at https://github.com/phnmnl/wft4galaxy under the Academic Free License v3.0. marcoenrico.piras@crs4.it.

  12. 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

  13. The SCUBA-2 Cosmology Legacy Survey: The EGS deep field - II. Morphological transformation and multi-wavelength properties of faint submillimetre galaxies

    Science.gov (United States)

    Zavala, J. A.; Aretxaga, I.; Dunlop, J. S.; Michałowski, M. J.; Hughes, D. H.; Bourne, N.; Chapin, E.; Cowley, W.; Farrah, D.; Lacey, C.; Targett, T.; van der Werf, P.

    2018-01-01

    We present a multi-wavelength analysis of galaxies selected at 450 and 850 {μ m} from the deepest SCUBA-2 observations in the Extended Groth Strip (EGS) field, which have an average depth of σ450 = 1.9 and σ _850=0.46 mJy beam^{-1} over ˜70 arcmin2. The final sample comprises 95 sources: 56 (59 %) are detected at both wavelengths, 31 (33 %) are detected only at 850 {μ m}, and 8 (8 %) are detected only at 450 {μ m}. We identify counterparts for 75 % of the whole sample. The redshift distributions of the 450 and 850 {μ m} samples peak at different redshifts with median values of \\bar{z}=1.66± 0.18 and \\bar{z}=2.30± 0.20, respectively. However, the two populations have similar IR luminosities, SFRs, and stellar masses, with mean values of 1.5 ± 0.2 × 1012 L⊙, 150 ± 20 M⊙/yr, and 9.0 ± 0.6 × 1010 M⊙, respectively. This places most of our sources (≳ 85 %) on the high-mass end of the `main-sequence' of star-forming galaxies. Exploring the IR excess vs UV-slope (IRX-β) relation we find that the most luminous galaxies are consistent with the Meurer law, while the less luminous galaxies lie below this relation. Using the results of a two-dimensional modelling of the HST H160-band imaging, we derive a median Sérsic index of n=1.4^{+0.3}_{-0.1} and a median half-light radius of r1/2 = 4.8 ± 0.4 kpc. Based on a visual-like classification in the same band, we find that the dominant component for most of the galaxies at all redshifts is a disk-like structure, although there is a transition from irregular disks to disks with a spheroidal component at z ˜ 1.4, which morphologically supports the scenario of SMGs as progenitors of massive elliptical galaxies.

  14. Radio Galaxy Zoo: A Search for Hybrid Morphology Radio Galaxies

    Science.gov (United States)

    Kapińska, A. D.; Terentev, I.; Wong, O. I.; Shabala, S. S.; Andernach, H.; Rudnick, L.; Storer, L.; Banfield, J. K.; Willett, K. W.; de Gasperin, F.; Lintott, C. J.; López-Sánchez, Á. R.; Middelberg, E.; Norris, R. P.; Schawinski, K.; Seymour, N.; Simmons, B.

    2017-12-01

    Hybrid morphology radio sources (HyMoRS) are a rare type of radio galaxy that display different Fanaroff-Riley classes on opposite sides of their nuclei. To enhance the statistical analysis of HyMoRS, we embarked on a large-scale search of these sources within the international citizen science project, Radio Galaxy Zoo (RGZ). Here, we present 25 new candidate hybrid morphology radio galaxies. Our selected candidates are moderate power radio galaxies ({L}{median}=4.7× {10}24 W Hz-1 sr-1) at redshifts 0.14 1 Mpc) radio galaxies, one resides at the center of a galaxy cluster, and one is hosted by a rare green bean galaxy. Although the origin of the hybrid morphology radio galaxies is still unclear, this type of radio source starts depicting itself as a rather diverse class. We discuss hybrid radio morphology formation in terms of the radio source environment (nurture) and intrinsically occurring phenomena (nature; activity cessation and amplification), showing that these peculiar radio galaxies can be formed by both mechanisms. While high angular resolution follow-up observations are still necessary to confirm our candidates, we demonstrate the efficacy of the RGZ in the pre-selection of these sources from all-sky radio surveys, and report the reliability of citizen scientists in identifying and classifying complex radio sources.

  15. Occurrence of LINER galaxies within the galaxy group environment

    Science.gov (United States)

    Coldwell, Georgina V.; Pereyra, Luis; Alonso, Sol; Donoso, Emilio; Duplancic, Fernanda

    2017-05-01

    We study the properties of a sample of 3967 low-ionization nuclear emission-line region (LINER) galaxies selected from SDSS-DR7, with respect to their proximity to galaxy groups. The host galaxies of LINERs have been analysed and compared with a well-defined control sample of 3841 non-LINER galaxies matched in redshift, luminosity, colour, morphology, age and stellar mass content. We find no difference between LINER and control galaxies in terms of the colour and age of stellar population as a function of the virial mass and distance to the geometric centre of the group. However, we find that LINERs are more likely to populate low-density environments in spite of their morphology, which is typical of high-density regions such as rich galaxy clusters. For rich (poor) galaxy groups, the occurrence of LINERs is approximately two times lower (higher) than the occurrence of matched, non-LINER galaxies. Moreover, LINER hosts do not seem to follow the expected morphology-density relation in groups of high virial mass. The high frequency of LINERs in low-density regions could be due to the combination of a sufficient gas reservoir to power the low-ionization emission and/or enhanced galaxy interaction rates benefiting the gas flow towards their central regions.

  16. Galaxy clusters and cosmology

    CERN Document Server

    White, S

    1994-01-01

    Galaxy clusters are the largest coherent objects in Universe. It has been known since 1933 that their dynamical properties require either a modification of the theory of gravity, or the presence of a dominant component of unseen material of unknown nature. Clusters still provide the best laboratories for studying the amount and distribution of this dark matter relative to the material which can be observed directly -- the galaxies themselves and the hot,X-ray-emitting gas which lies between them.Imaging and spectroscopy of clusters by satellite-borne X -ray telescopes has greatly improved our knowledge of the structure and composition of this intergalactic medium. The results permit a number of new approaches to some fundamental cosmological questions,but current indications from the data are contradictory. The observed irregularity of real clusters seems to imply recent formation epochs which would require a universe with approximately the critical density. On the other hand, the large baryon fraction observ...

  17. Galaxy mapping the cosmos

    CERN Document Server

    Geach, James

    2014-01-01

    Each night, we are able to gaze up at the night sky and look at the thousands of stars that stretch to the end of our individual horizons. But the stars we see are only those that make up our own Milky Way galaxy-but one of hundreds of billions in the whole of the universe, each separated  by inconceivably huge tracts of empty space. In this book, astronomer James Geach tells the rich stories of both the evolution of galaxies and our ability to observe them, offering a fascinating history of how we've come to realize humanity's tiny place in the vast universe.             Taking us on a compel

  18. The Anatomy of Galaxies

    Science.gov (United States)

    D'Onofrio, Mauro; Rampazzo, Roberto; Zaggia, Simone; Longair, Malcolm S.; Ferrarese, Laura; Marziani, Paola; Sulentic, Jack W.; van der Kruit, Pieter C.; Laurikainen, Eija; Elmegreen, Debra M.; Combes, Françoise; Bertin, Giuseppe; Fabbiano, Giuseppina; Giovanelli, Riccardo; Calzetti, Daniela; Moss, David L.; Matteucci, Francesca; Djorgovski, Stanislav George; Fraix-Burnet, Didier; Graham, Alister W. McK.; Tully, Brent R.

    Just after WWII Astronomy started to live its "Golden Age", not differently to many other sciences and human activities, especially in the west side countries. The improved resolution of telescopes and the appearance of new efficient light detectors (e.g. CCDs in the middle eighty) greatly impacted the extragalactic researches. The first morphological analysis of galaxies were rapidly substituted by "anatomic" studies of their structural components, star and gas content, and in general by detailed investigations of their properties. As for the human anatomy, where the final goal was that of understanding the functionality of the organs that are essential for the life of the body, galaxies were dissected to discover their basic structural components and ultimately the mystery of their existence.

  19. The Galaxy's Eating Habits

    Science.gov (United States)

    Putman, M. E.; Thom, C.; Gibson, B. K.; Staveley-Smith, L.

    2004-06-01

    The possibility of a gaseous halo stream which was stripped from the Sagittarius dwarf galaxy is presented. The total mass of the neutral hydrogen along the orbit of the Sgr dwarf in the direction of the Galactic Anti-Center is 4 - 10 × 106 M⊙ (at 36 kpc, the distance to the stellar debris in this region). Both the stellar and gaseous components have negative velocities in this part of the sky, but the gaseous component extends to higher negative velocities. We suggest this gaseous stream was stripped from the main body of the dwarf 0.2 - 0.3 Gyr ago during its current orbit after a passage through a diffuse edge of the Galactic disk with a density > 10-4 cm-3. The gas would then represent the dwarf's last source of star formation fuel and explains how the galaxy was forming stars 0.5-2 Gyr ago.

  20. Black holes and galaxy formation

    CERN Document Server

    Propst, Raphael J

    2010-01-01

    Galaxies are the basic unit of cosmology. The study of galaxy formation is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning. The physics of galaxy formation is complicated because it deals with the dynamics of stars, thermodynamics of gas and energy production of stars. A black hole is a massive object whose gravitational field is so intense that it prevents any form of matter or radiation to escape. It is hypothesized that the most massive galaxies in the universe- "elliptical galaxies"- grow simultaneously with the supermassive black holes at their centers, giving us much stronger evidence that black holes control galaxy formation. This book reviews new evidence in the field.

  1. A Century of Galaxy Spectroscopy

    Science.gov (United States)

    Rubin, Vera C.

    1995-10-01

    The first successful spectrum of a galaxy, M31, was obtained in 1898 and published in a two-page paper in the young Astrophysical Journal (Scheiner 1899). Thus the first century of galaxy spectroscopy and the first century of the Astrophysical Journal are almost coincident; I celebrate both in this paper. I describe the very early history of the determination of internal kinematics in spiral galaxies, often by quoting the astronomers' own published words. By mid-century, observations with improved optical and radio telescopes offered evidence that much of the matter in a galaxy is dark. As the century ends, research interests have enlarged to include study of spheroidal and disk galaxies with complex nuclear (and other) kinematics. These complicated velocity patterns are understood as the result of interactions, acquisitions, and mergers, and offer clear evidence of the important role of gravitational effects in galaxy evolution.

  2. Galaxies in the Early Universe

    DEFF Research Database (Denmark)

    Krogager, Jens-Kristian

    in Chapter 3 is found to be a young, star-forming galaxy with evidence for strong outflows of gas. This suggests that the more evolved and metal-rich DLAs overlap with the faint end of the luminosity selected galaxies in terms of mass, metallicity, star formation rate, and age. DLAs are generally observed......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...... analyses are biased towards the brightest galaxies at all times (as these are easier to observe and identify). A complementary method relies on the absorption imprint from neutral gas in galaxies, the so-called damped Ly absorbers (DLAs) seen towards distant bright objects. This thesis seeks to understand...

  3. Dust in External Galaxies

    OpenAIRE

    Calzetti, Daniela

    2009-01-01

    Existing (Spitzer Space Telescope) and upcoming (Herschel Space Telescope) facilities are deepening our understanding of the role of dust in tracing the energy budget and chemical evolution of galaxies. The tools we are developing while exploring the local Universe will in turn become pivotal in the interpretation of the high redshift Universe when near--future facilities (the Atacama Large Millimeter Array [ALMA], the Sub--Millimeter Array [SMA], the Large Millimeter Telescope [LMT], the Jam...

  4. ARCHANGEL: Galaxy Photometry System

    Science.gov (United States)

    Schombert, James

    2011-07-01

    ARCHANGEL is a Unix-based package for the surface photometry of galaxies. While oriented for large angular size systems (i.e. many pixels), its tools can be applied to any imaging data of any size. The package core contains routines to perform the following critical galaxy photometry functions: sky determination; frame cleaning; ellipse fitting; profile fitting; and total and isophotal magnitudes. The goal of the package is to provide an automated, assembly-line type of reduction system for galaxy photometry of space-based or ground-based imaging data. The procedures outlined in the documentation are flux independent, thus, these routines can be used for non-optical data as well as typical imaging datasets. ARCHANGEL has been tested on several current OS's (RedHat Linux, Ubuntu Linux, Solaris, Mac OS X). A tarball for installation is available at the download page. The main routines are Python and FORTRAN based, therefore, a current installation of Python and a FORTRAN compiler are required. The ARCHANGEL package also contains Python hooks to the PGPLOT package, an XML processor and network tools which automatically link to data archives (i.e. NED, HST, 2MASS, etc) to download images in a non-interactive manner.

  5. NCBI BLAST+ integrated into Galaxy

    OpenAIRE

    Cock, Peter J.A.; John M. Chilton; Gr?ning, Bj?rn; James E. Johnson; Soranzo, Nicola

    2015-01-01

    Background The NCBI BLAST suite has become ubiquitous in modern molecular biology and is used for small tasks such as checking capillary sequencing results of single PCR products, genome annotation or even larger scale pan-genome analyses. For early adopters of the Galaxy web-based biomedical data analysis platform, integrating BLAST into Galaxy was a natural step for sequence comparison workflows. Findings The command line NCBI BLAST+ tool suite was wrapped for use within Galaxy. Appropriate...

  6. AGN feedback in galaxy formation

    CERN Document Server

    Antonuccio-Delogu, Vincenzo

    2010-01-01

    During the past decade, convincing evidence has been accumulated concerning the effect of active galactic nuclei (AGN) activity on the internal and external environment of their host galaxies. Featuring contributions from well-respected researchers in the field, and bringing together work by specialists in both galaxy formation and AGN, this volume addresses a number of key questions about AGN feedback in the context of galaxy formation. The topics covered include downsizing and star-formation time scales in massive elliptical galaxies, the connection between the epochs of supermassive black h

  7. An Exploration of Dusty Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-04-01

    Submillimeter galaxies i.e., galaxies that we detect in the submillimeter wavelength range are mysterious creatures. Its only within the last couple decades that weve had telescope technology capable of observing them, and were only now getting to the point where angular resolution limits allow us to examine them closely. A new study has taken advantage of new capabilities to explore the properties of a sample of 52 of thesegalaxies.Dusty Star FormationSubmillimeter galaxies are generally observed in the early universe. Though theyre faint in other wavebands, theyre extremely luminous in infrared and submillimeter their infrared luminosities are typically trillions of times the Suns luminosity. This is thought to be because these galaxies are very actively forming stars at rates of hundreds of times that of the Milky Way!Example 10 10 true-color images of ten submillimeter galaxies in the authors ALMA-identified sample. [Simpson et al. 2017]Submillimeter galaxies are also extremely dusty, so we dont see their star formation directly in optical wavelengths. Instead, we see the stellar light after its been absorbed and reemitted by interstellar dust lanes were indirectly observing heavily obscured star formation.Why look for submillimeter galaxies? Studying them can help us to learn about galaxy and star formation early in our universes history, and help us to understand how the universe has evolved into what we see locally today.Submillimeter StrugglesDue to angular resolution limitations in the past, we often couldnt pin down the exact locations of submillimeter galaxies, preventing us from examining them properly. But now a team of scientists has used the Atacama Large Millimeter/submillimeter array (ALMA) to precisely locate 52 submillimeter galaxies identified by the Submillimeter Common-User Bolometer Array (SCUBA-2) in the UKIDSS Ultra Deep Survey field.The precise locations made possible by ALMA allowed the team led by James Simpson (University of Edinburgh

  8. The luminosity function of field galaxies

    OpenAIRE

    Mahtessian, A. P.

    2011-01-01

    Schmidt's method for construction of luminosity function of galaxies is generalized by taking into account the dependence of density of galaxies from the distance in the near Universe. The logarithmical luminosity function (LLF) of field galaxies depending on morphological type is constructed. We show that the LLF for all galaxies, and also separately for elliptical and lenticular galaxies can be presented by Schechter function in narrow area of absolute magnitudes. The LLF of spiral galaxies...

  9. The dwarf galaxy population of nearby galaxy clusters

    NARCIS (Netherlands)

    Lisker, Thorsten; Wittmann, Carolin; Pak, Mina; Janz, Joachim; Bialas, Daniel; Peletier, Reynier; Grebel, Eva; Falcon Barroso, Jesus; Toloba, Elisa; Smakced Collaboration, Focus Collaboration

    The Fornax, Virgo, Ursa Major and Perseus galaxy clusters all have very different characteristics, in terms of their density, mass, and large-scale environment. We can regard these clusters as laboratories for studying environmental influence on galaxy evolution, using the sensitive low-mass

  10. QUALITATIVE INTERPRETATION OF GALAXY SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-09-10

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

  11. Galaxy collisions: A preliminary study

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.H.; Smith, B.F.

    1980-01-15

    Collisions of spherical galaxies were studied in a series of numerical experiments to see what happens when galaxies collide. Each experiment starts with two model galaxies, each consisting of 50,000 stars, moving toward each other along a specified orbit. Th series of experiments provides a systematic sampling of the parameter space spanned by the initial orbital energy and the initial angular momentum. Deeply penetrating collisions are emphasized. The collisions reported here scale to relative velocities as great as 500 km s/sup -1/, well into the range for collisions within clusters of galaxies. We find: (1) The galaxies contract momentarily to about half their original sizes shortly after close passage. This means that (a) the galaxies have ample time to respond dynamically during close passage; (b) energy first transfers into coherent mass flows within each galaxy; (c) in turn, (a) means that the impulsive and restricted three-body approximations, in which the response is ignored, are not valid for collisions of 1000 km s/sup -1/ or less. (2) The initial galaxies blend into a single dynamical system while they are near each other. This means that concepts such as energy transfer from orbital motion to internal degrees of freedom are not well defined until long after close approach, when two density maxima are well separated and each has settled down to a reasonably steady state.

  12. Nuclear activity in nearby galaxies

    NARCIS (Netherlands)

    Filho, Mercedes Esteves

    2003-01-01

    The main focus of this thesis has been the search for and study of low luminosity AGN. We have detected severa low luminosity AGN in nearby galaxies, revealing that this type of activity can occur in a broad range of galaxy types and powers. Furthermore, we have been able to establish importan

  13. Red galaxies at high redshift

    NARCIS (Netherlands)

    Wuyts, Stijn Elisabeth Raphaël

    2007-01-01

    From its origin at the center of a star to the edge, through the surrounding gas and dust in the distant galaxy, through the intergalactic medium, traveling billions of light years only to be reflected by a mirror and captured by a detector; the little amount of light observed from galaxies in the

  14. Squelched Galaxies and Dark Halos

    NARCIS (Netherlands)

    Tully, R. Brent; Somerville, Rachel S.; Trentham, Neil; Verheijen, Marc A. W.

    2002-01-01

    There is accumulating evidence that the faint end of the galaxy luminosity function might be very different in different locations. The luminosity function might be rising in rich clusters and flat in regions of low density. If galaxies form according to the model of hierarchical clustering, then

  15. Dust tori in radio galaxies

    NARCIS (Netherlands)

    van der Wolk, G.; Barthel, P. D.; Peletier, R. F.; Pel, J. W.

    Aims. We investigate the quasar - radio galaxy unification scenario and detect dust tori within radio galaxies of various types. Methods. Using VISIR on the VLT, we acquired sub-arcsecond (similar to 0.40 '') resolution N-band images, at a wavelength of 11.85 mu m, of the nuclei of a sample of 27

  16. Three types of galaxy disks

    NARCIS (Netherlands)

    Pohlen, M.; Erwin, P.; Trujillo, I.; Beckman, J. E.; Knapen, JH; Mahoney, TJ; Vazdekis, A

    2008-01-01

    We present our new scheme for the classification of radial stellar surface brightness profiles for disk galaxies. We summarize the current theoretical attempts to understand their origin and give an example of an application by comparing local galaxies with their counterparts at high redshift (z

  17. The gravitational dynamics of galaxies

    Indian Academy of Sciences (India)

    called spheroidal or elliptical galaxies form a class more amenable to idealized models, we also have many disc .... use the apparent elliptical outline to infer the angle of inclination between the plane of the galaxy and the plane ..... of f along the trajectory of a given particle in phase space. The dynamical friction term clearly.

  18. Galaxy cluster's rotation

    Science.gov (United States)

    Manolopoulou, M.; Plionis, M.

    2017-03-01

    We study the possible rotation of cluster galaxies, developing, testing, and applying a novel algorithm which identifies rotation, if such does exist, as well as its rotational centre, its axis orientation, rotational velocity amplitude, and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z ≲ 0.1 with member galaxies selected from the Sloan Digital Sky Survey DR10 spectroscopic data base. After excluding a number of substructured clusters, which could provide erroneous indications of rotation, and taking into account the expected fraction of misidentified coherent substructure velocities for rotation, provided by our Monte Carlo simulation analysis, we find that ∼23 per cent of our clusters are rotating under a set of strict criteria. Loosening the strictness of the criteria, on the expense of introducing spurious rotation indications, we find this fraction increasing to ∼28 per cent. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation within 1.5 h^{-1}_{70} Mpc that the significance of their rotation is related to the dynamically younger phases of cluster formation but after the initial anisotropic accretion and merging has been completed. Finally, finding rotational modes in galaxy clusters could lead to the necessity of correcting the dynamical cluster mass calculations.

  19. Galaxy NGC 1850

    Science.gov (United States)

    1999-01-01

    By spying on a neighboring galaxy, NASA's Hubble Space Telescope has captured an image of a young, globular-like star cluster -- a type of object unknown in our Milky Way Galaxy. The image, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://oposite.stsci.edu/pubinfo/pr/2001/25 and http://www.jpl.nasa.gov/images/wfpc. The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The double cluster NGC 1850 lies in a neighboring satellite galaxy, the Large Magellanic Cloud. It has two relatively young components. The main, globular-like cluster is in the center. A smaller cluster is seen below and to the right, composed of extremely hot, blue stars and fainter red T-Tauri stars. The main cluster is about 50 million years old; the smaller one is 4 million years old. A filigree pattern of diffuse gas surrounds NGC 1850. Scientists believe the pattern formed millions of years ago when massive stars in the main cluster exploded as supernovas. Hubble can observe a range of star types in NGC 1850, including the faint, low-mass T-Tauri stars, which are difficult to distinguish with ground-based telescopes. Hubble's fine angular resolution can pick out these stars, even in other galaxies. Massive stars of the OB type emit large amounts of energetic ultraviolet radiation, which is absorbed by the Earth's atmosphere. From Hubble's position above the atmosphere, it can detect this ultraviolet light. NGC 1850, the brightest star cluster in the Large Magellanic Cloud, is in the southern constellation of Dorado, called the Goldfish or the Swordfish. This image was created from five archival exposures taken by the Wide Field Planetary Camera 2 between April 3, 1994 and February 6, 1996. More information about the Hubble Space Telescope is online at http://www.stsci.edu. More information about the Wide Field and Planetary Camera 2 is at http://wfpc2.jpl.nasa.gov. The Space Telescope Science Institute, Baltimore, Md., manages space

  20. Creating lenticular galaxies with mergers

    Science.gov (United States)

    Querejeta, Miguel; Eliche-Moral, M. Carmen; Tapia, Trinidad; Borlaff, Alejandro; van de Ven, Glenn; Lyubenova, Mariya; Martig, Marie; Falcón-Barroso, Jesús; Méndez-Abreu, Jairo; Zamorano, Jaime; Gallego, Jesús

    2017-03-01

    Lenticular galaxies (S0s) represent the majority of early-type galaxies in the local Universe, but their formation channels are still poorly understood. While galaxy mergers are obvious pathways to suppress star formation and increase bulge sizes, the marked parallelism between spiral and lenticular galaxies (e.g. photometric bulge-disc coupling) seemed to rule out a potential merger origin. Here, we summarise our recent work in which we have shown, through N-body numerical simulations, that disc-dominated lenticulars can emerge from major mergers of spiral galaxies, in good agreement with observational photometric scaling relations. Moreover, we show that mergers simultaneously increase the light concentration and reduce the angular momentum relative to their spiral progenitors. This explains the mismatch in angular momentum and concentration between spirals and lenticulars recently revealed by CALIFA observations, which is hard to reconcile with simple fading mechanisms (e.g. ram-pressure stripping).

  1. Observing and Simulating Galaxy Evolution

    DEFF Research Database (Denmark)

    Olsen, Karen Pardos

    , but 50% smaller _CO factors, with the latter decreasing towards the center of each model galaxy. In a second study, SÍGAME is adapted to model the fine-structure line of singly ionized carbon, [CII] at 158 _m, the most powerful emission line of neutral ISM. Applying SÍGAME to the same type of galaxies......It remains a quest for modern astronomy to answer what main mechanisms set the star formation rate (SFR) of galaxies. Massive galaxies present a good starting point for such a quest due to their relatively easy detection at every redshift. Since stars form out of cold and dense gas, a comprehensive...... model for galaxy evolution should explain any observed connection between SFR and the amount and properties of the molecular gas of the interstellar medium (ISM). In proposed models of that kind, an active galactic nucleus (AGN) phase is often invoked as the cause for the decrease or cease of star...

  2. Relic galaxies: where are they?

    Science.gov (United States)

    Peralta de Arriba, L.; Quilis, V.; Trujillo, I.; Cebrián, M.; Balcells, M.

    2017-03-01

    The finding that massive galaxies grow with cosmic time fired the starting gun for the search of objects which could have survived up to the present day without suffering substantial changes (neither in their structures, neither in their stellar populations). Nevertheless, and despite the community efforts, up to now only one firm candidate to be considered one of these relics is known: NGC 1277. Curiously, this galaxy is located at the centre of one of the most rich near galaxy clusters: Perseus. Is its location a matter of chance? Should relic hunters focus their search on galaxy clusters? In order to reply this question, we have performed a simultaneous and analogous analysis using simulations (Millennium I-WMAP7) and observations (New York University Value-Added Galaxy Catalogue). Our results in both frameworks agree: it is more probable to find relics in high density environments.

  3. Large-scale galaxy bias

    Science.gov (United States)

    Jeong, Donghui; Desjacques, Vincent; Schmidt, Fabian

    2018-01-01

    Here, we briefly introduce the key results of the recent review (arXiv:1611.09787), whose abstract is as following. This review presents a comprehensive overview of galaxy bias, that is, the statistical relation between the distribution of galaxies and matter. We focus on large scales where cosmic density fields are quasi-linear. On these scales, the clustering of galaxies can be described by a perturbative bias expansion, and the complicated physics of galaxy formation is absorbed by a finite set of coefficients of the expansion, called bias parameters. The review begins with a detailed derivation of this very important result, which forms the basis of the rigorous perturbative description of galaxy clustering, under the assumptions of General Relativity and Gaussian, adiabatic initial conditions. Key components of the bias expansion are all leading local gravitational observables, which include the matter density but also tidal fields and their time derivatives. We hence expand the definition of local bias to encompass all these contributions. This derivation is followed by a presentation of the peak-background split in its general form, which elucidates the physical meaning of the bias parameters, and a detailed description of the connection between bias parameters and galaxy (or halo) statistics. We then review the excursion set formalism and peak theory which provide predictions for the values of the bias parameters. In the remainder of the review, we consider the generalizations of galaxy bias required in the presence of various types of cosmological physics that go beyond pressureless matter with adiabatic, Gaussian initial conditions: primordial non-Gaussianity, massive neutrinos, baryon-CDM isocurvature perturbations, dark energy, and modified gravity. Finally, we discuss how the description of galaxy bias in the galaxies' rest frame is related to clustering statistics measured from the observed angular positions and redshifts in actual galaxy catalogs.

  4. Confronting semi-analytic galaxy models with galaxy-matter correlations observed by CFHTLenS

    Science.gov (United States)

    Saghiha, Hananeh; Simon, Patrick; Schneider, Peter; Hilbert, Stefan

    2017-05-01

    Testing predictions of semi-analytic models of galaxy evolution against observations helps to understand the complex processes that shape galaxies. We compare predictions from the Garching and Durham models implemented on the Millennium Simulation (MS) with observations of galaxy-galaxy lensing (GGL) and galaxy-galaxy-galaxy lensing (G3L) for various galaxy samples with stellar masses in the range 0.5 ≤ M∗/ 1010M⊙ Durham models are strongly excluded by the observations at the 95% confidence level because they largely over-predict the amplitudes of the GGL and G3L signals, probably because they predict too many satellite galaxies in massive halos.

  5. Combining Galaxy-Galaxy Lensing and Galaxy Clustering: A Practical Approach

    Science.gov (United States)

    Park, Youngsoo; Krause, Elisabeth; Dodelson, Scott; Jain, Bhuvnesh; Dark Energy Survey Collaboration

    2015-04-01

    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 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 data vectors, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. We also study the effect of external priors on different subsets of these parameters. We conclude that data from the first year of DES will provide powerful constraints on the evolution of structure growth in the universe, constraining the growth function to better than 5%.

  6. Lopsided Collections of Satellite Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2016-12-01

    You might think that small satellite galaxies would be distributed evenly around their larger galactic hosts but local evidence suggests otherwise. Are satellite distributions lopsided throughout the universe?Satellites in the Local GroupThe distribution of the satellite galaxies orbiting Andromeda, our neighboring galaxy, is puzzling: 21 out of 27 ( 80%) of its satellites are on the side of Andromeda closest to us. In a similar fashion, 4 of the 11 brightest Milky Way satellites are stacked on the side closest to Andromeda.It seems to be the case, then, that satellites around our pair of galaxies preferentially occupy the space between the two galaxies. But is this behavior specific to the Local Group? Or is it commonplace throughout the universe? In a recent study, a team of scientists led by Noam Libeskind (Leibniz Institute for Astrophysics Potsdam, Germany) set out to answer this question.Properties of the galaxies included in the authors sample. Left: redshifts for galaxy pairs. Right: Number of satellite galaxies around hosts. [Adapted from Libeskind et al. 2016]Asymmetry at LargeLibeskind and collaborators tested whether this behavior is common by searching through Sloan Digital Sky Survey observations for galaxy pairs that are similar to the Milky Way/Andromeda pair. The resulting sample consists of 12,210 pairs of galaxies, which have 46,043 potential satellites among them. The team then performed statistical tests on these observations to quantify the anisotropic distribution of the satellites around the host galaxies.Libeskind and collaborators find that roughly 8% more galaxies are seen within a 15 angle facing the other galaxy of a pair than would be expected in a uniform distribution. The odds that this asymmetric behavior is randomly produced, they show, are lower than 1 in 10 million indicating that the lopsidedness of satellites around galaxies in pairs is a real effect and occurs beyond just the Local Group.Caution for ModelingProbability that

  7. THE TULLY-FISHER RELATION FOR LOW SURFACE BRIGHTNESS GALAXIES - IMPLICATIONS FOR GALAXY EVOLUTION

    NARCIS (Netherlands)

    Zwaan, M.A.; VAN DER HULST, JM; DE BLOK, WJG; MCGAUGH, SS

    1995-01-01

    We present the B-band Tully-Fisher relation for low surface brightness (LSB) galaxies. These LSB galaxies follow the same Tully-Fisher relation as normal spiral galaxies. This implies that the mass-to-light ratio (M/L) of LSB galaxies is typically a factor of 2 larger than that of normal galaxies of

  8. Galaxy bias from galaxy-galaxy lensing in the DES science verification data

    Science.gov (United States)

    Prat, J.; Sánchez, C.; Miquel, R.; Kwan, J.; Blazek, J.; Bonnett, C.; Amara, A.; Bridle, S. L.; Clampitt, J.; Crocce, M.; Fosalba, P.; Gaztanaga, E.; Giannantonio, T.; Hartley, W. G.; Jarvis, M.; MacCrann, N.; Percival, W. J.; Ross, A. J.; Sheldon, E.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Fausti Neto, A.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Lima, M.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Nord, B.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; 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.

    2018-01-01

    We present a measurement of galaxy-galaxy lensing around a magnitude-limited (iAB 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 h-1 Mpc 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 and CMB lensing for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al., while, in the lowest redshift bin (z ∼ 0.3), they show some tension with the findings in Giannantonio et al. We measure b · r to be 0.87 ± 0.11, 1.12 ± 0.16 and 1.24 ± 0.23, respectively, for the three redshift bins of width Δz = 0.2 in the range 0.2 < z < 0.8, defined with the photometric-redshift algorithm BPZ. Using a different code to split the lens sample, TPZ, leads to changes in the measured biases at the 10-20 per cent level, but it does not alter the main conclusion of this work: when comparing with Crocce et al. 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 ∼ 0.3), where we find r = 0.71 ± 0.11 when using TPZ, and 0.83 ± 0.12 with BPZ.

  9. Galaxies into the Dark Ages

    Science.gov (United States)

    Carilli, C. L.; Murphy, E. J.; Ferrara, A.; Dayal, P.

    2017-10-01

    We consider the capabilities of current and future large facilities operating at 2-3 mm wavelength to detect and image the [C II] 158 μm line from galaxies into the cosmic “dark ages” (z ˜ 10-20). The [C II] line may prove to be a powerful tool in determining spectroscopic redshifts, and galaxy dynamics, for the first galaxies. We emphasize that the nature, and even existence, of such extreme redshift galaxies, remains at the frontier of open questions in galaxy formation. In 40 hr, the Atacama Large Millimeter Array has the sensitivity to detect the integrated [C II] line emission from a moderate metallicity, active star-forming galaxy [{Z}A=0.2 {Z}⊙ ; star formation rate ({SFR})=5 {M}⊙ yr-1], at z = 10 at a significance of 6σ. The next-generation Very Large Array (ngVLA) will detect the integrated [C II] line emission from a Milky Way-like SFR galaxy ({Z}A=0.2 {Z}⊙ , {SFR}=1 {M}⊙ yr-1), at z = 15 at a significance of 6σ. Imaging simulations show that the ngVLA can determine rotation dynamics for active star-forming galaxies at z˜ 15, if they exist. Based on our very limited knowledge of the extreme redshift universe, we calculate the count rate in blind, volumetric surveys for [C II] emission at z˜ 10-20. The detection rates in blind surveys will be slow (of the order of unity per 40 hr pointing). However, the observations are well suited to commensal searches. We compare [C II] with the [O III] 88 μm line, and other ancillary information in high z galaxies that would aid these studies.

  10. Stellar populations of shell galaxies

    Science.gov (United States)

    Carlsten, S. G.; Hau, G. K. T.; Zenteno, A.

    2017-12-01

    We present a study of the inner (out to ∼1 Reff) stellar populations of nine shell galaxies. We derive stellar population parameters from long-slit spectra by both analysing the Lick indices of the galaxies and by fitting single stellar population model spectra to the full galaxy spectra. The results from the two methods agree reasonably well. A few of the shell galaxies appear to have lower central Mg2 index values than the general population of galaxies of the same central velocity dispersion, which is possibly due to a past interaction event. Our sample shows a relation between central metallicity and velocity dispersion that is consistent with previous samples of non-shell galaxies. Analysing the metallicity gradients in our sample, we find an average gradient of -0.16 ± 0.10 dex decade-1 in radius. We compare this with formation models to constrain the merging history of shell galaxies. We argue that our galaxies likely have undergone major mergers but it is unclear whether the shells formed from these events or from separate minor mergers. Additionally, we find evidence for young stellar populations ranging in age from 500 Myr to 4-5 Gyr in four of the galaxies, allowing us to speculate on the age of the shells. For NGC 5670, we use a simple dynamical model to find the time required to produce the observed distribution of shells to be roughly consistent with the age of the young subpopulation, suggesting that the shells and subpopulation possibly formed from the same event.

  11. Fire within the Antennae Galaxies

    Science.gov (United States)

    2004-01-01

    This false-color image composite from NASA's Spitzer Space Telescope reveals hidden populations of newborn stars at the heart of the colliding 'Antennae' galaxies. These two galaxies, known individually as NGC 4038 and 4039, are located around 68 million light-years away and have been merging together for about the last 800 million years. The latest Spitzer observations provide a snapshot of the tremendous burst of star formation triggered in the process of this collision, particularly at the site where the two galaxies overlap. The image is a composite of infrared data from Spitzer and visible-light data from Kitt Peak National Observatory, Tucson, Ariz. Visible light from stars in the galaxies (blue and green) is shown together with infrared light from warm dust clouds heated by newborn stars (red). The two nuclei, or centers, of the merging galaxies show up as yellow-white areas, one above the other. The brightest clouds of forming stars lie in the overlap region between and left of the nuclei. Throughout the sky, astronomers have identified many of these so-called 'interacting' galaxies, whose spiral discs have been stretched and distorted by their mutual gravity as they pass close to one another. The distances involved are so large that the interactions evolve on timescales comparable to geologic changes on Earth. Observations of such galaxies, combined with computer models of these collisions, show that the galaxies often become forever bound to one another, eventually merging into a single, spheroidal-shaped galaxy. Wavelengths of 0.44 microns are represented in blue, .70 microns in green and 8.0 microns in red. This image was taken on Dec. 24, 2003.

  12. The Assembly of Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.

    2008-05-16

    We study the formation of fifty-three galaxy cluster-size dark matter halos (M = 10{sup 14.0-14.76} M{sub {circle_dot}}) formed within a pair of cosmological {Lambda}CDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host {approx} 0.1L{sub *} galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'pre-processing' in the group environment prior to their accretion into the cluster. On average, {approx} 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; and less than {approx} 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past ({approx}< 6 Gyr) than a field halo of the same mass. These results suggest that local, cluster processes like ram-pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass; and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with {approx} 20% incorporated into the cluster halo more than 7 Gyr ago and {approx} 20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate time-scale for late-type to early-type transformation within the cluster environment to be {approx} 6 Gyr.

  13. Surface photometry of new nearby dwarf galaxies

    OpenAIRE

    Makarova, L. N.; Karachentsev, I. D.; Grebel, E. K.; Barsunova, O. Yu.

    2002-01-01

    We present CCD surface photometry of 16 nearby dwarf galaxies, many of which were only recently discovered. Our sample comprises both isolated galaxies and galaxies that are members of nearby galaxy groups. The observations were obtained in the Johnson B and V bands (and in some cases in Kron-Cousins I). We derive surface brightness profiles, total magnitudes, and integrated colors. For the 11 galaxies in our sample with distance estimates the absolute B magnitudes lie in the range of -10>Mb>...

  14. Star Formation Histories of Nearby Dwarf Galaxies

    OpenAIRE

    Grebel, Eva K.

    2000-01-01

    Properties of nearby dwarf galaxies are briefly discussed. Dwarf galaxies vary widely in their star formation histories, the ages of their subpopulations, and in their enrichment history. Furthermore, many dwarf galaxies show evidence for spatial variations in their star formation history; often in the form of very extended old populations and radial gradients in age and metallicity. Determining factors in dwarf galaxy evolution appear to be both galaxy mass and environment. We may be observi...

  15. Thick Disks of Lenticular Galaxies

    OpenAIRE

    Pohlen, M.; Balcells, M.; Luetticke, R.; Dettmar, R. -J.

    2004-01-01

    Thick disks are faint and extended stellar components found around several disk galaxies including our Milky Way. The Milky Way thick disk, the only one studied in detail, contains mostly old disk stars (~10 Gyr), so that thick disks are likely to trace the early stages of disk evolution. Previous detections of thick disk stellar light in external galaxies have been originally made for early-type, edge-on galaxies but detailed 2D thick/thin disk decompositions have been reported for only a sc...

  16. The kinematics of lopsided galaxies

    OpenAIRE

    Noordermeer, Edo; Sparke, Linda S.; Levine, Stephen E.

    2001-01-01

    Lopsidedness is a common feature in galaxies, both in the distribution of light and in the kinematics. We investigate the kinematics of a model for lopsided galaxies that consists of a disc lying off-centre in a dark halo, and circling around the halo centre. We search for families of stable, closed, non-crossing orbits, and assume that gas in our galaxies moves on these orbits. Several of our models show strong lopsided gas kinematics, especially the ones in which the disc spins around its a...

  17. Samsung Galaxy Tabs for dummies

    CERN Document Server

    Gookin, Dan

    2013-01-01

    A colorful, entertaining, and informative guide to the Samsung Galaxy family of tablets Samsung's bestselling Galaxy Tabs may come in multiple sizes, but they all share the wildly popular Android operating system and are packed with tons of top-notch tablet features. This full-color book shows you how to enjoy all the things your Galaxy Tab can do, regardless of model: browse the web, handle e-mail, manage your social media, make phone calls and video chat, read e-books, take and share photos, play music, and more. Author Dan Gookin, famous for his skill in demystifying technology, takes you

  18. Dark matter in elliptical galaxies

    Science.gov (United States)

    Carollo, C. M.; Zeeuw, P. T. DE; Marel, R. P. Van Der; Danziger, I. J.; Qian, E. E.

    1995-01-01

    We present measurements of the shape of the stellar line-of-sight velocity distribution out to two effective radii along the major axes of the four elliptical galaxies NGC 2434, 2663, 3706, and 5018. The velocity dispersion profiles are flat or decline gently with radius. We compare the data to the predictions of f = f(E, L(sub z)) axisymmetric models with and without dark matter. Strong tangential anisotropy is ruled out at large radii. We conclude from our measurements that massive dark halos must be present in three of the four galaxies, while for the fourth galaxy (NGC 2663) the case is inconclusive.

  19. Observations and Models of Galaxy Assembly Bias

    Science.gov (United States)

    Campbell, Duncan A.

    2017-01-01

    The assembly history of dark matter haloes imparts various correlations between a halo’s physical properties and its large scale environment, i.e. assembly bias. It is common for models of the galaxy-halo connection to assume that galaxy properties are only a function of halo mass, implicitly ignoring how assembly bias may affect galaxies. Recently, programs to model and constrain the degree to which galaxy properties are influenced by assembly bias have been undertaken; however, the extent and character of galaxy assembly bias remains a mystery. Nevertheless, characterizing and modeling galaxy assembly bias is an important step in understanding galaxy evolution and limiting any systematic effects assembly bias may pose in cosmological measurements using galaxy surveys.I will present work on modeling and constraining the effect of assembly bias in two galaxy properties: stellar mass and star-formation rate. Conditional abundance matching allows for these galaxy properties to be tied to halo formation history to a variable degree, making studies of the relative strength of assembly bias possible. Galaxy-galaxy clustering and galactic conformity, the degree to which galaxy color is correlated between neighbors, are sensitive observational measures of galaxy assembly bias. I will show how these measurements can be used to constrain galaxy assembly bias and the peril of ignoring it.

  20. GREEN GALAXIES IN THE COSMOS FIELD

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-10-10

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

  1. Secular Evolution in Disk Galaxies

    Science.gov (United States)

    Kormendy, John

    2013-10-01

    Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via the evolution processes that are available to them. They do this by spreading -- the inner parts shrink while the outer parts expand -- provided that some physical process efficiently transports energy or angular momentum outward. The reason is that self-gravitating systems have negative specific heats. As a result, the evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks and galaxy disks are fundamentally similar. How evolution proceeds then depends on the evolution processes that are available to each kind of self-gravitating system. These processes and their consequences for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School. I begin with a review of the formation, growth and death of bars. Then I review the slow (`secular') rearrangement of energy, angular momentum, and mass that results from interactions between stars or gas clouds and collective phenomena such as bars, oval disks, spiral structure and triaxial dark haloes. The `existence-proof' phase of this work is largely over: we have a good heuristic understanding of how nonaxisymmetric structures rearrange disk gas into outer rings, inner rings and stuff dumped onto the centre. The results of simulations correspond closely to the morphology of barred and oval galaxies. Gas that is transported to small radii reaches high densities. Observations confirm that many barred and oval galaxies have dense central concentrations of gas and star formation. The result is to grow, on timescales of a few Gyr, dense central components that are frequently mistaken for classical (elliptical-galaxy-like) bulges but that were grown slowly out of the disk (not made rapidly by major mergers). The resulting picture of secular galaxy evolution accounts for the richness observed in galaxy structure. We can distinguish between classical and pseudo

  2. Astronomy: Quasars signpost massive galaxies

    Science.gov (United States)

    Bouwens, Rychard

    2017-05-01

    The neighbourhoods of extremely bright astronomical objects called quasars in the early Universe have been incompletely probed. Observations suggest that these regions harbour some of the most massive known galaxies. See Letter p.457

  3. Globular Clusters - Guides to Galaxies

    CERN Document Server

    Richtler, Tom; Joint ESO-FONDAP Workshop on Globular Clusters

    2009-01-01

    The principal question of whether and how globular clusters can contribute to a better understanding of galaxy formation and evolution is perhaps the main driving force behind the overall endeavour of studying globular cluster systems. Naturally, this splits up into many individual problems. The objective of the Joint ESO-FONDAP Workshop on Globular Clusters - Guides to Galaxies was to bring together researchers, both observational and theoretical, to present and discuss the most recent results. Topics covered in these proceedings are: internal dynamics of globular clusters and interaction with host galaxies (tidal tails, evolution of cluster masses), accretion of globular clusters, detailed descriptions of nearby cluster systems, ultracompact dwarfs, formations of massive clusters in mergers and elsewhere, the ACS Virgo survey, galaxy formation and globular clusters, dynamics and kinematics of globular cluster systems and dark matter-related problems. With its wide coverage of the topic, this book constitute...

  4. Secular Evolution of Spiral Galaxies

    National Research Council Canada - National Science Library

    Zhang, Xiaolei

    2003-01-01

    It is now a well established fact that galaxies undergo significant morphological transformation during their lifetimes, manifesting as an evolution along the Hubble sequence from the late to the early Hubble types...

  5. Massive star clusters in galaxies.

    Science.gov (United States)

    Harris, William E

    2010-02-28

    The ensemble of all star clusters in a galaxy constitutes its star cluster system. In this review, the focus of the discussion is on the ability of star clusters, particularly the systems of old massive globular clusters (GCs), to mark the early evolutionary history of galaxies. I review current themes and key findings in GC research, and highlight some of the outstanding questions that are emerging from recent work.

  6. Enhancement classification of galaxy images

    Science.gov (United States)

    Jenkinson, John

    With the advent of astronomical imaging technology developments, and the increased capacity of digital storage, the production of photographic atlases of the night sky have begun to generate volumes of data which need to be processed autonomously. As part of the Tonantzintla Digital Sky Survey construction, the present work involves software development for the digital image processing of astronomical images, in particular operations that preface feature extraction and classification. Recognition of galaxies in these images is the primary objective of the present work. Many galaxy images have poor resolution or contain faint galaxy features, resulting in the misclassification of galaxies. An enhancement of these images by the method of the Heap transform is proposed, and experimental results are provided which demonstrate the image enhancement to improve the presence of faint galaxy features thereby improving classification accuracy. The feature extraction was performed using morphological features that have been widely used in previous automated galaxy investigations. Principal component analysis was applied to the original and enhanced data sets for a performance comparison between the original and reduced features spaces. Classification was performed by the Support Vector Machine learning algorithm.

  7. Star Formation in Tadpole Galaxies

    Directory of Open Access Journals (Sweden)

    Casiana Muñoz-Tuñon

    2014-12-01

    Full Text Available Tadpole Galaxies look like a star forming head with a tail structure to the side. They are also named cometaries. In a series of recent works we have discovered a number of issues that lead us to consider them extremely interesting targets. First, from images, they are disks with a lopsided starburst. This result is rmly  established with long slit spectroscopy in a nearby representative sample. They rotate with the head following the rotation pattern but displaced from the rotation center. Moreover, in a search for extremely metal poor (XMP galaxies, we identied tadpoles as the dominant shapes in the sample - nearly 80% of the local XMP galaxies have a tadpole morphology. In addition, the spatially resolved analysis of the metallicity shows the remarkable result that there is a metallicity drop right at the position of the head. This is contrary to what intuition would say and dicult to explain if star formation has happened from gas processed in the disk. The result could however be understood if the star formation is driven by pristine gas falling into the galaxy disk. If conrmed, we could be unveiling, for the rst time, cool  ows in action in our nearby world. The tadpole class is relatively frequent at high redshift - 10% of resolvable galaxies in the Hubble UDF but less than 1% in the local Universe. They are systems that could track cool ows and test models of galaxy formation.

  8. AGN feedback in dwarf galaxies?

    Science.gov (United States)

    Dashyan, Gohar; Silk, Joseph; Mamon, Gary A.; Dubois, Yohan; Hartwig, Tilman

    2018-02-01

    Dwarf galaxy anomalies, such as their abundance and cusp-core problems, remain a prime challenge in our understanding of galaxy formation. The inclusion of baryonic physics could potentially solve these issues, but the efficiency of stellar feedback is still controversial. We analytically explore the possibility of feedback from active galactic nuclei (AGNs) in dwarf galaxies and compare AGN and supernova (SN) feedback. We assume the presence of an intermediate-mass black hole within low-mass galaxies and standard scaling relations between the relevant physical quantities. We model the propagation and properties of the outflow and explore the critical condition for global gas ejection. Performing the same calculation for SNe, we compare the ability of AGNs and SNe to drive gas out of galaxies. We find that a critical halo mass exists below which AGN feedback can remove gas from the host halo and that the critical halo mass for an AGN is greater than the equivalent for SNe in a significant part of the parameter space, suggesting that an AGN could provide an alternative and more successful source of negative feedback than SNe, even in the most massive dwarf galaxies.

  9. Do Galaxies Follow Darwinian Evolution?

    Science.gov (United States)

    2006-12-01

    Using VIMOS on ESO's Very Large Telescope, a team of French and Italian astronomers have shown the strong influence the environment exerts on the way galaxies form and evolve. The scientists have for the first time charted remote parts of the Universe, showing that the distribution of galaxies has considerably evolved with time, depending on the galaxies' immediate surroundings. This surprising discovery poses new challenges for theories of the formation and evolution of galaxies. The 'nature versus nurture' debate is a hot topic in human psychology. But astronomers too face similar conundrums, in particular when trying to solve a problem that goes to the very heart of cosmological theories: are the galaxies we see today simply the product of the primordial conditions in which they formed, or did experiences in the past change the path of their evolution? ESO PR Photo 17/06 ESO PR Photo 45/06 Galaxy Distribution in Space In a large, three-year long survey carried out with VIMOS [1], the Visible Imager and Multi-Object Spectrograph on ESO's VLT, astronomers studied more than 6,500 galaxies over a wide range of distances to investigate how their properties vary over different timescales, in different environments and for varying galaxy luminosities [2]. They were able to build an atlas of the Universe in three dimensions, going back more than 9 billion years. This new census reveals a surprising result. The colour-density relation, that describes the relationship between the properties of a galaxy and its environment, was markedly different 7 billion years ago. The astronomers thus found that the galaxies' luminosity, their initial genetic properties, and the environments they reside in have a profound impact on their evolution. "Our results indicate that environment is a key player in galaxy evolution, but there's no simple answer to the 'nature versus nurture' problem in galaxy evolution," said Olivier Le Fèvre from the Laboratoire d'Astrophysique de Marseille

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

    Energy Technology Data Exchange (ETDEWEB)

    Prat, J.; et al.

    2016-09-26

    We present a measurement of galaxy-galaxy lensing around a magnitude-limited ($i_{AB} < 22.5$) sample of galaxies selected from the Dark Energy Survey Science Verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias $b$ and cross-correlation coefficient between the galaxy and dark matter overdensity fields $r$ in each bin, using scales above 4 Mpc/$h$ comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering (Crocce et al. 2016) and CMB lensing (Giannantonio et al. 2016) for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al. (2016), while, in the lowest redshift bin ($z\\sim0.3$), they show some tension with the findings in Giannantonio et al. (2016). Our results are found to be rather insensitive to a large range of systematic effects. We measure $b\\cdot r$ to be $0.87\\pm 0.11$, $1.12 \\pm 0.16$ and $1.24\\pm 0.23$, respectively for the three redshift bins of width $\\Delta z = 0.2$ in the range $0.2galaxy sample, except possibly at the lowest redshift bin ($z\\sim 0.3$), where we find $r = 0.71 \\pm 0.11$ when using TPZ, and $0.83 \\pm 0.12$ with BPZ, assuming the difference between the results from the two probes can be solely attributed to the cross-correlation parameter.

  11. Globular Clusters for Faint Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    The origin of ultra-diffuse galaxies (UDGs) has posed a long-standing mystery for astronomers. New observations of several of these faint giants with the Hubble Space Telescope are now lending support to one theory.Faint-Galaxy MysteryHubble images of Dragonfly 44 (top) and DFX1 (bottom). The right panels show the data with greater contrast and extended objects masked. [van Dokkum et al. 2017]UDGs large, extremely faint spheroidal objects were first discovered in the Virgo galaxy cluster roughly three decades ago. Modern telescope capabilities have resulted in many more discoveries of similar faint galaxies in recent years, suggesting that they are a much more common phenomenon than we originally thought.Despite the many observations, UDGs still pose a number of unanswered questions. Chief among them: what are UDGs? Why are these objects the size of normal galaxies, yet so dim? There are two primary models that explain UDGs:UDGs were originally small galaxies, hence their low luminosity. Tidal interactions then puffed them up to the large size we observe today.UDGs are effectively failed galaxies. They formed the same way as normal galaxies of their large size, but something truncated their star formation early, preventing them from gaining the brightness that we would expect for galaxies of their size.Now a team of scientists led by Pieter van Dokkum (Yale University) has made some intriguing observations with Hubble that lend weight to one of these models.Globulars observed in 16 Coma-cluster UDGs by Hubble. The top right panel shows the galaxy identifications. The top left panel shows the derived number of globular clusters in each galaxy. [van Dokkum et al. 2017]Globulars GaloreVan Dokkum and collaborators imaged two UDGs with Hubble: Dragonfly 44 and DFX1, both located in the Coma galaxy cluster. These faint galaxies are both smooth and elongated, with no obvious irregular features, spiral arms, star-forming regions, or other indications of tidal interactions

  12. Galaxy Zoo: Mergers - Dynamical models of interacting galaxies

    Science.gov (United States)

    Holincheck, Anthony J.; Wallin, John F.; Borne, Kirk; Fortson, Lucy; Lintott, Chris; Smith, Arfon M.; Bamford, Steven; Keel, William C.; Parrish, Michael

    2016-06-01

    The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of citizen scientists, we sample 105 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the simulation parameters generated by the project. They are now publicly available in electronic format at http://data.galaxyzoo.org/mergers.html. Though our best-fitting model parameters are not an exact match to previously published models, our method for determining uncertainty measurements will aid future comparisons between models. The dynamical clocks from our models agree with previous results of the time since the onset of star formation from starburst models in interacting systems and suggest that tidally induced star formation is triggered very soon after closest approach.

  13. Star Formation Activity of Barred Spiral Galaxies

    Science.gov (United States)

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

    2017-08-01

    We study the star formation activity of nearby galaxies with bars using a sample of late-type galaxies at 0.02≤slant z≤slant 0.05489 and {M}rgas in strongly barred galaxies are smaller than those in non-barred galaxies, and the gas metallicity is higher in strongly barred galaxies than in non-barred galaxies. The gas properties of weakly barred galaxies again show no difference from those of non-barred galaxies. We stack the optical spectra of barred and non-barred galaxies in several mass bins and fit to the stacked spectra with a spectral fitting code, STARLIGHT. We find no significant difference in stellar populations between barred and non-barred galaxies for both strongly and weakly barred galaxies. Our results are consistent with the idea that the star formation activity of barred galaxies was enhanced in the past along with significant gas consumption, and is currently lower than or similar to that of non-barred galaxies. The past star formation enhancement depends on the strength of bars.

  14. The Thousand-Ruby Galaxy

    Science.gov (United States)

    2008-09-01

    ESO's Wide Field Imager has captured the intricate swirls of the spiral galaxy Messier 83, a smaller look-alike of our own Milky Way. Shining with the light of billions of stars and the ruby red glow of hydrogen gas, it is a beautiful example of a barred spiral galaxy, whose shape has led to it being nicknamed the Southern Pinwheel. Messier 83, M83 ESO PR Photo 25/08 Spiral Galaxy Messier 83 This dramatic image of the galaxy Messier 83 was captured by the Wide Field Imager at ESO's La Silla Observatory, located high in the dry desert mountains of the Chilean Atacama Desert. Messier 83 lies roughly 15 million light-years away towards the huge southern constellation of Hydra (the sea serpent). It stretches over 40 000 light-years, making it roughly 2.5 times smaller than our own Milky Way. However, in some respects, Messier 83 is quite similar to our own galaxy. Both the Milky Way and Messier 83 possess a bar across their galactic nucleus, the dense spherical conglomeration of stars seen at the centre of the galaxies. This very detailed image shows the spiral arms of Messier 83 adorned by countless bright flourishes of ruby red light. These are in fact huge clouds of glowing hydrogen gas. Ultraviolet radiation from newly born, massive stars is ionising the gas in these clouds, causing the great regions of hydrogen to glow red. These star forming regions are contrasted dramatically in this image against the ethereal glow of older yellow stars near the galaxy's central hub. The image also shows the delicate tracery of dark and winding dust streams weaving throughout the arms of the galaxy. Messier 83 was discovered by the French astronomer Nicolas Louis de Lacaille in the mid 18th century. Decades later it was listed in the famous catalogue of deep sky objects compiled by another French astronomer and famous comet hunter, Charles Messier. Recent observations of this enigmatic galaxy in ultraviolet light and radio waves have shown that even its outer desolate regions

  15. Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

    NARCIS (Netherlands)

    Khosroshahi, Habib G.; Raouf, Mojtaba; Miraghaei, Halime; Brough, Sarah; Croton, Darren J.; Driver, Simon; Graham, Alister; 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

  16. The Road to Galaxy Formation

    CERN Document Server

    Keel, William C

    2007-01-01

    The formation of galaxies is one of the greatest puzzles in astronomy, the solution is shrouded in the depths of space and time, but has profound implications for the universe we observe today. The book discusses the beginnings of the process from cosmological observations and calculations, considers the broad features of galaxies that we need to explain and what we know of their later history. The author compares the competing theories for galaxy formation and considers the progress expected from new generations of powerful telescopes both on earth and in space. In this second edition the author has retained the observationally-based approach of the first edition, a feature which was particularly well-reviewed: Writing in Nature, Carlton Baugh noted in February 2003 that “It is refreshing, in a market dominated by theorists, to come across a book on galaxy formation written from an observational perspective. The Road to Galaxy Formation should prove to be a handy primer on observations for graduate student...

  17. Three intervening galaxy absorbers towards GRB 060418

    DEFF Research Database (Denmark)

    Ellison, S. L.; Vreeswijk, P.; Ledoux, C.

    2006-01-01

    Dust, extinction: galaxies: ISM: quasars: absorption lines: gamma-rays: bursts Udgivelsesdato: 10 August......Dust, extinction: galaxies: ISM: quasars: absorption lines: gamma-rays: bursts Udgivelsesdato: 10 August...

  18. Statistical study of some Lee galaxy groups

    Science.gov (United States)

    Mohamed, Sabry A.; Fouad, Ahmed M.

    2017-12-01

    Compact groups of galaxies are systems of small number of galaxies close to each other. They are a good laboratory to study galaxy properties, such as structure, morphology and evolution which are affected by the environment and galaxy interactions. We applied the tree clustering technique (the Euclidean separation distance coefficients) to test the physical reality of groups and used certain criteria (Sabry et al., 2009) depending on the physical attributes of the galaxies. The sample of the data is the quintets groups of Lee compact groups of galaxies (Lee et al., 2004). It is based on a modified version of Hickson's criteria (Hickson, 1982). The results reveal the membership of each galaxy and how it is related to its group. The tables of groups and their members are included. Our results indicates that 12 Groups are real groups with real members while 18 Groups have one galaxy that has attribute discordant and should be discarded from its group.

  19. Cosmology: Photons from dwarf galaxy zap hydrogen

    Science.gov (United States)

    Erb, Dawn K.

    2016-01-01

    The detection of photons sufficiently energetic to ionize neutral hydrogen, coming from a compact, star-forming galaxy, offers clues to how the first generation of galaxies may have reionized hydrogen gas in the early Universe. See Letter p.178

  20. Multiple Supernova Explosions in a Forming Galaxy

    National Research Council Canada - National Science Library

    Masayuki Umemura; Andrea Ferrara

    2004-01-01

    Ultra-high resolution hydrodynamic simulations using 1024 3 grid points are performed of a very large supernova burst in a forming galaxy, with properties similar to those inferred for Lyman Break Galaxies (LBGs...

  1. DATA MINING THE GALAXY ZOO MERGERS

    Data.gov (United States)

    National Aeronautics and Space Administration — DATA MINING THE GALAXY ZOO MERGERS STEVEN BAEHR, ARUN VEDACHALAM, KIRK BORNE, AND DANIEL SPONSELLER Abstract. Collisions between pairs of galaxies usually end in the...

  2. Ammonia Thermometry of Star Forming Galaxies

    OpenAIRE

    Mangum, Jeffrey G.; Darling, Jeremy; Henkel, Christian; Menten, Karl M.; MacGregor, Meredith; Svoboda, Brian E.; Schinnerer, Eva

    2013-01-01

    With a goal toward deriving the physical conditions in external galaxies, we present a study of the ammonia (NH$_3$) emission and absorption in a sample of star forming systems. Using the unique sensitivities to kinetic temperature afforded by the excitation characteristics of several inversion transitions of NH$_3$, we have continued our characterization of the dense gas in star forming galaxies by measuring the kinetic temperature in a sample of 23 galaxies and one galaxy offset position se...

  3. Magnetogravitodynamics model of galaxy formation

    Science.gov (United States)

    Greyber, Howard D.

    1995-07-01

    Unless the tau neutrino is discovered to have an appropriate size mass, the theories of galaxy formation involving only gravity may not fit the observations. A model within the Big Bang hypothesis is described with processes occurring after ``Breakout'' that lead to the concentration of matter along thin spatially curved current sheets. When a critical density is reached, gravitational collapse occurs, forming galaxies in many places along thin spatially curved sheets surrounding huge voids, in a cellular structure, as in the observations by Geller, Huchra et al. The origin of a primordial magnetic field concentrated in the sheets is explained. The model predicts that much of the missing dark matter is located along the thin spatially curved sheets of galaxies.

  4. Statistics of the galaxy distribution

    CERN Document Server

    Martinez, Vicent J

    2001-01-01

    Over the last decade, statisticians have developed new statistical tools in the field of spatial point processes. At the same time, observational efforts have yielded a huge amount of new cosmological data to analyze. Although the main tools in astronomy for comparing theoretical results with observation are statistical, in recent years, cosmologists have not been generally aware of the developments in statistics and vice versa.Statistics of the Galaxy Distribution describes both the available observational data on the distribution of galaxies and the applications of spatial statistics in cosmology. It gives a detailed derivation of the statistical methods used to study the galaxy distribution and the cosmological physics needed to formulate the statistical models. Because the prevalent approach in cosmological statistics has been frequentist, the authors focus on the most widely used of these methods, but they also explore Bayesian techniques that have become popular in large-scale structure studies.Describi...

  5. Formation of dwarf ellipticals and dwarf irregular galaxies by interaction of giant galaxies under environmental influence

    OpenAIRE

    Chattopadhyay, Tanuka; Debsarma, Suma; Karmakar, Pradip; Davoust, Emmanuel

    2014-01-01

    A model is proposed for the formation of gas-rich dwarf irregular galaxies and gas-poor, rotating dwarf elliptical galaxies following the interaction between two giant galaxies as a function of space density. The formation of dwarf galaxies is considered to depend on a random variable, the tidal index theta, an environmental parameter defined by Karachentsev et al. (2004), such that for theta less than zero, the formation of dwarf irregular galaxy is assured whereas for theta greater than zer...

  6. Dark matter in low surface brightness galaxies

    NARCIS (Netherlands)

    de Blok, WJG; McGaugh, SS; Persic, M; Salucci, P

    1997-01-01

    Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that LSB

  7. Central condensations in Seyfert galaxies. Pt. 1

    Energy Technology Data Exchange (ETDEWEB)

    Afanas' ev, V.L.; Pimonov, A.A.; Terebizh, V.Yu. (AN SSSR, Nizhnij Arkhyz. Spetsial' naya Astrofizicheskaya Observatoriya)

    1982-10-01

    Results of observations with scanning photometer of 7 normal and 17 Seyfert galaxies show that in the Seyfert galaxies a central regions of 3-4 kpc in size exist noted for the high stellar density. A correlation between the volume luminosity of spherical component and the luminosity of the galaxy nucleus is found.

  8. 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.

  9. Resolving gas-phase metallicity in galaxies

    NARCIS (Netherlands)

    Carton, D.J.

    2017-01-01

    Galaxies are environments where gas coalesces, cools, and is converted into stars. However, it remains unclear the exact mechanisms through which galaxies acquire, redistribute and lose their gas. The fresh gas that flows into galaxies is primarily composed of Hydrogen and Helium. But because a

  10. The extraordinary structural evolution of massive galaxies

    NARCIS (Netherlands)

    Szomoru, Daniel

    2013-01-01

    Galaxies have changed drastically over the past 10 billion years. This thesis deals with these changes, focusing on evolution in the structure of very massive galaxies with a range of stellar population properties. The main subjects addressed are the rapid changes in the sizes of old galaxies, the

  11. Galaxies with "rows": A new catalog

    Science.gov (United States)

    Butenko, M. A.; Khoperskov, A. V.

    2017-07-01

    Galaxies with "rows" in Vorontsov-Velyaminov's terminology stand out among the variety of spiral galactic patterns. A characteristic feature of such objects is the sequence of straight-line segments that forms the spiral arm. In 2001 A. Chernin and co-authors published a catalog of such galaxies which includes 204 objects from the Palomar Atlas. In this paper, we supplement the catalog with 276 objects based on an analysis of all the galaxies from the New General Catalogue and Index Catalogue. The total number of NGC and IC galaxies with rows is 406, including the objects of Chernin et al. (2001). The use of more recent galaxy images allowed us to detect more "rows" on average, compared with the catalog of Chernin et al. When comparing the principal galaxy properties we found no significant differences between galaxies with rows and all S-typeNGC/IC galaxies.We discuss twomechanisms for the formation of polygonal structures based on numerical gas-dynamic and collisionless N-body calculations, which demonstrate that a spiral pattern with rows is a transient stage in the evolution of galaxies and a system with a powerful spiral structure can pass through this stage. The hypothesis of A. Chernin et al. (2001) that the occurrence frequency of interacting galaxies is twice higher among galaxies with rows is not confirmed for the combined set of 480 galaxies. The presence of a central stellar bar appears to be a favorable factor for the formation of a system of "rows".

  12. X-ray Galaxy Clusters & Cosmology

    Science.gov (United States)

    Ettori, Stefano

    2011-09-01

    I present a summary of the four lectures given on these topics: (i) Galaxy Clusters in a cosmological context: an introduction; (ii) Galaxy Clusters in X-ray: how and what we observe, limits and prospects; (iii) X-ray Galaxy Clusters and Cosmology: total mass, gas mass & systematics; (iv) Properties of the ICM: scaling laws and metallicity.

  13. Stars at Low Metallicity in Dwarf Galaxies

    NARCIS (Netherlands)

    Tolstoy, Eline; Battaglia, Giuseppina; Cole, Andrew; Hunt, LK; Madden, S; Schneider, R

    2008-01-01

    Dwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the, epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the

  14. The Metallicity of Void Dwarf Galaxies

    NARCIS (Netherlands)

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

    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

  15. Dark Matter in Low Surface Brightness Galaxies

    NARCIS (Netherlands)

    Blok, W. J. G. de; McGaugh, S. S.

    1996-01-01

    Abstract: Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that

  16. 10 billion years of massive Galaxies

    NARCIS (Netherlands)

    Taylor, Edward Nairne Cunningham

    2009-01-01

    The most massive galaxies in the local universe are not forming new stars -- but we don’t know why. As a step towards figuring out why big galaxies stop forming stars, we set out to measure when they stop forming stars. By looking at the colors of massive galaxies have changed over 10 billion

  17. Galaxy Mergers Moulding the CGM

    Science.gov (United States)

    Hani, Maan H.; Sparre, Martin; Ellison, Sara L.; Torrey, Paul; Vogelsberger, Mark

    2017-07-01

    Galaxies are surrounded by sizeable gas reservoirs which host a significant amount of metals: the circum-galactic medium (CGM). The CGM acts as a mediator between the galaxy and the extra-galactic medium. However, our understanding of how galaxy mergers, a major evolutionary transformation, impact the CGM remains deficient. We present a theoretical study of the effect of galaxy mergers on the CGM: We use hydrodynamical cosmological zoom-in simulations of a major merger selected from the Illustris project such that the z=0 descendant is a Milky Way-like galaxy, and then re-simulated at a 40 times higher mass resolution. We include post-processing ionization modelling. This work demonstrates the effect the merger has on the characteristic size of the CGM, its metallicity and the predicted covering fraction of various commonly observed gas-phase species, such as H I, C IV and O VI. We show that merger-induced outflows can increase the CGM metallicity by 0.2-0.3 dex within 0.5 Gyr post-merger. These effects last up to 6 Gyr post-merger. While the merger increases the total metal covering fractions by factors of 2-3, the covering fractions of commonly observed UV ions decrease due to the hard ionizing radiation from the active galactic nucleus. The case study of the single simulated major merger presented in this work demonstrates the significant impact that a galaxy interaction can have on the size, metallicity and observed column densities of the CGM (Hani et al. in prep).

  18. The HIX galaxy survey II: HI kinematics of HI 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.

    2018-02-01

    By analysing a sample of galaxies selected from the HI Parkes All Sky Survey (HIPASS) to contain more than 2.5 times their expected HI content based on their optical properties, we investigate what drives these HI eXtreme (HIX) galaxies to be so HI-rich. We model the H I kinematics with the Tilted Ring Fitting Code TiRiFiC and compare the observed HIX 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 HIX 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 HIX galaxies is comparable to the control sample, (3) HIX galaxies have higher H I and baryonic specific angular momenta than control galaxies, (4) most HIX galaxies live in higher-spin haloes than most control galaxies. These results suggest that HIX 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 HIX galaxies inherits their high specific angular momentum from their halo. The H I content of HIX galaxies might be further increased by gas-rich minor mergers. This paper is based on data obtained with the Australia Telescope Compact Array (ATCA) through the large program C 2705.

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

    DEFF Research Database (Denmark)

    Razoumov, A; Sommer-Larsen, Jesper

    2006-01-01

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

  20. Watching a Cannibal Galaxy Dine

    Science.gov (United States)

    2009-11-01

    A new technique using near-infrared images, obtained with ESO's 3.58-metre New Technology Telescope (NTT), allows astronomers to see through the opaque dust lanes of the giant cannibal galaxy Centaurus A, unveiling its "last meal" in unprecedented detail - a smaller spiral galaxy, currently twisted and warped. This amazing image also shows thousands of star clusters, strewn like glittering gems, churning inside Centaurus A. Centaurus A (NGC 5128) is the nearest giant, elliptical galaxy, at a distance of about 11 million light-years. One of the most studied objects in the southern sky, by 1847 the unique appearance of this galaxy had already caught the attention of the famous British astronomer John Herschel, who catalogued the southern skies and made a comprehensive list of nebulae. Herschel could not know, however, that this beautiful and spectacular appearance is due to an opaque dust lane that covers the central part of the galaxy. This dust is thought to be the remains of a cosmic merger between a giant elliptical galaxy and a smaller spiral galaxy full of dust. Between 200 and 700 million years ago, this galaxy is indeed believed to have consumed a smaller spiral, gas-rich galaxy - the contents of which appear to be churning inside Centaurus A's core, likely triggering new generations of stars. First glimpses of the "leftovers" of this meal were obtained thanks to observations with the ESA Infrared Space Observatory , which revealed a 16 500 light-year-wide structure, very similar to that of a small barred galaxy. More recently, NASA's Spitzer Space Telescope resolved this structure into a parallelogram, which can be explained as the remnant of a gas-rich spiral galaxy falling into an elliptical galaxy and becoming twisted and warped in the process. Galaxy merging is the most common mechanism to explain the formation of such giant elliptical galaxies. The new SOFI images, obtained with the 3.58-metre New Technology Telescope at ESO's La Silla Observatory

  1. Samsung Galaxy S5 for dummies

    CERN Document Server

    Hughes, Bill

    2014-01-01

    Explore Samsung's next generation Galaxy smartphone Do you want an easy-to-follow guide to everything your new Galaxy S5 smartphone can do? From the basics of texting and accessing the Internet to the most advanced features and new software apps, Samsung Galaxy S5 For Dummies makes the need for tech support obsolete. The Galaxy S5 is designed to be faster and more powerful than ever. This latest release in the market-leading line of smartphones is full of new features for you to explore with the help of Samsung Galaxy S5 For Dummies. With over 1 million apps available for the Google Android o

  2. Star-Formation Histories of MUSCEL Galaxies

    Science.gov (United States)

    Young, Jason; Kuzio de Naray, Rachel; Xuesong Wang, Sharon

    2018-01-01

    The MUSCEL program (MUltiwavelength observations of the Structure, Chemistry and Evolution of LSB galaxies) uses combined ground-based/space-based data to determine the spatially resolved star-formation histories of low surface brightness (LSB) galaxies. LSB galaxies are paradoxical in that they are gas rich but have low star-formation rates. Here we present our observations and fitting technique, and the derived histories for select MUSCEL galaxies. It is our aim to use these histories in tandem with velocity fields and metallicity profiles to determine the physical mechanism(s) that give these faint galaxies low star-formation rates despite ample gas supplies.

  3. Investigating Galaxy Merger Signatures with IGNITE

    Science.gov (United States)

    Zagursky, Matthew J.; Lotz, J. M.

    2009-01-01

    I present the software package IGNITE, the Interacting Galaxy Non-Interactive Tail Extractor. Its purpose is to locate tidal tails and quantify their morphological and photometric properties. I demonstrate the effective use of IGNITE on the case galaxy of NGC 2623 and report the photometric and morphological signatures of tidal tails in this galaxy. The future of the IGNITE package is a merge with other successful software packages aimed at quantifying merging galaxies to further enhance the accuracy of the quantitative measurements of morphologies and photometry profiles of merging galaxy candidates

  4. Galaxy Evolution in Clusters Since z ~ 1

    Science.gov (United States)

    Aragón-Salamanca, A.

    Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature" vs. "nurture" in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the Universe was half its present age. Many of the results presented here have been obtained within the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

  5. PROFILER: 1D galaxy light profile decomposition

    Science.gov (United States)

    Ciambur, Bogdan C.

    2017-05-01

    Written in Python, PROFILER analyzes the radial surface brightness profiles of galaxies. It accurately models a wide range of galaxies and galaxy components, such as elliptical galaxies, the bulges of spiral and lenticular galaxies, nuclear sources, discs, bars, rings, and spiral arms with a variety of parametric functions routinely employed in the field (Sérsic, core-Sérsic, exponential, Gaussian, Moffat and Ferrers). In addition, Profiler can employ the broken exponential model (relevant for disc truncations or antitruncations) and two special cases of the edge-on disc model: namely along the major axis (in the disc plane) and along the minor axis (perpendicular to the disc plane).

  6. 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.

  7. The Cambridge photographic atlas of galaxies

    CERN Document Server

    König, Michael

    2017-01-01

    Galaxies - the Milky Way's siblings - offer a surprising variety of forms and colours. Displaying symmetrical spiral arms, glowing red nebulae or diffuse halos, even the image of a galaxy can reveal much about its construction. All galaxies consist of gas, dust and stars, but the effects of gravity, dark matter and the interaction of star formation and stellar explosions all influence their appearances. This volume showcases more than 250 of the most beautiful galaxies within an amateur's reach and uses them to explain current astrophysical research. It features fantastic photographs, unique insights into our knowledge, tips on astrophotography and essential facts and figures based on the latest science. From the Andromeda Galaxy to galaxy clusters and gravitational lenses, the nature of galaxies is revealed through these stunning amateur photographs. This well illustrated reference atlas deserves a place on the bookshelves of astronomical imagers, observers and armchair enthusiasts.

  8. Colours, luminosity functions and counts of galaxies

    Science.gov (United States)

    Saracco, P.; Chincarini, G.; Iovino, A.

    1996-12-01

    Standard models for deep galaxy counts are based on luminosity functions (LFs) that have a relatively flat faint end (alpha~-1.0). Galaxy counts in the B band exceed the prediction of such models from a factor of 2 to more than a factor of 5, forcing the introduction of strong luminosity and/or density evolution. Recently Marzke, Huchra & Geller, using the CfA redshift survey sample, found that the number of galaxies in the range -16<2.5 for dwarf galaxies, we reproduce well also the observed K-band deep galaxy counts. This assumption is supported by the strong correlation we found between B-K colour of galaxies and their infrared absolute magnitude: galaxies become bluer with decreasing luminosity.

  9. Star formation suppression in compact group galaxies

    DEFF Research Database (Denmark)

    Alatalo, K.; Appleton, P. N.; Lisenfeld, U.

    2015-01-01

    on poststarburst galaxies with molecular reservoirs, indicates that galaxies do not need to expel their molecular reservoirs prior to quenching SF and transitioning from blue spirals to red early-type galaxies. This may imply that SF quenching can occur without the need to starve a galaxy of cold gas first.......We present CO(1-0) maps of 12 warm H-2-selected Hickson Compact Groups (HCGs), covering 14 individually imaged warm H2 bright galaxies, with the Combined Array for Research in Millimeter Astronomy. We found a variety of molecular gas distributions within the HCGs, including regularly rotating disks......, bars, rings, tidal tails, and possibly nuclear outflows, though the molecular gas morphologies are more consistent with spirals and earlytype galaxies than mergers and interacting systems. Our CO-imaged HCG galaxies, when plotted on the Kennicutt-Schmidt relation, shows star formation (SF) suppression...

  10. Angular Momentum of Dwarf Galaxies

    Science.gov (United States)

    Butler, Kirsty M.; Obreschkow, Danail; Oh, Se-Heon

    2017-01-01

    We present measurements of baryonic mass {M}{{b}} and specific angular momentum (sAM) {j}{{b}} in 14 rotating dwarf Irregular (dIrr) galaxies from the LITTLE THINGS sample. These measurements, based on 21 cm kinematic data from the Very Large Array and stellar mass maps from the Spitzer Space Telescope, extend previous AM measurements by more than two orders of magnitude in {M}{{b}}. The dwarf galaxies show systematically higher {j}{{b}} values than expected from the {j}{{b}}\\propto {M}{{b}}2/3 scaling of spiral galaxies, representative of a scale-free galaxy formation scenario. This offset can be explained by decreasing baryon mass fractions {f}{{M}}={M}{{b}}/{M}{dyn} (where {M}{dyn} is the dynamical mass) with decreasing {M}{{b}} (for {M}{{b}}< {10}11 {M}⊙ ). We find that the sAM of neutral atomic hydrogen (H I) alone is about 2.5 times higher than that of the stars. The M-j relation of H I is significantly steeper than that of the stars, as a direct consequence of the systematic variation of the H I fraction with {M}{{b}}.

  11. What powers luminous infrared galaxies?

    NARCIS (Netherlands)

    Lutz, D; Genzel, R; Sternberg, A; Netzer, H; Kunze, D; Rigopoulou, D; Sturm, E; Egami, E; Feuchtgruber, H; Moorwood, AFM; deGraauw, T

    1996-01-01

    Based on the initial data sets taken with the ISO short wavelength spectrometer (SWS) we present a first discussion of the source of luminosity of (ultra-)luminous infrared galaxies (ULIRGs). By comparison of observations of 2.5-45 mu m lines to classical starbursts and active galactic nuclei and by

  12. Galaxy Classifications with Deep Learning

    Science.gov (United States)

    Lukic, Vesna; Brüggen, Marcus

    2017-06-01

    Machine learning techniques have proven to be increasingly useful in astronomical applications over the last few years, for example in object classification, estimating redshifts and data mining. One example of object classification is classifying galaxy morphology. This is a tedious task to do manually, especially as the datasets become larger with surveys that have a broader and deeper search-space. The Kaggle Galaxy Zoo competition presented the challenge of writing an algorithm to find the probability that a galaxy belongs in a particular class, based on SDSS optical spectroscopy data. The use of convolutional neural networks (convnets), proved to be a popular solution to the problem, as they have also produced unprecedented classification accuracies in other image databases such as the database of handwritten digits (MNIST †) and large database of images (CIFAR ‡). We experiment with the convnets that comprised the winning solution, but using broad classifications. The effect of changing the number of layers is explored, as well as using a different activation function, to help in developing an intuition of how the networks function and to see how they can be applied to radio galaxy images.

  13. Interactions and Mergers of Galaxies

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 12; Issue 3. Interactions and Mergers of Galaxies. S M Alladin S N Hasan. General Article Volume 12 Issue 3 March 2007 pp 13-26. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/012/03/0013-0026 ...

  14. Galaxies on Top of Quasars: Probing Dwarf Galaxies in the SDSS

    Science.gov (United States)

    Straka, Lorrie; York, D. G.; Noterdaeme, P.; Srianand, R.; Bowen, D. V.; Khare, P.; Bishof, M.; Whichard, Z.; Kulkarni, V. P.

    2013-07-01

    Absorption lines from galaxies at intervening redshifts in quasar spectra are sensitive probes of metals and gas that are otherwise invisible due to distance or low surface brightness. However, in order to determine the environments these absorption lines arise in, we must detect these galaxies in emission as well. Galaxies on top of quasars (GOTOQs) are low-z galaxies found intervening with background quasars in the SDSS. These galaxies have been flagged for their narrow galactic emission lines present in quasar spectra in the SDSS. Typically, the low-z nature of these galaxies allows them to be easily detected in SDSS imaging. However, a number of GOTOQs (about 10%), despite being detected in spectral emission, are NOT seen in SDSS imaging. This implies that these may be dark galaxies, dwarf galaxies, or similarly low surface brightness galaxies. Additionally, about 25% of those detected in imaging are dwarf galaxies according to their L* values. Dwarf galaxies have long been underrepresented in observations compared to theory and are known to have large extents in dark matter. Given their prevalence here in our sample we must ask what role they play in quasar absorption line systems (QSOALS). Recent detections of 21-cm galaxies with few stars imply that aborted star formation in dark matter sub halos may produce QSOALS. Thus, this sub sample of galaxies offers a unique technique for probing dark and dwarf galaxies. The sample and its properties will be discussed, including star formation rates and dust estimates, as well as prospects for the future.

  15. 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 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.

  16. On the occurrence of galaxy harassment

    Science.gov (United States)

    Bialas, D.; Lisker, T.; Olczak, C.; Spurzem, R.; Kotulla, R.

    2015-04-01

    Context. Tidal interactions of galaxies in galaxy clusters have been proposed as one potential explanation of the morphology-density relation at low masses. Earlier studies have shown that galaxy harassment is a suitable mechanism for inducing a morphological transformation from low-mass late-type disk galaxies to the abundant early-type galaxies. Aims: The efficiency of tidal transformation is expected to depend strongly on the orbit of a galaxy within the cluster halo. The orbit determines both the strength of the cluster's global tidal field and the probability of encounters with other cluster members. Here we aim to explore these dependencies. Methods: We use a combination of N-body simulation and Monte-Carlo method to study the efficiency of the transformation of late-type galaxies by tidal interactions on different orbits in a galaxy cluster. Additionally, we investigate the effect of an inclination between the disk of the infalling galaxy and its orbital plane. We compare our results to observational data to assess the possible relevance of such transformations for the existing cluster galaxy population. Results: We find that galaxies that entered a cluster from the outskirts are unlikely to be significantly transformed (stellar mass loss ≤6%). Closer to the cluster centre, tidal interactions are a more efficient mechanism (stellar mass loss up to 50%) for producing harassed galaxies. The inclination of the disk can reduce the mass loss significantly, yet it amplifies the thickening of the galaxy disk. Galaxies with smaller sizes on intermediate orbits are nearly unaffected by tidal interactions. The tidal influence on an infalling galaxy and the likelihood that it leads to galaxy harassment make a very stochastical process that depends on the galaxy's specific history. Conclusions: We conclude that harassment is a suitable mechanism that could explain the transformation of at least a fraction of galaxies inside galaxy clusters. However, the transformation

  17. Galaxy-galaxy and galaxy-cluster lensing with the SDSS and FIRST surveys

    Science.gov (United States)

    Demetroullas, C.; Brown, M. L.

    2018-01-01

    We perform a galaxy-galaxy lensing study by correlating the shapes of ∼2.7 × 105 galaxies selected from the VLA FIRST (Faint Images of the Radio Sky at Twenty centimetres) radio survey with the positions of ∼38.5 million Sloan Digital Sky Survey (SDSS) galaxies, ∼132 000 Brightest Cluster Galaxies (BCGs) and ∼78 000 SDSS galaxies that are also detected in the VLA FIRST survey. The measurements are conducted on angular scales θ ≲ 1200 arcsec. On scales θ ≲ 200 arcsec, we find that the measurements are corrupted by residual systematic effects associated with the instrumental beam of the VLA data. Using simulations, we show that we can successfully apply a correction for these effects. Using the three lens samples (the SDSS DR10 sample, the BCG sample and the SDSS-FIRST matched object sample), we measure a tangential shear signal that is inconsistent with 0 at the 10.2σ, 3.8σ and 9σ levels, respectively. Fitting an NFW model to the detected signals, we find that the ensemble mass profile of the BCG sample agrees with the values in the literature. However, the mass profiles of the SDSS DR10 and the SDSS-FIRST matched object samples are found to be shallower and steeper than results in the literature, respectively. The best-fitting Virial masses for the SDSS DR10, BCG and SDSS-FIRST matched samples, derived using an NFW model and allowing for a varying concentration factor, are M_{200}^SDSS-DR10 = (1.2 ± 0.4) × 10^{12} M_{⊙}, M_{200}^BCG = (1.4 ± 1.3) × 10^{13} M_{⊙} and M_{200}^SDSS-FIRST =8.0 ± 4.2 × 10^{13} M_{⊙}, respectively. These results are in good agreement (within ∼2σ) with values in the literature. Our findings suggest that for galaxies to be bright both in the radio and in the optical, they must be embedded in very dense environment on scales R ≲ 1 Mpc.

  18. An Interacting Galaxy System along a Filament in a Void

    NARCIS (Netherlands)

    Beygu, B.; Kreckel, K.; van de Weijgaert, R.; van der Hulst, J. M.; van Gorkom, J. H.

    Cosmological voids provide a unique environment for the study of galaxy formation and evolution. The galaxy population in their interiors has properties significantly different from average field galaxies. As part of our Void Galaxy Survey (VGS), we have found a system of three interacting galaxies

  19. 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 AG; Erben, Thomas

    2018-01-01

    The spatial distribution of satellite galaxies encodes rich information of the structure and assembly history of galaxy clusters. In this paper, we select a redMaPPer 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 1σ error (r_s,gal=0.34_{-0.03}^{+0.04}Mpc vs r_s=0.37_{-0.10}^{+0.15}Mpc ).

  20. The Environment of Galaxies at Low Redshift

    Science.gov (United States)

    Cowan, Nicolas B.; Ivezić, Željko

    2008-02-01

    We compare environmental effects in two analogous samples of galaxies, one from the Sloan Digital Sky Survey (SDSS) and the other from a semianalytic model (SAM) based on the Millennium Simulation (MS), to test to what extent current SAMs of galaxy formation are reproducing environmental effects. We estimate the large-scale environment of each galaxy using a Bayesian density estimator based on distances to all 10 nearest neighbors, and we compare broadband photometric properties of the two samples as a function of environment. The feedbacks implemented in the semianalytic model produce a qualitatively correct galaxy population with similar environmental dependence as that seen in SDSS galaxies. In detail, however, the colors of MS galaxies exhibit an exaggerated dependence on environment: the field contains too many blue galaxies, whereas clusters contain too many red galaxies, compared to the SDSS sample. We also find that the MS contains a population of highly clustered, relatively faint red galaxies with velocity dispersions comparable to their Hubble flow. Such high-density galaxies, if they exist, would be overlooked in any low-redshift survey, since their membership to a cluster cannot be determined because of the "fingers-of-God" effect.

  1. Galaxy Zoo: quantitative visual morphological classifications for 48 000 galaxies from CANDELS

    Science.gov (United States)

    Simmons, B. D.; Lintott, Chris; Willett, Kyle W.; Masters, Karen L.; Kartaltepe, Jeyhan S.; Häußler, Boris; Kaviraj, Sugata; Krawczyk, Coleman; Kruk, S. J.; McIntosh, Daniel H.; Smethurst, R. J.; Nichol, Robert C.; Scarlata, Claudia; Schawinski, Kevin; Conselice, Christopher J.; Almaini, Omar; Ferguson, Henry C.; Fortson, Lucy; Hartley, William; Kocevski, Dale; Koekemoer, Anton M.; Mortlock, Alice; Newman, Jeffrey A.; Bamford, Steven P.; Grogin, N. A.; Lucas, Ray A.; Hathi, Nimish P.; McGrath, Elizabeth; Peth, Michael; Pforr, Janine; Rizer, Zachary; Wuyts, Stijn; Barro, Guillermo; Bell, Eric F.; Castellano, Marco; Dahlen, Tomas; Dekel, Avishai; Ownsworth, Jamie; Faber, Sandra M.; Finkelstein, Steven L.; Fontana, Adriano; Galametz, Audrey; Grützbauch, Ruth; Koo, David; Lotz, Jennifer; Mobasher, Bahram; Mozena, Mark; Salvato, Mara; Wiklind, Tommy

    2017-02-01

    We present quantified visual morphologies of approximately 48 000 galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified by participants in the Galaxy Zoo project. 90 per cent of galaxies have z ≤ 3 and are observed in rest-frame optical wavelengths by CANDELS. Each galaxy received an average of 40 independent classifications, which we combine into detailed morphological information on galaxy features such as clumpiness, bar instabilities, spiral structure, and merger and tidal signatures. We apply a consensus-based classifier weighting method that preserves classifier independence while effectively down-weighting significantly outlying classifications. After analysing the effect of varying image depth on reported classifications, we also provide depth-corrected classifications which both preserve the information in the deepest observations and also enable the use of classifications at comparable depths across the full survey. Comparing the Galaxy Zoo classifications to previous classifications of the same galaxies shows very good agreement; for some applications, the high number of independent classifications provided by Galaxy Zoo provides an advantage in selecting galaxies with a particular morphological profile, while in others the combination of Galaxy Zoo with other classifications is a more promising approach than using any one method alone. We combine the Galaxy Zoo classifications of `smooth' galaxies with parametric morphologies to select a sample of featureless discs at 1 ≤ z ≤ 3, which may represent a dynamically warmer progenitor population to the settled disc galaxies seen at later epochs.

  2. A class of compact dwarf galaxies from disruptive processes in galaxy clusters.

    Science.gov (United States)

    Drinkwater, M J; Gregg, M D; Hilker, M; Bekki, K; Couch, W J; Ferguson, H C; Jones, J B; Phillipps, S

    2003-05-29

    Dwarf galaxies have attracted increased attention in recent years, because of their susceptibility to galaxy transformation processes within rich galaxy clusters. Direct evidence for these processes, however, has been difficult to obtain, with a small number of diffuse light trails and intra-cluster stars being the only signs of galaxy disruption. Furthermore, our current knowledge of dwarf galaxy populations may be very incomplete, because traditional galaxy surveys are insensitive to extremely diffuse or compact galaxies. Aware of these concerns, we recently undertook an all-object survey of the Fornax galaxy cluster. This revealed a new population of compact members, overlooked in previous conventional surveys. Here we demonstrate that these 'ultra-compact' dwarf galaxies are structurally and dynamically distinct from both globular star clusters and known types of dwarf galaxy, and thus represent a new class of dwarf galaxy. Our data are consistent with the interpretation that these are the remnant nuclei of disrupted dwarf galaxies, making them an easily observed tracer of galaxy disruption.

  3. Properties and spatial distribution of galaxy superclusters

    Science.gov (United States)

    Liivamägi, Lauri Juhan

    2017-01-01

    Astronomy is a science that can offer plenty of unforgettable imagery, and the large-scale distribution of galaxies is no exception. Among the first features the viewer's eye is likely to be drawn to, are large concentrations of galaxies - galaxy superclusters, contrasting to the seemingly empty regions beside them. Superclusters can extend from tens to over hundred megaparsecs, they contain from hundreds to thousands of galaxies, and many galaxy groups and clusters. Unlike galaxy clusters, superclusters are clearly unrelaxed systems, not gravitationally bound as crossing times exceed the age of the universe, and show little to no radial symmetry. Superclusters, as part of the large-scale structure, are sensitive to the initial power spectrum and the following evolution. They are massive enough to leave an imprint on the cosmic microwave background radiation. Superclusters can also provide an unique environment for their constituent galaxies and galaxy clusters. In this study we used two different observational and one simulated galaxy samples to create several catalogues of structures that, we think, correspond to what are generally considered galaxy superclusters. Superclusters were delineated as continuous over-dense regions in galaxy luminosity density fields. When calculating density fields several corrections were applied to remove small-scale redshift distortions and distance-dependent selection effects. Resulting catalogues of objects display robust statistical properties, showing that flux-limited galaxy samples can be used to create nearly volume-limited catalogues of superstructures. Generally, large superclusters can be regarded as massive, often branching filamentary structures, that are mainly characterised by their length. Smaller superclusters, on the other hand, can display a variety of shapes. Spatial distribution of superclusters shows large-scale variations, with high-density concentrations often found in semi-regularly spaced groups. Future

  4. Compact quiescent galaxies at intermediate redshifts {sup ,}

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Li-Yen; Stockton, Alan; Shih, Hsin-Yi [Institute of Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2014-12-01

    From several searches of the area common to the Sloan Digital Sky Survey and the United Kingdom Infrared Telescope Infrared Deep Sky Survey, we have selected 22 luminous galaxies between z ∼ 0.4 and z ∼ 0.9 that have colors and sizes similar to those of the compact quiescent galaxies at z > 2. By exploring structural parameters and stellar populations, we found that most of these galaxies actually formed most of their stars at z < 2 and are generally less compact than those found at z > 2. Several of these young objects are disk-like or possibly prolate. This lines up with several previous studies that found that massive quiescent galaxies at high redshifts often have disk-like morphologies. If these galaxies were to be confirmed to be disk-like, their formation mechanism must be able to account for both compactness and disks. On the other hand, if these galaxies were to be confirmed to be prolate, the fact that prolate galaxies do not exist in the local universe would indicate that galaxy formation mechanisms have evolved over cosmic time. We also found five galaxies forming over 80% of their stellar masses at z > 2. Three of these galaxies appear to have been modified to have spheroid-like morphologies, in agreement with the scenario of 'inside-out' buildup of massive galaxies. The remaining galaxies, SDSS J014355.21+133451.4 and SDSS J115836.93+021535.1, have truly old stellar populations and disk-like morphologies. These two objects would be good candidates for nearly unmodified compact quiescent galaxies from high redshifts that are worth future study.

  5. 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.

  6. Are We Really Missing Small Galaxies?

    Science.gov (United States)

    Kohler, Susanna

    2018-02-01

    One long-standing astrophysical puzzle is that of so-called missing dwarf galaxies: the number of small dwarf galaxies that we observe is far fewer than that predicted by theory. New simulations, however, suggest that perhaps theres no mystery after all.Missing DwarfsDark-matter cosmological simulations predict many small galaxy halos for every large halo that forms. [The Via Lactea project]Models of a lambda-cold-dark-matter (CDM) universe predict the distribution of galaxy halo sizes throughout the universe, suggesting there should be many more small galaxies than large ones. In what has become known as the missing dwarf problem, however, we find that while we observe the expected numbers of galaxies at the larger end of the scale, we dont see nearly enough small galaxies to match the predictions.Are these galaxies actually missing? Are our predictions wrong? Or are the galaxies there and were just not spotting them? A recent study led by Alyson Brooks (Rutgers University) uses new simulations to explore whatscausing the difference between theory and observation.The fraction of detectable halos as a function of velocity, according to the authors simulations. Below 35 km/s, the detectability of the galaxies drops precipitously. [Brooks et al. 2017]Simulating Galactic VelocitiesBecause we cant weigh a galaxy directly, one proxy used for galaxy mass is its circular velocity; the more massive a galaxy, the faster gas and stars rotate around its center. The discrepancy between models and observations lies in whats known as the galaxy velocity function, which describes the number density of galaxies for a given circular velocity. While theory and observations agree for galaxies with circular velocities above 100 km/s, theory predicts far more dwarfs below this velocity than we observe.To investigate this problem, Brooks and collaborators ran a series of cosmological simulations based on our understanding of a CDM universe. Instead of exploring the result using only

  7. Dark Matter Equilibria in Galaxies and Galaxy Systems

    Science.gov (United States)

    Lapi, A.; Cavaliere, A.

    2009-02-01

    In the dark matter (DM) halos embedding galaxies and galaxy systems the "entropy" K ≡ σ2/ρ2/3 (a quantity that combines the radial velocity dispersion σ with the density ρ) is found from intensive N-body simulations to follow a power-law run K vprop r α throughout the halos' bulk, with α around 1.25. Taking up from phenomenology just that α≈ const. applies, we cut through the rich analytic contents of the Jeans equation describing the self-gravitating equilibria of the DM; we specifically focus on computing and discussing a set of novel physical solutions that we name α-profiles, marked by the entropy slope α itself, and by the maximal gravitational pull κcrit(α) required for a viable equilibrium to hold. We then use an advanced semianalytic description for the cosmological buildup of halos to constrain the values of α to within the narrow range 1.25-1.29 from galaxies to galaxy systems; these correspond to halos' current masses in the range 1011-1015 M sun. Our range of α applies since the transition time that—both in our semianalytic description and in state-of-the-art numerical simulations—separates two development stages: an early violent collapse that comprises a few major mergers and enforces dynamical mixing, followed by smoother mass addition through slow accretion. In our range of α we provide a close fit for the relation κcrit(α), and discuss a related physical interpretation in terms of incomplete randomization of the infall kinetic energy through dynamical mixing. We also give an accurate analytic representation of the α-profiles with parameters derived from the Jeans equation; this provides straightforward precision fits to recent detailed data from gravitational lensing in and around massive galaxy clusters, and thus replaces the empirical Navarro-Frenk-White formula relieving the related problems of high concentration and old age. We finally stress how our findings and predictions as to α and κcrit contribute to

  8. Spatially resolved galaxy kinematics from hydrodynamic simulations

    Science.gov (United States)

    Hung, Chao-Ling

    2018-01-01

    The recent advent of optical/near-infrared integral field spectrographs (IFS) have revealed the internal dynamics of hundreds of star-forming galaxies at 1work to use idealized galaxy merger simulations to determine the timescale over which interaction/merger signatures are visible, and the implications on our interpretation of the merger/disk nature of galaxies that display a smooth velocity gradient. Further, I will discuss our work to derive kinematic properties of simulated galaxies using the zoom-in cosmological simulations from the FIRE project. These results can inform us what might be the physical drivers of an enhanced intrinsic velocity dispersion of high-z star-forming galaxies, an important characteristic of these galaxies from recent large IFS surveys.

  9. Cosmology with void-galaxy correlations.

    Science.gov (United States)

    Hamaus, Nico; Wandelt, Benjamin D; Sutter, P M; Lavaux, Guilhem; Warren, Michael S

    2014-01-31

    Galaxy bias, the unknown relationship between the clustering of galaxies and the underlying dark matter density field is a major hurdle for cosmological inference from large-scale structure. While traditional analyses focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, we propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs we demonstrate that cross correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a static ruler thanks to the observable geometric nature of voids. We illustrate how the clustering of voids is related to mass compensation and show that volume-exclusion significantly reduces the degree of stochasticity in their spatial distribution. Extracting the spherically averaged distribution of galaxies inside voids from their cross correlations reveals a remarkable concordance with the mass-density profile of voids.

  10. Galaxy evolution in clusters since z=1

    Science.gov (United States)

    Aragón-Salamanca, A.

    2011-11-01

    It is now 30 years since Alan Dressler published his seminal paper onthe morphology-density relation. Although there is still much to learnon the effect of the environment on galaxy evolution, extensive progress has been made since then both observationally and theoretically.Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature'' vs. "nurture'' in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the universe was half its present age.Many of the results presented here have been obtainedwithin the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

  11. 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.

  12. Dissipational galaxy formation - Confrontation with observations

    Science.gov (United States)

    Silk, J.; Norman, C.

    1981-01-01

    An exploration is presented of the hypothesis that a protogalaxy consists of an aggregate of interacting gas clouds which undergo mergers with neighboring systems, as envisaged by both the hierarchical clustering and fragmentation schemes of galaxy formation. Both gaseous dissipation and violet relaxation play fundamental roles in this galaxy formation model, in order to account for such diverse structural and dynamical properties of spheroidal galaxies as velocity anisotropy and metallicity gradients. Protogalaxy mergers during the initial stages of galaxy clustering can account for the observed spatial distribution of spiral, S0, and elliptical galaxies, and galaxy formation can occur slowly and at late epochs, since the time scale for disk formation is less than about 10 to the 10th years.

  13. INTEGRATED OPTICAL POLARIZATION OF NEARBY GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Amy; Wang Lifan; Krisciunas, Kevin; Freeland, Emily, E-mail: ymamay@physics.tamu.edu [Department of Physics and Astronomy, George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States)

    2012-03-20

    We performed an integrated optical polarization survey of 70 nearby galaxies to study the relationship between linear polarization and galaxy properties. To date this is the largest survey of its kind. The data were collected at McDonald Observatory using the Imaging Grism Polarimeter on the Otto Struve 2.1 m telescope. Most of the galaxies did not have significant level of linear polarization, where the bulk is <1%. A fraction of the galaxies showed a loose correlation between the polarization and position angle of the galaxy, indicating that dust scattering is the main source of optical polarization. The unbarred spiral galaxies are consistent with the predicted relationship with inclination from scattering models of {approx}sin{sup 2} i.

  14. Malin1: interacting galaxy pair?

    Science.gov (United States)

    Reshetnikov, V. P.; Moiseev, A. V.; Sotnikova, N. Ya.

    2010-07-01

    Malin1 is a unique, extraordinarily large low-surface brightness galaxy. The structure and the origins of the galaxy are poorly understood. The reason for this is the absence of detailed observational data, especially of high-resolution kinematics. In this Letter, we study the stellar kinematics of the inner part (r probably interacting with the main galaxy - Malin1. This object is clearly seen in many published images of Malin1 but is not mentioned in any astronomical data bases. Malin1B is located at a projected distance of 14kpc from Malin1's nucleus and has small - 65 +/- 16km s-1 - relative velocity, which we determined for the first time. We suggest that the ongoing interaction with Malin1B can explain the main morphological features of Malin1's central region - two-armed spiral structure, a bar and an external one-armed spiral pattern. We also investigated the large-scale environment of Malin1 and postulated that the galaxy SDSSJ123708.91 + 142253.2 might be responsible for the formation of an extended low-surface brightness envelope by means of head-on collision with Malin1 (in the framework of the collision scenario proposed by Mapelli et al.). To test the collisional origins of Malin1's global structure, more observational data and new numerical models are needed. Partly based on observations collected with the 6-m telescope at the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences (RAS). E-mail: resh@astro.spbu.ru

  15. Tidal Disruption Event Host Galaxies in the Context of the Local Galaxy Population

    Science.gov (United States)

    Law-Smith, Jamie; Ramirez-Ruiz, Enrico; Ellison, Sara L.; Foley, Ryan J.

    2017-11-01

    We study the properties of tidal disruption event (TDE) host galaxies in the context of a catalog of ∼500,000 galaxies from the Sloan Digital Sky Survey. We explore whether selection effects can account for the overrepresentation of TDEs in E+A/post-starburst galaxies by creating matched galaxy samples. Accounting for possible selection effects due to black hole (BH) mass, redshift completeness, strong active galactic nucleus presence, bulge colors, and surface brightness can reduce the apparent overrepresentation of TDEs in E+A host galaxies by a factor of ∼4 (from ∼×100–190 to ∼×25–48), but cannot fully explain the preference. We find that TDE host galaxies have atypical photometric properties compared to similar, “typical” galaxies. In particular, TDE host galaxies tend to live in or near the “green valley” between star-forming and passive galaxies, and have bluer bulge colors ({{Δ }}(g-r)≈ 0.3 mag), lower half-light surface brightnesses (by ∼1 mag/arcsec2), higher Sérsic indices ({{Δ }}{n}{{g}}≈ 3), and higher bulge-to-total-light ratios ({{Δ }}B/T≈ 0.5) than galaxies with matched BH masses. We find that TDE host galaxies appear more centrally concentrated and that all have high galaxy Sérsic indices and B/T fractions—on average in the top 10% of galaxies of the same BH mass—suggesting a higher nuclear stellar density. We identify a region in the Sérsic index and BH mass parameter space that contains ∼2% of our reference catalog galaxies but ≥slant 60 % of TDE host galaxies. The unique photometric properties of TDE host galaxies may be useful for selecting candidate TDEs for spectroscopic follow-up observations in large transient surveys.

  16. The interstellar medium in galaxies

    CERN Document Server

    1997-01-01

    It has been more than five decades ago that Henk van de Hulst predicted the observability of the 21-cm line of neutral hydrogen (HI ). Since then use of the 21-cm line has greatly improved our knowledge in many fields and has been used for galactic structure studies, studies of the interstellar medium (ISM) in the Milky Way and other galaxies, studies of the mass distribution of the Milky Way and other galaxies, studies of spiral struc­ ture, studies of high velocity gas in the Milky Way and other galaxies, for measuring distances using the Tully-Fisher relation etc. Regarding studies of the ISM, there have been a number of instrumen­ tal developments over the past decade: large CCD's became available on optical telescopes, radio synthesis offered sensitive imaging capabilities, not only in the classical 21-cm HI line but also in the mm-transitions of CO and other molecules, and X-ray imaging capabilities became available to measure the hot component of the ISM. These developments meant that Milky Way was n...

  17. Evolution of the extinction curves in galaxies

    OpenAIRE

    Asano, Ryosuke S.; Takeuchi, Tsutomu T.; Hirashita, Hiroyuki; Nozawa, Takaya

    2014-01-01

    We investigate the evolution of extinction curves in galaxies based on our evolution model of grain size distribution. In this model, we considered various processes: dust formation by SNe II and AGB stars, dust destruction by SN shocks in the ISM, metal accretion onto the surface of grains (referred to as grain growth), shattering and coagulation. We find that the extinction curve is flat in the earliest stage of galaxy evolution. As the galaxy is enriched with dust, shattering becomes effec...

  18. New Observations of Polar Ring Galaxies

    Science.gov (United States)

    Sparke, L. S.; Cox, A. L.

    Polar ring systems are `multi-spin galaxies' (Rubin 1994): different components have discrepant axes of rotation. The outer gas-rich material in polar orbit appears to be a late acquisition; it shares neither the rotation nor the symmetry axis of the early-type inner galaxy, which contains little gas and consists largely of old stars. These systems represent galaxy mergers that are not yet completed.

  19. The resolved history of galaxy evolution.

    Science.gov (United States)

    Brinchmann, Jarle

    2002-12-15

    We briefly review the study of the evolution of galaxies from an observational point of view, with particular emphasis on the role of the Hubble Space Telescope in probing the evolution of the different morphological types of galaxy. We show how using the stellar mass of galaxies as a tracer of evolution can improve our understanding of the physical process taking place before turning our eyes towards the future and giving an overview of what we can expect from future advances in technology.

  20. Massive relic galaxies prefer dense environments

    Science.gov (United States)

    Peralta de Arriba, Luis; Quilis, Vicent; Trujillo, Ignacio; Cebrián, María; Balcells, Marc

    2016-09-01

    We study the preferred environments of z ∼ 0 massive relic galaxies (M⋆ ≳ 1010 M⊙ galaxies with little or no growth from star formation or mergers since z ∼ 2). Significantly, we carry out our analysis on both a large cosmological simulation and an observed galaxy catalogue. Working on the Millennium I-WMAP7 simulation we show that the fraction of today massive objects which have grown less than 10 per cent in mass since z ∼ 2 is ∼0.04 per cent for the whole massive galaxy population with M⋆ ≳ 1010 M⊙. This fraction rises to ∼0.18 per cent in galaxy clusters, confirming that clusters help massive galaxies remain unaltered. Simulations also show that massive relic galaxies tend to be closer to cluster centres than other massive galaxies. Using the New York University Value-Added Galaxy Catalogue, and defining relics as M⋆ ≳ 1010 M⊙ early-type galaxies with colours compatible with single-stellar population ages older than 10 Gyr, and which occupy the bottom 5-percentile in the stellar mass-size distribution, we find 1.11 ± 0.05 per cent of relics among massive galaxies. This fraction rises to 2.4 ± 0.4 per cent in high-density environments. Our findings point in the same direction as the works by Poggianti et al. and Stringer et al. Our results may reflect the fact that the cores of the clusters are created very early on, hence the centres host the first cluster members. Near the centres, high-velocity dispersions and harassment help cluster core members avoid the growth of an accreted stellar envelope via mergers, while a hot intracluster medium prevents cold gas from reaching the galaxies, inhibiting star formation.

  1. The TANGO Project: Thorough ANalysis of radio-Galaxies Observations

    Science.gov (United States)

    Ocaña Flaquer, Breezy; Leon Tanne, Stephane; Combes, Francoise; Lim, Jeremy

    2010-05-01

    We present a sample of radio galaxies selected only on the basis of radio continuum emission and we confirm that these galaxies have lower molecular gas mass than other elliptical galaxies with different selection criteria.

  2. Galaxy Zoo: Major Galaxy Mergers Are Not a Significant Quenching Pathway

    Science.gov (United States)

    Weigel, Anna K.; Schawinski, Kevin; Caplar, Neven; Carpineti, Alfredo; Hart, Ross E.; Kaviraj, Sugata; Keel, William C.; Kruk, Sandor J.; Lintott, Chris J.; Nichol, Robert C.; Simmons, Brooke D.; Smethurst, Rebecca J.

    2017-08-01

    We use stellar mass functions to study the properties and the significance of quenching through major galaxy mergers. In addition to SDSS DR7 and Galaxy Zoo 1 data, we use samples of visually selected major galaxy mergers and post-merger galaxies. We determine the stellar mass functions of the stages that we would expect major-merger-quenched galaxies to pass through on their way from the blue cloud to the red sequence: (1) major merger, (2) post-merger, (3) blue early type, (4) green early type, and (5) red early type. Based on their similar mass function shapes, we conclude that major mergers are likely to form an evolutionary sequence from star formation to quiescence via quenching. Relative to all blue galaxies, the major-merger fraction increases as a function of stellar mass. Major-merger quenching is inconsistent with the mass and environment quenching model. At z˜ 0, major-merger-quenched galaxies are unlikely to constitute the majority of galaxies that transition through the green valley. Furthermore, between z˜ 0-0.5, major-merger-quenched galaxies account for 1%-5% of all quenched galaxies at a given stellar mass. Major galaxy mergers are therefore not a significant quenching pathway, neither at z˜ 0 nor within the last 5 Gyr. The majority of red galaxies must have been quenched through an alternative quenching mechanism that causes a slow blue to red evolution. .

  3. Galaxy Zoo: evidence for rapid, recent quenching within a population of AGN host galaxies

    Science.gov (United States)

    Smethurst, R. J.; Lintott, C. J.; Simmons, B. D.; Schawinski, K.; Bamford, S. P.; Cardamone, C. N.; Kruk, S. J.; Masters, K. L.; Urry, C. M.; Willett, K. W.; Wong, O. I.

    2016-12-01

    We present a population study of the star formation history of 1244 Type 2 active galactic nuclei (AGN) host galaxies, compared to 6107 inactive galaxies. A Bayesian method is used to determine individual galaxy star formation histories, which are then collated to visualize the distribution for quenching and quenched galaxies within each population. We find evidence for some of the Type 2 AGN host galaxies having undergone a rapid drop in their star formation rate within the last 2 Gyr. AGN feedback is therefore important at least for this population of galaxies. This result is not seen for the quenching and quenched inactive galaxies whose star formation histories are dominated by the effects of downsizing at earlier epochs, a secondary effect for the AGN host galaxies. We show that histories of rapid quenching cannot account fully for the quenching of all the star formation in a galaxy's lifetime across the population of quenched AGN host galaxies, and that histories of slower quenching, attributed to secular (non-violent) evolution, are also key in their evolution. This is in agreement with recent results showing that both merger-driven and non-merger processes are contributing to the co-evolution of galaxies and supermassive black holes. The availability of gas in the reservoirs of a galaxy, and its ability to be replenished, appear to be the key drivers behind this co-evolution.

  4. Are ring galaxies the ancestors of giant low surface brightness galaxies?

    NARCIS (Netherlands)

    Mapelli, M.; Moore, B.; Ripamonti, E.; Mayer, L.; Colpi, M.; Giordan, L.

    2008-01-01

    We simulate the collisional formation of a ring galaxy and we integrate its evolution up to 1.5 Gyr after the interaction. About 100-200 Myr after the collision, the simulated galaxy is very similar to observed ring galaxies (e.g. Cartwheel). After this stage, the ring keeps expanding and fades.

  5. Deep spectroscopy in nearby galaxy clusters - III. Orbital structure of galaxies in Abell 85

    Science.gov (United States)

    Aguerri, J. A. L.; Agulli, I.; Diaferio, A.; Dalla Vecchia, C.

    2017-06-01

    Galaxies in clusters are strongly affected by their environment. They evolve according to several physical mechanisms that are active in clusters. Their efficiency can strongly depend on the orbital configuration of the galaxies. Our aim is to analyse the orbits of the galaxies in the cluster Abell 85, based on the study of the galaxy velocity anisotropy parameter. We have solved the Jeans equation under the assumption that the galaxies in A 85 are collisionless objects, within the spherically symmetric gravitational potential of the virialized cluster. The mass of the cluster was estimated with X-ray and caustic analyses. We find that the anisotropy profile of the full galaxy population in A 85 is an increasing monotonic function of the distance from the cluster centre: on average, galaxies in the central region (r/r200 blue galaxies are on less radial orbits than red galaxies. The different families of cluster galaxies considered here have the pseudo phase-space density profiles Q(r) and Qr(r) consistent with the profiles expected in virialized dark matter haloes in N-body simulations. This result suggests that the galaxies in A 85 have reached dynamical equilibrium within the cluster potential. Our results indicate that the origin of the blue and red colours of the different galaxy populations is the different orbital shape rather than the accretion time.

  6. Extinction in the Galaxy from surface brightnesses of ESO-LV galaxies : Testing "standard" extinction maps

    NARCIS (Netherlands)

    Choloniewski, J.; Valentijn, E. A.

    A new method for the determination of the extinction in the Galaxy is proposed. The method uses surface brightnesses of external galaxies in the B and R-bands. The observational data have been taken from the ESO-LV galaxy catalog. As a first application of our model we derive the ratio of R-band to

  7. 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.

  8. Detailed Quantitative Classifications of Galaxy Morphology

    Science.gov (United States)

    Nair, Preethi

    2018-01-01

    Understanding the physical processes responsible for the growth of galaxies is one of the key challenges in extragalactic astronomy. The assembly history of a galaxy is imprinted in a galaxy’s detailed morphology. The bulge-to-total ratio of galaxies, the presence or absence of bars, rings, spiral arms, tidal tails etc, all have implications for the past merger, star formation, and feedback history of a galaxy. However, current quantitative galaxy classification schemes are only useful for broad binning. They cannot classify or exploit the wide variety of galaxy structures seen in nature. Therefore, comparisons of observations with theoretical predictions of secular structure formation have only been conducted on small samples of visually classified galaxies. However large samples are needed to disentangle the complex physical processes of galaxy formation. With the advent of large surveys, like the Sloan Digital Sky Survey (SDSS) and the upcoming Large Synoptic Survey Telescope (LSST) and WFIRST, the problem of statistics will be resolved. However, the need for a robust quantitative classification scheme will still remain. Here I will present early results on promising machine learning algorithms that are providing detailed classifications, identifying bars, rings, multi-armed spiral galaxies, and Hubble type.

  9. 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.

  10. Search for High Redshift Galaxy Clusters

    Science.gov (United States)

    Haarsma, D. B.; Butler, A. R.; Donahue, M. E.; Bruch, S. S.

    2005-12-01

    Distant galaxy clusters are key to understanding many current questions in cosmology, structure formation, and galaxy evolution, yet few z>1 clusters have been identified. The ROSAT Optical X-ray Survey (Donahue et al. 2002 ApJ 569, 689) searched for galaxy clusters using both optical and x-ray detection methods. While many clusters appeared in both wavebands, 10 targets which showed extended x-ray emission (a unique signature of cluster gas) did not show significant I-band emission (expected from elliptical galaxies in the cluster). These targets may be galaxy clusters with redshift greater than 1, which would appear faint in I due to the 400 nm break in elliptical galaxy spectra. In J and K bands, such galaxies would be easier to detect, and in April 2005 we imaged the 10 fields in J and K with the FLAMINGOS camera on the NOAO 4m telescope. The infrared colors are useful in identifying clusters, because all elliptical galaxies in a cluster are expected to have similar colors (i.e. the red sequence). We report preliminary identifications of high redshift galaxy clusters in our sample.

  11. BioBlend.objects: metacomputing with Galaxy.

    Science.gov (United States)

    Leo, Simone; Pireddu, Luca; Cuccuru, Gianmauro; Lianas, Luca; Soranzo, Nicola; Afgan, Enis; Zanetti, Gianluigi

    2014-10-01

    BioBlend.objects is a new component of the BioBlend package, adding an object-oriented interface for the Galaxy REST-based application programming interface. It improves support for metacomputing on Galaxy entities by providing higher-level functionality and allowing users to more easily create programs to explore, query and create Galaxy datasets and workflows. BioBlend.objects is available online at https://github.com/afgane/bioblend. The new object-oriented API is implemented by the galaxy/objects subpackage. © The Author 2014. Published by Oxford University Press.

  12. Merging Galaxies Create a Binary Quasar

    Science.gov (United States)

    2010-02-01

    Astronomers have found the first clear evidence of a binary quasar within a pair of actively merging galaxies. Quasars are the extremely bright centers of galaxies surrounding super-massive black holes, and binary quasars are pairs of quasars bound together by gravity. Binary quasars, like other quasars, are thought to be the product of galaxy mergers. Until now, however, binary quasars have not been seen in galaxies that are unambiguously in the act of merging. But images of a new binary quasar from the Carnegie Institution's Magellan telescope in Chile show two distinct galaxies with "tails" produced by tidal forces from their mutual gravitational attraction. "This is really the first case in which you see two separate galaxies, both with quasars, that are clearly interacting," says Carnegie astronomer John Mulchaey who made observations crucial to understanding the galaxy merger. Most, if not all, large galaxies, such as our galaxy the Milky Way, host super-massive black holes at their centers. Because galaxies regularly interact and merge, astronomers have assumed that binary super-massive black holes have been common in the Universe, especially during its early history. Black holes can only be detected as quasars when they are actively accreting matter, a process that releases vast amounts of energy. A leading theory is that galaxy mergers trigger accretion, creating quasars in both galaxies. Because most such mergers would have happened in the distant past, binary quasars and their associated galaxies are very far away and therefore difficult for most telescopes to resolve. The binary quasar, labeled SDSS J1254+0846, was initially detected by the Sloan Digital Sky Survey, a large scale astronomical survey of galaxies and over 120,000 quasars. Further observations by Paul Green of the Harvard-Smithsonian Center for Astrophysics and colleagues* using NASA's Chandra's X-ray Observatory and telescopes at Kitt Peak National Observatory in Arizona and Palomar

  13. 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.

  14. A COMPARISON OF THE CLUSTERING PROPERTIES BETWEEN GALAXIES AND GROUPS OF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Deng Xinfa [School of Science, Nanchang University, Jiangxi 330031 (China)

    2013-03-01

    In this study, I apply cluster analysis and perform comparative studies of clustering properties between galaxies and groups of galaxies. It is found that the number of objects N{sub max} of the richest system and the maximal length D{sub max} of the largest system for groups in all samples are apparently larger than ones for galaxies, and that galaxies preferentially form isolated, paired, and small systems, while groups preferentially form grouped and clustered systems. These results show that groups are more strongly clustered than galaxies, which is consistent with statistical results of the correlation function.

  15. 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

  16. A Modern Picture of Barred Galaxy Dynamics

    Science.gov (United States)

    Petersen, Michael; Weinberg, Martin; Katz, Neal

    2018-01-01

    Observations of disk galaxies suggest that bars are responsible for altering global galaxy parameters (e.g. structures, gas fraction, star formation rate). The canonical understanding of the mechanisms underpinning bar-driven secular dynamics in disk galaxies has been largely built upon the analysis of linear theory, despite galactic bars being clearly demonstrated to be nonlinear phenomena in n-body simulations. We present simulations of barred Milky Way-like galaxy models designed to elucidate nonlinear barred galaxy dynamics. We have developed two new methodologies for analyzing n-body simulations that give the best of both powerful analytic linear theory and brute force simulation analysis: orbit family identification and multicomponent torque analysis. The software will be offered publicly to the community for their own simulation analysis.The orbit classifier reveals that the details of kinematic components in galactic disks (e.g. the bar, bulge, thin disk, and thick disk components) are powerful discriminators of evolutionary paradigms (i.e. violent instabilities and secular evolution) as well as the basic parameters of the dark matter halo (mass distribution, angular momentum distribution). Multicomponent torque analysis provides a thorough accounting of the transfer of angular momentum between orbits, global patterns, and distinct components in order to better explain the underlying physics which govern the secular evolution of barred disk galaxies.Using these methodologies, we are able to identify the successes and failures of linear theory and traditional n-body simulations en route to a detailed understanding of the control bars exhibit over secular evolution in galaxies. We present explanations for observed physical and velocity structures in observations of barred galaxies alongside predictions for how structures will vary with dynamical properties from galaxy to galaxy as well as over the lifetime of a galaxy, finding that the transfer of angular

  17. Parametrizing the stellar haloes of galaxies

    Science.gov (United States)

    D'Souza, Richard; Kauffman, Guinevere; Wang, Jing; Vegetti, Simona

    2014-09-01

    We study the stellar haloes of galaxies out to 70-100 kpc as a function of stellar mass and galaxy type by stacking aligned r- and g-band images from a sample of 45 508 galaxies from Sloan Digital Sky Survey Data Release 9 in the redshift range 0.06 ≤ z ≤ 0.1 and in the mass range 1010.0 M⊙ < M* < 1011.4 M⊙. We derive surface brightness profiles to a depth of almost μr ˜ 32 mag arcsec-2. We find that the ellipticity of the stellar halo is a function of galaxy stellar mass and that the haloes of high-concentration galaxies are more elliptical than those of low-concentration galaxies. Where the g - r colour of the stellar halo can be measured, we find that the stellar light is always bluer than in the main galaxy. The colour of the stellar halo is redder for more massive galaxies. We further demonstrate that the full two-dimensional surface intensity distribution of our galaxy stacks can only be fit through multicomponent Sérsic models. Using the fraction of light in the outer component of the models as a proxy for the fraction of accreted stellar light, we show that this fraction is a function of stellar mass and galaxy type. The fraction of accreted stellar light rises from 30 to 70 per cent and from 2 to 25 per cent for high- and low-concentration galaxies, respectively, over the mass range 1010.0-1011.4 M⊙.

  18. Important Nearby Galaxies without Accurate Distances

    Science.gov (United States)

    McQuinn, Kristen

    2014-10-01

    The Spitzer Infrared Nearby Galaxies Survey (SINGS) and its offspring programs (e.g., THINGS, HERACLES, KINGFISH) have resulted in a fundamental change in our view of star formation and the ISM in galaxies, and together they represent the most complete multi-wavelength data set yet assembled for a large sample of nearby galaxies. These great investments of observing time have been dedicated to the goal of understanding the interstellar medium, the star formation process, and, more generally, galactic evolution at the present epoch. Nearby galaxies provide the basis for which we interpret the distant universe, and the SINGS sample represents the best studied nearby galaxies.Accurate distances are fundamental to interpreting observations of galaxies. Surprisingly, many of the SINGS spiral galaxies have numerous distance estimates resulting in confusion. We can rectify this situation for 8 of the SINGS spiral galaxies within 10 Mpc at a very low cost through measurements of the tip of the red giant branch. The proposed observations will provide an accuracy of better than 0.1 in distance modulus. Our sample includes such well known galaxies as M51 (the Whirlpool), M63 (the Sunflower), M104 (the Sombrero), and M74 (the archetypal grand design spiral).We are also proposing coordinated parallel WFC3 UV observations of the central regions of the galaxies, rich with high-mass UV-bright stars. As a secondary science goal we will compare the resolved UV stellar populations with integrated UV emission measurements used in calibrating star formation rates. Our observations will complement the growing HST UV atlas of high resolution images of nearby galaxies.

  19. A Curious Pair of Galaxies

    Science.gov (United States)

    2009-03-01

    The ESO Very Large Telescope has taken the best image ever of a strange and chaotic duo of interwoven galaxies. The images also contain some surprises -- interlopers both far and near. ESO PR Photo 11a/09 A Curious Pair of Galaxies ESO PR Video 11a/09 Arp 261 zoom in ESO PR Video 11b/09 Pan over Arp 261 Sometimes objects in the sky that appear strange, or different from normal, have a story to tell and prove scientifically very rewarding. This was the idea behind Halton Arp's catalogue of Peculiar Galaxies that appeared in the 1960s. One of the oddballs listed there is Arp 261, which has now been imaged in more detail than ever before using the FORS2 instrument on ESO's Very Large Telescope. The image proves to contain several surprises. Arp 261 lies about 70 million light-years distant in the constellation of Libra, the Scales. Its chaotic and very unusual structure is created by the interaction of two galaxies that are engaged in a slow motion, but highly disruptive close encounter. Although individual stars are very unlikely to collide in such an event, the huge clouds of gas and dust certainly do crash into each other at high speed, leading to the formation of bright new clusters of very hot stars that are clearly seen in the picture. The paths of the existing stars in the galaxies are also dramatically disrupted, creating the faint swirls extending to the upper left and lower right of the image. Both interacting galaxies were probably dwarfs not unlike the Magellanic Clouds orbiting our own galaxy. The images used to create this picture were not actually taken to study the interacting galaxies at all, but to investigate the properties of the inconspicuous object just to the right of the brightest part of Arp 261 and close to the centre of the image. This is an unusual exploding star, called SN 1995N, that is thought to be the result of the final collapse of a massive star at the end of its life, a so-called core collapse supernova. SN 1995N is unusual because

  20. 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.

  1. Quantitative Morphology of High-Redshift Galaxies Using GALEX Ultraviolet Images of Nearby Galaxies

    Directory of Open Access Journals (Sweden)

    Bum-Suk Yeom

    2017-09-01

    Full Text Available We present simulations of the optical-band images of high-redshift galaxies utilizing 845 near-ultraviolet (NUV images of nearby galaxies obtained through the Galaxy Evolution Explorer (GALEX. We compute the concentration (C, asymmetry (A, Gini (G, and M20 parameters of the GALEX NUV/Sloan Digital Sky Survey r-band images at z ~ 0 and their artificially redshifted optical images at z = 0.9 and 1.6 in order to quantify the morphology of galaxies at local and high redshifts. The morphological properties of nearby galaxies in the NUV are presented using a combination of morphological parameters, in which earlytype galaxies are well separated from late-type galaxies in the G–M20, C–M20, A–C, and A–M20 planes. Based on the distribution of galaxies in the A–C and G–M20 planes, we examine the morphological K-correction (i.e., cosmological distance effect and bandshift effect. The cosmological distance effect on the quantitative morphological parameters is found to be significant for early-type galaxies, while late-type galaxies are more greatly affected by the bandshift effect. Knowledge of the morphological K-correction will set the foundation for forthcoming studies on understanding the quantitative assessment of galaxy evolution.

  2. Galaxy and Mass Assembly (GAMA): probing the merger histories of massive galaxies via stellar populations

    Science.gov (United States)

    Ferreras, I.; Hopkins, A. M.; Gunawardhana, M. L. P.; Sansom, A. E.; Owers, M. S.; Driver, S.; Davies, L.; Robotham, A.; Taylor, E. N.; Konstantopoulos, I.; Brough, S.; Norberg, P.; Croom, S.; Loveday, J.; Wang, L.; Bremer, M.

    2017-06-01

    The merging history of galaxies can be traced with studies of dynamically close pairs. These consist of a massive primary galaxy and a less massive secondary (or satellite) galaxy. The study of the stellar populations of secondary (lower mass) galaxies in close pairs provides a way to understand galaxy growth by mergers. Here we focus on systems involving at least one massive galaxy - with stellar mass above 1011M⊙ in the highly complete Galaxy and Mass Assembly (GAMA) survey. Our working sample comprises 2692 satellite galaxy spectra (0.1 ≤ z ≤ 0.3). These spectra are combined into high S/N stacks, and binned according to both an 'internal' parameter, the stellar mass of the satellite galaxy (i.e. the secondary), and an 'external' parameter, selecting either the mass of the primary in the pair, or the mass of the corresponding dark matter halo. We find significant variations in the age of the populations with respect to environment. At fixed mass, satellites around the most massive galaxies are older and possibly more metal-rich, with age differences ˜1-2 Gyr within the subset of lower mass satellites (˜1010 M⊙). These variations are similar when stacking with respect to the halo mass of the group where the pair is embedded. The population trends in the lower mass satellites are consistent with the old stellar ages found in the outer regions of massive galaxies.

  3. The Unexpected Past of a Dwarf Galaxy

    Science.gov (United States)

    1996-08-01

    New Light on Cannibalism in the Local Group of Galaxies The Local Group of Galaxies consists of a few large spiral galaxies - for instance the Milky Way galaxy in which we live, and the Andromeda galaxy that is visible to the unaided eye in the northern constellation of the same name - as well as two dozen much smaller galaxies of mostly irregular shape. Whereas the larger galaxies have extended halos of very old stars, no such halos have ever been seen around the smaller ones. Now, however, Dante Minniti and Albert Zijlstra [1], working at the ESO 3.5-metre New Technology Telescope (NTT), have found a large halo of old and metal-poor stars around one of the dwarf galaxies in the Local Group. This finding is quite unexpected. It revises our understanding of star formation in these galaxies and provides important information about the past evolution of galaxies [2]. Galaxy halos The Milky Way galaxy is surrounded by a large, roughly spherical halo of old stars. The diameter is about 100,000 light years and the stars therein, known as Population II stars, are among the oldest known, with ages of 10 billion years or even more. They also differ from the younger stars nearer to the main plane of the Milky Way (in which our 4.7 billion year old Sun is located) by being very metal-poor. Many of the halo stars consist almost solely of hydrogen and helium, reflecting the composition of matter in the young Universe. This halo is important for our understanding of the processes that led to the formation of the Milky Way galaxy. It is believed that many of the halo stars and those of the same type found in globular clusters existed already before the Milky Way had fully formed. Galaxy cannibalism Many astronomers suspect that galaxies evolve and gradually grow larger and heavier by practising cannibalism on their own kind. In this picture, when two galaxies collide in space, the stars and nebulae in the smaller one will disperse and soon be taken over by the larger one, which

  4. Host Galaxy Identification for Supernova Surveys

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Ravi R.; Kuhlmann, Steve; Kovacs, Eve; Spinka, Harold; Kessler, Richard; Goldstein, Daniel A.; Liotine, Camille; Pomian, Katarzyna; D’Andrea, Chris B.; Sullivan, Mark; Carretero, Jorge; Castander, Francisco J.; Nichol, Robert C.; Finley, David A.; Fischer, John A.; Foley, Ryan J.; Kim, Alex G.; Papadopoulos, Andreas; Sako, Masao; Scolnic, Daniel M.; Smith, Mathew; Tucker, Brad E.; Uddin, Syed; Wolf, Rachel C.; Yuan, Fang; Abbott, Tim M. C.; Abdalla, Filipe B.; Benoit-Lévy, Aurélien; Bertin, Emmanuel; Brooks, David; Rosell, Aurelio Carnero; Kind, Matias Carrasco; Cunha, Carlos E.; Costa, Luiz N. da; Desai, Shantanu; Doel, Peter; Eifler, Tim F.; Evrard, August E.; Flaugher, Brenna; Fosalba, Pablo; Gaztañaga, Enrique; Gruen, Daniel; Gruendl, Robert; James, David J.; Kuehn, Kyler; Kuropatkin, Nikolay; Maia, Marcio A. G.; Marshall, Jennifer L.; Miquel, Ramon; Plazas, Andrés A.; Romer, A. Kathy; Sánchez, Eusebio; Schubnell, Michael; Sevilla-Noarbe, Ignacio; Sobreira, Flávia; Suchyta, Eric; Swanson, Molly E. C.; Tarle, Gregory; Walker, Alistair R.; Wester, William

    2016-11-08

    Host galaxy identification is a crucial step for modern supernova (SN) surveys such as the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST), which will discover SNe by the thousands. Spectroscopic resources are limited, so in the absence of real-time SN spectra these surveys must rely on host galaxy spectra to obtain accurate redshifts for the Hubble diagram and to improve photometric classification of SNe. In addition, SN luminosities are known to correlate with host-galaxy properties. Therefore, reliable identification of host galaxies is essential for cosmology and SN science. We simulate SN events and their locations within their host galaxies to develop and test methods for matching SNe to their hosts. We use both real and simulated galaxy catalog data from the Advanced Camera for Surveys General Catalog and MICECATv2.0, respectively. We also incorporate "hostless" SNe residing in undetected faint hosts into our analysis, with an assumed hostless rate of 5%. Our fully automated algorithm is run on catalog data and matches SNe to their hosts with 91% accuracy. We find that including a machine learning component, run after the initial matching algorithm, improves the accuracy (purity) of the matching to 97% with a 2% cost in efficiency (true positive rate). Although the exact results are dependent on the details of the survey and the galaxy catalogs used, the method of identifying host galaxies we outline here can be applied to any transient survey.

  5. The void galaxy survey: Star formation properties

    NARCIS (Netherlands)

    Beygu, B.; Kreckel, K.; van der Hulst, J. M.; Jarrett, T. H.; Peletier, R.; van de Weygaert, R.; van Gorkom, J. H.; Aragon-Calvo, M. A.

    2016-01-01

    We study the star formation properties of 59 void galaxies as part of the Void Galaxy Survey (VGS). Current star formation rates are derived from H α and recent star formation rates from near-UV imaging. In addition, infrared 3.4, 4.6, 12 and 22 μm Wide-field Infrared Survey Explorer emission is

  6. Star clusters in the Whirlpool Galaxy

    NARCIS (Netherlands)

    Scheepmaker, R.A.

    2009-01-01

    This thesis presents the results of observational studies of the star cluster population in the interacting spiral galaxy M51, also known as the Whirlpool galaxy. Observations taken by the Hubble Space Telescope in the optical and the near-UV are used to determine fundamental properties of the star

  7. AO Observations of Three Powerful Radio Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    de Vries, W; van Bruegel, W; Quirrenbach, A

    2002-08-01

    The host galaxies of powerful radio sources are ideal laboratories to study active galactic nuclei (AGN). The galaxies themselves are among the most massive systems in the universe, and are believed to harbor supermassive black holes (SMBH). If large galaxies are formed in a hierarchical way by multiple merger events, radio galaxies at low redshift represent the end-products of this process. However, it is not clear why some of these massive ellipticals have associated radio emission, while others do not. Both are thought to contain SMBHs, with masses proportional to the total luminous mass in the bulge. It either implies every SMBH has recurrent radio-loud phases, and the radio-quiet galaxies happen to be in the ''low'' state, or that the radio galaxy nuclei are physically different from radio-quiet ones, i.e. by having a more massive SMBH for a given bulge mass. Here we present the first results from our adaptive optics imaging and spectroscopy pilot program on three nearby powerful radio galaxies. Initiating a larger, more systematic AO survey of radio galaxies (preferentially with Laser Guide Star equipped AO systems) has the potential of furthering our understanding of the physical properties of radio sources, their triggering, and their subsequent evolution.

  8. Nature and nurture in galaxy formation simulations

    NARCIS (Netherlands)

    Haas, Marcel Richard

    2010-01-01

    We study several aspects of the formation of galaxies, using numerical simulations. We investigate the influence of about thirty different sub-grid physics recipes for cooling, star formation, supernova feedback, AGN feedback etc. on the resulting galaxy populations with large SPH simulations. We

  9. Relics as Probes of Galaxy Cluster Mergers

    Indian Academy of Sciences (India)

    Galaxy clusters grow by mergers with other clusters and galaxy groups. These mergers create shocks within the intracluster medium (ICM). It is proposed that particles can be accelerated to extreme energies within the shocks. In the presence of a magnetic field these particles should then form large regions emitting ...

  10. Star Formation in Merging Galaxies Using FIRE

    Science.gov (United States)

    Perez, Adrianna; Hung, Chao-Ling; Naiman, Jill; Moreno, Jorge; Hopkins, Philip

    2018-01-01

    Galaxy interactions and mergers are efficient mechanisms to birth stars at rates that are significantly higher than found in our Milky Way galaxy. The Kennicut-Schmidt (KS) relation is an empirical relationship between the star-forming rate and gas surface densities of galaxies (Schmidt 1959; Kennicutt 1998). Although most galaxies follow the KS relation, the high levels of star formation in galaxy mergers places them outside of this otherwise tight relationship. The goal of this research is to analyze the gas content and star formation of simulated merging galaxies. Our work utilizes the Feedback In Realistic Environments (FIRE) model (Hopkins et al., 2014). The FIRE project is a high-resolution cosmological simulation that resolves star-forming regions and incorporates stellar feedback in a physically realistic way. In this work, we have noticed a significant increase in the star formation rate at first and second passage, when the two black holes of each galaxy approach one other. Next, we will analyze spatially resolved star-forming regions over the course of the interacting system. Then, we can study when and how the rates that gas converts into stars deviate from the standard KS. These analyses will provide important insights into the physical mechanisms that regulate star formation of normal and merging galaxies and valuable theoretical predictions that can be used to compare with current and future observations from ALMA or the James Webb Space Telescope.

  11. Measuring galaxy potentials using shell kinematics

    NARCIS (Netherlands)

    Merrifield, MR; Kuijken, K

    1998-01-01

    We show that the kinematics of the shells seen around some elliptical galaxies provide a new, independent means for measuring the gravitational potentials of elliptical galaxies out to large radii. A numerical simulation of a set of shells formed in the merger between an elliptical and a smaller

  12. 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

  13. Dwarf Galaxies in the Local Group

    NARCIS (Netherlands)

    Tolstoy, Eline; Bruzual, GA; Charlot, S

    2010-01-01

    Within the Local Universe galaxies can be studied in great detail star by star. The Color-Magnitude Diagram synthesis analysis method is well established as the most accurate way to determine the detailed star formation history of galaxies going back to the earliest times. This approach received a

  14. HNC, HCN and CN in seyfert galaxies

    NARCIS (Netherlands)

    Perez-Beaupuits, J. P.; Aalto, S.; Gerebro, H.

    2007-01-01

    Aims. Bright HNC 1-0 emission, rivalling that of HCN 1-0, has been found towards several Seyfert galaxies. This is unexpected since traditionally HNC is a tracer of cold (10 K) gas, and the molecular gas of luminous galaxies like Seyferts is thought to have bulk kinetic temperatures surpassing 50 K.

  15. Stellar Relics from the Early Galaxy

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Galactic halo; chemical evolution; metal poor stars; chemical abundances; inner halo; outer halo; globular clusters; ultra-faint dwarf galaxies. Abstract. We reviewed the recent progress in the field of stellar/galactic archeology, which is a study of the relics from the early galaxy. The oldest and most pristine ...

  16. The Evolution of Nearby Dwarf Galaxies

    NARCIS (Netherlands)

    Tolstoy, E.; Koleva, M; Prugniel, P; Vauglin,

    Within the Local Universe galaxies can be studied in great detail star by star. The Colour-Magnitude Diagram synthesis analysis method is well established as the most accurate way to determine the detailed star formation history of galaxies going back to the earliest times. This approach has

  17. Galaxies interactions and induced star formation

    CERN Document Server

    Kennicutt Jr, Robert C; Barnes, JE

    1998-01-01

    The papers that make up this volume present a comprehensive review of the field of galaxy interaction. Galaxies are dynamic forces that evolve, interact, merge, blaze and reshape. This book offers a historical perspective and studies such topics as induced star formation.

  18. Kinematic analysis of Sculptor Group galaxies

    NARCIS (Netherlands)

    Schoenmakers, RHM; Valtonen, MJ; Flynn, C

    2000-01-01

    An analysis of the kinematics of the five major spiral galaxies in the Sculptor Group is presented. These galaxies are analyzed using the method of harmonic expansion of the velocity field as described in Schoenmakers, Franx and de Zeeuw (1997). Three different types of kinematic distortions were

  19. 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⋆ galaxies are located in the rich Virgo cluster. This is in contrast to low-mass spiral galaxies with star formation, which inhabit a range of 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.

  20. Kinematically Decoupled Cores in Dwarf (Elliptical) Galaxies

    NARCIS (Netherlands)

    Toloba, E.; Peletier, R. F.; Guhathakurta, P.; van de Ven, G.; Boissier, S.; Boselli, A.; Brok, M. d.; Falcón-Barroso, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Lisker, T.; Paudel, S.; Ryś, A.; Salo, H.

    An overview is given of what we know about the frequency of kinematically decoupled cores in dwarf elliptical galaxies. New observations show that kinematically decoupled cores happen just as often in dwarf elliptical as in ordinary early-type galaxies. This has important consequences for the

  1. 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

  2. The Blue Compact Dwarf Galaxy IZw18

    NARCIS (Netherlands)

    Musella, I.; Marconi, M.; Fiorentino, G.; Clementini, G.; Aloisi, A.; Annibali, F.; Contreras, R.; Saha, A.; Tosi, M.; van der Marel, R. P.

    2012-01-01

    We present the results obtained for the Blue compact galaxy IZw18 on the basis of ACS HST data obtained from our group. In particular, we discuss the stellar population and the variable stars content of this galaxy to get information about its star formation history and distance.

  3. Gas Kinematics in GRB Host Galaxies

    DEFF Research Database (Denmark)

    Arabsalmani, Maryam

    The star formation history of the Universe is one of the most complex and interesting chapters in our quest to understand galaxy formation and evolution. Gamma Ray Bursts (GRBs) are beacons of actively star forming galaxies from redshifts near zero back to the cosmic dawn. In addition, they provide...

  4. Galaxy kinematics from counter-dispersed imaging

    NARCIS (Netherlands)

    Douglas, NG; Taylor, K

    1999-01-01

    Determining the internal kinematics of a galaxy from planetary nebulae (PN) is usually a two-step process in which the candidate PN are first identified in a target galaxy and then, in a follow-up run, spectra are obtained. We have implemented a new technique in which two dispersed images at the

  5. The HIX Galaxy Survey: The Most HI Rich Galaxies In The Southern Hemisphere

    Science.gov (United States)

    Lutz, Katharina

    2016-10-01

    When comparing the gas content of galaxies with their current star formation rate, it has been found that the gas consumption time scale is much smaller than the age of galaxies. In addition, the metallicity within galaxies is much smaller than expected from closed box modelling of galaxies. These discrepancies suggest that galaxies must replenish their gas reservoirs by accretion of metal-poor gas from the intergalactic medium.In order to investigate this process of gas accretion in more detail we target local galaxies that host an atomic hydrogen (HI) disc at least 2.5 times more massive than expected from their optical properties using scaling relations. For this sample of galaxies, we have been collecting a multiwavelength data set consisting of deep ATCA HI interferometry, ANU SSO 2.3m WiFeS optical integral field spectroscopy and publicly available photometry from GALEX (ultraviolet), WISE and 2MASS (both infrared).We find that these galaxies are normal star-forming spiral galaxies. However, their specific angular momentum is higher than in control galaxies, which allows these galaxies to support a massive HI disc.With the help of the HI interferometry and the optical IFU spectra, we are searching for signs of recent gas accretion. These signs may include among other things non-circular motion of HI, warped or lopsided HI discs, both of which can be identified through tilted-ring modelling of the HI disc or inhomogeneities in the IFU-based metallicity maps.In my talk I will first compare the HI rich galaxies to the control sample and the general galaxy population. I will then move on to the most HI massive galaxy in our sample and discuss its HI kinematics and its gas-phase oxygen abundance distribution in more detail. To conclude I will give an outlook on the more detailed HI kinematics of the remaining HI rich sample.

  6. Evolution of Galaxies in the Cosmic Web

    Science.gov (United States)

    Darvish Sarvestani, Behnam

    2015-12-01

    We study the effects of environment on the evolution of galaxies, with an emphasis on two different approaches towards the definition of environment: (1) environment defined based on the local surface density of galaxies and (2) environment defined based on the major components of the cosmic web; i.e., filaments, clusters and the field. In the first approach, surface density field is estimated using a variety of estimators and tested with simulations. Using the estimated surface densities assigned to galaxies, we observe a strong environmental dependence on the properties of galaxies (e.g., SFR, sSFR and the quiescent fraction) at z ≤ 1. We explore the fractional role of stellar mass and environment in quenching the star-formation. In the second approach, we use the Multi-scale Morphology Filter algorithm to disentangle the density field into its component. We apply this method to a sample of star-forming galaxies for a large-scale structure at z ˜0.84 in the HiZELS-COSMOS field. We show that the observed median SFR, stellar mass, sSFR, the mean SFR-mass relation and its scatter for star-forming galaxies do not strongly depend on the cosmic web. However, the fraction of Halpha star-forming galaxies varies with environment and is enhanced in filaments. Furthermore, we study the physical properties of a spectroscopic sample of star-forming galaxies in a large filament in the COSMOS field at z ˜0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of field galaxies. We spectroscopically confirm the presence of a large galaxy filament (˜ 8 Mpc). We show that within the uncertainties, the ionization parameter, EW, EW versus sSFR relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that on average, filament star-forming galaxies are more metal-enriched (˜ 0

  7. A panchromatic view of galaxies

    CERN Document Server

    Boselli, Alessandro

    2012-01-01

    Describing how to investigate all kinds of galaxies through a multifrequency analysis, this text is divided into three different sections. The first describes the data currently available at different frequencies, from X-rays to UV, optical, infrared and radio millimetric and centimetric, while explaining their physical meaning. In the second section, the author explains how these data can be used to determine physical parameters and quantities, such as mass and temperature. The final section is devoted to describing how the derived quantities can be used in a multifrequency analysis to study

  8. Birth of a new galaxy

    CERN Document Server

    Rodgers, L

    2001-01-01

    Scientists using the Hubble telescope have been amazed by the number of stars being created in galaxy NGC 3310. But while some scientists are observing the birth of new stars, others are predicting the end of the universe. According to supersymmetry it is possible that the universe could spontaneously change to a state where the electric force is switched off, resulting in the disintegration of all matter. Called 'vacuum fluctuation', this event is even less likely than winning the lottery jackpot twice in the same day however (1/2 page).

  9. Star Formation Rate Maps of Nearby Galaxies

    Science.gov (United States)

    Stone, Frances H.; Pooley, David

    2018-01-01

    A key component of many extragalactic studies is the correlation of a galaxy’s overall star formation rate with a particular type of astronomical object (like supernovae or luminous X-ray sources). While these correlations have allowed for considerable progress in understanding the nature, formation, and diversity of these objects, the overall star formation rate is a rather blunt instrument. Star formation is not uniform across a galaxy, and maps of local star formation rates can be made. A well calibrated method by Leroy et al. (2007) employs a weighted combination of far ultraviolet (FUV) data from the Galaxy Evolution Explorer Telescope (GALEX) and 24-micron data from the Spitzer Space Telescope. We have applied this method to archival images of several nearby galaxy as part of an ongoing effort to build a star formation rate atlas of thousands of nearby galaxies. We present results for some of the most active star forming galaxies we have analyzed so far.

  10. Linear clusters of galaxies - A194

    Science.gov (United States)

    Chapman, G. N. F.; Geller, M. J.; Huchra, J. P.

    1988-01-01

    New measurements for 160 redshifts and previous measurements for 108 other redshifts are presented for galaxies within 5 deg of A194. The galaxy distribution in A194 is shown to be inconsistent with a spherically symmetric King model. A mass-to-light ratio is derived using the virial theorem which is lower than the mean for the groups in the CfA redshift survey (Huchra and Geller, 1982; Geller, 1984). A nonparametric test for galaxy-cluster alignment and a Chi-squared test are used to search for alignment of galaxy major axes with the axis of A194. Evidence for neither luminosity segregation nor significant differences in the velocity or surface distributions of galaxies as a function of morphological type is found.

  11. Quasar Absorption Lines and SDSS Galaxies

    Science.gov (United States)

    Shoemaker, Emileigh Suzanne; Scott, Jennifer E.; Oldak, Katarzyna

    2017-01-01

    We present the results of a study of the sightlines of 45 low redshift quasars (0.06 footprint of the Sloan Digital Sky Survey. We use both the SDSS DR12 galaxy photometric data, including photometric redshifts, and the measured properties of the absorbers along with the known absorption characteristics of the intergalactic medium and the circumgalactic medium of galaxies to assign the most probable galaxy matches for each absorber in the sample, using estimated galaxy luminosities and virial radii as a discriminator. We show that the scheme can recover known galaxy-absorber matches found from spectroscopic data and thus provides a method for identifying likely pairs in photometric data sets as well as targets for spectroscopic follow up.

  12. Spectroscopy of superluminous supernova host galaxies

    DEFF Research Database (Denmark)

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

    2015-01-01

    Superluminous supernovae (SLSNe) are very bright explosions that were only discovered recently and that show a preference for occurring in faint dwarf galaxies. Understanding why stellar evolution yields different types of stellar explosions in these environments is fundamental in order to both...... uncover the elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In this paper, we present the first results of our project to study SUperluminous Supernova Host galaxIES, focusing on the sample for which we have obtained spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen......-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...

  13. Clusters and Groups of Galaxies : International Meeting

    CERN Document Server

    Giuricin, G; Mezzetti, M

    1984-01-01

    The large-scale structure of the Universe and systems Clusters, and Groups of galaxies are topics like Superclusters, They fully justify the meeting on "Clusters of great interest. and Groups of Galaxies". The topics covered included the spatial distribution and the clustering of galaxies; the properties of Superclusters, Clusters and Groups of galaxies; radio and X-ray observations; the problem of unseen matter; theories concerning hierarchical clustering, pancakes, cluster and galaxy formation and evolution. The meeting was held at the International Center for Theoretical Physics in Trieste (Italy) from September 13 to September 16, 1983. It was attended by about 150 participants from 22 nations who presented 67 invited lectures (il) and contributed papers (cp), and 45 poster papers (pp). The Scientific Organizing Committee consisted of F. Bertola, P. Biermann, A. Cavaliere, N. Dallaporta, D. Gerba1, M. Hack, J . V . Peach, D. Sciama (Chairman), G. Setti, M. Tarenghi. We are particularly indebted to D. Scia...

  14. KINEMATICS OF M51-TYPE INTERACTING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Günthardt, G. I.; Agüero, M. P. [Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, 5000 Córdoba (Argentina); Díaz, R. J., E-mail: guillermo.gunthardt@unc.edu.ar, E-mail: mpaguero@oac.uncor.edu, E-mail: rdiaz@gemini.edu [Gemini Observatory, AURA (United States)

    2016-11-01

    We present a kinematic catalog for 21 M51-type galaxies. It consists of radial velocity distributions observed with long-slit spectroscopy along different position angles, for both the main and satellite components. We detect deviations from circular motion in most of the main galaxies of each pair, due to the gravitational perturbation produced by the satellite galaxy. However, some systems do not show significant distortions in their radial velocity curves. We found some differences between the directions of the photometric and kinematic major axes in the main galaxies with a bar subsystem. The Tully–Fisher relation in the B -band and Ks -band for the present sample of M51-type systems is flatter than in isolated galaxies. Using the radial velocity data set, we built a synthetic normalized radial velocity distribution, as a reference for future modeling of these peculiar systems. The synthetic rotation curve, representing the typical rotation curve of the main galaxy in an M51-type pair, is near to solid body-like inside 4 kpc, and then is nearly flat within the radial range 5–15 kpc. The relative position angles between the major axis of the main galaxy and the companion’s location, as well as the amplitude of the velocity difference, indicate that the orbital motion of the satellite has a large projection on the equatorial plane of the main galaxy. In addition, the differences in radial velocity between the two galaxies indicate that the satellite’s orbital motion is within the range of amplitudes of the rotation curve of the main galaxy, and all the M51-type systems studied here, except for one, are gravitationally bound.

  15. Ring galaxies as the cradle for ULXs

    Science.gov (United States)

    Wolter, Anna

    2015-08-01

    Ring galaxies are unique laboratories where the effects of galaxy interactions can be studied and the final stages of stellar evolution investigated. They are characterized by high star formation rates (SFR) and low metallicity, which favours the formation of high mass remnants. The few ring galaxies for which high resolution X-ray data are available show enhanced X-ray emission, and large numbers of Ultraluminous X-ray sources (ULXs). Due to the peculiar morphology of ring galaxies, detected point sources in the ring are very likely to be physically associated with the galaxy, reducing the problem of contamination from spurious sources which affects other samples. However the evidence in the X-ray band is based on a very scanty sample of four galaxies.In order to find an unbiased sample with which to compare these findings, we have selected all the peculiar galaxies labelled as collisional rings with a spectroscopic redshift z<0.02 from the Arp & Madore `Catalogue of southern peculiar galaxies and associations'. This selection produces a sample of 12 galaxies which we have observed with Chandra and XMM-Newton. We will discuss the results of these observations and support for current models that propose low metallicity environments as the ideal cradle for ULXs. We will compare the results from this statistically selected sample with those from brighter and known ring galaxies in order to asses the likelihood to find IMBHs due to collision events. We will address the presence of other signs of interaction, from high SFR to multiwavelenght morphology and spectra (eg. IR, Halpha..).

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

    Energy Technology Data Exchange (ETDEWEB)

    Park, Y.; Krause, E.; Dodelson, S.; Jain, B.; Amara, A.; Becker, M. R.; Bridle, S. L.; Clampitt, J.; Crocce, M.; Fosalba, P.; Gaztanaga, E.; Honscheid, K.; Rozo, E.; Sobreira, F.; Sánchez, C.; Wechsler, R. H.; Abbott, T.; Abdalla, F. B.; Allam, S.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Fausti Neto, A.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; James, D. J.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Melchior, P.; Miller, C. J.; Miquel, R.; Nichol, R. C.; Ogando, R.; Plazas, A. A.; Roe, N.; Romer, A. K.; Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Vikram, V.; Walker, A. R.; Weller, J.; Zuntz, J.

    2016-09-30

    The joint analysis of galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth function of large scale structure. Our analysis will be carried out on data from the Dark Energy Survey (DES), with its measurements of both the distribution of galaxies and the tangential shears of background galaxies induced by these foreground lenses. We develop a practical approach to modeling the assumptions and systematic effects affecting small scale lensing, which provides halo masses, 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 sub-dominant. The impact of HOD parameters and their degeneracies necessitate the detailed joint modeling of the galaxy sample that we employ. Finally, 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 covered 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.

  18. Metallic Winds in Dwarf Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Robles-Valdez, F.; Rodríguez-González, A.; Hernández-Martínez, L.; Esquivel, A., E-mail: fatima.robles@correo.nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A.P. 70-543, 04510, Mexico City (Mexico)

    2017-02-01

    We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters, which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N -Body/Smooth Particle Hydrodynamics simulations of galactic winds using the gadget-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration index, gas fraction of the galactic disk, and radial distance of the starburst. We show that an off-center starburst in dwarf galaxies is the most effective mechanism to produce a significant loss of metals (material from the starburst itself). At the same time, a non-nuclear starburst produces a high efficiency of metal loss, in spite of having a moderate to low mass loss rate.

  19. The HIX galaxy survey I: Study of the most gas rich galaxies from HIPASS

    Science.gov (United States)

    Lutz, K. A.; Kilborn, V. A.; Catinella, B.; Koribalski, B. S.; Brown, T. H.; Cortese, L.; Dénes, H.; Józsa, G. I. G.; Wong, O. I.

    2017-05-01

    We present the H I eXtreme (HIX) galaxy survey targeting some of the most H I rich galaxies in the Southern hemisphere. The 13 HIX galaxies have been selected to host the most massive H I discs at a given stellar luminosity. We compare these galaxies to a control sample of average galaxies detected in the H I Parkes All Sky Survey (HIPASS). As the control sample is matched in stellar luminosity, we find that the stellar properties of HIX galaxies are similar to the control sample. Furthermore, the specific star formation rate and optical morphology do not differ between HIX and control galaxies. We find, however, the HIX galaxies to be less efficient in forming stars. For the most H I massive galaxy in our sample (ESO075-G006, log M_{H I} [M⊙] = (10.8 ± 0.1)), the kinematic properties are the reason for inefficient star formation and H I excess. Examining the Australian Telescope Compact Array (ATCA) H I imaging and Wide Field Spectrograph (WiFeS) optical spectra of ESO075-G006 reveals an undisturbed galaxy without evidence for recent major, violent accretion events. A tilted ring fitted to the H I disc together with the gas-phase oxygen abundance distribution supports the scenario that gas has been constantly accreted on to ESO075-G006 but the high specific angular momentum makes ESO075-G006 very inefficient in forming stars. Thus, a massive H I disc has been built up.

  20. Tracking Galaxy Evolution Through Low-Frequency Radio ...

    Indian Academy of Sciences (India)

    Galaxies: active—galaxies: evolution—galaxies: individual: Speca—galaxies: individual: NGC ..... AGN-heated hot gas bubbles is nearly 1056 ergs and that is comparable to ener- getic impact of low-power ..... the probability may be, can create the central engines capable of launching massive energy feedback to the host ...

  1. Evolution of dwarf galaxies in the Centaurus A group

    OpenAIRE

    Makarova, L.; Makarov, D.

    2007-01-01

    We consider star formation properties of dwarf galaxies in Cen A group observed within our HST/ACS projects number 9771 and 10235. We model color-magnitude diagrams of the galaxies under consideration and measure star formation rate and metallicity dependence on time. We study environmental dependence of the galaxy evolution and probable origin of the dwarf galaxies in the group.

  2. Diverse Group of Galaxy Types, NGC 3190 Field

    Science.gov (United States)

    2005-01-01

    Ultraviolet image of a diverse group of galaxy types. NGC 3190 is a dusty edge on spiral galaxy. NGC 3187 is highly distorted. The two are separated by only 35 kilo-parsecs (about half the diameter of our own Milky Way galaxy). A ring, elliptical, and other irregular galaxies are also present.

  3. Dusty Feedback from Massive Black Holes in Two Elliptical Galaxies

    Science.gov (United States)

    Temi, P.; Brighenti, F.; Mathews, W. G.; Amblard, A.; Riguccini, L.

    2013-01-01

    Far-infrared dust emission from elliptical galaxies informs us about galaxy mergers, feedback energy outbursts from supermassive black holes and the age of galactic stars. We report on the role of AGN feedback observationally by looking for its signatures in elliptical galaxies at recent epochs in the nearby universe. We present Herschel observations of two elliptical galaxies with strong and spatially extended FIR emission from colder grains 5-10 kpc distant from the galaxy cores. Extended excess cold dust emission is interpreted as evidence of recent feedback-generated AGN energy outbursts in these galaxies, visible only in the FIR, from buoyant gaseous outflows from the galaxy cores.

  4. Small-scale galaxy clustering in the eagle simulation

    Science.gov (United States)

    Artale, M. Celeste; Pedrosa, Susana E.; Trayford, James W.; Theuns, Tom; Farrow, Daniel J.; Norberg, Peder; Zehavi, Idit; Bower, Richard G.; Schaller, Matthieu

    2017-09-01

    We study present-day galaxy clustering in the eagle cosmological hydrodynamical simulation. eagle's galaxy formation parameters were calibrated to reproduce the redshift z = 0.1 galaxy stellar mass function, and the simulation also reproduces galaxy colours well. The simulation volume is too small to correctly sample large-scale fluctuations and we therefore concentrate on scales smaller than a few mega parsecs. We find very good agreement with observed clustering measurements from the Galaxy And Mass Assembly (GAMA) survey, when galaxies are binned by stellar mass, colour or luminosity. However, low-mass red galaxies are clustered too strongly, which is at least partly due to limited numerical resolution. Apart from this limitation, we conclude that eagle galaxies inhabit similar dark matter haloes as observed GAMA galaxies, and that the radial distribution of satellite galaxies, as a function of stellar mass and colour, is similar to that observed as well.

  5. Galaxy clusters in the cosmic web

    Science.gov (United States)

    Acebrón, A.; Durret, F.; Martinet, N.; Adami, C.; Guennou, L.

    2014-12-01

    Simulations of large scale structure formation in the universe predict that matter is essentially distributed along filaments at the intersection of which lie galaxy clusters. We have analysed 9 clusters in the redshift range 0.4DAFT/FADA survey, which combines deep large field multi-band imaging and spectroscopic data, in order to detect filaments and/or structures around these clusters. Based on colour-magnitude diagrams, we have selected the galaxies likely to be in the cluster redshift range and studied their spatial distribution. We detect a number of structures and filaments around several clusters, proving that colour-magnitude diagrams are a reliable method to detect filaments around galaxy clusters. Since this method excludes blue (spiral) galaxies at the cluster redshift, we also apply the LePhare software to compute photometric redshifts from BVRIZ images to select galaxy cluster members and study their spatial distribution. We then find that, if only galaxies classified as early-type by LePhare are considered, we obtain the same distribution than with a red sequence selection, while taking into account late-type galaxies just pollutes the background level and deteriorates our detections. The photometric redshift based method therefore does not provide any additional information.

  6. Galaxy luminosity function: evolution at high redshift

    Science.gov (United States)

    Martinet, N.; Durret, F.; Guennou, L.; Adami, C.

    2014-12-01

    There are some disagreements about the abundance of faint galaxies in high redshift clusters. DAFT/FADA (Dark energy American French Team) is a medium redshift (0.4galaxy clusters ideal to tackle these problems. We present cluster galaxy luminosity functions (GLFs) based on photometric redshifts for 30 clusters in B, V, R and I restframe bands. We show that completeness is a key parameter to understand the different observed behaviors when fitting the GLFs. We also investigate the evolution of GLFs with redshift for red and blue galaxy populations separately. We find a drop of the faint end of red GLFs which is more important at higher redshift while the blue GLF faint end remains flat in our redshift range. These results can be interpreted in terms of galaxy quenching. Faint blue galaxies transform into red ones which enrich the red sequence from high to low redshifts in clusters while some blue galaxies are still accreted from the environment, compensating for this evolution so that the global GLF does not seem to evolve.

  7. Efficiency of Metal Mixing in Dwarf Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, Yutaka [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Saitoh, Takayuki R., E-mail: yutaka.hirai@nao.ac.jp [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2017-04-01

    Metal mixing plays a critical role in the enrichment of metals in galaxies. The abundance of elements such as Mg, Fe, and Ba in metal-poor stars helps us understand the metal mixing in galaxies. However, the efficiency of metal mixing in galaxies is not yet understood. Here we report a series of N -body/smoothed particle hydrodynamics simulations of dwarf galaxies with different efficiencies of metal mixing using a turbulence-induced mixing model. We show that metal mixing apparently occurs in dwarf galaxies from Mg and Ba abundances. We find that a scaling factor for metal diffusion larger than 0.01 is necessary to reproduce the measured abundances of Ba in dwarf galaxies. This value is consistent with the value expected from turbulence theory and experiments. We also find that the timescale of metal mixing is less than 40 Myr. This timescale is shorter than the typical dynamical times of dwarf galaxies. We demonstrate that the determination of a degree of scatters of Ba abundance by the observation will help us to better constrain the efficiency of metal mixing.

  8. Tidal dwarf galaxies in cosmological simulations

    Science.gov (United States)

    Ploeckinger, Sylvia; Sharma, Kuldeep; Schaye, Joop; Crain, Robert A.; Schaller, Matthieu; Barber, Christopher

    2018-02-01

    The formation and evolution of gravitationally bound, star forming substructures in tidal tails of interacting galaxies, called tidal dwarf galaxies (TDG), has been studied, until now, only in idealized simulations of individual pairs of interacting galaxies for pre-determined orbits, mass ratios and gas fractions. Here, we present the first identification of TDG candidates in fully cosmological simulations, specifically the high-resolution simulations of the EAGLE suite. The finite resolution of the simulation limits their ability to predict the exact formation rate and survival time-scale of TDGs, but we show that gravitationally bound baryonic structures in tidal arms already form in current state-of-the-art cosmological simulations. In this case, the orbital parameter, disc orientations as well as stellar and gas masses and the specific angular momentum of the TDG forming galaxies are a direct consequence of cosmic structure formation. We identify TDG candidates in a wide range of environments, such as multiple galaxy mergers, clumpy high-redshift (up to z = 2) galaxies, high-speed encounters and tidal interactions with gas-poor galaxies. We present selection methods, the properties of the identified TDG candidates and a road map for more quantitative analyses using future high-resolution simulations.

  9. X-raying galaxies: a Chandra legacy.

    Science.gov (United States)

    Wang, Q Daniel

    2010-04-20

    This presentation reviews Chandra's major contribution to the understanding of nearby galaxies. After a brief summary on significant advances in characterizing various types of discrete x-ray sources, the presentation focuses on the global hot gas in and around galaxies, especially normal ones like our own. The hot gas is a product of stellar and active galactic nuclear feedback--the least understood part in theories of galaxy formation and evolution. Chandra observations have led to the first characterization of the spatial, thermal, chemical, and kinetic properties of the gas in our galaxy. The gas is concentrated around the galactic bulge and disk on scales of a few kiloparsec. The column density of chemically enriched hot gas on larger scales is at least an order magnitude smaller, indicating that it may not account for the bulk of the missing baryon matter predicted for the galactic halo according to the standard cosmology. Similar results have also been obtained for other nearby galaxies. The x-ray emission from hot gas is well correlated with the star formation rate and stellar mass, indicating that the heating is primarily due to the stellar feedback. However, the observed x-ray luminosity of the gas is typically less than a few percent of the feedback energy. Thus the bulk of the feedback (including injected heavy elements) is likely lost in galaxy-wide outflows. The results are compared with simulations of the feedback to infer its dynamics and interplay with the circumgalactic medium, hence the evolution of galaxies.

  10. Rapidly growing black holes and host galaxies in the distant Universe from the Herschel Radio Galaxy Evolution Project

    NARCIS (Netherlands)

    Drouart, G.; De Breuck, C.; Vernet, J.; Seymour, N.; Lehnert, M.; Barthel, P.; Bauer, F. E.; Ibar, E.; Galametz, A.; Haas, M.; Hatch, N.; Mullaney, J. R.; Nesvadba, N.; Rocca-Volmerange, B.; Röttgering, H. J. A.; Stern, D.; Wylezalek, D.

    2014-01-01

    We present results from a comprehensive survey of 70 radio galaxies at redshifts 1 2.5 are higher than the sSFR of typical star forming galaxies over the same redshift range, but are similar or perhaps lower than the galaxy population for radio galaxies at z<2.5. By comparing the sSFR and the

  11. Ammonia thermometry of star-forming galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Mangum, Jeffrey G.; MacGregor, Meredith; Svoboda, Brian E. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Darling, Jeremy [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, Box 389, University of Colorado, Boulder, CO 80309-0389 (United States); Henkel, Christian; Menten, Karl M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Schinnerer, Eva, E-mail: jmangum@nrao.edu, E-mail: mmacgreg@fas.harvard.edu, E-mail: svobodb@email.arizona.edu, E-mail: jdarling@origins.colorado.edu, E-mail: chenkel@mpifr-bonn.mpg.de, E-mail: kmenten@mpifr-bonn.mpg.de, E-mail: schinner@mpia.de [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)

    2013-12-10

    With a goal toward deriving the physical conditions in external galaxies, we present a study of the ammonia (NH{sub 3}) emission and absorption in a sample of star-forming systems. Using the unique sensitivities to kinetic temperature afforded by the excitation characteristics of several inversion transitions of NH{sub 3}, we have continued our characterization of the dense gas in star-forming galaxies by measuring the kinetic temperature in a sample of 23 galaxies and one galaxy offset position selected for their high infrared luminosity. We derive kinetic temperatures toward 13 galaxies, 9 of which possess multiple kinetic temperature and/or velocity components. Eight of these galaxies exhibit kinetic temperatures >100 K, which are in many cases at least a factor of two larger than kinetic temperatures derived previously. Furthermore, the derived kinetic temperatures in our galaxy sample, which are in many cases at least a factor of two larger than derived dust temperatures, point to a problem with the common assumption that dust and gas kinetic temperatures are equivalent. As previously suggested, the use of dust emission at wavelengths greater than 160 μm to derive dust temperatures, or dust heating from older stellar populations, may be skewing derived dust temperatures in these galaxies to lower values. We confirm the detection of high-excitation OH {sup 2}Π{sub 3/2} J = 9/2 absorption toward Arp 220. We also report the first detections of non-metastable NH{sub 3} inversion transitions toward external galaxies in the (2,1) (NGC 253, NGC 660, IC 342, and IC 860), (3,1), (3,2), (4,3), (5,4) (all in NGC 660), and (10,9) (Arp 220) transitions.

  12. Galaxy Zoo: Observing secular evolution through bars

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, Edmond; Faber, S. M.; Koo, David C. [Department of Astronomy and Astrophysics, 1156 High Street, University of California, Santa Cruz, CA 95064 (United States); Athanassoula, E.; Bosma, A. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Masters, Karen L.; Nichol, Robert C.; Melvin, Thomas [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Lintott, Chris [Oxford Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Schawinski, Kevin [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); Skibba, Ramin A. [Center for Astrophysics and Space Sciences, Department of Physics, 9500 Gilman Drive, University of California, San Diego, CA 92093 (United States); Willett, Kyle W., E-mail: ec2250@gmail.com [School of Physics and Astronomy, University of Minnesota, MN 55455 (United States)

    2013-12-20

    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).

  13. Dwarf Galaxies Swimming in Tidal Tails

    Science.gov (United States)

    2005-01-01

    This false-color infrared image from NASA's Spitzer Space Telescope shows little 'dwarf galaxies' forming in the 'tails' of two larger galaxies that are colliding together. The big galaxies are at the center of the picture, while the dwarfs can be seen as red dots in the red streamers, or tidal tails. The two blue dots above the big galaxies are stars in the foreground. Galaxy mergers are common occurrences in the universe; for example, our own Milky Way galaxy will eventually smash into the nearby Andromeda galaxy. When two galaxies meet, they tend to rip each other apart, leaving a trail, called a tidal tail, of gas and dust in their wake. It is out of this galactic debris that new dwarf galaxies are born. The new Spitzer picture demonstrates that these particular dwarfs are actively forming stars. The red color indicates the presence of dust produced in star-forming regions, including organic molecules called polycyclic aromatic hydrocarbons. These carbon-containing molecules are also found on Earth, in car exhaust and on burnt toast, among other places. Here, the molecules are being heated up by the young stars, and, as a result, shine in infrared light. This image was taken by the infrared array camera on Spitzer. It is a 4-color composite of infrared light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange), and 8.0 microns (red). Starlight has been subtracted from the orange and red channels in order to enhance the dust features.

  14. The SAMI Galaxy Survey: disc-halo interactions in radio-selected star-forming galaxies

    Science.gov (United States)

    Leslie, S. K.; Bryant, J. J.; Ho, I.-T.; Sadler, E. M.; Medling, A. M.; Groves, B.; Kewley, L. J.; Bland-Hawthorn, J.; Croom, S. M.; Wong, O. I.; Brough, S.; Tescari, E.; Sweet, S. M.; Sharp, R.; Green, A. W.; López-Sánchez, Á. R.; Allen, J. T.; Fogarty, L. M. R.; Goodwin, M.; Lawrence, J. S.; Konstantopoulos, I. S.; Owers, M. S.; Richards, S. N.

    2017-10-01

    In this paper, we compare the radio emission at 1.4 GHz with optical outflow signatures of edge-on galaxies. We report observations of six edge-on star-forming galaxies in the Sydney-AAO Multiobject Integral-field spectrograph Galaxy Survey with 1.4 GHz luminosities >1 × 1021 W Hz-1. Extended minor axis optical emission is detected with enhanced [N II]/H α line ratios and velocity dispersions consistent with galactic winds in three of six galaxies. These galaxies may host outflows driven by a combination of thermal and cosmic ray processes. We find that galaxies with the strongest wind signatures have extended radio morphologies. Our results form a baseline for understanding the driving mechanisms of galactic winds.

  15. Kinematic Effects of Tidal Interaction on Galaxy Rotation Curves

    OpenAIRE

    Barton, Elizabeth J.; Bromley, Benjamin C.; Geller, Margaret J.

    1998-01-01

    We use self-consistent N-body models, in conjunction with models of test particles moving in galaxy potentials, to explore the initial effects of interactions on the rotation curves of spiral galaxies. Using nearly self-consistent disk/bulge/halo galaxy models (Kuijken & Dubinski 1995), we simulate the first pass of galaxies on nearly parabolic orbits; we vary orbit inclinations, galaxy halo masses and impact parameters. For each simulation, we mimic observed rotation curves of the model gala...

  16. A dearth of dark matter in ordinary elliptical galaxies.

    Science.gov (United States)

    Romanowsky, Aaron J; Douglas, Nigel G; Arnaboldi, Magda; Kuijken, Konrad; Merrifield, Michael R; Napolitano, Nicola R; Capaccioli, Massimo; Freeman, Kenneth C

    2003-09-19

    The kinematics of the outer parts of three intermediate-luminosity elliptical galaxies were studied with the Planetary Nebula Spectrograph. The galaxies' velocity-dispersion profiles were found to decline with the radius, and dynamical modeling of the data indicates the presence of little if any dark matter in these galaxies' halos. This unexpected result conflicts with findings in other galaxy types and poses a challenge to current galaxy formation theories.

  17. Samsung Galaxy S4 for dummies

    CERN Document Server

    Hughes, Bill

    2013-01-01

    Explore a world of possibilities with your Samsung Galaxy S 4 smartphone Everything's more exciting when you've got the Galaxy in your hand. Let For Dummies be your guide to getting the most out of your Galaxy S 4. You'll cruise through the smartphone basics and set up process before moving on to the fun stuff like staying in touch with e-mail and texting, surfing the web, navigating with maps, shooting and sharing photos and video, watching movies, listening to music, and so much more. Whether you're entering the smartphone world for the first time or just moving up to

  18. Samsung Galaxy S6 for dummies

    CERN Document Server

    Hughes, Bill

    2015-01-01

    Explore the capabilities of your Samsung Galaxy S 6 with this definitive guide! Learning to use a new phone can be both difficult and frustrating. With confusing documentation and baffling support, the references provided by phone manufacturers can be intimidating. Enter Samsung Galaxy S 6 For Dummies! This extensive yet practical guide walks you through the most useful features of your new Samsung Galaxy S 6-and it shows you all the best tricks to getting the most out of your device. With an accessible and fun, yet informative writing style, this is a text that you'll refer to again and agai

  19. Samsung Galaxy Tab S for dummies

    CERN Document Server

    Gookin, Dan

    2015-01-01

    Explore your Galaxy Tab S with an expert tour guide at your side Samsung Galaxy Tab S For Dummies is a user-friendly guide to getting the most out of your new tablet. You'll discover how different the tablet experience is from the desktop, laptop, or smartphone, and learn how to take advantage of everything your Galaxy Tab S has to offer. This entertaining guide walks you through each feature one by one, helping you learn exactly what your tablet can do for you. With everything from reading to playing games and surfing the Internet, you will learn how to be productive and have fun, too! Nav

  20. Practical statistics for the voids between galaxies

    Directory of Open Access Journals (Sweden)

    Zaninetti L.

    2010-01-01

    Full Text Available The voids between galaxies are identified with the volumes of the Poisson Voronoi tessellation. Two new survival functions for the apparent radii of voids are derived. The sectional normalized area of the Poisson Voronoi tessellation is modelled by the Kiang function and by the exponential function. Two new survival functions with equivalent sectional radius are therefore derived; they represent an alternative to the survival function of voids between galaxies as given by the self-similar distribution. The spatial appearance of slices of the 2dF Galaxy Redshift Survey is simulated.

  1. Practical Statistics for the Voids Between Galaxies

    Directory of Open Access Journals (Sweden)

    Zaninetti, L.

    2010-12-01

    Full Text Available The voids between galaxies are identified withthe volumes of the Poisson Voronoi tessellation.Two new survival functions for the apparent radii of voids are derived. The sectional normalized area ofthe Poisson Voronoi tessellation is modelledby the Kiang function and by the exponential function. Two new survival functions with equivalent sectional radius are therefore derived; they represent an alternative to the survival function of voids between galaxies as given by the self-similar distribution. The spatial appearance of slices of the 2dF Galaxy Redshift Survey is simulated.

  2. The orbital evolution of binary galaxies

    Science.gov (United States)

    Chan, R.; Junqueira, S.

    2001-02-01

    We present the results of self-consistent numerical simulations performed to study the orbital circularization of binary galaxies. We have generalized a previous model (Junqueira & de Freitas Pacheco 1994) and confirmed partially their results. The orbital evolution of pairs of galaxies is faster when we consider interacting pairs with contacting ``live'' galaxy halos but the circularization time remains larger than the Hubble time. Besides, the time behavior of the orbits has changed in comparison with previous work because of tidal forces and dynamical friction acting on the halos.

  3. Inside-out formation of massive galaxies

    Science.gov (United States)

    de la Rosa, I. G.

    2017-03-01

    A significant fraction of the present day massive galaxies have compact cores embedded inside their disks or halos. Strikingly, those compact cores are similar to the massive high-redshift quiescent compact galaxies, nicknamed red-nuggets. We present observational evidence supporting an inside-out formation scenario, where present-day massive galaxies can begin as dense spheroidal cores (red-nuggets), around which either a spheroidal halo or a disk are accreted later. This contribution is based on the paper by de la Rosa et al. (2016).

  4. Monolithic View of Galaxy Formation and Evolution

    Directory of Open Access Journals (Sweden)

    Cesare Chiosi

    2014-07-01

    Full Text Available We review and critically discuss the current understanding of galaxy formation and evolution limited to Early Type Galaxies (ETGs as inferred from the observational data and briefly contrast the hierarchical and quasi-monolithic paradigms of formation and evolution. Since in Cold Dark Matter (CDM cosmogony small scale structures typically collapse early and form low-mass haloes that subsequently can merge to assembly larger haloes, galaxies formed in the gravitational potential well of a halo are also expected to merge thus assembling their mass hierarchically. Mergers should occur all over the Hubble time and large mass galaxies should be in place only recently. However, recent observations of high redshift galaxies tell a different story: massive ETGs are already in place at high redshift. To this aim, we propose here a revision of the quasi-monolithic scenario as an alternative to the hierarchical one, in which mass assembling should occur in early stages of a galaxy lifetime and present recent models of ETGs made of Dark and Baryonic Matter in a Λ-CDM Universe that obey the latter scheme. The galaxies are followed from the detachment from the linear regime and Hubble flow at z ≥ 20 down to the stage of nearly complete assembly of the stellar content (z ∼ 2 − 1 and beyond.  It is found that the total mass (Mh = MDM + MBM and/or initial over-density of the proto-galaxy drive the subsequent star formation histories (SFH. Massive galaxies (Mh ~ _1012M⊙ experience a single, intense burst of star formation (with rates ≥ 103M⊙/yr at early epochs, consistently with observations, with a weak dependence on the initial over-density; intermediate mass haloes (Mh~_ 1010 − 1011M⊙ have star formation histories that strongly depend on their initial over-density; finally, low mass haloes (Mh ~_ 109M⊙ always have erratic, burst-like star forming histories. The present-day properties (morphology, structure, chemistry and photometry of the

  5. Image processing of galaxy photographs

    Science.gov (United States)

    Arp, H.; Lorre, J.

    1976-01-01

    New computer techniques for analyzing and processing photographic images of galaxies are presented, with interesting scientific findings gleaned from the processed photographic data. Discovery and enhancement of very faint and low-contrast nebulous features, improved resolution of near-limit detail in nebulous and stellar images, and relative colors of a group of nebulosities in the field are attained by the methods. Digital algorithms, nonlinear pattern-recognition filters, linear convolution filters, plate averaging and contrast enhancement techniques, and an atmospheric deconvolution technique are described. New detail is revealed in images of NGC 7331, Stephan's Quintet, Seyfert's Sextet, and the jet in M87, via processes of addition of plates, star removal, contrast enhancement, standard deviation filtering, and computer ratioing to bring out qualitative color differences.

  6. Chaos in elliptical galaxy models

    CERN Document Server

    Karanis, G I

    2003-01-01

    We investigate the properties of motion in a logarithmic galactic potential. The model can be considered to describe the motion in the meridian, r-z plane, of an elliptical galaxy with a dense nucleus or bulge of radius c. For a given value of c, there is a critical value of the angular momentum L sub z sub c such as for L sub z<=L sub z sub c , stars, moving near the galactic plane, are scattered to higher scale z heights displaying chaotic motion. Our numerical calculations show that there exists a linear relationship between the radius of the nucleus and the critical value of the angular momentum. This linear relationship can be found using some elementary theoretical arguments. We use the distribution of radial velocities in order to distinguish ordered from chaotic motion. Comparison with previous work is also made.

  7. Chaos in elliptical galaxy models

    Energy Technology Data Exchange (ETDEWEB)

    Karanis, G.I.; Caranicolas, N.D

    2003-07-01

    We investigate the properties of motion in a logarithmic galactic potential. The model can be considered to describe the motion in the meridian, r-z plane, of an elliptical galaxy with a dense nucleus or bulge of radius c. For a given value of c, there is a critical value of the angular momentum L{sub zc} such as for L{sub z}{<=}L{sub zc}, stars, moving near the galactic plane, are scattered to higher scale z heights displaying chaotic motion. Our numerical calculations show that there exists a linear relationship between the radius of the nucleus and the critical value of the angular momentum. This linear relationship can be found using some elementary theoretical arguments. We use the distribution of radial velocities in order to distinguish ordered from chaotic motion. Comparison with previous work is also made.

  8. Exploring Our Galaxy's Thick Disk

    Science.gov (United States)

    Kohler, Susanna

    2017-12-01

    What is the structure of the Milky Ways disk, and how did it form? A new study uses giant stars to explore these questions.A View from the InsideSchematic showing an edge-on, not-to-scale view of what we think the Milky Ways structurelookslike. The thick disk is shown in yellow and the thin disk is shown in green. [Gaba p]Spiral galaxies like ours are often observed to have disks consisting of two components: a thin disk that lies close to the galactic midplane, and a thick disk that extends above and below this. Past studies have suggested that the Milky Ways disk hosts the same structure, but our position embedded in the Milky Way makes this difficult to confirm.If we can measure the properties of a broad sample of distant tracer stars and use this to better understand the construction of the Milky Ways disk, then we can start to ask additional questions like, how did the disk components form? Formation pictures for the thick disk generally fall into two categories:Stars in the thick disk formed within the Milky Way either in situ or by migrating to their current locations.Stars in the thick disk formed in satellite galaxies around the Milky Way and then accreted when the satellites were disrupted.Scientists Chengdong Li and Gang Zhao (NAO Chinese Academy of Sciences, University of Chinese Academy of Sciences) have now used observations of giant stars which can be detected out to great distances due to their brightness to trace the properties of the Milky Ways thick disk and address the question of its origin.Best fits for the radial (top) and vertical (bottom) metallicity gradients of the thick-disk stars. [Adapted from Li Zhao 2017]Probing OriginsLi and Zhao used data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) in China to examine a sample of 35,000 giant stars. The authors sorted these stars into different disk components halo, thin disk, and thick disk based on their kinematic properties, and then explored how the orbital and

  9. Galaxy models with live halos

    CERN Document Server

    Sellwood, J A

    1980-01-01

    Computer models of galaxies are described, in which the disc stars and the halo stars are both treated fully self consistently. These were used to test the validity of the 'rigid halo' approximation usually employed when studying the instabilities of a disc of stars. The models show that very little interaction between the populations occurs while the disc remains nearly axisymmetric, but a strong bar is able to transfer angular momentum from the disc to the halo. The global bar stability of the disc is not greatly affected by the interaction between the two stellar populations, and it is found that a large fraction of the total galactic mass is still required in the spheroidal component if bar formation is to be prevented. (36 refs).

  10. Massive Black Holes and Galaxies

    CERN Multimedia

    CERN. Geneva

    2016-01-01

    Evidence has been accumulating for several decades that many galaxies harbor central mass concentrations that may be in the form of black holes with masses between a few million to a few billion time the mass of the Sun. I will discuss measurements over the last two decades, employing adaptive optics imaging and spectroscopy on large ground-based telescopes that prove the existence of such a massive black hole in the Center of our Milky Way, beyond any reasonable doubt. These data also provide key insights into its properties and environment. Most recently, a tidally disrupting cloud of gas has been discovered on an almost radial orbit that reached its peri-distance of ~2000 Schwarzschild radii in 2014, promising to be a valuable tool for exploring the innermost accretion zone. Future interferometric studies of the Galactic Center Black hole promise to be able to test gravity in its strong field limit.

  11. Les amas de galaxies : une sonde pour l'évolution des galaxies et la cosmologie

    OpenAIRE

    Martinet, Nicolas

    2015-01-01

    This thesis presents some recent results concerning galaxy evolution and cosmology,based on the observation of galaxy clusters at optical wavelengths. We first introduce the main properties of galaxy clusters (Sect. 1.1) and how they can be used for cosmology within the standard cosmological model (Sect. 1.2). A large fraction of the presented results comes from the study of the DAFT/FADA galaxy cluster survey at redshifts 0.4 < z < 0.9 (Sect. 1.3). We divide our study in two parts according ...

  12. Bar-spheroid interaction in galaxies

    Science.gov (United States)

    Hernquist, Lars; Weinberg, Martin D.

    1992-01-01

    N-body simulation and linear analysis is employed to investigate the secular evolution of barred galaxies, with emphasis on the interaction between bars and spheroidal components of galaxies. This interaction is argued to drive secular transfer of angular momentum from bars to spheroids, primarily through resonant coupling. A moderately strong bar, having mass within corotation about 0.3 times the enclosed spheroid mass, is predicted to shed all its angular momentum typically in less than about 10 exp 9 yr. Even shorter depletion time scales are found for relatively more massive bars. It is suggested either that spheroids around barred galaxies are structured so as to inhibit strong coupling with bars, or that bars can form by unknown processes long after disks are established. The present models reinforce the notion that bars can drive secular evolution in galaxies.

  13. Traces de l'interaction entre galaxies

    Science.gov (United States)

    Duc, Pierre-Alain

    2016-08-01

    Within a galaxy, collisions between stars are exceptional; collisions between galaxies are themselves much more frequent. They are even supposed to play a major role in the formation of structures according to the standard hierarchical cosmological model. Gravitational interactions, tidal forces and following mergers shape the morphology of galaxies, and leave vestiges which can survive for a few Gyr. They consist of stellar shells, streams, tails and plumes which emit a diffuse and extended optical light. Several deep imaging projects use telescopes of all sizes to try to detect this light. We detail here what the census of collisional debris can tel us about the past history of galaxies and about the models and simulations supposedly accounting for it.

  14. Dynamics of Galaxy Clusters and their Outskirts

    DEFF Research Database (Denmark)

    Falco, Martina

    Galaxy clusters have demonstrated to be powerful probes of cosmology, since their mass and abundance depend on the cosmological model that describes the Universe and on the gravitational formation process of cosmological structures. The main challenge in using clusters to constrain cosmology...... is that their masses cannot be measured directly, but need to be inferred indirectly through their observable properties. The most common methods extract the cluster mass from their strong X-ray emission or from the measured redshifts of the galaxy members. The gravitational lensing effect caused by clusters...... on the background galaxies is also an important trace of their total mass distribution.In the work presented within this thesis, we exploit the connection between the gravitational potential of galaxy clusters and the kinematical properties of their surroundings, in order to determine the total cluster mass...

  15. Optical spectrophotometry of Wolf-Rayet galaxies

    Science.gov (United States)

    Vacca, William D.; Conti, Peter S.

    1992-01-01

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

  16. Biased galaxy formation with baryonic dark matter.

    Science.gov (United States)

    Morikawa, M.

    The author studies the possibility of baryonic dark matter associated with a galaxy/halo in the light of the biasing which segregates the luminous inner region and the dark outer region of a galaxy. He proposes a biasing mechanism based on the fact that stellar luminosity is highly sensitive to the strength of the gravitational force. He uses a nonconformal scalar field model in which the scalar field accumulates around the gravitational potential formed by the baryonic matter and yields a slight galactocentric gradient of the effective gravitational constant G. A small gradient (the value of G becomes half of the ordinary value at the distance about 100 kpc from the center of the galaxy) is sufficient to explain the smooth flat rotation curve of the spiral galaxies as well as a sharp cutoff of the luminosity profile. Several tests of this scenario are studied.

  17. Curious Case of a Stripped Elliptical Galaxy

    Science.gov (United States)

    Kohler, Susanna

    2017-05-01

    MUSE fields of view (1 1 for each square) are superimposed on a pseudo-color image of the elliptical galaxy in Abell 2670. The blue blobs lie in the opposite direction to the galactic center. [Sheen et al. 2017]An elliptical galaxy in the cluster Abell 2670 has been discovered with some unexpected features. What conditions led to this galaxys unusual morphology?Unexpected JellyfishWe often see galaxies that have been disrupted or reshaped due to their motion within a cluster but these are usually late-type galaxies like our own. Such gas-rich galaxies are distorted by ram pressure as they fall into the cluster center, growing long tails of stripped gas and young stars that earn them the name jellyfish galaxies.But early-type, elliptical galaxies have long since used up or cleared out most of their gas, and they correspondingly form very few new stars. Its therefore unsurprising that theyve never before been spotted to have jellyfish-like features.Panels a and b show zoomed-in observations of some of the star-forming blobs with tadpole-like morphology. Panel c shows a schematic illustration of how ram-pressure stripping causes this shape. [Adapted from Sheen et al. 2017]New deep observations of an elliptical galaxy in the cluster Abell 2670, however, have revealed some unexpected structures for an early-type galaxy. Led by Yun-Kyeong Sheen (Korea Astronomy and Space Science Institute), a team of scientists now reports on the optical and spectroscopic observations of this galaxy, made with the MUSE instrument on the Very Large Telescope in Chile.Tadpole BlobsThese observations reveal a number of features, including starbursts at the galactic center, 80-parsec-long tails of ionized gas, disturbed halo features, and several blue star-forming blobs with tadpole-like morphology in the surrounding region. The blobs have stellar tails that point in the direction of motion of the galaxy (toward the cluster center) and streams of ionized gas that point in the opposite

  18. 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

  19. In Pursuit of the Least Luminous Galaxies

    Directory of Open Access Journals (Sweden)

    Beth Willman

    2010-01-01

    Full Text Available The dwarf galaxy companions to the Milky Way are unique cosmological laboratories. With luminosities as low as 10−7LMW, they inhabit the lowest mass dark matter halos known to host stars and are presently the most direct tracers of the distribution, mass spectrum, and clustering scale of dark matter. Their resolved stellar populations also facilitate detailed studies of their history and mass content. To fully exploit this potential requires a well-defined census of virtually invisible galaxies to the faintest possible limits and to the largest possible distances. I review the past and present impacts of survey astronomy on the census of Milky Way dwarf galaxy companions and discuss the future of finding ultra-faint dwarf galaxies around the Milky Way and beyond in wide-field survey data.

  20. Detecting supernova remnants in external galaxies

    Science.gov (United States)

    Dickel, J. R.; Dodorico, S.

    1985-01-01

    Identification of supernova remnants (SNR) in external galaxies through the combined use of radio, optical and X-ray surveys is discussed. Some 24 likely distant galaxy SNR have been found in the past six years, though confirmation is often difficult. Radio surveys of other galaxies are restricted by background object contamination in the field, and confirmation of these candidates requires other techniques. Optical measurement of the ratio of the forbidden SII doublet at .6717 and .6731 microns to H-alpha, followed by spectroscopic or radio confirmation, has successfully identified SNR in the LMC and other galaxies, though few in number. Most of the SNR in the Magellanic Clouds have been detected as X-ray emitters, but towards M31 there are no coincidences between the lists of optical SNR and X-ray sources. An increase in SNR identifications should result from use of the Space Telescope and continued use of the VLA.

  1. The Cosmic Dance of Distant Galaxies

    Science.gov (United States)

    2006-03-01

    GIRAFFE at VLT reveals the turbulent life of distant galaxies Studying several tens of distant galaxies, an international team of astronomers found that galaxies had the same amount of dark matter relative to stars 6 billion years ago as they have now. If confirmed, this suggests a much closer interplay between dark and normal matter than previously believed. The scientists also found that as many as 4 out of 10 galaxies are out of balance. These results shed a new light on how galaxies form and evolve since the Universe was only half its current age. ESO PR Photo 10a/06 ESO PR Photo 10a/06 Collision Between Galaxies (Artist's Impression) "This may imply that collisions and merging are important in the formation and evolution of galaxies", said François Hammer, Paris Observatory, France, and one of the leaders of the team [1]. The scientists were interested in finding out how galaxies that are far away - thus seen as they were when the Universe was younger - evolved into the ones nearby. In particular, they wanted to study the importance of dark matter in galaxies. "Dark matter, which composes about 25% of the Universe, is a simple word to describe something we really don't understand," said Hector Flores, co-leader. "From looking at how galaxies rotate, we know that dark matter must be present, as otherwise these gigantic structures would just dissolve." In nearby galaxies, and in our own Milky Way for that matter, astronomers have found that there exists a relation between the amount of dark matter and ordinary stars: for every kilogram of material within a star there is roughly 30 kilograms of dark matter. But does this relation between dark and ordinary matter still hold in the Universe's past? ESO PR Photo 10b/06 ESO PR Photo 10b/06 Mapping Distant Galaxies (FLAMES-GIRAFFE/VLT) This required measuring the velocity in different parts of distant galaxies, a rather tricky experiment: previous measurements were indeed unable to probe these galaxies in sufficient

  2. Enhancement of features in galaxy images

    Science.gov (United States)

    Djorgovski, S.

    1986-01-01

    Several image-enhancement techniques useful for morphological analysis of galactic or cometary images are described and compared. Such techniques can be used to search for, and investigate the properties of dust lanes, stellar disks or rings, jets, shells, tidal distortions, etc. Applications of the techniques are illustrated on CCD images of the peculiar galaxy Arp 230; this object has a rich morphology, indicative of a merger of two disk galaxies.

  3. Selections from 2016: A Very Dark Galaxy

    Science.gov (United States)

    Kohler, Susanna

    2016-12-01

    Editors note:In these last two weeks of 2016, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.A High Stellar Velocity Dispersion and 100 Globular Clusters for the Ultra-Diffuse Galaxy Dragonfly 44Published August2016Main takeaway:Using the Keck Observatory and the Gemini North telescope in Hawaii, a team led by Pieter van Dokkum (Yale University) discovered the very dim galaxy Dragonfly 44, located in the Coma cluster. The team estimated the center of this galaxys disk to be a whopping 98% dark matter.Why its interesting:Dragonfly 44, though dim, was discovered to host around 100 globular clusters. Measuring the dynamics of these clusters allowed van Dokkum and collaborators to estimate the mass of Dragonfly 44: roughly a trillion times the mass of the Sun. This is similar to the mass of the Milky Way, and yet the Milky Way has over a hundred times more stars than this intriguing galaxy. Its very unexpected to find a galaxy this massive that has a dark-matter fraction this high.What we can learn from this:How do ultra-faint galaxies like these form? One theory is that theyre failed normal galaxies: they have the sizes, dark-matter content, and globular cluster systems of much more luminous galaxies, but they were prevented from building up a normal stellar population. So far, Dragonfly 44s properties seem consistent with this picture.CitationPieter van Dokkum et al 2016 ApJL 828 L6. doi:10.3847/2041-8205/828/1/L6

  4. Metallicities of Galaxies in the Local Universe

    Science.gov (United States)

    Hirschauer, Alec Seth

    2018-01-01

    The degree of heavy-element enrichment for star-forming galaxies in the universe is a fundamental astrophysical characteristic which traces the amount of stellar nucleosynthesis undertaken by the constituent population of stars. Estimating this quantity via the so-called "direct-method" is observationally challenging and requires measurement of intrinsically weak temperature-sensitive nebular emission lines, however these are typically not found for galaxies unless their emission lines are exceptionally bright. Metal abundances ("metallicities") must then therefore be estimated by empirical means utilizing ratios of strong emission lines, calibrated to sources of known abundance and/or theoretical models, which are measurable in essentially any nebular spectrum of a star-forming system. Relationships concerning metallicities in galaxies such as the luminosity-metallicity and mass-metallicity are critically dependent upon reliable estimations of abundances. Therefore, having a reliable observational constraint is paramount to developing models which accurately reflect the universe. This dissertation presentation explores metallicities for galaxies in the local universe through a variety of means. First, an attempt is made to improve calibrations of empirical relationships for estimating abundances for star-forming galaxies at high-metallicities, finding some intrinsic shortcomings but also revealing some interesting new findings regarding the computation of the electron gas of star-forming systems, as well as detecting some anomalously under-abundant, overly-luminous galaxies. Second, the development of a self-consistent scale for estimating metallicities allows for the creation of luminosity-metallicity and mass-metallicity relations for a statistically representative sample of star-forming galaxies in the local universe. Finally, a discovery is made of an extremely metal-poor star-forming galaxy, which opens the possibility to find more similar systems and to

  5. Tiny galaxies help unravel dark matter mystery

    CERN Document Server

    O'Hanlon, Larry

    2007-01-01

    "The 70-year effort to unravel the mysteries of dark matter just got a big boost from some very puny galaxies. In the pas few years, a score of dwarf galaxies have been discovered hanging about the fringes of the Milky way. Now new measurements of the few stars int hese dwarfs reveal them to be dark mater distilleries, with upwards of 1'000 times more dark than normal matter." (3 pages)

  6. Formation of dwarf galaxies in tidal tails

    Science.gov (United States)

    Barnes, Joshua E.; Hernquist, Lars

    1992-01-01

    The results are reported of numerical simulations of encounters between disk galaxies, each modeled with a central bulge, an exponential disk, and a spheroidal dark-matter halo. It is found that dwarf systems form in material drawn out during the encounter; these objects can capture large amounts of moderately enriched gas but retain little dark matter from their parents' haloes. They should therefore have lower mass-to-light ratios than galaxies formed directly by the collapse of primordial matter.

  7. Shell galaxies as laboratories for testing MOND

    Czech Academy of Sciences Publication Activity Database

    Bílek, Michal; Ebrová, Ivana; Jungwiert, Bruno; Jílková, L.; Bartošková, Kateřina

    2015-01-01

    Roč. 93, č. 2 (2015), s. 203-212 ISSN 0008-4204 Grant - others:GA MŠk(CZ) LM2010005; Operational Program Research and Development for Innovations(XE) CZ. 1.05/3.2.00/08.0144 Institutional support: RVO:67985815 Keywords : modified newtonian dynamics * dwarf spheroidal galaxy * elliptic galaxies Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.724, year: 2015

  8. Dynamical theory of dense groups of galaxies

    Science.gov (United States)

    Mamon, Gary A.

    1990-01-01

    It is well known that galaxies associate in groups and clusters. Perhaps 40% of all galaxies are found in groups of 4 to 20 galaxies (e.g., Tully 1987). Although most groups appear to be so loose that the galaxy interactions within them ought to be insignificant, the apparently densest groups, known as compact groups appear so dense when seen in projection onto the plane of the sky that their members often overlap. These groups thus appear as dense as the cores of rich clusters. The most popular catalog of compact groups, compiled by Hickson (1982), includes isolation among its selection critera. Therefore, in comparison with the cores of rich clusters, Hickson's compact groups (HCGs) appear to be the densest isolated regions in the Universe (in galaxies per unit volume), and thus provide in principle a clean laboratory for studying the competition of very strong gravitational interactions. The $64,000 question here is then: Are compact groups really bound systems as dense as they appear? If dense groups indeed exist, then one expects that each of the dynamical processes leading to the interaction of their member galaxies should be greatly enhanced. This leads us to the questions: How stable are dense groups? How do they form? And the related question, fascinating to any theorist: What dynamical processes predominate in dense groups of galaxies? If HCGs are not bound dense systems, but instead 1D change alignments (Mamon 1986, 1987; Walke & Mamon 1989) or 3D transient cores (Rose 1979) within larger looser systems of galaxies, then the relevant question is: How frequent are chance configurations within loose groups? Here, the author answers these last four questions after comparing in some detail the methods used and the results obtained in the different studies of dense groups.

  9. Watching the Birth of a Galaxy Cluster?

    Science.gov (United States)

    1999-07-01

    First Visiting Astronomers to VLT ANTU Observe the Early Universe When the first 8.2-m VLT Unit Telescope (ANTU) was "handed over" to the scientists on April 1, 1999, the first "visiting astronomers" at Paranal were George Miley and Huub Rottgering from the Leiden Observatory (The Netherlands) [1]. They obtained unique pictures of a distant exploding galaxy known as 1138 - 262 . These images provide new information about how massive galaxies and clusters of galaxies may have formed in the early Universe. Formation of clusters of galaxies An intriguing question in modern astronomy is how the first galaxies and groupings or clusters of galaxies emerged from the primeval gas produced in the Big Bang. Some theories predict that giant galaxies, often found at the centres of rich galaxy clusters, are built up through a step-wise process. Clumps develop in this gas and stars condense out of those clumps to form small galaxies. Finally these small galaxies merge together to form larger units. An enigmatic class of objects important for investigating such scenarios are galaxies which emit intense radio emission from explosions that occur deep in their nuclei. The explosions are believed to be triggered when material from the merging swarm of smaller galaxies is fed into a rotating black hole located in the central regions. There is strong evidence that these distant radio galaxies are amongst the oldest and most massive galaxies in the early Universe and are often located at the heart of rich clusters of galaxies. They can therefore help pinpoint regions of the Universe in which large galaxies and clusters of galaxies are being formed. The radio galaxy 1138-262 The first visiting astronomers pointed ANTU towards a particularly important radio galaxy named 1138-262 . It is located in the southern constellation Hydra (The Water Snake). This galaxy was discovered some years ago using ESO's 3.5-m New Technology Telescope (NTT) at La Silla. Because 1138-262 is at a distance of

  10. 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.

  11. Galaxy Evolution with Stellar Disks, Halos, and Streams in Nearby Galaxies

    Science.gov (United States)

    Staudaher, Shawn M.

    This thesis begins with a deep-dive into the stellar properties of the nearby spiral galaxy, M 63, a member of the EDGES (Extended Disk Galaxy Exploration Science) survey. Deep ( 28 AB mag arcsec-2) 3.6 mum imaging from the Spitzer Space Telescope reveals that the spiral structure of this galaxy is enveloped by an extended stellar halo, the result of the accretion of smaller galaxies. The mass of this stellar halo agrees well with results from the latest large scale LambdaCDM based galaxy evolution models. M 63 is also host to a tidal stream, an actively accreting satellite. The mass of the progenitor satellite is large enough that only sixteen similarly sized accretion events would account for the mass in the stellar halo. In addition, the majority of satellite accretion must have happened in the past as the average accretion rate derived from the stellar halo is significantly larger than the average accretion rate derived from the more recent tidal stream. The scope of the thesis is then extended to include the full sample of 92 nearby galaxies from EDGES. This is the largest Spitzer Space Telescope survey to probe the extended stellar properties of nearby galaxies. The surface brightness profiles of EDGES galaxies contain an unprecedented number of breaks (transitions from one galactic component to the next) given the sample size of EDGES, proving that studies of break statistics are incomplete without significantly deep imaging. The surface brightness profiles are decomposed into their individual components and the stellar mass for each component is measured. Seven galaxies contain strong evidence for the presence of stellar halos, and the masses of these halos agree with predictions from LambdaCDM based galaxy evolution models. However, the lack of stellar halos in general may be evidence that simulations continue to suffer from the so-called "missing satellite problem", where the number of satellite galaxies is overpredicted compared to observations.

  12. Faint Submillimeter Galaxies Behind Lensing Clusters

    Science.gov (United States)

    Hsu, Li-Yen; Lauchlan Cowie, Lennox; Barger, Amy J.; Desai, Vandana; Murphy, Eric J.

    2017-01-01

    Faint submillimeter galaxies are the major contributors to the submillimeter extragalactic background light and hence the dominant star-forming population in the dusty universe. Determining how much these galaxies overlap the optically selected samples is critical to fully account for the cosmic star formation history. Observations of massive cluster fields are the best way to explore this faint submillimeter population, thanks to gravitational lensing effects. We have been undertaking a lensing cluster survey with the SCUBA-2 camera on the James Clerk Maxwell Telescope to map nine galaxy clusters, including the northern five clusters in the HST Frontier Fields program. We have also been using the Submillimeter Array and the Very Large Array to determine the accurate positions of our detected sources. Our observations have discovered high-redshift dusty galaxies with far-infrared luminosities similar to that of the Milky Way or luminous infrared galaxies. Some of these galaxies are still undetected in deep optical and near-infrared images. These results suggest that a substantial amount of star formation in even the faint submillimeter population may be hidden from rest-frame optical surveys.

  13. Tackling The Dragon: Investigating Lensed Galaxy Structure

    Science.gov (United States)

    Fortenberry, Alexander; Livermore, Rachael

    2018-01-01

    Galaxies have been seen to have a rapid decrease in star formation beginning at a redshift of around 1-2 up to the present day. To understand the processes underpinning this change, we need to observe the inner structure of galaxies and understand where and how the stellar mass builds up. However, at high redshifts our observable resolution is limited, which hinders the accuracy of the data. The lack of resolution at high redshift can be counteracted with the use of gravitational lensing. The magnification provided by the gravitational lens between us and the galaxies in question enables us to see extreme detail within the galaxies. To begin fine-tuning this process, we used Hubble data of Abell 370, a galaxy cluster, which lenses a galaxy know as “The Dragon” at z=0.725. With the increased detail proved by the gravitational lens we provide a detailed analysis of the galaxy’s spatially resolved star formation rate, stellar age, and masses.

  14. The ACS Nearby Galaxy Survey Treasury: Overview

    Science.gov (United States)

    Dalcanton, Julianne

    2006-12-01

    The ACS Nearby Galaxy Survey Treasury program (ANGST) consists of a carefully crafted imaging survey of a volume-limited sample of galaxies in the Local Universe outside the Local Group. The resulting images will allow unprecedented measurements of: (1) the SFH of a >100 Mpc3 volume of the Universe with a time resolution of Delta[log(t)]=0.25; (2) correlations between spatially resolved SFHs and environment; (3) the structure and properties of thick disks and stellar halos; and (4) the color distributions, sizes, and specific frequencies of globular and disk clusters as a function of galaxy mass and environment. To reach these goals, we are using a combination of wide-field tiling, pointed deep imaging, and archival data to carry out a uniform analysis of the ancient and recent star formation histories of 70 galaxies within a volume-limited sample extending to 3.5 Mpc, with an extension to the M81 group. For all galaxies, a radial strip of imaging will cover out to beyond the optical radius and will reach photometric depths of at least 2 magnitudes below the tip of the red giant branch throughout the limits of the survey volume. Additional deep pointings will reach SNR 10 for red clump stars, sufficient to recover the ancient star formation history (SFH) from the color-magnitude diagram for the galaxies that provide more than 99% of the star formation in the local volume. The resulting analysis will produce photometric information for several million stars.

  15. Massive Black Holes in Central Cluster Galaxies

    Science.gov (United States)

    Volonteri, Marta; Ciotti, Luca

    2013-05-01

    We explore how the co-evolution of massive black holes (MBHs) and galaxies is affected by environmental effects, addressing in particular MBHs hosted in the central cluster galaxies (we will refer to these galaxies in general as "CCGs"). Recently, the sample of MBHs in CCGs with dynamically measured masses has increased, and it has been suggested that these MBH masses (M BH) deviate from the expected correlations with velocity dispersion (σ) and mass of the bulge (M bulge) of the host galaxy: MBHs in CCGs appear to be "overmassive." This discrepancy is more pronounced when considering the M BH-σ relation than the M BH-M bulge one. We show that this behavior stems from a combination of two natural factors: (1) CCGs experience more mergers involving spheroidal galaxies and their MBHs and (2) such mergers are preferentially gas poor. We use a combination of analytical and semi-analytical models to investigate the MBH-galaxy co-evolution in different environments and find that the combination of these two factors is in accordance with the trends observed in current data sets.

  16. MASSIVE BLACK HOLES IN CENTRAL CLUSTER GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Volonteri, Marta [Institut d' Astrophysique de Paris, 98bis Bd. Arago, F-75014 Paris (France); Ciotti, Luca [Dipartimento di Fisica e Astronomia, Universita di Bologna, via Ranzani 1, I-40127 Bologna (Italy)

    2013-05-01

    We explore how the co-evolution of massive black holes (MBHs) and galaxies is affected by environmental effects, addressing in particular MBHs hosted in the central cluster galaxies (we will refer to these galaxies in general as ''CCGs''). Recently, the sample of MBHs in CCGs with dynamically measured masses has increased, and it has been suggested that these MBH masses (M{sub BH}) deviate from the expected correlations with velocity dispersion ({sigma}) and mass of the bulge (M{sub bulge}) of the host galaxy: MBHs in CCGs appear to be ''overmassive''. This discrepancy is more pronounced when considering the M{sub BH}-{sigma} relation than the M{sub BH}-M{sub bulge} one. We show that this behavior stems from a combination of two natural factors: (1) CCGs experience more mergers involving spheroidal galaxies and their MBHs and (2) such mergers are preferentially gas poor. We use a combination of analytical and semi-analytical models to investigate the MBH-galaxy co-evolution in different environments and find that the combination of these two factors is in accordance with the trends observed in current data sets.

  17. Angular momentum evolution of galaxies in EAGLE

    Science.gov (United States)

    Lagos, Claudia del P.; Theuns, Tom; Stevens, Adam R. H.; Cortese, Luca; Padilla, Nelson D.; Davis, Timothy A.; Contreras, Sergio; Croton, Darren

    2017-02-01

    We use the EAGLE cosmological hydrodynamic simulation suite to study the specific angular momentum of galaxies, j, with the aims of (i) investigating the physical causes behind the wide range of j at fixed mass and (ii) examining whether simple, theoretical models can explain the seemingly complex and non-linear nature of the evolution of j. We find that j of the stars, jstars, and baryons, jbar, are strongly correlated with stellar and baryon mass, respectively, with the scatter being highly correlated with morphological proxies such as gas fraction, stellar concentration, (u-r) intrinsic colour, stellar age and the ratio of circular velocity to velocity dispersion. We compare with available observations at z = 0 and find excellent agreement. We find that jbar follows the theoretical expectation of an isothermal collapsing halo under conservation of specific angular momentum to within ≈50 per cent, while the subsample of rotation-supported galaxies are equally well described by a simple model in which the disc angular momentum is just enough to maintain marginally stable discs. We extracted evolutionary tracks of the stellar spin parameter of EAGLE galaxies and found that the fate of their jstars at z = 0 depends sensitively on their star formation and merger histories. From these tracks, we identified two distinct physical channels behind low jstars galaxies at z = 0: (i) galaxy mergers, and (ii) early star formation quenching. The latter can produce galaxies with low jstars and early-type morphologies even in the absence of mergers.

  18. Ultramassive black hole feedback in compact galaxies

    Science.gov (United States)

    Ishibashi, W.; Fabian, A. C.

    2017-12-01

    Recent observations confirm the existence of ultra-massive black holes (UMBH) in the nuclei of compact galaxies, with physical properties similar to NGC 1277. The nature of these objects poses a new puzzle to the `black hole-host galaxy co-evolution' scenario. We discuss the potential link between UMBH and galaxy compactness, possibly connected via extreme active galactic nucleus (AGN) feedback at early times ($z > 2$). In our picture, AGN feedback is driven by radiation pressure on dust. We suggest that early UMBH feedback blows away all the gas beyond a $\\sim$kpc or so, while triggering star formation at inner radii, eventually leaving a compact galaxy remnant. Such extreme UMBH feedback can also affect the surrounding environment on larger scales, e.g. the outflowing stars may form a diffuse stellar halo around the compact galaxy, or even escape into the intergalactic or intracluster medium. On the other hand, less massive black holes will drive less powerful feedback, such that the stars formed within the AGN feedback-driven outflow remain bound to the host galaxy, and contribute to its size growth over cosmic time.

  19. The baryonic mass function of galaxies.

    Science.gov (United States)

    Read, J I; Trentham, Neil

    2005-12-15

    In the Big Bang about 5% of the mass that was created was in the form of normal baryonic matter (neutrons and protons). Of this about 10% ended up in galaxies in the form of stars or of gas (that can be in molecules, can be atomic, or can be ionized). In this work, we measure the baryonic mass function of galaxies, which describes how the baryonic mass is distributed within galaxies of different types (e.g. spiral or elliptical) and of different sizes. This can provide useful constraints on our current cosmology, convolved with our understanding of how galaxies form. This work relies on various large astronomical surveys, e.g. the optical Sloan Digital Sky Survey (to observe stars) and the HIPASS radio survey (to observe atomic gas). We then perform an integral over our mass function to determine the cosmological density of baryons in galaxies: Omega(b,gal)=0.0035. Most of these baryons are in stars: Omega(*)=0.0028. Only about 20% are in gas. The error on the quantities, as determined from the range obtained between different methods, is ca 10%; systematic errors may be much larger. Most (ca 90%) of the baryons in the Universe are not in galaxies. They probably exist in a warm/hot intergalactic medium. Searching for direct observational evidence and deeper theoretical understanding for this will form one of the major challenges for astronomy in the next decade.

  20. The host galaxy of GRB 990712

    DEFF Research Database (Denmark)

    Christensen, L.; Hjorth, J.; Gorosabel, J.

    2004-01-01

    galaxy types shows that the host is similar to a moderately kreddened starburst galaxy with a young stellar population. The estimated internal extinction in the host is A(V) = 0.15 +/- 0.1 and the star-formation rate (SFR) from the UV continuum is 1.3 +/- 0.3 M-circle dot yr(-1) (not corrected......We present a comprehensive study of the z = 0.43 host galaxy of GRB 990712, involving ground-based photometry, spectroscopy, and HST imaging. The broad-band UBVRIJHKs photometry is used to determine the global spectral energy distribution (SED) of the host galaxy. Comparison with that of known...... for the effects of extinction). Other galaxy template spectra than starbursts failed to reproduce the observed SED. We also present VLT spectra leading to the detection of Halpha from the GRB host galaxy. A SFR of 2.8 +/- 0.7 M-circle dot yr(-1) is inferred from the Halpha line flux, and the presence of a young...

  1. Bulge-Disk Evolution in Interacting Bulgeless Galaxies

    Science.gov (United States)

    Das, M.; Ramya, S.; Sengupta, C.; Mishra, K.

    2013-10-01

    Bulgeless galaxies are an extreme class of late type spiral galaxies that have practically no bulge and are nearly pure disk in morphology. Their lack of evolution is a puzzle for theories of galaxy formation and the secular evolution of galaxy disks. However, one of the processes by which these galaxies could evolve is through interactions with other galaxies. In this study we present radio (GMRT) observations of star formation in a sample of bulgeless galaxies. We did followup Hα imaging and optical spectroscopy of two galaxies, NGC 3445 and NGC 4027. Both galaxies have extended emission associated with their tidal interactions. Their nuclei show ongoing star formation but no signs of AGN activity. The R band images suggest that their centers have oval distortions or pseudobulges that may later evolve into larger bulges. Thus interactions are an important trigger for the formation of bulges in such disk dominated systems.

  2. Workshop on the Magellanic Clouds and other Dwarf Galaxies

    CERN Document Server

    Richtler, T; Richtler, Tom; Braun, Jochen M.

    1998-01-01

    The Workshop 'The Magellanic Clouds and Other Dwarf Galaxies' was held at the Physikzentrum Bad Honnef in January 1998. The proceedings comprise 79 contributions. About 1/3 of the 352 pages contain the following Reviews: The Violent Interstellar Medium in Dwarf Galaxies: Atomic Gas (Elias Brinks and Fabian Walter), Hot Gas in the Large Magellanic Cloud (You-Hua Chu), Astrophysics of Dwarf Galaxies: Structures and Stellar Populations (John S. Gallagher), Star-forming regions and ionized gas in irregular galaxies (Deidre A. Hunter), The Law of Star Formation in Disk Galaxies (Joachim Koeppen), Strange Dark Matters in Nearby Dwarf Galaxies (Mario Mateo), Holes and Shells in Galaxies: Observations versus Theoretical Concepts (Jan Palous), Detailed Recent Star Formation Histories of Dwarf Irregular Galaxies and Their Many Uses (Evan D. Skillman et al.), and Nearby Young Dwarf Galaxies (Trinh X. Thuan and Yuri I. Izotov). See the complete electronic version for further details.

  3. Galaxy Collisions Forging New Worlds from Cosmic Crashes

    CERN Document Server

    Struck, Curtis

    2011-01-01

    Galaxy collisions are the key process in building galaxies, triggering the formation of stars and the build-up of heavy elements that allow the formation of planets and solar systems. This book presents the revolutionary research advances achieved in the last decade and lucidly explains the underlying dynamical processes. Galaxy Collisions takes a comprehensive trip through the visually spectacular world of galaxy collisions; investigates the interactions of stars, gas clouds, and dark matter in galaxy collisions; uses analogies and metaphors to help comprehend the bizarre world of galaxies; presents recent research results to enhance the understanding of galaxy formation and evolution; includes discoveries of minor collisions within our own group of galaxies; shows how a galaxy collision might affect a solar system, or a planet like ours.

  4. A Cluster and a Sea of Galaxies

    Science.gov (United States)

    2010-05-01

    A new wide-field image released today by ESO displays many thousands of distant galaxies, and more particularly a large group belonging to the massive galaxy cluster known as Abell 315. As crowded as it may appear, this assembly of galaxies is only the proverbial "tip of the iceberg", as Abell 315 - like most galaxy clusters - is dominated by dark matter. The huge mass of this cluster deflects light from background galaxies, distorting their observed shapes slightly. When looking at the sky with the unaided eye, we mostly only see stars within our Milky Way galaxy and some of its closest neighbours. More distant galaxies are just too faint to be perceived by the human eye, but if we could see them, they would literally cover the sky. This new image released by ESO is both a wide-field and long-exposure one, and reveals thousands of galaxies crowding an area on the sky roughly as large as the full Moon. These galaxies span a vast range of distances from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos, especially in the upper part of the image. The more distant appear just like the faintest of blobs - their light has travelled through the Universe for eight billion years or more before reaching Earth. Beginning in the centre of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a massive galaxy cluster, designated with the number 315 in the catalogue compiled by the American astronomer George Abell in 1958 [1]. The cluster is located between the faint, red and blue galaxies and the Earth, about two billion light-years away from us. It lies in the constellation of Cetus (the Whale). Galaxy clusters are some of the largest structures in the Universe held together by gravity. But there is more in these structures than the many galaxies we can see. Galaxies in these giants contribute to only ten percent of the mass, with hot gas in between galaxies

  5. Galaxy Zoo: morphological classifications for 120 000 galaxies in HST legacy imaging

    Science.gov (United States)

    Willett, Kyle W.; Galloway, Melanie A.; Bamford, Steven P.; Lintott, Chris J.; Masters, Karen L.; Scarlata, Claudia; Simmons, B. D.; Beck, Melanie; Cardamone, Carolin N.; Cheung, Edmond; Edmondson, Edward M.; Fortson, Lucy F.; Griffith, Roger L.; Häußler, Boris; Han, Anna; Hart, Ross; Melvin, Thomas; Parrish, Michael; Schawinski, Kevin; Smethurst, R. J.; Smith, Arfon M.

    2017-02-01

    We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour-composite images. Images in GZH were selected from various publicly released Hubble Space Telescope legacy programmes conducted with the Advanced Camera for Surveys, with filters that probe the rest-frame optical emission from galaxies out to z ˜ 1. The bulk of the sample is selected to have mI814W = 0.9 ± 0.6, with a tail extending out to z ≃ 4. The GZH morphological data include measurements of both bulge- and disc-dominated galaxies, details on spiral disc structure that relate to the Hubble type, bar identification, and numerous measurements of clump identification and geometry. This paper also describes a new method for calibrating morphologies for galaxies of different luminosities and at different redshifts by using artificially redshifted galaxy images as a baseline. The GZH catalogue contains both raw and calibrated morphological vote fractions for 119 849 galaxies, providing the largest data set to date suitable for large-scale studies of galaxy evolution out to z ˜ 1.

  6. The SAMI Galaxy Survey: the intrinsic shape of kinematically selected galaxies

    Science.gov (United States)

    Foster, C.; van de Sande, J.; D'Eugenio, F.; Cortese, L.; McDermid, R. M.; Bland-Hawthorn, J.; Brough, S.; Bryant, J.; Croom, S. M.; Goodwin, M.; Konstantopoulos, I. S.; Lawrence, J.; López-Sánchez, Á. R.; Medling, A. M.; Owers, M. S.; Richards, S. N.; Scott, N.; Taranu, D. S.; Tonini, C.; Zafar, T.

    2017-11-01

    Using the stellar kinematic maps and ancillary imaging data from the Sydney AAO Multi Integral field (SAMI) Galaxy Survey, the intrinsic shape of kinematically selected samples of galaxies is inferred. We implement an efficient and optimized algorithm to fit the intrinsic shape of galaxies using an established method to simultaneously invert the distributions of apparent ellipticities and kinematic misalignments. The algorithm output compares favourably with previous studies of the intrinsic shape of galaxies based on imaging alone and our re-analysis of the ATLAS3D data. Our results indicate that most galaxies are oblate axisymmetric. We show empirically that the intrinsic shape of galaxies varies as a function of their rotational support as measured by the `spin' parameter proxy λ _{R_e}. In particular, low-spin systems have a higher occurrence of triaxiality, while high-spin systems are more intrinsically flattened and axisymmetric. The intrinsic shape of galaxies is linked to their formation and merger histories. Galaxies with high-spin values have intrinsic shapes consistent with dissipational minor mergers, while the intrinsic shape of low-spin systems is consistent with dissipationless multimerger assembly histories. This range in assembly histories inferred from intrinsic shapes is broadly consistent with expectations from cosmological simulations.

  7. Neutral hydrogen in nearby elliptical and lenticular galaxies : the continuing formation of early-type galaxies

    NARCIS (Netherlands)

    Morganti, R.; de Zeeuw, P. T.; Oosterloo, T. A.; McDermid, R. M.; Krajnovic, D.; Cappellari, M.; Kenn, F.; Weijmans, A.; Sarzi, M.

    2006-01-01

    We present the results of deep Westerbork Synthesis Radio Telescope observations of neutral hydrogen in 12 nearby elliptical and lenticular galaxies. The selected objects come from a representative sample of nearby galaxies earlier studied at optical wavelengths with the integral-field spectrograph

  8. Galaxies in turmoil the active and starburst galaxies and the black holes that drive them

    CERN Document Server

    Kitchin, C R

    2007-01-01

    Aimed at active amateur astronomers this book provides an up-to-date account of active galaxies. Lists and images of such objects are an important component of this book. The book makes sense of the chaotic and apparently innumerable types of violently active galaxies.

  9. HI observations of low surface brightness galaxies : Probing low-density galaxies

    NARCIS (Netherlands)

    deBlok, WJG; McGaugh, SS; vanderHulst, JM

    1996-01-01

    We present Very Large Array (VLA) and Westerbork Synthesis Radio Telescope (WSRT) 21-cm HI observations of 19 late-type low surface brightness (LSB) galaxies. Our main findings are that these galaxies, as well as having low surface brightnesses, have low HI surface densities, about a factor of

  10. Elemental abundances in Milky Way-like galaxies from a hierarchical galaxy formation model

    NARCIS (Netherlands)

    De Lucia, Gabriella; Tornatore, Luca; Frenk, Carlos S.; Helmi, Amina; Navarro, Julio F.; White, Simon D. M.

    2014-01-01

    We develop a new method to account for the finite lifetimes of stars and trace individual abundances within a semi-analytic model of galaxy formation. At variance with previous methods, based on the storage of the (binned) past star formation history of model galaxies, our method projects the

  11. Hα Velocity Fields and Galaxy Interaction in the Quartet of Galaxies ...

    Indian Academy of Sciences (India)

    2015-10-07

    Oct 7, 2015 ... of SN is in good agreement with the known correlations of core-collapse (Types Ibc and II) SNe with star formation in galaxies (e.g. James & Anderson 2006; Hakobyan et al. 2008), including also star formation induced by an interaction with neighbor galaxies (e.g. Nazaryan et al. 2013; Hakobyan et al.

  12. Looking Wider and Further: The Evolution of Galaxies Inside Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yuanyuan [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-01-01

    Galaxy clusters are rare objects in the universe, but on-going wide field optical surveys are identifying many thousands of them to redshift 1.0 and beyond. Using early data from the Dark Energy Survey (DES) and publicly released data from the Sloan Digital Sky Survey (SDSS), this dissertation explores the evolution of cluster galaxies in the redshift range from 0 to 1.0. As it is common for deep wide field sky surveys like DES to struggle with galaxy detection efficiency at cluster core, the first component of this dissertation describes an efficient package that helps resolving the issue. The second part focuses on the formation of cluster galaxies. The study quantifies the growth of cluster bright central galaxies (BCGs), and argues for the importance of merging and intra-cluster light production during BCG evolution. An analysis of cluster red sequence galaxy luminosity function is also performed, demonstrating that the abundance of these galaxies is mildly dependent on cluster mass and redshift. The last component of the dissertation characterizes the properties of galaxy filaments to help understanding cluster environments

  13. Dynamical masses of early-type galaxies at z ~ 2

    Science.gov (United States)

    Cappellari, Michele

    2013-07-01

    The evolution of masses and sizes of passive (early-type) galaxies with redshift provides ideal constraints to galaxy formation models. These parameters can in principle be obtained for large galaxy samples from multi-band photometry alone. However the accuracy of photometric masses is limited by the non-universality of the IMF. Galaxy sizes can be biased at high redshift due to the inferior quality of the imaging data. Both problems can be avoided using galaxy dynamics, and in particular by measuring the galaxies stellar velocity dispersion. Here we provide an overview of the efforts in this direction.

  14. Bidimensional spectroscopy of interacting galaxies

    Science.gov (United States)

    Chatzichristou, E. T.

    We have undertaken a program of studying the central few kpc regions of interacting/merger candidates, that were specifically chosen to have a range of nuclear activity, IR properties and strength of interaction. Here we present data obtained using the integral field spectrograph ARGUS, on the CFHT for few of these objects. Unlike slit spectroscopy, these data provide a direct two-dimensional picture of the wavelength-dependant emission and absorption line properties of these galaxies. The main conclusions are: (1) Mkn 789 is a recent merger product, undergoing a strong burst of star formation, while the older stellar component did not have yet the time to relax. It has no compact nuclear structure and its strong star formation powers a large scale outflow ("superwind"), which gives characteristic multiple profiles. Mkn 463 on the other hand, appears at an intermediate merging stage where at least one of its two visible nuclei had time to become activated, showing a Seyfert-like spectrum. The distinct kinematic feature here is a strongly blueshifted component that is interpreted in terms of bowshocks driven by a radio jet into the ambient gas. (2) UGC 3995 is the brightest member of a pair of interacting spirals, has a low-ionization, Seyfert-like spectrum. The velocity field is smooth, characteristic of a retrogradely rotating disk, but we find rotation of the kinematic axis with wavelength, that correspond to isophotal distortions and an obvious line profile substructure. It seems that this is a distinct kinematic feature in Seyfert-like nuclei independently of their interaction stage, indicating radial gas motions that might be related to the activation of the central engine. (3) Both mergers (Mkn 463, Mkn 789) have higher IR activity, as expressed by the LFIR excess and "warm" far-IR colours, among the objects in our sample. This seems to be independent of the nature of the central engine. On the other hand, the 25 microns characteristic excess emission of

  15. IceCube search for dark matter annihilation in nearby galaxies and galaxy clusters

    Science.gov (United States)

    Aartsen, M. G.; Abbasi, R.; Abdou, Y.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Altmann, D.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Bechet, S.; Becker Tjus, J.; Becker, K.-H.; Benabderrahmane, M. L.; BenZvi, S.; Berghaus, P.; Berley, D.; Bernardini, E.; Bernhard, A.; Bertrand, D.; Besson, D. Z.; Binder, G.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohaichuk, S.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brayeur, L.; Bretz, H.-P.; Brown, A. M.; Bruijn, R.; Brunner, J.; Carson, M.; Casey, J.; Casier, M.; Chirkin, D.; Christov, A.; Christy, B.; Clark, K.; Clevermann, F.; Coenders, S.; Cohen, S.; Cowen, D. F.; Cruz Silva, A. H.; Danninger, M.; Daughhetee, J.; Davis, J. C.; Day, M.; De Clercq, C.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; Dunkman, M.; Eagan, R.; Eberhardt, B.; Eisch, J.; Ellsworth, R. W.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Flis, S.; Franckowiak, A.; Frantzen, K.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Golup, G.; Gonzalez, J. G.; Goodman, J. A.; Góra, D.; Grandmont, D. T.; Grant, D.; Groß, A.; Ha, C.; Haj Ismail, A.; Hallen, P.; Hallgren, A.; Halzen, F.; Hanson, K.; Heereman, D.; Heinen, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Homeier, A.; Hoshina, K.; Huelsnitz, W.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Jagielski, K.; Japaridze, G. S.; Jero, K.; Jlelati, O.; Kaminsky, B.; Kappes, A.; Karg, T.; Karle, A.; Kelley, J. L.; Kiryluk, J.; Kläs, J.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krasberg, M.; Krings, K.; Kroll, G.; Kunnen, J.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Landsman, H.; Larson, M. J.; Lesiak-Bzdak, M.; Leuermann, M.; Leute, J.; Lünemann, J.; Macías, O.; Madsen, J.; Maggi, G.; Maruyama, R.; Mase, K.; Matis, H. S.; McNally, F.; Meagher, K.; Merck, M.; Meures, T.; Miarecki, S.; Middell, E.; Milke, N.; Miller, J.; Mohrmann, L.; Montaruli, T.; Morse, R.; Nahnhauer, R.; Naumann, U.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke, A.; Odrowski, S.; Olivas, A.; Omairat, A.; O'Murchadha, A.; Paul, L.; Pepper, J. A.; Pérez de los Heros, C.; Pfendner, C.; Pieloth, D.; Pinat, E.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rädel, L.; Rameez, M.; Rawlins, K.; Redl, P.; Reimann, R.; Resconi, E.; Rhode, W.; Ribordy, M.; Richman, M.; Riedel, B.; Rodrigues, J. P.; Rott, C.; Ruhe, T.; Ruzybayev, B.; Ryckbosch, D.; Saba, S. M.; Salameh, T.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Scheriau, F.; Schmidt, T.; Schmitz, M.; Schoenen, S.; Schöneberg, S.; Schönwald, A.; Schukraft, A.; Schulte, L.; Schulz, O.; Seckel, D.; Sestayo, Y.; Seunarine, S.; Shanidze, R.; Sheremata, C.; Smith, M. W. E.; Soldin, D.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stasik, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Sullivan, G. W.; Taavola, H.; Taboada, I.; Tamburro, A.; Tepe, A.; Ter-Antonyan, S.; Tešić, G.; Tilav, S.; Toale, P. A.; Toscano, S.; Unger, E.; Usner, M.; Vallecorsa, S.; van Eijndhoven, N.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Vraeghe, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Weaver, Ch.; Wellons, M.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Ziemann, J.; Zierke, S.; Zoll, M.

    2013-12-01

    We present the results of a first search for self-annihilating dark matter in nearby galaxies and galaxy clusters using a sample of high-energy neutrinos acquired in 339.8 days of live time during 2009/10 with the IceCube neutrino observatory in its 59-string configuration. The targets of interest include the Virgo and Coma galaxy clusters, the Andromeda galaxy, and several dwarf galaxies. We obtain upper limits on the cross section as a function of the weakly interacting massive particle mass between 300 GeV and 100 TeV for the annihilation into bb¯, W+W-, τ+τ-, μ+μ-, and νν¯. A limit derived for the Virgo cluster, when assuming a large effect from subhalos, challenges the weakly interacting massive particle interpretation of a recently observed GeV positron excess in cosmic rays.

  16. Two channels for the formation of compact dwarf galaxies in clusters of galaxies

    Science.gov (United States)

    Martinović, Nemanja; Micic, Miroslav

    2017-10-01

    We have identified two channels for the formation of compact dwarf galaxies in the Illustris simulation by reconstructing mass and distance histories of candidates located in the vicinity of the simulation's most massive cluster galaxies. One channel is tidal stripping of Milky Way-mass galaxies that form outside of clusters and eventually sink into them, spiralling in towards central massive objects. The second channel of formation is an in situ formation (in reference to the parent cluster) of dwarf mass galaxies, with negligible evolution and limited change in stellar mass. We find 19 compact dwarf galaxies at the centres of 14 clusters, consistent with observations: 30 per cent of these have an external origin while 70 per cent are formed in situ.

  17. Galaxy evolution. Isolated compact elliptical galaxies: stellar systems that ran away.

    Science.gov (United States)

    Chilingarian, Igor; Zolotukhin, Ivan

    2015-04-24

    Compact elliptical galaxies form a rare class of stellar system (~30 presently known) characterized by high stellar densities and small sizes and often harboring metal-rich stars. They were thought to form through tidal stripping of massive progenitors, until two isolated objects were discovered where massive galaxies performing the stripping could not be identified. By mining astronomical survey data, we have now found 195 compact elliptical galaxies in all types of environment. They all share similar dynamical and stellar population properties. Dynamical analysis for nonisolated galaxies demonstrates the feasibility of their ejection from host clusters and groups by three-body encounters, which is in agreement with numerical simulations. Hence, isolated compact elliptical and isolated quiescent dwarf galaxies are tidally stripped systems that ran away from their hosts. Copyright © 2015, American Association for the Advancement of Science.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1986-06-01

    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. 14 references.

  19. The bispectrum of galaxies from high-redshift galaxy surveys: Primordial non-Gaussianity and non-linear galaxy bias

    Energy Technology Data Exchange (ETDEWEB)

    Sefusatti, Emiliano; /Fermilab; Komatsu, Eiichiro; /Texas U., Astron. Dept.

    2007-05-01

    The greatest challenge in the interpretation of galaxy clustering data from any surveys is galaxy bias. Using a simple Fisher matrix analysis, we show that the bispectrum provides an excellent determination of linear and non-linear bias parameters of intermediate and high-z galaxies, when all measurable triangle configurations down to mildly non-linear scales, where perturbation theory is still valid, are included. The bispectrum is also a powerful probe of primordial non-Gaussianity. The planned galaxy surveys at z {approx}> 2 should yield constraints on non-Gaussian parameters, f{sub NL}{sup loc.} and f{sub NL}{sup eq.}, that are comparable to, or even better than, those from CMB experiments. We study how these constraints improve with volume, redshift range, as well as the number density of galaxies. Finally we show that a halo occupation distribution may be used to improve these constraints further by lifting degeneracies between gravity, bias, and primordial non-Gaussianity.

  20. 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.

  1. A unified multiwavelength model of galaxy formation

    Science.gov (United States)

    Lacey, Cedric G.; Baugh, Carlton M.; Frenk, Carlos S.; Benson, Andrew J.; Bower, Richard G.; Cole, Shaun; Gonzalez-Perez, Violeta; Helly, John C.; Lagos, Claudia D. P.; Mitchell, Peter D.

    2016-11-01

    We present a new version of the GALFORM semi-analytical model of galaxy formation. This brings together several previous developments of GALFORM into a single unified model, including a different initial mass function (IMF) in quiescent star formation and in starbursts, feedback from active galactic nuclei suppressing gas cooling in massive haloes, and a new empirical star formation law in galaxy discs based on their molecular gas content. In addition, we have updated the cosmology, introduced a more accurate treatment of dynamical friction acting on satellite galaxies, and updated the stellar population model. The new model is able to simultaneously explain both the observed evolution of the K-band luminosity function and stellar mass function, and the number counts and redshift distribution of sub-mm galaxies selected at 850 μm. This was not previously achieved by a single physical model within the Λcold dark matter framework, but requires having an IMF in starbursts that is somewhat top-heavy. The new model is tested against a wide variety of observational data covering wavelengths from the far-UV to sub-mm, and redshifts from z = 0 to 6, and is found to be generally successful. These observations include the optical and near-infrared (IR) luminosity functions, H I mass function, fraction of early type galaxies, Tully-Fisher, metallicity-luminosity and size-luminosity relations at z = 0, as well as far-IR number counts, and far-UV luminosity functions at z ˜ 3-6. Discrepancies are, however, found in galaxy sizes and metallicities at low luminosities, and in the abundance of low-mass galaxies at high-z, suggesting the need for a more sophisticated model of supernova feedback.

  2. Jellyfish Galaxy Candidates at Low Redshift

    Science.gov (United States)

    Poggianti, B. M.; Fasano, G.; Omizzolo, A.; Gullieuszik, M.; Bettoni, D.; Moretti, A.; Paccagnella, A.; Jaffé, Y. L.; Vulcani, B.; Fritz, J.; Couch, W.; D'Onofrio, M.

    2016-03-01

    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 LX. Interestingly, convincing cases of candidates are also found in groups and lower mass halos (1011-1014M⊙), although the physical mechanism at work needs to be securely identified. All the candidates are disky, have stellar masses ranging from log M/M⊙ 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.

  3. EXTREMELY METAL-POOR GALAXIES: THE ENVIRONMENT

    Energy Technology Data Exchange (ETDEWEB)

    Filho, M. E. [Universidad de Las Palmas de Gran Canaria–Universidad de La Laguna, CIE Canarias: Tri-Continental Atlantic Campus, Canary Islands (Spain); Almeida, J. Sánchez; Muñoz-Tuñón, C. [Instituto Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Nuza, S. E.; Kitaura, F.; Heß, S., E-mail: mfilho@astro.up.pt [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

    2015-04-01

    We have analyzed bibliographical observational data and theoretical predictions, in order to probe the environment in which extremely metal-poor dwarf galaxies (XMPs) reside. We have assessed the H i component and its relation to the optical galaxy, the cosmic web type (voids, sheets, filaments and knots), the overdensity parameter and analyzed the nearest galaxy neighbors. The aim is to understand the role of interactions and cosmological accretion flows in the XMP observational properties, particularly the triggering and feeding of the star formation. We find that XMPs behave similarly to Blue Compact Dwarfs; they preferably populate low-density environments in the local universe: ∼60% occupy underdense regions, and ∼75% reside in voids and sheets. This is more extreme than the distribution of irregular galaxies, and in contrast to those regions preferred by elliptical galaxies (knots and filaments). We further find results consistent with previous observations; while the environment does determine the fraction of a certain galaxy type, it does not determine the overall observational properties. With the exception of five documented cases (four sources with companions and one recent merger), XMPs do not generally show signatures of major mergers and interactions; we find only one XMP with a companion galaxy within a distance of 100 kpc, and the H i gas in XMPs is typically well-behaved, demonstrating asymmetries mostly in the outskirts. We conclude that metal-poor accretion flows may be driving the XMP evolution. Such cosmological accretion could explain all the major XMP observational properties: isolation, lack of interaction/merger signatures, asymmetric optical morphology, large amounts of unsettled, metal-poor H i gas, metallicity inhomogeneities, and large specific star formation.

  4. Dark energy in systems of galaxies

    Science.gov (United States)

    Chernin, A. D.

    2013-11-01

    The precise observational data of the Hubble Space Telescope have been used to study nearby galaxy systems. The main result is the detection of dark energy in groups, clusters, and flows of galaxies on a spatial scale of about 1-10 Mpc. The local density of dark energy in these systems, which is determined by various methods, is close to the global value or even coincides with it. A theoretical model of the nearby Universe has been constructed, which describes the Local Group of galaxies with the flow of dwarf galaxies receding from this system. The key physical parameter of the group-flow system is zero gravity radius, which is the distance at which the gravity of dark matter is compensated by dark-energy antigravity. The model predicts the existence of local regions of space where Einstein antigravity is stronger than Newton gravity. Six such regions have been revealed in the data of the Hubble space telescope. The nearest of these regions is at a distance of 1-3 Mpc from the center of the Milky Way. Antigravity in this region is several times stronger than gravity. Quasiregular flows of receding galaxies, which are accelerated by the dark-energy antigravity, exist in these regions. The model of the nearby Universe at the scale of groups of galaxies (˜1 Mpc) can be extended to the scale of clusters (˜10 Mpc). The systems of galaxies with accelerated receding flows constitute a new and probably widespread class of metagalactic populations. Strong dynamic effects of local dark energy constitute the main characteristic feature of these systems.

  5. Morphology-based Query for Galaxy Image Databases

    Science.gov (United States)

    Shamir, Lior

    2017-02-01

    Galaxies of rare morphology are of paramount scientific interest, as they carry important information about the past, present, and future Universe. Once a rare galaxy is identified, studying it more effectively requires a set of galaxies of similar morphology, allowing generalization and statistical analysis that cannot be done when N=1. Databases generated by digital sky surveys can contain a very large number of galaxy images, and therefore once a rare galaxy of interest is identified it is possible that more instances of the same morphology are also present in the database. However, when a researcher identifies a certain galaxy of rare morphology in the database, it is virtually impossible to mine the database manually in the search for galaxies of similar morphology. Here we propose a computer method that can automatically search databases of galaxy images and identify galaxies that are morphologically similar to a certain user-defined query galaxy. That is, the researcher provides an image of a galaxy of interest, and the pattern recognition system automatically returns a list of galaxies that are visually similar to the target galaxy. The algorithm uses a comprehensive set of descriptors, allowing it to support different types of galaxies, and it is not limited to a finite set of known morphologies. While the list of returned galaxies is neither clean nor complete, it contains a far higher frequency of galaxies of the morphology of interest, providing a substantial reduction of the data. Such algorithms can be integrated into data management systems of autonomous digital sky surveys such as the Large Synoptic Survey Telescope (LSST), where the number of galaxies in the database is extremely large. The source code of the method is available at http://vfacstaff.ltu.edu/lshamir/downloads/udat.

  6. Weak Lensing by Galaxy Troughs in DES Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Gruen, D. [Ludwig Maximilian Univ., Munich (Germany); Max Planck Inst. for Extraterrestrial Physics, Garching (Germany). et al.

    2015-09-29

    We measure the weak lensing shear around galaxy troughs, i.e. the radial alignment of background galaxies relative to underdensities in projections of the foreground galaxy field over a wide range of redshift in Science Verification data from the Dark Energy Survey. Our detection of the shear signal is highly significant (10σ–15σ for the smallest angular scales) for troughs with the redshift range z ϵ [0.2, 0.5] of the projected galaxy field and angular diameters of 10 arcmin…1°. These measurements probe the connection between the galaxy, matter density, and convergence fields. By assuming galaxies are biased tracers of the matter density with Poissonian noise, we find agreement of our measurements with predictions in a fiducial Λ cold dark matter model. Furthermore, the prediction for the lensing signal on large trough scales is virtually independent of the details of the underlying model for the connection of galaxies and matter. Our comparison of the shear around troughs with that around cylinders with large galaxy counts is consistent with a symmetry between galaxy and matter over- and underdensities. In addition, we measure the two-point angular correlation of troughs with galaxies which, in contrast to the lensing signal, is sensitive to galaxy bias on all scales. Finally, the lensing signal of troughs and their clustering with galaxies is therefore a promising probe of the statistical properties of matter underdensities and their connection to the galaxy field.

  7. 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.

  8. Astronomers Discover Spectacular Structure in Distant Galaxy

    Science.gov (United States)

    1999-01-01

    Researchers using the National Science Foundation's Very Large Array (VLA) radio telescope have imaged a "spectacular and complex structure" in a galaxy 50 million light-years away. Their work both resolves a decades-old observational mystery and revises current theories about the origin of X-ray emission coming from gas surrounding the galaxy. The new VLA image is of the galaxy M87, which harbors at its core a supermassive black hole spewing out jets of subatomic particles at nearly the speed of light and also is the central galaxy of the Virgo Cluster of galaxies. The VLA image is the first to show detail of a larger structure that originally was detected by radio astronomers more than a half-century ago. Analysis of the new image indicates that astronomers will have to revise their ideas about the physics of what causes X-ray emission in the cores of many galaxy clusters. Frazer Owen of the National Radio Astronomy Observatory (NRAO) in Socorro, NM; Jean Eilek of the New Mexico Institute of Mining and Technology (NM Tech) in Socorro, NM; and Namir Kassim of the Naval Research Laboratory in Washington, DC, announced their discovery at the American Astronomical Society's meeting today in Austin, TX. The new observations show two large, bubble-like lobes, more than 200,000 light-years across, that emit radio waves. These lobes, which are intricately detailed, apparently are powered by gravitational energy released from the black hole at the galaxy's center. "We think that material is flowing outward from the galaxy's core into these large, bright, radio-emitting 'bubbles,'" Owen said. The newly-discovered "bubbles" sit inside a region of the galaxy known to be emitting X-rays. Theorists have speculated that this X-ray emission arises when gas that originally was part of the Virgo Cluster of galaxies, cools and falls inwards onto M87 itself, at the center of the cluster. Such "cooling flows" are commonly thought to be responsible for strong X-ray emission in many

  9. Dark Galaxies and Lost Baryons (IAU S244)

    Science.gov (United States)

    Davies, Jonathan I.; Disney, Michael J.

    2008-05-01

    Preface; Conference prelims; The HI that barked in the night M. J. Disney; The detection of dark galaxies in blind HI surveys J. I. Davies; Red haloes of galaxies - reservoirs of baryonic dark matter? E. Zackrisson, N. Bergvall, C. Flynn, G. Ostlin, G. Micheva and B. Baldwell; Constraints on dark and visible mass in galaxies from strong gravitational lensing S. Dye and S. Warren; Lost baryons at low redshift S. Mathur, F. Nicastro and R. Williams; Observed properties of dark matter on small spatial scales R. Wyse and G. Gilmore; The mass distribution in spiral galaxies P. Salucci; Connecting lost baryons and dark galaxies via QSO absorption lines T. Tripp; ALFALFA: HI cosmology in the local universe R. Giovanelli; The ALFALFA search for (almost) dark galaxies across the HI mass function M. Haynes; HI clouds detected towards Virgo with the Arecibo Legacy Fast ALFA Survey B. Kent; Cosmic variance in the HI mass function S. Schneider; The Arecibo Galaxy Environments Survey - potential for finding dark galaxies and results so far R. Minchin et al.; Free-floating HI clouds in the M81 group E. Brinks, F. Walter and E. Skillman; Where are the stars in dark galaxies J. Rosenberg, J. Salzer and J. Cannon; The halo by halo missing baryon problem S. McGaugh; The local void is really empty R. Tully; Voids in the local volume: a limit on appearance of a galaxy in a dark matter halo A. Tikhonov and A. Klypin; Dim baryons in the cosmic web C. Impey; A census of baryons in galaxy clusters and groups A. Gonzalez, D. Zaritsky and A. Zabludo; Statistical properties of the intercluster light from SDSS image stacking S. Zibetti; QSO strong gravitational lensing and the detection of dark halos A. Maccio; Strong gravitational lensing: bright galaxies and lost dark-matter L. Koopmans; Mapping the distribution of luminous and dark matter in strong lensing galaxies I. Ferreras, P. Saha, L. Williams and S. Burles; Tidal debris posing as dark galaxies P. Duc, F. Bournaud and E. Brinks

  10. Which Galaxies Are the Most Habitable?

    Science.gov (United States)

    Kohler, Susanna

    2015-09-01

    Habitable zones are a hot topic in exoplanet studies: where, around a given star, could a planet exist that supports life? But if you scale this up, you get a much less common question: which type of galaxy is most likely to host complex life in the universe? A team of researchers from the UK believes it has the answer.Criteria for HabitabilityLed by Pratika Dayal of the University of Durham, the authors of this study set out to estimate the habitability of a large population of galaxies. The first step in this process is to determine what elements contribute to a galaxys habitability. The authors note three primary factors:Total number of starsMore stars means more planets!Metallicity of the starsPlanets are more likely to form in stellar vicinities with higher metallicities, since planet formation requires elements heavier than iron.Likelihood of Type II supernovae nearbyPlanets that are located out of range of supernovae have a higher probability of being habitable, since a major dose of cosmic radiation is likely to cause mass extinctions or delay evolution of complex life. Galaxies supernova rates can be estimated from their star formation rates (the two are connected via the initial mass function).Hospitable Cosmic GiantsLower panel: the number of Earth-like habitable planets (given by the color bar, which shows the log ratio relative to the Milky Way) increases in galaxies with larger stellar mass and lower star formation rates. Upper panel: the larger stellar-mass galaxies tend to be elliptical (blue line) rather than spiral (red line). Click for larger view. [Dayal et al. 2015]Interestingly, these three conditions have previously been shown to be linked via something termed the fundamental metallicity relation, which relates the total stellar masses, metallicities, and star formation rates of galaxies. By using this relation, the authors were able to create predictions for the number of habitable planets in more than 100,000 galaxies in the local universe

  11. 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

  12. Star Formation Quenching in Quasar Host Galaxies

    Directory of Open Access Journals (Sweden)

    Stefano Carniani

    2017-10-01

    Full Text Available Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN. In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionized and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ~ 2.4 obtained with SINFONI in the H- and K-band. All the quasars show [Oiii]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM < 500 km/s, which is spatially extended and associated with star formation in the host galaxy. On paper fast outflows are spatially anti-correlated with star-formation powered emission, i.e., star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50–100 M⊙ yr−1, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2 ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2 transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

  13. The Galex Large Galaxy Atlas (glga)

    Science.gov (United States)

    Seibert, Mark

    GALEX surveys contain the most comprehensive collection of UV imaged extended galaxies likely to exist for decades. Unfortunately, with the exception of the 1,000 galaxies contained in the Nearby Galaxy Atlas (NGA), this impressive resource is under-utilized because 1) the pipeline-generated source catalogs split extended objects into many pieces (""shredding"") and 2) co-adding of data using multiple survey types is not regularly performed. We propose to solve both of these problems by constructing the GALEX Large Galaxy Atlas (GLGA) using all observations of galaxies with diameters of at least 1 arcmin, make it available to the public via the NASA/IPAC Extragalactic Database (NED), and provide our software for the co-adding and mosaicing of GALEX data to the astronomical community. The GLGA will build upon and extend the NGA in three significant ways; it will 1) contain 21,000 galaxies, 2) co-add data from multiple survey types, and 3) preserve multi-epoch observations to facilitate time domain studies. Extending the NGA to 21,000 galaxies will be a major contribution to the legacy of GALEX. Although the GLGA will be a tremendous resource available to anyone, our team was inspired to its construction for several projects. We will use the GLGA to measure proper UV-optical-NIR colors for a large sample of extended galaxies for the first time. This is a critical step for locating examples of nearby ``green-valley"" or transition galaxies which may be the best objects for understanding blue-red sequence evolution. We are compiling a matching catalog of HI single dish fluxes and images with the goal of using it to study the detailed relationship between gas content and star formation rate, implications for star formation ``laws'' and the triggering and quenching of star formation. Finally, we are compiling IRAS HiRes data for objects with diameters >2 arcmin with the objective of constraining UV extinction derived from the UV spectral-slope/infrared-excess correlation."

  14. DWARF GALAXIES AND THE COSMIC WEB

    Energy Technology Data Exchange (ETDEWEB)

    Benitez-Llambay, Alejandro; Abadi, Mario G. [Observatorio Astronomico, Universidad Nacional de Cordoba, Cordoba X5000BGR (Argentina); Navarro, Julio F. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2 (Canada); Gottloeber, Stefan; Steinmetz, Matthias [Leibniz Institute for Astrophysics, An der Sternwarte 16, D-14482 Potsdam (Germany); Yepes, Gustavo [Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Hoffman, Yehuda [Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904 (Israel)

    2013-02-01

    We use a cosmological simulation of the formation of the Local Group of Galaxies to identify a mechanism that enables the removal of baryons from low-mass halos without appealing to feedback or reionization. As the Local Group forms, matter bound to it develops a network of filaments and pancakes. This moving web of gas and dark matter drifts and sweeps a large volume, overtaking many halos in the process. The dark matter content of these halos is unaffected but their gas can be efficiently removed by ram pressure. The loss of gas is especially pronounced in low-mass halos due to their lower binding energy and has a dramatic effect on the star formation history of affected systems. This 'cosmic web stripping' may help to explain the scarcity of dwarf galaxies compared with the numerous low-mass halos expected in {Lambda}CDM and the large diversity of star formation histories and morphologies characteristic of faint galaxies. Although our results are based on a single high-resolution simulation, it is likely that the hydrodynamical interaction of dwarf galaxies with the cosmic web is a crucial ingredient so far missing from galaxy formation models.

  15. Imprints of reionization in galaxy clustering

    Science.gov (United States)

    Schmidt, Fabian; Beutler, Florian

    2017-10-01

    Reionization, the only phase transition in the Universe since recombination, is a key event in the cosmic history of baryonic matter. We derive, in the context of the large-scale bias expansion, the imprints of the epoch of reionization in the large-scale distribution of galaxies and identify two contributions of particular importance. First, the Compton scattering of cosmic microwave background photons off the free electrons lead to a drag force on the baryon fluid. This drag induces a relative velocity between baryons and cold dark matter, which is of the same order of magnitude as the primordially induced relative velocity, and enters in the evolution of the relative velocity as calculated by Boltzmann codes. This leads to a unique contribution to galaxy bias involving the matter velocity squared. The second important effect is a modulation of the galaxy density by the ionizing radiation field through radiative-transfer effects, which is captured in the bias expansion by so-called higher-derivative terms. We constrain both of these imprints using the power spectrum of the BOSS DR12 galaxy sample. While they do not lead to a shift in the baryon acoustic oscillation scale, including these terms is important for unbiased cosmology constraints from the shape of the galaxy power spectrum.

  16. Circumgalactic Matter Matters in Galaxy Evolution

    Science.gov (United States)

    Werk, Jessica

    2018-01-01

    The circumgalactic medium (CGM; non-ISM gas within a galaxy virial radius) regulates the gas flows that shape the assembly and evolution of galaxies. Owing to the vastly improved capabilities in space-based UV spectroscopy with the installation of HST/COS, observations and simulations of the CGM have emerged as the new frontier of galaxy evolution studies. In the last decade, we have learned that the CGM of Milky Way mass galaxies likely contains enough material to harbor most of the metals lost in galaxy winds and to sustain star-formation for billions of years. Remarkably, this implies that most of the heavy elements on earth cycled back and forth multiple times through the Milky Way’s own CGM before the formation of the solar system. In this talk, I will describe constraints we have placed on the origin and fate of this material by studying the gas kinematics, metallicity and ionization state. I will conclude by posing several unanswered questions about the CGM that will be addressed with future survey data and hydrodynamic simulations in a cosmological context.

  17. Galaxy Formation from the Primordial Black Holes

    Directory of Open Access Journals (Sweden)

    Morikawa Masahiro

    2017-01-01

    Full Text Available Supermassive black hole (SMBH of size MBH = 106-10M⊙ is common in the Universe and it defines the center of the galaxy. A galaxy and the SMBH are generally thought to have co-evolved. However, the SMBH cannot evolve so fast as commonly observed even at redshift z > 6. Therefore, we explore a natural hypothesis that the SMBH has been already formed mature at z ⪆ 10 before stars and galaxies. The SMBH forms energetic jets and out-flows which trigger massive star formation in the ambient gas. They eventually construct globular clusters and classical bulge as well as the body of elliptical galaxies. We propose simple models which implement these processes. We point out that the globular clusters and classical bulges have a common origin but are in different phases. The same is true for the elliptical and spiral galaxies. Physics behind these phase division is the runaway star formation process with strong feedback to SMBH. This is similar to the forest-fire model that displays self-organized criticality.

  18. An Elegant Galaxy in an Unusual Light

    Science.gov (United States)

    2010-09-01

    A new image taken with the powerful HAWK-I camera on ESO's Very Large Telescope at Paranal Observatory in Chile shows the beautiful barred spiral galaxy NGC 1365 in infrared light. NGC 1365 is a member of the Fornax cluster of galaxies, and lies about 60 million light-years from Earth. NGC 1365 is one of the best known and most studied barred spiral galaxies and is sometimes nicknamed the Great Barred Spiral Galaxy because of its strikingly perfect form, with the straight bar and two very prominent outer spiral arms. Closer to the centre there is also a second spiral structure and the whole galaxy is laced with delicate dust lanes. This galaxy is an excellent laboratory for astronomers to study how spiral galaxies form and evolve. The new infrared images from HAWK-I are less affected by the dust that obscures parts of the galaxy than images in visible light (potw1037a) and they reveal very clearly the glow from vast numbers of stars in both the bar and the spiral arms. These data were acquired to help astronomers understand the complex flow of material within the galaxy and how it affects the reservoirs of gas from which new stars can form. The huge bar disturbs the shape of the gravitational field of the galaxy and this leads to regions where gas is compressed and star formation is triggered. Many huge young star clusters trace out the main spiral arms and each contains hundreds or thousands of bright young stars that are less than ten million years old. The galaxy is too remote for single stars to be seen in this image and most of the tiny clumps visible in the picture are really star clusters. Over the whole galaxy, stars are forming at a rate of about three times the mass of our Sun per year. While the bar of the galaxy consists mainly of older stars long past their prime, many new stars are born in stellar nurseries of gas and dust in the inner spiral close to the nucleus. The bar also funnels gas and dust gravitationally into the very centre of the galaxy

  19. Tidal Dwarf Galaxies and Missing Baryons

    Directory of Open Access Journals (Sweden)

    Frederic Bournaud

    2010-01-01

    Full Text Available Tidal dwarf galaxies form during the interaction, collision, or merger of massive spiral galaxies. They can resemble “normal” dwarf galaxies in terms of mass, size, and become dwarf satellites orbiting around their massive progenitor. They nevertheless keep some signatures from their origin, making them interesting targets for cosmological studies. In particular, they should be free from dark matter from a spheroidal halo. Flat rotation curves and high dynamical masses may then indicate the presence of an unseen component, and constrain the properties of the “missing baryons,” known to exist but not directly observed. The number of dwarf galaxies in the Universe is another cosmological problem for which it is important to ascertain if tidal dwarf galaxies formed frequently at high redshift, when the merger rate was high, and many of them survived until today. In this paper, “dark matter” is used to refer to the nonbaryonic matter, mostly located in large dark halos, that is, CDM in the standard paradigm, and “missing baryons” or “dark baryons” is used to refer to the baryons known to exist but hardly observed at redshift zero, and are a baryonic dark component that is additional to “dark matter”.

  20. The Milky Way and other spiral galaxies

    Directory of Open Access Journals (Sweden)

    Wang J.L.

    2012-02-01

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

  1. What Drives the Kinematic Evolution of Galaxies?

    Science.gov (United States)

    Hung, Chao-Ling

    2017-07-01

    One important result from recent large integral field spectrograph (IFS) surveys is that the intrinsic velocity dispersion of galaxies increases at high redshift. While massive, rotation-dominated disks are already in place at z 2, they are dynamically hotter compared to spiral galaxies in the local Universe. Although several plausible mechanisms have been proposed (e.g., star formation feedback, elevated gas supply, or galaxy interaction), it remains unclear what is the fundamental driver of the velocity dispersion enhancement at high-z. We investigate the origin of this kinematic evolution using a suite of cosmological simulations from the FIRE (Feedback In Realistic Environments) project. Although the velocity dispersion of simulated galaxies is systematically lower compared to the observed values, the simulations successfully reproduce the observed trends between velocity dispersion, SFR, and redshift. In the FIRE simulations, the variation in velocity dispersion is highly dynamic across cosmic time, and it can vary significantly within a timescale of 100 Myr. These variations closely mirror the evolution of star formation and gas inflow histories. By cross-correlating any two parameters of velocity dispersion, gas inflow rates, and SFR, we show that the increase of gas inflowing into the galaxy lead to the subsequent star formation activities, and the enhancement of velocity dispersion follows closely in time with the increasing gas inflow rates and SFR.

  2. Galaxy rotation curves with lognormal density distribution

    Science.gov (United States)

    Marr, John H.

    2015-04-01

    The lognormal distribution represents the probability of finding randomly distributed particles in a micro canonical ensemble with high entropy. To a first approximation, a modified form of this distribution with a truncated termination may represent an isolated galactic disc, and this disc density distribution model was therefore run to give the best fit to the observational rotation curves for 37 representative galaxies. The resultant curves closely matched the observational data for a wide range of velocity profiles and galaxy types with rising, flat or descending curves in agreement with Verheijen's classification of `R', `F' and `D' type curves, and the corresponding theoretical total disc masses could be fitted to a baryonic Tully-Fisher relation. Nine of the galaxies were matched to galaxies with previously published masses, suggesting a mean excess dynamic disc mass of dex 0.61 ± 0.26 over the baryonic masses. Although questionable with regard to other measurements of the shape of disc galaxy gravitational potentials, this model can accommodate a scenario in which the gravitational mass distribution, as measured via the rotation curve, is confined to a thin plane without requiring a dark matter halo or the use of modified Newtonian dynamics.

  3. Creating reusable tools from scripts: the Galaxy Tool Factory.

    Science.gov (United States)

    Lazarus, Ross; Kaspi, Antony; Ziemann, Mark

    2012-12-01

    Galaxy is a software application supporting high-throughput biology analyses and work flows, available as a free on-line service or as source code for local deployment. New tools can be written to extend Galaxy, and these can be shared using public Galaxy Tool Shed (GTS) repositories, but converting even simple scripts into tools requires effort from a skilled developer. The Tool Factory is a novel Galaxy tool that automates the generation of all code needed to execute user-supplied scripts, and wraps them into new Galaxy tools for upload to a GTS, ready for review and installation through the Galaxy administrative interface. The Galaxy administrative interface supports automated installation from the main GTS. Source code and support are available at the project website, https://bitbucket.org/fubar/galaxytoolfactory. The Tool Factory is implemented as an installable Galaxy tool. ross.lazarus@channing.harvard.edu.

  4. Classification of X-ray point sources in external galaxies

    Science.gov (United States)

    Vrtilek, Saeqa Dil; Islam, Nazma; Kim, Dong-Woo; McCollough, Michael

    2017-08-01

    The exquisite spatial resolution of the Chandra X-ray satellite allows us to resolve individual X-ray point sources in external galaxies. We have extracted data on extragalactic X-ray binary candidates from 150 external galaxies including a selection of elliptical, spiral, and starburst galaxies with a range of metallicities. By using X-ray binaries containing neutron stars or black holes from our own Galaxy that were multiply observed by Chandra as a training set we classify the accretion type of each object individually identified in the external galaxies. We find systematic differences in the binary populations of different classes of galaxy. Our study provides information on populations of X-ray sources in different galaxy types which has implications for the evolution of galaxies, as well as clues about how the different classes of XRBs are related to each other.

  5. Environmental Effects On Galaxy Evolution In Semi-analytic Models

    Science.gov (United States)

    Lee, Jaehyun; Jung, I.; Yi, S.

    2012-01-01

    We have investigated the evolution of galaxy morphology and its mixture in various halo environments by taking advantages of N-body simulations and semi-analytic approach. Dark matter halos have different growth histories depending on the long-range density (voids vs clusters). Since dynamical properties of dark matter halos decide their merger timescales and galaxy properties residing in the halos, different dark matter halo assemblies make different galaxy merger histories. Thus, it is expected that galaxies in voids and clusters may show different evolutionary histories and morphology mixtures because galaxy mergers play a pivotal role in the galaxy morphology transformation. To examine it, dark matter halo merger trees in various density regions are extracted from N-body simulations, and the evolutionary histories of galaxies are computed with our semi-analytic model code based on the N-body backbones. We present the difference of evolutionary histories and morphology mixtures of galaxies that reside in voids and dense regions.

  6. Unusually gas-rich central galaxies in small groups

    Science.gov (United States)

    Janowiecki, Steven; xGASS Team

    2017-01-01

    Observations of gas in galaxies have shown dramatic differences between rich clusters and isolated field environments. However, pre-processing in intermediate group environments is expected to be responsible for much of the transformation between gas-rich blue and gas-poor red galaxies. We investigate this by taking advantage of the deepest observations to date of atomic and molecular gas in local galaxies from the GASS and COLD GASS surveys and their extensions to low stellar masses. This sample is uniquely suited to quantify gas and star formation properties of galaxies across environments, reaching the gas-poor regime of groups and clusters. We find that central galaxies in small groups are unusually gas rich and star-forming, compared to isolated galaxies. Below log Mst/Msun = 10, gas-poor group central galaxies are rare. We suggest that these central galaxies are being fed by the filaments of the cosmic web.

  7. On the galaxy-halo connection in the EAGLE simulation

    Science.gov (United States)

    Desmond, Harry; Mao, Yao-Yuan; Wechsler, Risa H.; Crain, Robert A.; Schaye, Joop

    2017-10-01

    Empirical models of galaxy formation require assumptions about the correlations between galaxy and halo properties. These may be calibrated against observations or inferred from physical models such as hydrodynamical simulations. In this Letter, we use the EAGLE simulation to investigate the correlation of galaxy size with halo properties. We motivate this analysis by noting that the common assumption of angular momentum partition between baryons and dark matter in rotationally supported galaxies overpredicts both the spread in the stellar mass-size relation and the anticorrelation of size and velocity residuals, indicating a problem with the galaxy-halo connection it implies. We find the EAGLE galaxy population to perform significantly better on both statistics, and trace this success to the weakness of the correlations of galaxy size with halo mass, concentration and spin at fixed stellar mass. Using these correlations in empirical models will enable fine-grained aspects of galaxy scalings to be matched.

  8. Seyfert galaxies: A study of brightness variation and stellar concentration

    Science.gov (United States)

    Dawson, D. W.

    1976-01-01

    Ultraviolet photometry of Seyfert galaxies is analyzed for variations in nuclear magnitude. Using multiple apertures permits the estimation of stellar concentration; four Seyfert and two normal spiral galaxies are compared.

  9. Probability of lensing magnification by cosmologically distributed galaxies

    Science.gov (United States)

    Pei, Yichuan C.

    1993-01-01

    We present the analytical formulae for computing the magnification probability caused by cosmologically distributed galaxies. The galaxies are assumed to be singular, truncated-isothermal spheres without both evolution and clustering in redshift. We find that, for a fixed total mass, extended galaxies produce a broader shape in the magnification probability distribution and hence are less efficient as gravitational lenses than compact galaxies. The high-magnification tail caused by large galaxies is well approximated by an A exp -3 form, while the tail by small galaxies is slightly shallower. The mean magnification as a function of redshift is, however, found to be independent of the size of the lensing galaxies. In terms of the flux conservation, our formulae for the isothermal galaxy model predict a mean magnification to within a few percent with the Dyer-Roeder model of a clumpy universe.

  10. The Promise of First Spectroscopy of Normal and Dwarf Galaxies

    National Research Council Canada - National Science Library

    Fischer, J

    2001-01-01

    ISO spectroscopic studies of galaxies gave us a taste of the diversity of IR spectroscopic signatures of galaxies and their potential to characterize stellar populations and their effects on the local...

  11. Star Forming Galaxies and AGN Hosts: The Seagull Wings

    Science.gov (United States)

    Stasińska, Grazyna; Cid Fernandes, Roberto; Mateus, Abîlio; Sodré, Laerte; Asari, Natalia V.

    2007-05-01

    We discuss the spectral signatures of normal star forming (NSF) galaxies and of AGN hosts of and present physically motivated techniques to distinguish these two classes of galaxies. We have determined the emission line intensities for a complete sample of galaxies extracted from the Sloan Digital sky Survey, after subtracting the stellar continuum obtained from spectral synthesis. With the help of sequences of photoionization models, we explain why, in the famous [OIII]/Hbeta vs [NII]/Halpha diagram, NSF galaxies and AGN hosts form two separate sequences, which look like the open wings of a seagull. We also examine other techniques to distinguish star forming galaxies from AGN hosts. Finally, we propose a new diagnostic diagram which can be used with optical spectra of galaxies with redshifts up to z=1.3. This new diagram has also the advantage of allowing one to show all the galaxies of a sample in one plot, including passive galaxies.

  12. 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.

  13. Automatic Detection of Galaxy Type From Datasets of Galaxies Image Based on Image Retrieval Approach.

    Science.gov (United States)

    Abd El Aziz, Mohamed; Selim, I M; Xiong, Shengwu

    2017-06-30

    This paper presents a new approach for the automatic detection of galaxy morphology from datasets based on an image-retrieval approach. Currently, there are several classification methods proposed to detect galaxy types within an image. However, in some situations, the aim is not only to determine the type of galaxy within the queried image, but also to determine the most similar images for query image. Therefore, this paper proposes an image-retrieval method to detect the type of galaxies within an image and return with the most similar image. The proposed method consists of two stages, in the first stage, a set of features is extracted based on shape, color and texture descriptors, then a binary sine cosine algorithm selects the most relevant features. In the second stage, the similarity between the features of the queried galaxy image and the features of other galaxy images is computed. Our experiments were performed using the EFIGI catalogue, which contains about 5000 galaxies images with different types (edge-on spiral, spiral, elliptical and irregular). We demonstrate that our proposed approach has better performance compared with the particle swarm optimization (PSO) and genetic algorithm (GA) methods.

  14. 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.

  15. Census of the Local Universe (CLU) Hα Galaxy Survey: Characterization of Galaxy Catalogs from Preliminary Fields

    Science.gov (United States)

    Cook, David O.; Kasliwal, Mansi; Van Sistine, Anglea; Kaplan, David; iPTF

    2018-01-01

    In this talk I introduce the Census of the Local Universe (CLU) galaxy survey. The survey uses 4 wavelength-adjacent, narrowband filters to search for emission-line (Hα) sources across ~3π (26,470 deg2) of the sky and out to distance of 200 Mpc. I will present an analysis of galaxy candidates in 14 preliminary fields (out of 3626) to assess the limits of the survey and the potential for finding new galaxies in the local Universe. We anticipate finding tens-of-thousands of new galaxies in the full ~3π survey. In addition, I present some interesting galaxies found in these fields, which include: newly discovered blue compact dwarfs (e.g., blueberries), 1 new green pea, 1 new QSO, and a known planetary nebula. The majority of the CLU galaxies show properties similar to normal star-forming galaxies; however, the newly discovered blueberries tend to have high star formation rates for their given stellar mass.

  16. MaNGA: Mapping Nearby Galaxies at Apache Point Observatory

    Science.gov (United States)

    Weijmans, A.-M.; MaNGA Team

    2016-10-01

    MaNGA (Mapping Nearby Galaxies at APO) is a galaxy integral-field spectroscopic survey within the fourth generation Sloan Digital Sky Survey (SDSS-IV). It will be mapping the composition and kinematics of gas and stars in 10,000 nearby galaxies, using 17 differently sized fiber bundles. MaNGA's goal is to provide new insights in galaxy formation and evolution, and to deliver a local benchmark for current and future high-redshift studies.

  17. The Influence of the Environment on the Evolution of Galaxies

    Science.gov (United States)

    Sikkema, Geert

    2009-03-01

    In this thesis, we explore how the properties of galaxies depend on environment where they reside. The thesis consists of two parts, with each having its own data-set. Part 1 consists of observations done with a wide-field CCD-camera mounted on a middle-sized telescope. In Groningen, a software system ASTRO-WISE has been developed that will reduce observations the upcoming wide-field camera OmegaCAM. Our observations were used as a testbed for ASTRO-WISE. We looked at a region on the sky with a size of 16 full moons, which contains several galaxy clusters at a distance of about 1 billion lightyears. One type of galaxy, the so-called S0 galaxies, seem to have formed quite fast in the past few billion years in clusters. These type of galaxies probably evolve from spiral galaxies. Our observations give clues about how and where this transformation occurs. We find that the so-called red spirals might be a transition type of galaxy: between normal spirals and S0s. Furthermore, we find morphological differences between several types of galaxies in low and high density regions. Part 2 consists of Hubble Space Telescope dataof six relatively nearby shell galaxies. Shell galaxies are elliptical galaxies which deviations (shells) in their light distribution. We have determined very precisely the colours and shapes of shells as well as the presence of dust in these galaxies. The results imply that shells are the remains of small dwarf galaxies that have merged with the much larger elliptical galaxy. We also looked if the shell galaxies contain recently formed globular clusters. We find that two out of six of our shell galaxies show evidence for young globular clusters.

  18. Harassment Origin for Kinematic Substructures in Dwarf Elliptical Galaxies?

    OpenAIRE

    Gonzalez-Garcia, A. C.; Aguerri, J. A. L.; Balcells, M.

    2005-01-01

    [EN]We have run high resolution N-body models simulating the encounter of a dwarf galaxy with a bright elliptical galaxy. The dwarf absorbs orbital angular momentum and shows counter-rotating features in the external regions of the galaxy. To explain the core-envelope kinematic decoupling observed in some dwarf galaxies in high-density environments requires nearly head-on collisions and very little dark matter bound to the dwarf. These kinematic structures appear under rather restrictive cond...

  19. HOST GALAXIES AS GAMMA-RAY BURST DISTANCE INDICATORS

    Energy Technology Data Exchange (ETDEWEB)

    D. BAND; ET AL

    2001-01-01

    We calculate the distributions of the total burst energy, the peak luminosity and the X-ray afterglow energy using burst observations and distances to the associated host galaxies. To expand the sample, we include redshift estimates for host galaxies without spectroscopic redshifts. The methodology requires a model of the host galaxy population; we find that in the best model the burst rate is proportional to the host galaxy luminosity at the time of the burst.

  20. Black Hole Caught Zapping Galaxy into Existence?

    Science.gov (United States)

    2009-11-01

    Which come first, the supermassive black holes that frantically devour matter or the enormous galaxies where they reside? A brand new scenario has emerged from a recent set of outstanding observations of a black hole without a home: black holes may be "building" their own host galaxy. This could be the long-sought missing link to understanding why the masses of black holes are larger in galaxies that contain more stars. "The 'chicken and egg' question of whether a galaxy or its black hole comes first is one of the most debated subjects in astrophysics today," says lead author David Elbaz. "Our study suggests that supermassive black holes can trigger the formation of stars, thus 'building' their own host galaxies. This link could also explain why galaxies hosting larger black holes have more stars." To reach such an extraordinary conclusion, the team of astronomers conducted extensive observations of a peculiar object, the nearby quasar HE0450-2958 (see eso0523 for a previous study of this object), which is the only one for which a host galaxy has not yet been detected [1]. HE0450-2958 is located some 5 billion light-years away. Until now, it was speculated that the quasar's host galaxy was hidden behind large amounts of dust, and so the astronomers used a mid-infrared instrument on ESO's Very Large Telescope for the observations [2]. At such wavelengths, dust clouds shine very brightly, and are readily detected. "Observing at these wavelengths would allow us to trace dust that might hide the host galaxy," says Knud Jahnke, who led the observations performed at the VLT. "However, we did not find any. Instead we discovered that an apparently unrelated galaxy in the quasar's immediate neighbourhood is producing stars at a frantic rate." These observations have provided a surprising new take on the system. While no trace of stars is revealed around the black hole, its companion galaxy is extremely rich in bright and very young stars. It is forming stars at a rate

  1. Galaxy Zoo: Morphological Classification of Galaxy Images from the Illustris  Simulation

    Science.gov (United States)

    Dickinson, Hugh; Fortson, Lucy; Lintott, Chris; Scarlata, Claudia; Willett, Kyle; Bamford, Steven; Beck, Melanie; Cardamone, Carolin; Galloway, Melanie; Simmons, Brooke; Keel, William; Kruk, Sandor; Masters, Karen; Vogelsberger, Mark; Torrey, Paul; Snyder, Gregory F.

    2018-02-01

    Modern large-scale cosmological simulations model the universe with increasing sophistication and at higher spatial and temporal resolutions. These ongoing enhancements permit increasingly detailed comparisons between the simulation outputs and real observational data. Recent projects such as Illustris are capable of producing simulated images that are designed to be comparable to those obtained from local surveys. This paper tests the degree to which Illustris achieves this goal across a diverse population of galaxies using visual morphologies derived from Galaxy Zoo citizen scientists. Morphological classifications provided by these volunteers for simulated galaxies are compared with similar data for a compatible sample of images drawn from the Sloan Digital Sky Survey (SDSS) Legacy Survey. This paper investigates how simple morphological characterization by human volunteers asked to distinguish smooth from featured systems differs between simulated and real galaxy images. Significant differences are identified, which are most likely due to the limited resolution of the simulation, but which could be revealing real differences in the dynamical evolution of populations of galaxies in the real and model universes. Specifically, for stellar masses {M}\\star ≲ {10}11 {M}ȯ , a substantially larger proportion of Illustris galaxies that exhibit disk-like morphology or visible substructure, relative to their SDSS counterparts. Toward higher masses, the visual morphologies for simulated and observed galaxies converge and exhibit similar distributions. The stellar mass threshold indicated by this divergent behavior confirms recent works using parametric measures of morphology from Illustris simulated images. When {M}\\star ≳ {10}11 {M}ȯ , the Illustris data set contains substantially fewer galaxies that classifiers regard as unambiguously featured. In combination, these results suggest that comparison between the detailed properties of observed and simulated galaxies

  2. The Stripe 82 Massive Galaxy Project. III. A Lack of Growth among Massive Galaxies

    Science.gov (United States)

    Bundy, Kevin; Leauthaud, Alexie; Saito, Shun; Maraston, Claudia; Wake, David A.; Thomas, Daniel

    2017-12-01

    The average stellar mass (M *) of high-mass galaxies ({log}{M}* /{M}⊙ > 11.5) is expected to grow by ˜30% since z˜ 1, largely through ongoing mergers that are also invoked to explain the observed increase in galaxy sizes. Direct evidence for the corresponding growth in stellar mass has been elusive, however, in part because the volumes sampled by previous redshift surveys have been too small to yield reliable statistics. In this work, we make use of the Stripe 82 Massive Galaxy Catalog (S82-MGC) to build a mass-limited sample of 41,770 galaxies ({log}{M}* /{M}⊙ > 11.2) with optical-to-near-IR photometry and a large fraction (>55%) of spectroscopic redshifts. Our sample spans 139 deg2, significantly larger than most previous efforts. After accounting for a number of potential systematic errors, including the effects of M * scatter, we measure galaxy stellar mass functions over 0.3history assumed for M * estimates, although our inability to characterize low-surface-brightness outskirts may be the most important limitation of our study. Even among these high-mass galaxies, we find evidence for differential evolution when splitting the sample by recent SF activity. While low-SF systems appear to become completely passive, we find a mostly subdominant population of galaxies with residual, but low rates of SF (˜1 M ⊙ yr-1) whose number density does not evolve. Interestingly, these galaxies become more prominent at higher M *, representing ˜10% of all galaxies at {10}12 {M}⊙ and perhaps dominating at even larger masses.

  3. Galaxy And Mass Assembly (GAMA): The mechanisms for quiescent galaxy formation at z < 1

    Science.gov (United States)

    Rowlands, K.; Wild, V.; Bourne, N.; Bremer, M.; Brough, S.; Driver, S. P.; Hopkins, A. M.; Owers, M. S.; Phillipps, S.; Pimbblet, K.; Sansom, A. E.; Wang, L.; Alpaslan, M.; Bland-Hawthorn, J.; Colless, M.; Holwerda, B. W.; Taylor, E. N.

    2018-01-01

    One key problem in astrophysics is understanding how and why galaxies switch off their star formation, building the quiescent population that we observe in the local Universe. From the Galaxy And Mass Assembly and VIsible MultiObject Spectrograph Public Extragalactic Redshift surveys, we use spectroscopic indices to select quiescent and candidate transition galaxies. We identify potentially rapidly transitioning post-starburst (PSB) galaxies and slower transitioning green-valley galaxies. Over the last 8 Gyr, the quiescent population has grown more slowly in number density at high masses ({M}_\\ast >10^{11}{M_{⊙}) than at intermediate masses ({M}_\\ast >10^{10.6}{M_{⊙}). There is evolution in both the PSB and green-valley stellar mass functions, consistent with higher mass galaxies quenching at earlier cosmic times. At intermediate masses ({M}_\\ast >10^{10.6}{M_{⊙}), we find a green-valley transition time-scale of 2.6 Gyr. Alternatively, at z ∼ 0.7, the entire growth rate could be explained by fast-quenching PSB galaxies, with a visibility time-scale of 0.5 Gyr. At lower redshift, the number density of PSBs is so low that an unphysically short visibility window would be required for them to contribute significantly to the quiescent population growth. The importance of the fast-quenching route may rapidly diminish at z 10^{11}{M_{⊙}), there is tension between the large number of candidate transition galaxies compared to the slow growth of the quiescent population. This could be resolved if not all high-mass PSB and green-valley galaxies are transitioning from star forming to quiescent, for example if they rejuvenate out of the quiescent population following the accretion of gas and triggering of star formation, or if they fail to completely quench their star formation.

  4. Constraints on the alignment of galaxies in galaxy clusters from ~14 000 spectroscopic members

    Science.gov (United States)

    Sifón, Cristóbal; Hoekstra, Henk; Cacciato, Marcello; Viola, Massimo; Köhlinger, Fabian; van der Burg, Remco F. J.; Sand, David J.; Graham, Melissa L.

    2015-03-01

    Torques acting on galaxies lead to physical alignments, but the resulting ellipticity correlations are difficult to predict. As they constitute a major contaminant for cosmic shear studies, it is important to constrain the intrinsic alignment signal observationally. We measured the alignments of satellite galaxies within 90 massive galaxy clusters in the redshift range 0.05 data from the Canada-France-Hawaii Telescope. We used phase-space information to select 14 576 cluster members, 14 250 of which have shape measurements and measured three different types of alignment: the radial alignment of satellite galaxies toward the brightest cluster galaxies (BCGs), the common orientations of satellite galaxies and BCGs, and the radial alignments of satellites with each other. Residual systematic effects are much smaller than the statistical uncertainties. We detect no galaxy alignment of any kind out to at least 3r200. The signal is consistent with zero for both blue and red galaxies, bright and faint ones, and also for subsamples of clusters based on redshift, dynamical mass, and dynamical state. These conclusions are unchanged if we expand the sample with bright cluster members from the red sequence. We augment our constraints with those from the literature to estimate the importance of the intrinsic alignments of satellites compared to those of central galaxies, for which the alignments are described by the linear alignment model. Comparison of the alignment signals to the expected uncertainties of current surveys such as the Kilo-Degree Survey suggests that the linear alignment model is an adequate treatment of intrinsic alignments, but it is not clear whether this will be the case for larger surveys. Table is available in electronic form at

  5. The scaling relation of early-type galaxies in clusters II. Spectroscopic data for galaxies in eight nearby clusters

    DEFF Research Database (Denmark)

    Bettoni, D.; Moles, M.; Fasano, G.

    2006-01-01

    Galaxies: elliptical and lenticulars, cD, distances and redshifts - clusters: general Udgivelsesdato: June......Galaxies: elliptical and lenticulars, cD, distances and redshifts - clusters: general Udgivelsesdato: June...

  6. Gamma-ray Spectra of Starburst Galaxies

    Science.gov (United States)

    Moncada, Roberto Jose; Paglione, Timothy

    2018-01-01

    Starburst galaxies offer a unique window into the nature of star formation, its driving forces, and the energetic interactions within the galaxy. Their supernovae enrich the surrounding environment with cosmic rays that interact with the interstellar medium and galactic magnetic fields producing gamma-rays and non-thermal radio emission. We generated gamma-ray spectra for the 7 brightest starburst galaxies using 8.6 years of Pass 8 Large Area Telescope (LAT) data from the Fermi Gamma-ray Space Telescope. In addition to new detections, we will report on the results of simultaneously modeling the gamma-ray and radio spectra. These results confirm prior studies favoring high magnetic field strengths in the starburst regions.

  7. Mosfire Spectroscopy Of Galaxies In Cosmic Noon

    Science.gov (United States)

    Nanayakkara, Themiya

    2017-07-01

    The recent development of sensitive, multiplexed near infra-red instruments has presented astronomers the unique opportunity to survey mass/magnitude complete samples of galaxies at Cosmic Noon, a time period where ˜ 80% of the observed baryonic mass is generated and galaxies are actively star-forming and evolving rapidly. This thesis takes advantage of the recently commissioned MOSFIRE spectrograph on Keck, to conduct a survey (ZFIRE) of galaxies at 1.5 frame optical colours. I present a thorough analysis of stellar population properties of the ZFIRE sample via multiple synthetic stellar population models and stellar libraries. Due to an excess of high Hα-EW galaxies that are up to 0.3-0.5 dex above the Salpeter locus, the Hα-EW distribution is much broader (10-500˚A) than can be explained by a simple monotonic SFH with a standard Salpeter-slope IMF. This result is robust against uncertainties in dust correction and observational bias, and no single IMF (i.e. non-Salpeter slope) can explain the distribution. Starburst models cannot explain the Hα-EW distribution because: 1) spectral stacking still shows an excess Hα-EW in composite populations and 2) Monte Carlo burst models show that the timescale for high Hα-EW is too short to explain their abundance in the ZFIRE sample. Other possible physical mechanisms that could produce excess ionising photons for a given star-formation rate, and hence high equivalent widths, including models with variations in stellar rotation, binary star evolution, metallicity, and upper mass cutoff of the IMF are investigated and ruled out. IMF variation is one possible explanation for the high Hα-EWs. However, the highest Hα-EW values would require very shallow slopes (Γ > -1.0) and no single IMF change can explain the large variation in Hα-EWs. Instead the IMF would have to vary stochastically. Therefore, currently there is no simple physical model to explain the large variation in Hα-EWs at z ˜ 2, but the distinct

  8. Multiwavelength Mapping of Galaxy Formation and Evolution

    CERN Document Server

    Renzini, Alvio; ESO Workshop

    2005-01-01

    The possibilities of astronomical observation have dramatically increased over the last decade. Major satellites, like the Hubble Space Telescope, Chandra and XMM Newton, are complemented by numerous large ground-based observatories, from 8m-10m optical telescopes to sub-mm and radio facilities. As a result, observational astronomy has access to virtually the whole electromagnetic spectrum of galaxies, even at high redshifts. Theoretical models of galaxy formation and cosmological evolution now face a serious challenge to match the plethora of observational data. In October 2003, over 170 astronomers from 15 countries met for a 4-day workshop to extensively illustrate and discuss all major observational projects and ongoing theoretical efforts to model galaxy formation and evolution. This volume contains the complete proceedings of this meeting and is therefore a unique and timely overview of the current state of research in this rapidly evolving field.

  9. Measuring our Universe from Galaxy Redshift Surveys

    Directory of Open Access Journals (Sweden)

    Lahav Ofer

    2004-07-01

    Full Text Available Galaxy redshift surveys have achieved significant progress over the last couple of decades. Those surveys tell us in the most straightforward way what our local Universe looks like. While the galaxy distribution traces the bright side of the Universe, detailed quantitative analyses of the data have even revealed the dark side of the Universe dominated by non-baryonic dark matter as well as more mysterious dark energy (or Einstein's cosmological constant. We describe several methodologies of using galaxy redshift surveys as cosmological probes, and then summarize the recent results from the existing surveys. Finally we present our views on the future of redshift surveys in the era of precision cosmology.

  10. Representative galaxy age-metallicity relationships

    Science.gov (United States)

    Piatti, Andrés E.; Aparicio, Antonio; Hidalgo, Sebastián L.

    2017-07-01

    The ongoing surveys of galaxies and those for the next generation of telescopes will demand the execution of high-CPU consuming machine codes for recovering detailed star formation histories (SFHs) and hence age-metallicity relationships (AMRs). We present here an expeditive method which provides quick-look AMRs on the basis of representative ages and metallicities obtained from colour-magnitude diagram (CMD) analyses. We have tested its performance by generating synthetic CMDs for a wide variety of galaxy SFHs. The representative AMRs turn out to be reliable down to a magnitude limit with a photometric completeness factor higher than ˜85 per cent, and trace the chemical evolution history for any stellar population (represented by a mean age and an intrinsic age spread) with a total mass within ˜40 per cent of the more massive stellar population in the galaxy.

  11. Circumnuclear Structures in Megamaser Host Galaxies

    Science.gov (United States)

    Pjanka, Patryk; Greene, Jenny E.; Seth, Anil C.; Braatz, James A.; Henkel, Christian; Lo, Fred K. Y.; Läsker, Ronald

    2017-08-01

    Using the Hubble Space Telescope, we identify circumnuclear (100-500 pc scale) structures in nine new H2O megamaser host galaxies to understand the flow of matter from kpc-scale galactic structures down to the supermassive black holes (SMBHs) at galactic centers. We double the sample analyzed in a similar way by Greene et al. and consider the properties of the combined sample of 18 sources. We find that disk-like structure is virtually ubiquitous when we can resolve hosts. We find marginal evidence that the disk-like nuclear structures show increasing misalignment from the kpc-scale host galaxy disk as the scale of the structure decreases. In turn, we find that the orientation of both the ˜100 pc scale nuclear structures and their host galaxy large-scale disks is consistent with random with respect to the orientation of their respective megamaser disks.

  12. Mapping Dark Matter in Simulated Galaxy Clusters

    Science.gov (United States)

    Bowyer, Rachel

    2018-01-01

    Galaxy clusters are the most massive bound objects in the Universe with most of their mass being dark matter. Cosmological simulations of structure formation show that clusters are embedded in a cosmic web of dark matter filaments and large scale structure. It is thought that these filaments are found preferentially close to the long axes of clusters. We extract galaxy clusters from the simulations "cosmo-OWLS" in order to study their properties directly and also to infer their properties from weak gravitational lensing signatures. We investigate various stacking procedures to enhance the signal of the filaments and large scale structure surrounding the clusters to better understand how the filaments of the cosmic web connect with galaxy clusters. This project was supported in part by the NSF REU grant AST-1358980 and by the Nantucket Maria Mitchell Association.

  13. Hot interstellar matter in elliptical galaxies

    CERN Document Server

    Kim, Dong-Woo

    2012-01-01

    Based on a number of new discoveries resulting from 10 years of Chandra and XMM-Newton observations and corresponding theoretical works, this is the first book to address significant progress in the research of the Hot Interstellar Matter in Elliptical Galaxies. A fundamental understanding of the physical properties of the hot ISM in elliptical galaxies is critical, because they are directly related to the formation and evolution of elliptical galaxies via star formation episodes, environmental effects such as stripping, infall, and mergers, and the growth of super-massive black holes. Thanks to the outstanding spatial resolution of Chandra and the large collecting area of XMM-Newton, various fine structures of the hot gas have been imaged in detail and key physical quantities have been accurately measured, allowing theoretical interpretations/predictions to be compared and tested against observational results. This book will bring all readers up-to-date on this essential field of research.

  14. Study of the global environment of small galaxy groups

    Science.gov (United States)

    Duplancic, F.; Dávila, F.; Coldwell, G.

    2017-07-01

    The present work presents a study of the global density environment of small galaxy groups. To this end we use a catalog of small galaxy systems constructed from the 10th Data Release of the Sloan Digital Sky Survey. To characterize the global environment of small galaxy groups we use different estimators, including the number of significant neighbors within a fixed aperture, the distance to the nearest neighbor and the number density profile of these systems. In order to perform a comparative study, we select different categories of systems considering galaxy pairs, triplets of galaxies and groups with at least four member galaxies. We found differences between the global environment of pairs compared to triplet of galaxies and groups. Galaxy pairs inhabit environments of lower global density than triplets and groups which are located in higher global density regions. This result is in agreement with different studies in the literature which propose that triplets of galaxies and compact groups have similarities in their fundamental properties and are different from galaxy pairs. Our findings suggest that the global density environment of small galaxy groups plays a fundamental role in the characterization of the main properties of these systems and their member galaxies.

  15. Dust in FIR-bright ADF-S galaxies

    Science.gov (United States)

    Małek, K.; Pollo, A.; Takeuchi, T. T.; Buat, V.; Burgarella, D.; Malkan, M.

    2015-02-01

    Multiwavelength Spectral Energy Distributions (SEDs) of far-infrared (FIR) galaxies detected in the AKARI South Ecliptic Poles Survey (ADF-S) allow to trace differences between [Ultra]-Luminous Infrared Galaxies ([U]LIRGS) and other types of star-forming galaxies (SF).

  16. 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 Legacy survey. Once the star formation contribution to the X-ray emission is subtracted, the AGN luminosities of the 40 dwarf galaxies are in the range L(0.5-10 keV)~1039 - 1044 erg/s. With 12 sources at z > 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.

  17. Galaxy Zoo: Exploring the Motivations of Citizen Science Volunteers

    Science.gov (United States)

    Raddick, M. Jordan; Bracey, Georgia; Gay, Pamela L.; Lintott, Chris J.; Murray, Phil; Schawinski, Kevin; Szalay, Alexander S.; Vandenberg, Jan

    2010-01-01

    The Galaxy Zoo citizen science website invites anyone with an Internet connection to participate in research by classifying galaxies from the Sloan Digital Sky Survey. As of April 2009, more than 200,000 volunteers have made more than 100 million galaxy classifications. In this article, we present results of a pilot study into the motivations and…

  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. Archaeology of active galaxies across the electromagnetic spectrum

    NARCIS (Netherlands)

    Morganti, Raffaella

    2017-01-01

    Analytical and numerical galaxy-formation models indicate that active galactic nuclei (AGNs) likely play a prominent role in the formation and evolution of galaxies. However, quantifying this effect requires knowledge of how the nuclear activity proceeds throughout the life of a galaxy, whether it

  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. Planetary Nebulae as kinematic and dynamical tracers of galaxy halos

    NARCIS (Netherlands)

    Coccato, Lodovico; Napolitano, Nicola; Arnaboldi, Magda; Cortesi, Arianna; Romanowsky, Aaron; Gerhard, Ortwin; Merrifield, Michael; Kuijken, Konrad; Freeman, Ken; Douglas, Nigel

    2015-01-01

    The kinematics and dynamical properties of galaxy halos are difficult to measure, given the faint stellar surface brightness that characterizes those regions. Gas-rich systems such as spiral galaxies can be probed using the radio emission of their gas component. Early type galaxies contain less gas,

  2. Gas accretion from minor mergers in local spiral galaxies

    NARCIS (Netherlands)

    Di Teodoro, E. M.; Fraternali, F.

    We quantify the gas accretion rate from minor mergers onto star-forming galaxies in the local Universe using Hi observations of 148 nearby spiral galaxies (WHISP sample). We developed a dedicated code that iteratively analyses Hi data-cubes, finds dwarf gas-rich satellites around larger galaxies,

  3. Alignments of Galaxies within Cosmic Filaments from SDSS DR7

    Science.gov (United States)

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

    2013-12-01

    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.

  4. From Nearby Low Luminosity AGN to High Redshift Radio Galaxies ...

    Indian Academy of Sciences (India)

    'radio-quiet' AGN (Croton et al. 2006; Best & Heckman 2012). There is also evidence to suggest that galaxy mergers influence the radio-loudness of sources (Heckman et al. 1986; Deane et al. 2014). We know that galaxy mergers are an important phase of galaxy evolution (Schweizer 1982; Mihos & Hernquist. 1996; Cox et ...

  5. Statistical Properties of Gamma-Ray Burst Host Galaxies

    Indian Academy of Sciences (India)

    A statistical analysis of gamma-ray burst host galaxies is presented and a clear metallicity-stellar mass relation is found in our sample. A trend that a more massive host galaxy tends to have a higher star-formation rate is also found. No correlation is found between V and H. GRB host galaxies at a higher redshift also tend ...

  6. Early death of massive galaxies in the distant universe

    NARCIS (Netherlands)

    Straatman, Caroline Margaretha Stefanie

    2016-01-01

    One of the major unresolved questions in astronomy is: how do galaxies form and evolve? In the local universe we can distinguish between actively star-forming and quiescent galaxies. Quiescent galaxies are typically the most massive, with elliptical morphologies and red optical colors. The

  7. On order and chaos in the mergers of galaxies

    Science.gov (United States)

    Vandervoort, Peter O.

    2018-03-01

    This paper describes a low-dimensional model of the merger of two galaxies. The governing equations are the complete sets of moment equations of the first and second orders derived from the collisionless Boltzmann equations representing the galaxies. The moment equations reduce to an equation governing the relative motion of the galaxies, tensor virial equations, and equations governing the kinetic energy tensors. We represent the galaxies as heterogeneous ellipsoids with Gaussian stratifications of their densities, and we represent the mean stellar motions in terms of velocity fields that sustain those densities consistently with the equation of continuity. We reduce and solve the governing equations for a head-on encounter of a dwarf galaxy with a giant galaxy. That reduction includes the effect of dynamical friction on the relative motion of the galaxies. Our criterion for chaotic behaviour is sensitivity of the motion to small changes in the initial conditions. In a survey of encounters and mergers of a dwarf galaxy with a giant galaxy, chaotic behaviour arises mainly in non-linear oscillations of the dwarf galaxy. The encounter disrupts the dwarf, excites chaotic oscillations of the dwarf, or excites regular oscillations. Dynamical friction can drive a merger to completion within a Hubble time only if the dwarf is sufficiently massive. The survey of encounters and mergers is the basis for a simple model of the evolution of a `Local Group' consisting of a giant galaxy and a population of dwarf galaxies bound to the giant as satellites on radial orbits.

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

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging Solutions)

    tribution of hot, young stars in star forming regions of normal and starburst galaxies. Extensive Hα surveys of samples of normal galaxies were carried out by Kennicutt &. Kent (1983). They found that the integrated emission of a galaxy is strongly correlated with its Hubble type and colour. They also inferred that the variation ...

  9. Giant Low Surface Brightness Galaxies: Evolution in Isolation M. Das

    Indian Academy of Sciences (India)

    Abstract. Giant Low Surface Brightness (GLSB) galaxies are amongst the most massive spiral galaxies that we know of in our Universe. Although they fall in the class of late type spiral galaxies, their properties are far more extreme. They have very faint stellar disks that are extremely rich in neutral hydrogen gas but low in ...

  10. Demise of faint satellites around isolated early-type galaxies

    Science.gov (United States)

    Park, Changbom; Hwang, Ho Seong; Park, Hyunbae; Lee, Jong Chul

    2018-02-01

    The hierarchical galaxy formation scenario in the Cold Dark Matter cosmology with a non-vanishing cosmological constant Λ and geometrically flat space (ΛCDM) has been very successful in explaining the large-scale distribution of galaxies. However, there have been claims that ΛCDM over-predicts the number of satellite galaxies associated with massive galaxies compared with observations—the missing satellite galaxy problem1-3. Isolated groups of galaxies hosted by passively evolving massive early-type galaxies are ideal laboratories for identifying the missing physics in the current theory4-11. Here, we report—based on a deep spectroscopic survey—that isolated massive and passive early-type galaxies without any signs of recent wet mergers or accretion episodes have almost no satellite galaxies fainter than the r-band absolute magnitude of about Mr = -14. If only early-type satellites are used, the cutoff is at the somewhat brighter magnitude of about Mr = -15. Such a cutoff has not been found in other nearby satellite galaxy systems hosted by late-type galaxies or those with merger features. Various physical properties of satellites depend strongly on the host-centric distance. Our observations indicate that the satellite galaxy luminosity function is largely determined by the interaction of satellites with the environment provided by their host.

  11. The Frequency of Active and Quiescent Galaxies with Companions

    OpenAIRE

    Schmitt, Henrique R.

    2002-01-01

    We study the percentage of active, HII and quiescent galaxies with companions in the Palomar survey. We find that when we separate the galaxies by their morphological types (ellipticals or spirals), to avoid morphology-density effects, there is no difference in the percentage of galaxies with companions among the different activity types.

  12. Giant Low Surface Brightness Galaxies: Evolution in Isolation

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Giant Low Surface Brightness (GLSB) galaxies are amongst the most massive spiral galaxies that we know of in our Universe. Although they fall in the class of late type spiral galaxies, their properties are far more extreme. They have very faint stellar disks that are extremely rich in neutral hydrogen gas but ...

  13. The Evolution of Galaxies in Cluster Environment; HI Perspective

    NARCIS (Netherlands)

    Fujita, A.; van Gorkom, J.; van Kampen, E.

    1999-01-01

    We investigate the degree to which the environment affects the evolution of galaxies in clusters. One way is to study the fate of gas in cluster galaxies by deep HI synthesis imaging. We are interested in the correlation between HI deficiency of galaxies and the dynamical states of clusters/the

  14. Dwarf elliptical galaxies with kinematically decoupled cores

    Science.gov (United States)

    De Rijcke, S.; Dejonghe, H.; Zeilinger, W. W.; Hau, G. K. T.

    2004-10-01

    We present, for the first time, photometric and kinematical evidence, obtained with FORS2 on the VLT, for the existence of kinematically decoupled cores (KDCs) in two dwarf elliptical galaxies; FS76 in the NGC 5044 group and FS373 in the NGC 3258 group. Both kinematically peculiar subcomponents rotate in the same sense as the main body of their host galaxy but betray their presence by a pronounced bump in the rotation velocity profiles at a radius of about 1''. The KDC in FS76 rotates at 10 ± 3 km s-1, with the host galaxy rotating at 15 ± 6 km s-1; the KDC in FS373 has a rotation velocity of 6 ± 2 km s-1 while the galaxy itself rotates at 20 ± 5 km s-1. FS373 has a very complex rotation velocity profile with the velocity changing sign at 1.5 Re. The velocity and velocity dispersion profiles of FS76 are asymmetric at larger radii. This could be caused by a past gravitational interaction with the giant elliptical NGC 5044, which is at a projected distance of 50 kpc. We argue that these decoupled cores are most likely not produced by mergers in a group or cluster environment because of the prohibitively large relative velocities. A plausible alternative is offered by flyby interactions between a dwarf elliptical or its disky progenitor and a massive galaxy. The tidal forces during an interaction at the relative velocities and impact parameters typical for a group environment exert a torque on the dwarf galaxy that, according to analytical estimates, transfers enough angular momentum to its stellar envelope to explain the observed peculiar kinematics.

  15. Organisation of railway freight transport: case study CIM/SMGS between Slovakia and Ukraine

    National Research Council Canada - National Science Library

    Abramović, Borna; Zitricky, Vladislav; Biškup, Vedran

    2016-01-01

    ...) and Ukraine.In Eastern Europe a considerable volume of goods is usually carried by rail. On the Ukrainian side there is the Chop railway station, the largest entry/exit rail point and on the Slovakian side there is the...

  16. VizieR Online Data Catalog: S2CLS: multiwavelength counterparts to SMGs (Chen+, 2016)

    Science.gov (United States)

    Chen, C.-C.; Smail, I.; Ivison, R. J.; Arumugam, V.; Almaini, O.; Conselice, C. J.; Geach, J. E.; Hartley, W. G.; Ma, C.-J.; Mortlock, A.; Simpson, C.; Simpson, J. M.; Swinbank, A. M.; Aretxaga, I.; Blain, A.; Chapman, S. C.; Dunlop, J. S.; Farrah, D.; Halpern, M.; Michalowski, M. J.; van der Werf, P.; Wilkinson, A.; Zavala, J. A.

    2016-05-01

    The SCUBA-2 data at 850um in the UDS field were taken as part of the SCUBA-2 Cosmology Legacy Survey (S2CLS). The full data reduction steps are described fully in J. E. Geach et al. (2016, in preparation). In total we detect 1088 submillimeter sources at >=3.5σ within the region where rms noise is =4.0σ, for which we expect a false detection rate of ~1% based on simulations and source extractions on negative signals. We also define a supplementary sample of 372 submillimeter sources that are detected at 3.5-4.0σ and have a false detection rate of ~10%. In this paper, we provide counterpart candidates for both main and supplementary samples; however, the scientific analyses were performed on the main sample. We have carried out ALMA follow-up observations at 870um on 30 of the brighter SCUBA-2 sources in a Cycle 1 project 2012.1.00090.S (Simpson et al. 2015ApJ...807..128S, 2015ApJ...799...81S). The K-band-based multiwavelength photometry adopted in this paper is based on the UDS data release 8 (DR8) of the UKIRT Infrared Deep Sky Survey (UKIDSS; Lawrence et al. 2007, see II/319). The VLA radio observations at 1.4GHz (20cm) were carried out by the project UDS20 (V. Arumugam et al. 2016, in preparation), which comprises a mosaic of 14 pointings covering a total area of ~1.3deg2 centered on the UDS. The ~1 square degree UDS field contains a rich set of ancillary data (see section 2 for further details). (2 data files).

  17. DGSAT: Dwarf Galaxy Survey with Amateur Telescopes. I. Discovery of low surface brightness systems around nearby spiral galaxies

    Science.gov (United States)

    Javanmardi, B.; Martinez-Delgado, D.; Kroupa, P.; Henkel, C.; Crawford, K.; Teuwen, K.; Gabany, R. J.; Hanson, M.; Chonis, T. S.; Neyer, F.

    2016-04-01

    Context. We introduce the Dwarf Galaxy Survey with Amateur Telescopes (DGSAT) project and report the discovery of eleven low surface brightness (LSB) galaxies in the fields of the nearby galaxies NGC 2683, NGC 3628, NGC 4594 (M 104), NGC 4631, NGC 5457 (M 101), and NGC 7814. Aims: The DGSAT project aims to use the potential of small-sized telescopes to probe LSB features around large galaxies and to increase the sample size of the dwarf satellite galaxies in the Local Volume. Methods: Using long exposure images, fields of the target spiral galaxies are explored for extended LSB objects. After identifying dwarf galaxy candidates, their observed properties are extracted by fitting models to their light profiles. Results: We find three, one, three, one, one, and two new LSB galaxies in the fields of NGC 2683, 3628, 4594, 4631, 5457, and 7814, respectively. In addition to the newly found galaxies, we analyse the structural properties of nine already known galaxies. All of these 20 dwarf galaxy candidates have effective surface brightnesses in the range 25.3 ≲ μe ≲ 28.8 mag arcsec-2 and are fit with Sersic profiles with indices n ≲ 1. Assuming that they are in the vicinity of the above mentioned massive galaxies, their r-band absolute magnitudes, their effective radii, and their luminosities are in the ranges -15.6 ≲ Mr ≲ -7.8, 160 pc ≲ Re ≲ 4.1 kpc, and 0.1 × 106 ≲ (L/L⊙)r ≲ 127 × 106, respectively. To determine whether these LSB galaxies are indeed satellites of the above mentioned massive galaxies, their distances need to be determined via further observations. Conclusions: Using small telescopes, we are readily able to detect LSB galaxies with similar properties to the known dwarf galaxies of the Local Group.

  18. Double-Barred Galaxies: I. A Catalog of Barred Galaxies with Stellar Secondary Bars and Inner Disks

    OpenAIRE

    Erwin, Peter

    2003-01-01

    I present a catalog of 67 barred galaxies which contain distinct, elliptical stellar structures inside their bars. Fifty of these are double-barred galaxies: a small-scale, "inner" or "secondary" bar is embedded within a large-scale, "outer" or "primary" bar. I provide homogenized measurements of the sizes, ellipticities, and orientations of both inner and outer bars, along with with global parameters for the galaxies. The other 17 are classified as "inner-disk" galaxies, where a large-scale ...

  19. Combinatorics and companion galaxies: Paradox lost

    Science.gov (United States)

    Newman, William I.; Terzian, Yervant

    1995-01-01

    Arp (1994) has presented redshift data for the Local Group of galaxies and for the next major group, whose largest galaxies are M31 and M81, respectively. He observed that the relative redshifts of all 22 of their companions were positive and claimed that the likelihood that this would occur is 1 in 4 x 10(exp 6). We show using the classical combinatoric paradigm of ordered samples (without replacement) that the correct probability for the dominant member of each cluster to possess the lowest observed redshift is approximately 8%.

  20. Evolution of Compact Extreme Starburst Galaxies

    Science.gov (United States)

    Lowenthal, James; Bershady, Matthew; Gallego, Jesus; Guzman, Rafael; Hameed, Salman; Koo, David

    2006-05-01

    The global SFR was tenfold greater at z=1 than at z=0, and "downsizing" scenarios of galaxy formation maintain that the strong evolution in SFR progresses from high- to low-mass systems with time. Meanwhile, large reservoirs of star formation previously hidden from the optical by obscuring dust are being uncovered in the IR and submm in diverse populations of galaxies over a wide range of redshift. We propose deep IRAC imaging and MIPS photometry of a unique sample of well-studied 26 extreme starburst galaxies, half of them nearby HII galaxies and the other half luminous compact blue galaxies (LCBGs) at redshift z~0.5. These intensely starforming but mostly low-mass systems, like their massive cousins the ultraluminous infrared galaxies (ULIRGs), apparently evolve significantly: they can account for as much as 40% of the increase in global SFR observed between z=0 and z=1. They may also include local analogs of Lyman break galaxies at z~3, and are probably the same class of UV-bright starbursts recently observed in the local universe with GALEX. Coverage of our sample has two significant advantages over other multiwavelength surveys: spatially resolved HST/STIS-UV and optical imaging and spectroscopy, and high spectral and spatial resolution 2D spectroscopy with Keck/HIRES. Thus we can measure important physical parameters that are unavailable with the FLS, EGSS, GOODS, and other surveys. Our main science goal is (1) to use the mid- and far-IR emission to measure optically obscured star formation from z~1 to z=0 as a function of dynamical mass and rest-UV size and morphology; this will directly address inconsistencies in our current downsizing picture of galaxy evolution and the role of compact extreme starbursts. We also plan (2) to compare the SEDs of our samples to those of LBGs, to test the hypothesis that LCBGs include local analogs of LBGs; and (3) to measure the starbursts' stellar masses in the rest-NIR, which is necessary for analysis of SFH, b parameter

  1. The global warming of group satellite galaxies

    OpenAIRE

    Yozin, C.; Bekki, K.

    2016-01-01

    Recent studies adopting $\\lambda_{\\rm Re}$, a proxy for specific angular momentum, have highlighted how early-type galaxies (ETGs) are composed of two kinematic classes for which distinct formation mechanisms can be inferred. With upcoming surveys expected to obtain $\\lambda_{\\rm Re}$ from a broad range of environments (e.g. SAMI, MaNGA), we investigate in this numerical study how the $\\lambda_{\\rm Re}$-$\\epsilon_{\\rm e}$ distribution of fast-rotating dwarf satellite galaxies reflects their e...

  2. CONNECTING TRANSITIONS IN GALAXY PROPERTIES TO REFUELING

    Energy Technology Data Exchange (ETDEWEB)

    Kannappan, Sheila J.; Stark, David V.; Eckert, Kathleen D.; Moffett, Amanda J.; Norris, Mark A.; Weinberg-Wolf, Jennifer [Department of Physics and Astronomy, University of North Carolina, 290 Phillips Hall CB 3255, Chapel Hill, NC 27599 (United States); Wei, Lisa H.; Fabricant, Daniel G. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS-20, Cambridge, MA 02138 (United States); Pisano, D. J. [Department of Physics, West Virginia University, P.O. Box 6315, Morgantown, WV 26506 (United States); Baker, Andrew J. [Department of Physics and Astronomy, Rutgers, the State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States); Vogel, Stuart N. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Laine, Seppo [Spitzer Science Center, Caltech, MS 220-6, Pasadena, CA 91125 (United States); Jogee, Shardha [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Lepore, Natasha [Department of Radiology, University of Southern California and Children' s Hospital Los Angeles, 4650 W Sunset Boulevard, MS 81, Los Angeles, CA 90027 (United States); Hough, Loren E., E-mail: sheila@physics.unc.edu [Department of Physics, University of Colorado at Boulder, Boulder, CO 80309-0390 (United States)

    2013-11-01

    We relate transitions in galaxy structure and gas content to refueling, here defined to include both the external gas accretion and the internal gas processing needed to renew reservoirs for star formation. We analyze two z = 0 data sets: a high-quality ∼200 galaxy sample (the Nearby Field Galaxy Survey, data release herein) and a volume-limited ∼3000 galaxy sample with reprocessed archival data. Both reach down to baryonic masses ∼10{sup 9} M{sub ☉} and span void-to-cluster environments. Two mass-dependent transitions are evident: (1) below the 'gas-richness threshold' scale (V ∼ 125 km s{sup –1}), gas-dominated quasi-bulgeless Sd-Im galaxies become numerically dominant; while (2) above the 'bimodality' scale (V ∼ 200 km s{sup –1}), gas-starved E/S0s become the norm. Notwithstanding these transitions, galaxy mass (or V as its proxy) is a poor predictor of gas-to-stellar mass ratio M{sub gas}/M{sub *}. Instead, M{sub gas}/M{sub *} correlates well with the ratio of a galaxy's stellar mass formed in the last Gyr to its preexisting stellar mass, such that the two ratios have numerically similar values. This striking correspondence between past-averaged star formation and current gas richness implies routine refueling of star-forming galaxies on Gyr timescales. We argue that this refueling underlies the tight M{sub gas}/M{sub *} versus color correlations often used to measure 'photometric gas fractions'. Furthermore, the threshold and bimodality scale transitions reflect mass-dependent demographic shifts between three refueling regimes—accretion-dominated, processing-dominated, and quenched. In this picture, gas-dominated dwarfs are explained not by inefficient star formation but by overwhelming gas accretion, which fuels stellar mass doubling in ∼<1 Gyr. Moreover, moderately gas-rich bulged disks such as the Milky Way are transitional, becoming abundant only in the narrow range between the threshold and bimodality

  3. Distributions of Gas and Galaxies from Galaxy Clusters to Larger Scales

    Science.gov (United States)

    Patej, Anna

    This thesis addresses the distributions of baryonic matter on three scales: the outskirts of the gas and galaxy profiles in galaxy clusters, the clustering of galaxies of galaxies on large scales and its relation to the underlying matter distribution, and the extremes of the galaxy distribution: the connections between the most distant galaxies ever discovered and the closest galaxies to our own, the Local Group Dwarfs. We begin with investigations of the outskirts of galaxy clusters, where long-standing analytical models of structure formation as well as recent simulations predict the existence of steep density jumps in the gas (the 'virial shock') and dark matter profiles near the virial radius. We describe a new method for deriving models for the gas distribution in galaxy clusters, which relies on a few basic assumptions--including the existence of the virial shock and a coincident density jump in the dark matter--and show a resulting profile for the gas that is in good agreement both with X-ray observations of cluster interiors and simulations of the outskirts, and requires fewer parameters than the traditional three-parameter beta-model. Recent simulations have strengthened the arguments in favor of the existence of a dark matter density jump, arising from the accumulation of particles at the apocenter of their first orbit. Since cluster member galaxies are expected to follow similar collisionless dynamics as the dark matter, the galaxy density profile should show a steep density jump as well. We present evidence for a feature consistent with a density jump in galaxy density profiles constructed from photometry from the Sloan Digital Sky Survey and Hectospec (MMT) spectroscopy of cluster members and discuss avenues for probing the density jumps with future data sets. Moving to larger scales where massive galaxies of different types are expected to trace the same large-scale structure, we present a test of this prediction by measuring the clustering of red and

  4. The Westerbork HI survey of spiral and irregular galaxies - III. HI observations of early-type disk galaxies

    NARCIS (Netherlands)

    Noordermeer, E; van der Hulst, JM; Sancisi, R; Swaters, RA; van Albada, TS

    2005-01-01

    We present H. observations of 68 early-type disk galaxies from the WHISP survey. They have morphological types between S0 and Sab and absolute B-band magnitudes between - 14 and - 22. These galaxies form the massive, high surface-brightness extreme of the disk galaxy population, few of which have

  5. Extinction in the Galaxy from Surface Brightnesses of ESO-LV Galaxies : Determination of A_R/A_B ratio

    NARCIS (Netherlands)

    Choloniewski, J.; Valentijn, E. A.

    A new method for the determination of the extinction in the Galaxy is proposed. The method uses surface brightnesses of external galaxies in the B and R-bands. The observational data have been taken from the ESO-LV galaxy catalog. As a first application of our model we derive the ratio of R-band to

  6. The Westerbork HI Survey os spiral and irregular galaxies III : HI observations of early-type disk galaxies

    NARCIS (Netherlands)

    Noordermeer, E.; Hulst, J.M. van der; Sancisi, R.; Swaters, R.A.; Abada, T.S. van

    2005-01-01

    Abstract: We present HI observations of 68 early-type disk galaxies from the WHISP survey. They have morphological types between S0 and Sab and absolute B-band magnitudes between -14 and -22. These galaxies form the massive, high surface-brightness extreme of the disk galaxy population, few of which

  7. The Arecibo Galaxy Environment Survey - VIII. Discovery of an isolated dwarf galaxy in the Local Volume

    Czech Academy of Sciences Publication Activity Database

    Taylor, Rhys; Minchin, R.F.; Herbst, H.; Smith, R.

    2014-01-01

    Roč. 442, č. 1 (2014), L46-L50 ISSN 0035-8711 Institutional support: RVO:67985815 Keywords : surveys * galaxies * distances and redshifts Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.107, year: 2014

  8. Extragalactic astronomy. Book 1. Galaxies: the basic physical properties

    Science.gov (United States)

    Kudrya, Yu. M.; Vavilova, I. B.

    2016-09-01

    This book on extragalaxy astronomy deals with the morphology and basic physical and photometric properties of normal galaxies, namely, their linear sizes, kinematics, luminosity, and mass. Separate sections are devoted to our Galaxy, methods of determination of the distances to galaxies, modern observational galaxy surveys and catalogues. The book introduces both the newest observational and theoretical results as well as classical data about properties of galaxies in the optical spectral range. For students and high school teachers, graduate students and researchers in the field of astrophysics and physics, as well as all those who are interested in extragalactic astronomy.

  9. Clusters of galaxies in the HST Medium Deep Survey database

    Science.gov (United States)

    Ratnatunga, K. U.; Ostrander, E. J.; Griffiths, R. E.; Nichol, R. C.

    1997-12-01

    Quantitative morphological and structural parameters estimated for galaxies detected in the HST WFPC2 observations are now available on a set of CDROMS and is searchable via a web-interface at http://archive.stsci.edu/mds/ . A modeling approach based on maximum likelihood is used for the 2-dimensional Disk + Bulge decomposition of the faint undersampled galaxy images. We present a new objectively selected sample of galaxy overdensites found using the MDS database. These galaxy clusters represent some of the most distant systems ever detected and will facilitate more detailed studies of cluster and galaxy evolution.

  10. RASS-SDSS Galaxy cluster survey. IV. A ubiquitous dwarf galaxy population in clusters

    Science.gov (United States)

    Popesso, P.; Biviano, A.; Böhringer, H.; Romaniello, M.

    2006-01-01

    We analyze the Luminosity Functions (LFs) of a subsample of 69 clusters from the RASS-SDSS galaxy cluster catalog. When calculated within the cluster physical sizes, given by r200 or r500, all the cluster LFs appear to have the same shape, well fitted by a composite of two Schechter functions with a marked upturn and a steepening at the faint-end. Previously reported cluster-to-cluster variations of the LF faint-end slope are due to the use of a metric cluster aperture for computing the LF of clusters of different masses. We determine the composite LF for early- and late-type galaxies, where the typing is based on the galaxy u-r colors. The late-type LF is well fitted by a single Schechter function with a steep slope (α=-2.0 in the r band, within r200). The early-type LF instead cannot be fitted by a single Schechter function, and a composite of two Schechter functions is needed. The faint-end upturn of the global cluster LF is due to the early-type cluster galaxies. The shape of the bright-end tail of the early-type LF does not seem to depend upon the local galaxy density or the distance from the cluster center. The late-type LF shows a significant variation only very near the cluster center. On the other hand, the faint-end tail of the early-type LF shows a significant and continuous variation with the environment. We provide evidence that the process responsible for creating the excess population of dwarf early type galaxies in clusters is a threshold process that occurs when the density exceeds ˜ 500 times the critical density of the Universe. We interpret our results in the context of the "harassment" scenario, where faint early-type cluster galaxies are predicted to be the descendants of tidally-stripped late-type galaxies.

  11. The Smallest Galaxies in the Universe: Investigating the Origins of Ultra-faint Galaxies

    Science.gov (United States)

    Qi, Yuewen; Graus, Andrew; Bullock, James

    2018-01-01

    One outstanding question in cosmology is, what are the smallest galaxies that can form? The answer to this question can tell us much about galaxy formation, and even of the properties of dark matter itself. A candidate for the smallest galaxies that can form are the ultrafaint galaxies. The star formation of ultrafaints appears to have been shut off during the epoch of reionization, when radiation from the first stars ionized all the free hydrogen in the universe. This would imply ultrafaints should exist everywhere in the universe. However, we can only observe ultrafaints as satellites of the Milky Way, due to their low brightness. This will change with the next generation of telescopes such as the Large Synoptic Survey Telescope (LSST). The focus of this work is to predict the number of ultrafaints that should be seen with future surveys. To that end, we use the ELVIS suite, which contains 14 dark matter only simulations of Local Group like systems containing a Milky Way and Andromeda-like galaxy and the substructure out to around 1 Mpc of the barycenter. We mock observe the simulations in order to mimic current surveys such as the Sloan Digital Sky Survey (SDSS), and the Dark Energy Survey (DES), and use the population of galaxies found by those surveys to project the population of dwarf galaxies out beyond the virial radius of either galaxy. This number will depend sensitively on the formation mechanism of ultrafaint dwarfs, and comparisons of future surveys to this work could help rule out certain formation scenarios.

  12. 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.

  13. Atomic Hydrogen Properties of AGN Host Galaxies: HI in 16 NUclei of GAlaxies (NUGA) Sources

    OpenAIRE

    S. de Haan; Schinnerer, E.; Mundell, C. G.; Garcia-Burillo, S.; Combes, F.

    2007-01-01

    We present a comprehensive spectroscopic imaging survey of the distribution and kinematics of atomic hydrogen (HI) in 16 nearby spiral galaxies hosting low luminosity AGN, observed with high spectral and spatial resolution (resolution: ~20 arcsec, 5 km/s) 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 inte...

  14. The SAMI Galaxy Survey: kinematics of dusty early-type galaxies

    Science.gov (United States)

    Bassett, R.; Bekki, K.; Cortese, L.; Couch, W. J.; Sansom, A. E.; van de Sande, J.; Bryant, J. J.; Foster, C.; Croom, S. M.; Brough, S.; Sweet, S. M.; Medling, A. M.; Owers, M. S.; Driver, S. P.; Davies, L. J. M.; Wong, O. I.; Groves, B. A.; Bland-Hawthorn, J.; Richards, S. N.; Goodwin, M.; Konstantopoulos, I. S.; Lawrence, J. S.

    2017-09-01

    Recently, large samples of visually classified early-type galaxies (ETGs) containing dust have been identified using space-based infrared observations with the Herschel Space Telescope. The presence of large quantities of dust in massive ETGs is peculiar as X-ray haloes of these galaxies are expected to destroy dust in ˜107 yr (or less). This has sparked a debate regarding the origin of the dust: Is it internally produced by asymptotic giant branch stars, or is it accreted externally through mergers? We examine the 2D stellar and ionized gas kinematics of dusty ETGs using integral field spectroscopy observations from the SAMI Galaxy Survey, and integrated star formation rates, stellar masses and dust masses from the GAMA survey. Only 8 per cent (4/49) of visually classified ETGs are kinematically consistent with being dispersion-supported systems. These 'dispersion-dominated galaxies' exhibit discrepancies between stellar and ionized gas kinematics, either offsets in the kinematic position angle or large differences in the rotational velocity, and are outliers in star formation rate at a fixed dust mass compared to normal star-forming galaxies. These properties are suggestive of recent merger activity. The remaining ˜90 per cent of dusty ETGs have low velocity dispersions and/or large circular velocities, typical of 'rotation-dominated galaxies'. These results, along with the general evidence of published works on X-ray emission in ETGs, suggest that they are unlikely to host hot, X-ray gas consistent with their low M* when compared to dispersion-dominated galaxies. This means that dust will be long-lived and thus these galaxies do not require external scenarios for the origin of their dust content.

  15. Simple stellar population modelling of low S/N galaxy spectra and quasar host galaxy applications

    Science.gov (United States)

    Mosby, G.; Tremonti, C. A.; Hooper, E. J.; Wolf, M. J.; Sheinis, A. I.; Richards, J. W.

    2015-02-01

    To study the effect of supermassive black holes (SMBHs) on their host galaxies it is important to study the hosts when the SMBH is near its peak activity. A method to investigate the host galaxies of high luminosity quasars is to obtain optical spectra at positions offset from the nucleus where the relative contribution of the quasar and host is comparable. However, at these extended radii the galaxy surface brightness is often low (20-22 mag arcsec-2) and the resulting spectrum might have such low signal-to-noise ratio (S/N) that it hinders analysis with standard stellar population modelling techniques. To address this problem, we have developed a method that can recover galaxy star formation histories (SFHs) from rest-frame optical spectra with S/N ˜ 5 Å-1. This method uses the statistical technique diffusion k-means to tailor the stellar population modelling basis set. Our diffusion k-means minimal basis set, composed of four broad age bins, is successful in recovering a range of galaxy SFHs. Additionally, using an analytic prescription for seeing conditions, we are able to simultaneously model scattered quasar light and the SFH of quasar host galaxies (QHGs). We use synthetic data to compare results of our novel method with previous techniques. We also present the modelling results on a previously published QHG and show that galaxy properties recovered from a diffusion k-means basis set are less sensitive to noise added to this QHG spectrum. Our new method has a clear advantage in recovering information from QHGs and could also be applied to the analysis of other low S/N galaxy spectra such as those typically obtained for high redshift objects or integral field spectroscopic surveys.

  16. Weak Gravitational Lensing by Galaxies - Implications for Dark Matter Halos

    Science.gov (United States)

    Brainerd, T. G.; Blandford, R. D.; Smail, I.

    1996-05-01

    A detection of weak, tangential distortion of the images of cosmologically distant, faint galaxies caused by gravitational lensing by foreground galaxies is reported. The imaging data consist of a 24 ksec integration in Gunn-r of a single blank field obtained with the COSMIC imaging spectrograph on the Hale 5-m telescope. The orientations of faint (23 right > = 0.011 +/- 0.006 (95% confidence bounds) is found for the faint galaxies. The variation of right > with both differential lens-source separation and the maximum radius of the annulus is investigated. From Monte Carlo simulations of galaxy-galaxy lensing that incorporate measured properties of local galaxies and modest extrapolations of the observed redshift distribution of faint galaxies, formal best-fit parameters for the dark matter halos associated with the lens galaxies are obtained. For L(*) galaxies a characteristic circular velocity of V(*) ~ 220+/- 80 km/s and outer scale radius of s(*) >= 100h(-1) kpc is found. These parameters imply a typical mass for the lens galaxies within 100 h(-1) kpc of order 1.0(+1.2}_{-0.5) x 10(12) h(-1) M_sun (90% confidence bounds), in good agreement with recent dynamical estimates of the masses of local spiral galaxies

  17. An automatic taxonomy of galaxy morphology using unsupervised machine learning

    Science.gov (United States)

    Hocking, Alex; Geach, James E.; Sun, Yi; Davey, Neil

    2018-01-01

    We present an unsupervised machine learning technique that automatically segments and labels galaxies in astronomical imaging surveys using only pixel data. Distinct from previous unsupervised machine learning approaches used in astronomy we use no pre-selection or pre-filtering of target galaxy type to identify galaxies that are similar. We demonstrate the technique on the Hubble Space Telescope (HST) Frontier Fields. By training the algorithm using galaxies from one field (Abell 2744) and applying the result to another (MACS 0416.1-2403), we show how the algorithm can cleanly separate early and late type galaxies without any form of pre-directed training for what an 'early' or 'late' type galaxy is. We then apply the technique to the HST Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) fields, creating a catalogue of approximately 60 000 classifications. We show how the automatic classification groups galaxies of similar morphological (and photometric) type and make the classifications public via a catalogue, a visual catalogue and galaxy similarity search. We compare the CANDELS machine-based classifications to human-classifications from the Galaxy Zoo: CANDELS project. Although there is not a direct mapping between Galaxy Zoo and our hierarchical labelling, we demonstrate a good level of concordance between human and machine classifications. Finally, we show how the technique can be used to identify rarer objects and present lensed galaxy candidates from the CANDELS imaging.

  18. The new galaxy evolution paradigm revealed by the Herschel surveys

    Science.gov (United States)

    Eales, Stephen; Smith, Dan; Bourne, Nathan; Loveday, Jon; Rowlands, Kate; van der Werf, Paul; Driver, Simon; Dunne, Loretta; Dye, Simon; Furlanetto, Cristina; Ivison, R. J.; Maddox, Steve; Robotham, Aaron; Smith, Matthew W. L.; Taylor, Edward N.; Valiante, Elisabetta; Wright, Angus; Cigan, Philip; De Zotti, Gianfranco; Jarvis, Matt J.; Marchetti, Lucia; Michałowski, Michał J.; Phillipps, Steven; Viaene, Sebastien; Vlahakis, Catherine

    2018-01-01

    The Herschel Space Observatory has revealed a very different galaxyscape from that shown by optical surveys which presents a challenge for galaxy-evolution models. The Herschel surveys reveal (1) that there was rapid galaxy evolution in the very recent past and (2) that galaxies lie on a single Galaxy Sequence (GS) rather than a star-forming 'main sequence' and a separate region of 'passive' or 'red-and-dead' galaxies. The form of the GS is now clearer because far-infrared surveys such as the Herschel ATLAS pick up a population of optically red star-forming galaxies that would have been classified as passive using most optical criteria. The space-density of this population is at least as high as the traditional star-forming population. By stacking spectra of H-ATLAS galaxies over the redshift range 0.001 < z < 0.4, we show that the galaxies responsible for the rapid low-redshift evolution have high stellar masses, high star-formation rates but, even several billion years in the past, old stellar populations - they are thus likely to be relatively recent ancestors of early-type galaxies in the Universe today. The form of the GS is inconsistent with rapid quenching models and neither the analytic bathtub model nor the hydrodynamical EAGLE simulation can reproduce the rapid cosmic evolution. We propose a new gentler model of galaxy evolution that can explain the new Herschel results and other key properties of the galaxy population.

  19. Dwarf Galaxies in Voids: Dark Matter Halos and Gas Cooling

    Directory of Open Access Journals (Sweden)

    Matthias Hoeft

    2010-01-01

    Full Text Available Galaxy surveys have shown that luminous galaxies are mainly distributed in large filaments and galaxy clusters. The remaining large volumes are virtually devoid of luminous galaxies. This is in concordance with the formation of the large-scale structure in the universe as derived from cosmological simulations. However, the numerical results indicate that cosmological voids are abundantly populated with dark matter haloes which may in principle host dwarf galaxies. Observational efforts have in contrast revealed that voids are apparently devoid of dwarf galaxies. We investigate the formation of dwarf galaxies in voids by hydrodynamical cosmological simulations. Due to the cosmic ultraviolet background radiation low-mass haloes show generally a reduced baryon fraction. We determine the characteristic mass below which dwarf galaxies are baryon deficient. We show that the circular velocity below which the accretion of baryons is suppressed is approximately 40 kms−1. The suppressed baryon accretion is caused by the photo-heating due to the UV background. We set up a spherical halo model and show that the effective equation of the state of the gas in the periphery of dwarf galaxies determines the characteristic mass. This implies that any process which heats the gas around dwarf galaxies increases the characteristic mass and thus reduces the number of observable dwarf galaxies.

  20. DISCOVERY OF A PSEUDOBULGE GALAXY LAUNCHING POWERFUL RELATIVISTIC JETS

    Energy Technology Data Exchange (ETDEWEB)

    Kotilainen, Jari K.; Olguín-Iglesias, Alejandro [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, FI-21500 Piikkiö (Finland); León-Tavares, Jonathan; Baes, Maarten [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281-S9, B-9000 Gent (Belgium); Anórve, Christopher [Facultad de Ciencias de la Tierra y del Espacio de la Universidad Autónoma de Sinaloa, Blvd. de la Americas y Av. Universitarios S/N, Ciudad Universitaria, C.P. 80010, Culiacán Sinaloa, México (Mexico); Chavushyan, Vahram; Carrasco, Luis, E-mail: jarkot@utu.fi [Instituto Nacional de Astrofísica Óptica y Electrónica (INAOE), Apartado Postal 51 y 216, 72000 Puebla (Mexico)

    2016-12-01

    Supermassive black holes launching plasma jets at close to the speed of light, producing gamma-rays, have ubiquitously been found to be hosted by massive elliptical galaxies. Since elliptical galaxies are generally believed to be built through galaxy mergers, active galactic nuclei (AGN) launching relativistic jets are associated with the latest stages of galaxy evolution. We have discovered a pseudobulge morphology in the host galaxy of the gamma-ray AGN PKS 2004-447. This is the first gamma-ray emitter radio-loud AGN found to have been launched from a system where both the black hole and host galaxy have been actively growing via secular processes. This is evidence of an alternative black hole–galaxy co-evolutionary path to develop powerful relativistic jets, which is not merger driven.

  1. Isolated Galaxies versus Interacting Pairs with MaNGA

    Directory of Open Access Journals (Sweden)

    María del Carmen Argudo Fernández

    2015-10-01

    Full Text Available We present preliminary results of the spectral analysis on the radial distributions of the star formation history in both a galaxy merger and a spiral isolated galaxy observed with MaNGA. We find that the central part of the isolated galaxy is composed by older stellar population (~2 Gyr than in the outskirts (~7 Gyr. Also, the time-scale is gradually larger from 1 Gyr in the inner part to 3 Gyr in the outer regions of the galaxy. In the case of the merger, the stellar population in the central region is older than in the tails, presenting a longer time-scale in comparison to central part in the isolated galaxy. Our results are in agreement with a scenario where spiral galaxies are built from inside-out. In the case of the merger, we find evidence that interactions enhance star formation in the central part of the galaxy.

  2. 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.

  3. (Almost) Dark Galaxies in the ALFALFA Survey: HI-bearing Ultra-Diffuse Galaxies, and Beyond

    Science.gov (United States)

    Leisman, Luke; Haynes, Martha P.; Giovanelli, Riccardo; ALFALFA Almost Darks Team

    2017-01-01

    Scaling relations between HI and stars in galaxies suggest strong ties between their atomic gas content and star formation laws. The Arecibo Legacy Fast ALFA (ALFALFA) blind extragalactic HI survey is well positioned to locate very low surface brightness sources that lie off these relations, the most extreme of which may fall below optical detection limits. Thus, the ALFALFA (Almost) Darks Project has been investigating extreme outliers from these relations by studying the ~1% of ALFALFA sources without apparent stellar counterparts in major optical surveys. We have obtained deep HI and optical imaging of 25 of these candidate "dark" sources. We find that most "dark" sources are not extreme "(almost) dark" galaxies. A few are rare OH Megamasers, redshifted into the ALFALFA bandpass, and many are part of large galactic plumes, stretching as far as 600 kpc from their host galaxy. However, a small handful of sources appear to be galaxies with extreme stellar systems. We find multiple systems with HI mass to stellar mass ratios an order of magnitude larger than typical gas rich dwarfs. Further, we find an isolated population of HI-bearing "ultra diffuse" galaxies (UDGs), with stellar masses of dwarfs, but HI and optical radii of L* galaxies. We suggest that these sources may be related to recently reported gas poor, quiescent UDGs.

  4. OPPL-Galaxy, a Galaxy tool for enhancing ontology exploitation as part of bioinformatics workflows

    Science.gov (United States)

    2013-01-01

    Background Biomedical ontologies are key elements for building up the Life Sciences Semantic Web. Reusing and building biomedical ontologies requires flexible and versatile tools to manipulate them efficiently, in particular for enriching their axiomatic content. The Ontology Pre Processor Language (OPPL) is an OWL-based language for automating the changes to be performed in an ontology. OPPL augments the ontologists’ toolbox by providing a more efficient, and less error-prone, mechanism for enriching a biomedical ontology than that obtained by a manual treatment. Results We present OPPL-Galaxy, a wrapper for using OPPL within Galaxy. The functionality delivered by OPPL (i.e. automated ontology manipulation) can be combined with the tools and workflows devised within the Galaxy framework, resulting in an enhancement of OPPL. Use cases are provided in order to demonstrate OPPL-Galaxy’s capability for enriching, modifying and querying biomedical ontologies. Conclusions Coupling OPPL-Galaxy with other bioinformatics tools of the Galaxy framework results in a system that is more than the sum of its parts. OPPL-Galaxy opens a new dimension of analyses and exploitation of biomedical ontologies, including automated reasoning, paving the way towards advanced biological data analyses. PMID:23286517

  5. Study of the Lynx-Cancer void galaxies. - V. The extremely isolated galaxy UGC 4722

    Science.gov (United States)

    Chengalur, J. N.; Pustilnik, S. A.; Makarov, D. I.; Perepelitsyna, Y. A.; Safonova, E. S.; Karachentsev, I. D.

    2015-04-01

    We present a detailed study of the extremely isolated Sdm galaxy UGC 4722 (MB = -17.4) located in the nearby Lynx-Cancer void. UGC 4722 is a member of the Catalogue of Isolated Galaxies, and has also been identified as one of the most isolated galaxies in the Local Supercluster. Optical images of the galaxy however show that it has a peculiar morphology with an elongated ˜14 kpc-long plume. New observations with the Russian 6-m telescope (BTA) and the Giant Metrewave Radio Telescope (GMRT) of the ionized and neutral gas in UGC 4722 reveal the second component responsible for the disturbed morphology of the system. This is a small, almost completely destroyed, very gas-rich dwarf (MB = -15.2, M(H I)/LB ˜ 4.3) We estimate the oxygen abundance for both galaxies to be 12 + log (O/H) ˜ 7.5-7.6 which is two to three times lower than what is expected from the luminosity-metallicity relation for similar galaxies in denser environments. The ugr colours of the plume derived from Sloan Digital Sky Survey (SDSS) images are consistent with a simple stellar population with a post starburst age of 0.45-0.5 Gyr. This system hence appears to be the first known case of a minor merger with a prominent tidal feature consisting of a young stellar population.

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

    Science.gov (United States)

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

    2016-04-01

    We look for correlated changes in stellar mass and star formation rate (SFR) along filaments in the cosmic web by examining the stellar masses and UV-derived SFRs of 1799 ungrouped and unpaired spiral galaxies that reside in filaments. We devise multiple distance metrics to characterize the complex geometry of filaments, and find that galaxies closer to the cylindrical centre of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. In addition, these peripheral spiral galaxies have higher SFRs at a given mass. Complementing our sample of filament spiral galaxies with spiral galaxies in tendrils and voids, we find that the average SFR of these objects in different large-scale environments are similar to each other with the primary discriminant in SFR being stellar mass, in line with previous works. However, the distributions of SFRs are found to vary with large-scale environment. Our results thus suggest a model in which in addition to stellar mass as the primary discriminant, the large-scale environment is imprinted in the SFR as a second-order effect. Furthermore, our detailed results for filament galaxies suggest a model in which gas accretion from voids on to filaments is primarily in an orthogonal direction. Overall, we find our results to be in line with theoretical expectations of the thermodynamic properties of the intergalactic medium in different large-scale environments.

  7. Galaxy Evolution at the Frontier: The Rate of Galaxy Buildup Between z~11 and z~8

    Science.gov (United States)

    Bradley, Larry

    2013-10-01

    Understanding the evolution of early galaxies and their contribution to reionization has been a longstanding goal of observational astronomy. Hubble's WFC3/IR camera has revolutionized our knowledge of 7 8 galaxies due to their faint luminosities {M*> -20.3} and low volume densities. In particular, blank-field studies suggest a very dramatic buildup in cosmic star-formation rate density {SFRD} in the 165 Myr between z 8-10. These results are in tension with lensed-field studies which suggest a smooth buildup of galaxies from z 10 to 4. To distinguish between these scenarios, deeper observations are required to increase z > 9 number statistics and to reduce the significant cosmic variance due to a single blank field with sufficient depth {UDF + surrounding regions}. The upcoming HST Frontier Fields {HSTFF} program will obtain ultra deep observations of both "blank" and cluster-lensed fields. The latter are more efficient for high-z searches but introduce magnification uncertainties which we have quantified and found to be subdominant to Poisson uncertainties. Based on the archival first-year HSTFF data, we will identify a large sample of 35-54 galaxies at 89 galaxy evolution and placing new constraints on reionization. Additionally, we will measure the rest-frame UV continuum slopes of z 6-8 galaxies to improve dust extinction estimates at high redshift, a key ingredient in SFRD measurements. We will also perform strong lensing analyses to produce some of the highest resolution cluster dark matter maps to date.

  8. HI-Selected Galaxies in Hierarchical Models of Galaxy Formation and Evolution

    Science.gov (United States)

    Zoldan, Anna

    2017-07-01

    This poster presents the main results of a statistical study of HI-selected galaxies based on six different semi-analytic models, all run on the same cosmological N-body simulation. One of these models includes an explicit treatment for the partition of cold gas into atomic and molecular hydrogen. All models considered agree nicely with the measured HI mass function in the local Universe and with the measured scaling relations between HI and galaxy stellar mass. Most models also reproduce the observed 2-point correlation function for HI rich galaxies, with the exception of one model that predicts very little HI associated with galaxies in haloes above 10^12 Msun. We investigated the influence of satellite treatment on the final HI content and found that it introduces large uncertainties at low HI masses. We found that the assumption of instantaneous stripping of hot gas in satellites does not translate necessarily in lower HI masses. We demonstrate that the assumed stellar feedback, combined with star formation, also affect significantly the gas content of satellite galaxies. Finally, we also analyse the origin of the correlation between HI content of model galaxies and the spin of the parent haloes. Zoldan et al., 2016, MNRAS, 465, 2236

  9. Dark-ages reionization and galaxy formation simulation - IX. Economics of reionizing galaxies

    Science.gov (United States)

    Duffy, Alan R.; Mutch, Simon J.; Poole, Gregory B.; Geil, Paul M.; Kim, Han-Seek; Mesinger, Andrei; Wyithe, J. Stuart B.

    2017-09-01

    Using a series of high-resolution hydrodynamical simulations we show that during the rapid growth of high-redshift (z > 5) galaxies, reserves of molecular gas are consumed over a time-scale of 300 Myr, almost independent of feedback scheme. We find that there exists no such simple relation for the total gas fractions of these galaxies, with little correlation between gas fractions and specific star formation rates. The bottleneck or limiting factor in the growth of early galaxies is in converting infalling gas to cold star-forming gas. Thus, we find that the majority of high-redshift dwarf galaxies are effectively in recession, with demand (of star formation) never rising to meet supply (of gas), irrespective of the baryonic feedback physics modelled. We conclude that the basic assumption of self-regulation in galaxies - that they can adjust total gas consumption within a Hubble time - does not apply for the dwarf galaxies thought to be responsible for providing most UV photons to reionize the high-redshift Universe. We demonstrate how this rapid molecular time-scale improves agreement between semi-analytic model predictions of the early Universe and observed stellar mass functions.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-12

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

  11. A vast, thin plane of corotating dwarf galaxies orbiting the Andromeda galaxy.

    Science.gov (United States)

    Ibata, Rodrigo A; Lewis, Geraint F; Conn, Anthony R; Irwin, Michael J; McConnachie, Alan W; Chapman, Scott C; Collins, Michelle L; Fardal, Mark; Ferguson, Annette M N; Ibata, Neil G; Mackey, A Dougal; Martin, Nicolas F; Navarro, Julio; Rich, R Michael; Valls-Gabaud, David; Widrow, Lawrence M

    2013-01-03

    Dwarf satellite galaxies are thought to be the remnants of the population of primordial structures that coalesced to form giant galaxies like the Milky Way. It has previously been suspected that dwarf galaxies may not be isotropically distributed around our Galaxy, because several are correlated with streams of H I emission, and may form coplanar groups. These suspicions are supported by recent analyses. It has been claimed that the apparently planar distribution of satellites is not predicted within standard cosmology, and cannot simply represent a memory of past coherent accretion. However, other studies dispute this conclusion. Here we report the existence of a planar subgroup of satellites in the Andromeda galaxy (M 31), comprising about half of the population. The structure is at least 400 kiloparsecs in diameter, but also extremely thin, with a perpendicular scatter of less than 14.1 kiloparsecs. Radial velocity measurements reveal that the satellites in this structure have the same sense of rotation about their host. This shows conclusively that substantial numbers of dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum. Intriguingly, the plane we identify is approximately aligned with the pole of the Milky Way's disk and with the vector between the Milky Way and Andromeda.

  12. The Fueling of Active Galaxies: A Near-Infrared Imaging Survey of Seyfert and Normal Galaxies

    Science.gov (United States)

    Kundu, A.; Mulchaey, J. S.; Regan, M. W.

    1996-12-01

    Galactic bars are frequently invoked as a candidate for facilitating the transfer of mass from the interstellar medium of active galaxies to their central engines. However, studies of large Seyfert samples show little evidence that Seyferts occur preferentially in barred systems. The failure to find evidence for bars in many Seyfert galaxies may be due to the fact that most studies have concentrated on optical wavelengths where the presence of extinction or a young stellar population might mask any bar structures. In contrast, the near-infrared is expected to be a good place to study the host galaxy of Seyferts because neither dust nor young stars strongly affect the observed emission at these wavelengths. To study the role bars play in the fueling of active galaxies, we have obtained K' images of a large sample of nearby Seyfert and `` normal'' \\ galaxies, matched in redshift, Hubble type, inclination and blue luminosity. We use these images to compare the incidence of bars in Seyfert and normal galaxies and constrain the importance of bars in the fueling of nuclear activity.

  13. Clusters of galaxies with modified Newtonian dynamics

    NARCIS (Netherlands)

    Sanders, RH

    2003-01-01

    I consider X-ray emitting clusters of galaxies in the context of modified Newtonian dynamics (MOND). Self-gravitating isothermal gas spheres are not good representations of rich clusters; the X-ray luminosity at a given temperature is typically an order of magnitude larger than observed, and the

  14. Galaxy Zoo: Motivations of Citizen Scientists

    Science.gov (United States)

    Raddick, M. Jordan; Bracey, Georgia; Gay, Pamela L.; Lintott, Chris J.; Cardamone, Carie; Murray, Phil; Schawinski, Kevin; Szalay, Alexander S.; Vandenberg, Jan

    2013-01-01

    Citizen science, in which volunteers work with professional scientists to conduct research, is expanding due to large online datasets. To plan projects, it is important to understand volunteers' motivations for participating. This paper analyzes results from an online survey of nearly 11000 volunteers in Galaxy Zoo, an astronomy citizen science…

  15. Winds of change: reionization by starburst galaxies

    Science.gov (United States)

    Sharma, Mahavir; Theuns, Tom; Frenk, Carlos; Bower, Richard G.; Crain, Robert A.; Schaller, Matthieu; Schaye, Joop

    2017-06-01

    We investigate the properties of the galaxies that reionized the Universe and the history of cosmic reionization using the 'Evolution and Assembly of Galaxies and their Environments' (eagle) cosmological hydrodynamical simulations. We obtain the evolution of the escape fraction of ionizing photons in galaxies assuming that galactic winds create channels through which 20 per cent of photons escape when the local surface density of star formation is greater than 0.1 M⊙ yr-1 kpc-2. Such threshold behaviour for the generation of winds is observed, and the rare local objects that have such high star formation surface densities exhibit high escape fractions of ˜10 per cent. In our model, the luminosity-weighted mean escape fraction increases with redshift as \\bar{f}_esc=0.045 ((1+z)/4)^{1.1} at z > 3, and the galaxy number weighted mean as = 2.2 × 10-3 ((1 + z)/4)4, and becomes constant ≈0.2 at redshift z > 10. The escape fraction evolves as an increasingly large fraction of stars forms above the critical surface density of star formation at earlier times. This evolution of the escape fraction, combined with that of the star formation rate density from eagle, reproduces the inferred evolution of the filling factor of ionized regions during the reionization epoch (6 z z < 6) hydrogen photoionization rate and the optical depth due to Thomson scattering of the cosmic microwave background photons measured by the Planck satellite.

  16. Ultraluminous Infrared Mergers: Elliptical Galaxies in Formation?

    Science.gov (United States)

    Genzel, R.; Tacconi, L. J.; Rigopoulou, D.; Lutz, D.; Tecza, M.

    2001-12-01

    We report high-quality near-IR spectroscopy of 12 ultraluminous infrared galaxy mergers (ULIRGs). Our new VLT and Keck data provide ~0.5" resolution, stellar and gas kinematics of these galaxies, most of which are compact systems in the last merger stages. We confirm that ULIRG mergers are ``ellipticals in formation.'' Random motions dominate their stellar dynamics, but significant rotation is common. Gasdynamics and stellar dynamics are decoupled in most systems. ULIRGs fall on or near the fundamental plane of hot stellar systems, and especially on its less evolution-sensitive, reff-σ projection. The ULIRG velocity dispersion distribution, their location in the fundamental plane, and their distribution of vrotsini/σ closely resemble those of intermediate-mass (~L*), elliptical galaxies with moderate rotation. As a group ULIRGs do not resemble giant ellipticals with large cores and little rotation. Our results are in good agreement with other recent studies indicating that disky ellipticals with compact cores or cusps can form through dissipative mergers of gas-rich disk galaxies while giant ellipticals with large cores have a different formation history. Based on observations at the European Southern Observatory, Chile (ESO 65.N-0266, 65.N-0289), and on observations 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 Keck Observatory was made possible by the general financial support by the W. M. Keck Foundation.

  17. Galaxy Zoo: Infrared and Optical Morphology

    Science.gov (United States)

    Carla Shanahan, Jesse; Lintott, Chris; Zoo, Galaxy

    2018-01-01

    We present the detailed, visual morphologies of approximately 60,000 galaxies observed by the UKIRT Infrared Deep Sky Survey and then classified by participants in the Galaxy Zoo project. Our sample is composed entirely of nearby objects with redshifts of z ≤ 0.3, which enables us to robustly analyze their morphological characteristics including smoothness, bulge properties, spiral structure, and evidence of bars or rings. The determination of these features is made via a consensus-based analysis of the Galaxy Zoo project data in which inconsistent and outlying classifications are statistically down-weighted. We then compare these classifications of infrared morphology to the objects’ optical classifications in the Galaxy Zoo 2 release (Willett et al. 2013). It is already known that morphology is an effective tool for uncovering a galaxy’s dynamical past, and previous studies have shown significant correlations with physical characteristics such as stellar mass distribution and star formation history. We show that majority of the sample has agreement or expected differences between the optical and infrared classifications, but also present a preliminary analysis of a subsample of objects with striking discrepancies.

  18. Assembly of filamentary void galaxy configurations

    NARCIS (Netherlands)

    Rieder, Steven; van de Weijgaert, Rien; Cautun, Marius; Beygu, Burcu; Zwart, Simon Portegies

    2013-01-01

    We study the formation and evolution of filamentary configurations of dark matter haloes in voids. Our investigation uses the high-resolution Lambda cold dark matter simulation CosmoGrid to look for void systems resembling the VGS_31 elongated system of three interacting galaxies that was recently

  19. Central condensations in Seyfert galaxies. I

    Energy Technology Data Exchange (ETDEWEB)

    Afanas' ev, V.L.; Pimonov, A.A.; Terebizh, V.Y.

    1982-09-01

    Scanning-photometer observations of 7 normal and 17 Seyfert galaxies show that Seyferts contain a central region 3--4 kpc across characterized by a high density of stars. The luminosity of the spherical component per unit volume is correlated with the luminosity of the central starlike core.

  20. Star formation history of barred disc galaxies

    NARCIS (Netherlands)

    Sanchez-Blazquez, P.; Ocvirk, P.; Gibson, B. K.; Perez, I.; Peletier, R. F.

    We present the first results of a pilot study aimed at understanding the influence of bars on the evolution of galaxy discs through the study of their stellar content. We examine here the kinematics, star formation history, mass-weighted, luminosity-weighted and single stellar population (SSP)

  1. Origin of Disk Lopsidedness in Spiral Galaxies

    NARCIS (Netherlands)

    Angiras, R. A.; Jog, C. J.; Dwarakanath, K. S.; Omar, A.; Verheijen, M. A. W.; Saikia, D.J.; Green, D.A.; Gupta, Y.; Venturi, T.

    2009-01-01

    In our work we have used the atomic hydrogen [H I] gas distribution in the H I 21-cm line emission to study the dark matter halo perturbations. For this analysis, the 2-D H I surface density and velocity maps (archival) of the galaxies in the Eridanus group (obtained using the GMRT) and in the Ursa

  2. Star-forming AGN host galaxies

    NARCIS (Netherlands)

    Barthel, P

    2001-01-01

    The symbiosis of nuclear activity and star-formation in galaxies, as manifested in their spectral energy distributions (SEDs) is reviewed. Attention is drawn to an Hertzsprung-Russell diagram - equivalent for such objects, as well as to the importance of the SEDs in cosmological context. (C) 2001

  3. Extracting science from surveys of our Galaxy

    Indian Academy of Sciences (India)

    Our knowledge of the Galaxy is being revolutionized by a series of photometric, spectroscopic and astrometric surveys. Already an enormous body of data is available from completed surveys, and data of ever-increasing quality and richness will accrue at least until the end of this decade. To extract science from these ...

  4. The Distribution of Mass in Spiral Galaxies.

    NARCIS (Netherlands)

    Swaters, Rob; Andersen, David; Bershady, Matthew; Verheijen, Marc

    2002-01-01

    Little is known about the content and distribution of dark matter in spiral galaxies. Mass modeling of any rotation curve can yield an alarming range of results - from entirely halo-dominated, centrally- concentrated dark distributions, to disk-dominated inner potentials with shallow, low density

  5. Deep learning for studies of galaxy morphology

    Science.gov (United States)

    Tuccillo, D.; Huertas-Company, M.; Decencière, E.; Velasco-Forero, S.

    2017-06-01

    Establishing accurate morphological measurements of galaxies in a reasonable amount of time for future big-data surveys such as EUCLID, the Large Synoptic Survey Telescope or the Wide Field Infrared Survey Telescope is a challenge. Because of its high level of abstraction with little human intervention, deep learning appears to be a promising approach. Deep learning is a rapidly growing discipline that models high-level patterns in data as complex multilayered networks. In this work we test the ability of deep convolutional networks to provide parametric properties of Hubble Space Telescope like galaxies (half-light radii, Sérsic indices, total flux etc..). We simulate a set of galaxies including point spread function and realistic noise from the CANDELS survey and try to recover the main galaxy parameters using deep-learning. We compare the results with the ones obtained with the commonly used profile fitting based software GALFIT. This way showing that with our method we obtain results at least equally good as the ones obtained with GALFIT but, once trained, with a factor 5 hundred time faster.

  6. Kairic Rhythmicity in the Turing-Galaxy

    DEFF Research Database (Denmark)

    Jensen, Sisse Siggaard

    2001-01-01

    are that time has be-come one of our major problems, almost an obstacle rather than a rich source of life, in the epoch of the Turing-galaxy or in the network society, and it is ar-gued, that we have to deal with time in a new way different from during the industrial epoch. In order to discuss these assumptions...

  7. Dense gas in luminous infrared galaxies

    NARCIS (Netherlands)

    Baan, W. A.; Henkel, C.; Loenen, A. F.; Baudry, A.; Wiklind, T.

    Aims. Molecules that trace the high-density regions of the interstellar medium have been observed in (ultra-) luminous (far-) infrared galaxies, in order to initiate multiple-molecule multiple-transition studies to evaluate the physical and chemical environment of the nuclear medium and its response

  8. Galaxy Evolution Spectroscopic Explorer: Scientific Rationale

    Science.gov (United States)

    Heap, Sara; Ninkov, Zoran; Robberto, Massimo; Hull, Tony; Purves, Lloyd

    2016-01-01

    GESE is a mission concept consisting of a 1.5-m space telescope and UV multi-object slit spectrograph designed to help understand galaxy evolution in a critical era in the history of the universe, where the rate of star-formation stopped increasing and started to decline. To isolate and identify the various processes driving the evolution of these galaxies, GESE will obtain rest-frame far-UV spectra of 100,000 galaxies at redshifts, z approximately 1-2. To obtain such a large number of spectra, multiplexing over a wide field is an absolute necessity. A slit device such as a digital micro-mirror device (DMD) or a micro-shutter array (MSA) enables spectroscopy of a hundred or more sources in a single exposure while eliminating overlapping spectra of other sources and blocking unwanted background like zodiacal light. We find that a 1.5-m space telescope with a MSA slit device combined with a custom orbit enabling long, uninterrupted exposures (approximately 10 hr) are optimal for this spectroscopic survey. GESE will not be operating alone in this endeavor. Together with x-ray telescopes and optical/near-IR telescopes like Subaru/Prime Focus Spectrograph, GESE will detect "feedback" from young massive stars and massive black holes (AGN's), and other drivers of galaxy evolution.

  9. Densitometry and Thermometry of Starburst Galaxies

    Science.gov (United States)

    Mangum, J. G.; Darling, J.; Menten, K. M.; Henkel, C.; Aalto, S.; Spaans, M.; van der Werf, P.; Ginsburg, A.; Fomalont, E.; Cotton, B.; Kent, B.

    2015-05-01

    With a goal toward deriving the physical conditions in external galaxies, we have conducted a survey and subsequent high spatial resolution imaging of formaldehyde (H2CO) and ammonia (NH3) emission and absorption in a sample of starburst galaxies. In this article we present the results from a subset of this survey which focuses on high spatial resolution measurements of volume density- and kinetic temperature-sensitive transitions of the H2CO molecule. The volume density structure toward the nuclear region of NGC 253 has been derived from θ ≃ 4 arcsec NRAO Very Large Array (VLA) measurements of the 110 - 111 and 211 - 212 K-doublet transitions of H2CO. The kinetic temperature structure toward NGC 253 and NGC 4945 has been derived from θ ≃ 0.5 - 1.0 arcsec measurements of the H2CO 3K-1K+1 - 2K-1K+1 (near 218 GHz) and 5K-1K+1 - 4K-1K+1 (near 365 GHz) transitions acquired using the Atacama Large Millimeter/submillimeter Array (ALMA). These measurements have allowed us to characterize the dense gas and kinetic temperature structure within these star forming galaxies, which is a first step toward associating dense star-forming gas and the heating processes at work within galaxies.

  10. Dwarf Galaxies, MOND, and Relativistic Gravitation

    Directory of Open Access Journals (Sweden)

    Arthur Kosowsky

    2010-01-01

    Certain limits of these theories can also give the accelerating expansion of the Universe. The standard dark matter cosmology boasts numerous manifest triumphs; however, alternatives should also be pursued as long as outstanding observational issues remain unresolved, including the empirical successes of MOND on galaxy scales and the phenomenology of dark energy.

  11. Metals and ionizing photons from dwarf galaxies

    NARCIS (Netherlands)

    Salvadori, S.; Tolstoy, E.; Ferrara, A.; Zaroubi, S.

    We estimate the potential contribution of M <10(9)M(circle dot) dwarf galaxies to the reionization and early metal enrichment of the Milky Way environment, or circum-Galactic medium. Our approach is to use the observed properties of ancient stars ()under tilde>12 Gyr old) measured in nearby dwarf

  12. Extracting science from surveys of our Galaxy

    Indian Academy of Sciences (India)

    reservations one may have about the extent to which model galaxies extracted from cosmo- logical simulations are based on irrefutable physics, these models have had a big impact on our thinking, and they will undoubtedly play a significant role in the future. Nevertheless,. I shall now argue that we need other types of ...

  13. Orbital decomposition of CALIFA spiral galaxies

    Science.gov (United States)

    Zhu, Ling; van den Bosch, Remco; van de Ven, Glenn; Lyubenova, Mariya; Falcón-Barroso, Jesús; Meidt, Sharon E.; Martig, Marie; Shen, Juntai; Li, Zhao-Yu; Yildirim, Akin; Walcher, C. Jakob; Sanchez, Sebastian F.

    2018-01-01

    Schwarzschild orbit-based dynamical models are widely used to uncover the internal dynamics of early-type galaxies and globular clusters. Here we present for the first time the Schwarzschild models of late-type galaxies: an SBb galaxy NGC 4210 and an S0 galaxy NGC 6278 from the Calar Alto Legacy Integral Field Area (CALIFA) survey. The mass profiles within 2Re are constrained well with 1σ statistical error of ˜ 10 per cent. The luminous and dark mass can be disentangled with uncertainties of ˜20 and ˜ 50 per cent, respectively. From Re to 2Re, the dark matter fraction increases from 14 ± 10 to 18 ± 10 per cent for NGC 4210 and from 15 ± 10 to 30 ± 20 per cent for NGC 6278. The velocity anisotropy profiles of both σr/σt and σz/σR are well constrained. The inferred internal orbital distributions reveal clear substructures. The orbits are naturally separated into three components: a cold component with near circular orbits; a hot component with near radial orbits and a warm component in between. The photometrically identified exponential discs are predominantly made up of cold orbits only beyond ˜1Re, while they are constructed mainly with the warm orbits inside. Our dynamical hot components are concentrated in the inner regions, similar to the photometrically identified bulges. The reliability of the results, especially the orbit distribution, is verified by applying the model to mock data.

  14. Discovering the Rotation of our own Galaxy

    Indian Academy of Sciences (India)

    IAS Admin

    Bikram Phookun and Biman Nath, Dark matter – what you see ain't what you got, Resonance, Vol.4, No.9, 1999. It is fascinating that the motions of stars in the plane of our galaxy, within a small neighbourhood of the Sun were able to reveal so much to the right detective. Our. Classics section also includes the first three ...

  15. Clusters of galaxies: beyond the thermal view

    NARCIS (Netherlands)

    Kaastra, J.S.; Bykov, A.M.; Schindler, S.; Bleeker, J.A.M.; Borgani, S.; Diaferio, A.; Dolag, K.; Durret, F.; Nevalainen, J.; Ohashi, T.; Paerels, F.; Petrosian, V.; Rephaeli, Y.; Richter, P.; Schaye, J.; Werner, N.

    2008-01-01

    We present the work of an international team at the International Space Science Institute (ISSI) in Bern that worked together to review the current observational and theoretical status of the non-virialised X-ray emission components in clusters of galaxies. The subject is important for the study of

  16. Modelling colour-dependent galaxy clustering in cosmological simulations

    Science.gov (United States)

    Masaki, Shogo; Lin, Yen-Ting; Yoshida, Naoki

    2013-12-01

    We extend the subhalo abundance matching method to assign galaxy colour to subhaloes. We separate a luminosity-binned subhalo sample into two groups by a secondary subhalo property which is presumed to be correlated with galaxy colour. The two subsamples then represent red and blue galaxy populations. We explore two models for the secondary property, namely subhalo assembly time and local dark matter density around each subhalo. The model predictions for the galaxy two-point correlation functions are compared with the recent results from the Sloan Digital Sky Survey. We show that the observed colour dependence of galaxy clustering can be reproduced well by our method applied to cosmological N-body simulations without baryonic processes. We then compare the model predictions for the colour-dependent galaxy-mass cross-correlation functions with the results from gravitational lensing observations. The comparison allows us to distinguish the models, and also to discuss what subhalo property should be used to assign colour to subhaloes accurately. We show that the extended abundance matching method using the local dark matter density as a colour proxy provides an accurate description of the galaxy populations in the local universe. We also study impacts of scatter on the local dark matter density-colour relations. Introducing scatter improves agreements of our model predictions with the observed red and blue galaxy clustering and is needed to explain observed correlation functions in finer colour bins. Finally, we study red galaxy fraction profiles in galaxy group- and cluster-sized haloes and find that the red fraction profiles have a relatively strong dependence on our model parameters. We argue that the red fraction profiles can be an important observational clue, in addition to galaxy clustering and galaxy-galaxy lensing, to explore the galaxy-(sub)halo connections.

  17. GLOBAL H I KINEMATICS IN DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Stilp, Adrienne M.; Dalcanton, Julianne J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Warren, Steven R.; Skillman, Evan [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Ott, Juergen [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States); Koribalski, Baerbel [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)

    2013-03-10

    H I line widths are typically interpreted as a measure of interstellar medium turbulence, which is potentially driven by star formation (SF). In an effort to better understand the possible connections between line widths and SF, we have characterized H I kinematics in a sample of nearby dwarf galaxies by co-adding line-of-sight spectra after removing the rotational velocity to produce average global H I line profiles. These ''superprofiles'' are composed of a central narrow peak ({approx}6-10 km s{sup -1}) with higher-velocity wings to either side that contain {approx}10%-15% of the total flux. The superprofiles are all very similar, indicating a universal global H I profile for dwarf galaxies. We compare characteristics of the superprofiles to various galaxy properties, such as mass and measures of SF, with the assumption that the superprofile represents a turbulent peak with energetic wings to either side. We use these quantities to derive average scale heights for the sample galaxies. When comparing to physical properties, we find that the velocity dispersion of the central peak is correlated with ({Sigma}{sub HI}). The fraction of mass and characteristic velocity of the high-velocity wings are correlated with measures of SF, consistent with the picture that SF drives surrounding H I to higher velocities. While gravitational instabilities provide too little energy, the SF in the sample galaxies does provide enough energy through supernovae, with realistic estimates of the coupling efficiency, to produce the observed superprofiles.

  18. Multiband Observations of a Local Tadpole Galaxy

    Science.gov (United States)

    Elmegreen, Bruce

    2014-10-01

    We propose WFC3 broadband and Halpha observations of a local tadpole galaxy with a starburst and low metallicity in the head suggestive of ram pressure triggering from cosmological inflow. Such head-tail structure dominates local ultra-low metallicity Blue Compact Dwarfs and it represents 10% of resolved galaxies in the Hubble UDF. We will identify star clusters and measure their properties, including masses and ages, two-point correlations for position as a function of mass and age, and the cluster mass distribution as a function of age. We will also determine the star formation fraction in clusters. These measurements can suggest definite processes for star formation including the importance of turbulent fragmentation. The presence of a super star cluster, if found, will be a model for the formation of metal-poor globular clusters in high redshift dwarf galaxies, which could have formed in similar conditions. The Halpha observations will also show bright rims and nebular structures down to 10's of pc scales. Such structures can indicate pressure sources and nebular flow directions that allow us to understand gas motions inside the starburst head, including pressurized outflows and cosmological inflows. The head is so bright in Halpha that even if only 25% of the ionizing radiation escapes, an inflowing halo stream as far away as 1' will be ionized sufficiently on the surface for our observations to detect it. Thus the proposed galaxy, Kiso 5639, is a prime laboratory to study processes that may be related to cosmic accretion, starburst conditions in primitive galaxies, and the formation of metal-poor globular clusters.

  19. How does ionizing radiation escape from galaxies?

    Science.gov (United States)

    Orlitova, Ivana

    2016-10-01

    Search for sources that reionized the Universe from z 15 to z 6 is one of the main drivers of present-day astronomy. Low-mass star-forming galaxies are the most favoured sources of ionizing photons, but the searches of escaping Lyman continuum (LyC) have not been extremely successful. Our team has recently detected prominent LyC escape from five Green Pea galaxies at redshift 0.3, using the HST/COS spectrograph, which represents a significant breakthrough. We propose here to study the LyC escape of the strongest among these leakers, J1152, with spatial resolution. From the comparison of the ionizing and non-ionizing radiation maps, and surface brightness profiles, we will infer the major mode in which LyC is escaping: from the strongest starburst, from the galaxy edge, through a hole along our line-of-sight, through clumpy medium, or directly from all the production sites due to highly ionized medium in the entire galaxy. In parallel, we will test the predictive power of two highly debated indirect indicators of LyC leakage: the [OIII]5007/[OII]3727 ratio, and Lyman-alpha. We predict that their spatial distribution should closely follow that of the ionizing continuum if column densities of the neutral gas are low. This combined study, which relies on the HST unique capabilities, will bring crucial information on the structure of the leaking galaxies, provide constraints for hydrodynamic simulations, and will lead to efficient future searches for LyC leakers across a large range of redshifts.

  20. Molecular content of polar-ring galaxies

    Science.gov (United States)

    Combes, F.; Moiseev, A.; Reshetnikov, V.

    2013-06-01

    We have searched for CO lines in a sample of 21 new morphologically determined polar-ring galaxies (of which nine are kinematically confirmed), obtained from a wide search in the Galaxy Zoo project by Moiseev and collaborators. Polar-ring galaxies (PRGs) are a unique class of objects, tracing special episodes in the galaxy mass assembly: they can be formed through galaxy interaction and merging, but also through accretion from cosmic filaments. Furthermore, they enable the study of dark matter haloes in three dimensions. The polar ring itself is a sub-system rich in gas, where molecular gas is expected, and new stars are formed. Among the sample of 21 PRGs, we have detected five CO-rich systems, that can now be followed up with higher spatial resolution. Their average molecular mass is 9.4 × 109M⊙, and their average gas fraction is 27% of their baryonic mass, with a range from 15 to 43%, implying that they have just accreted a large amount of gas. The position of the detected objects in the velocity-magnitude diagram is offset from the Tully-Fisher relation of normal spirals, as was already found for PRGs. This work is part of our multi-wavelength project to determine the detailed morphology and dynamics of PRGs, test through numerical models their formation scenario, and deduce their dark matter content and 3D-shape. Based on observations carried out with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Spectra of detections are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5">130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/554/A11