Browsing by Subject "galaxies: luminosity function, mass function"
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Item The ACS Survey Of Galactic Globular Clusters. VI. NGC 6366: A Heavily Stripped Galactic Globular Cluster(2009-01) Paust, Nathaniel E. Q.; Aparicio, Antonio; Piotto, Giampaolo; Reid, I. Neill; Anderson, Jay; Sarajedini, Ata; Bedin, Luigi R.; Chaboyer, Brian; Dotter, Aaron; Hempel, Maren; Majewski, Steven; Marin-Franch, A.; Milone, Antonio; Rosenberg, Alfred; Siegel, Michael; Siegel, MichaelWe have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic globular clusters (GCs) to construct a color-magnitude diagram for the bulge cluster, NGC 6366. The luminosity function derived from those data extends to M(F606W) similar to 9, or masses of similar to 0.3 M(circle dot). Unlike most GCs, the mass function peaks near the main-sequence turnoff with significantly fewer low-mass stars even after correction for completeness and mass segregation. Using a multimass King model, we extrapolate the global cluster behavior and find the global mass function to be poorly matched by a power law, with a particular deficit of stars with masses between 0.5 and 0.7 M(circle dot). We briefly discuss this interesting anomaly within the context of tidal stripping.Item The Galaxy Stellar Mass Function At 3.5 <= Z <= 7.5 In The CANDELS/UDS, GOODS-South, And HUDF Fields(2015-03) Grazian, A.; Fontana, A.; Santini, P.; Dunlop, J. S.; Ferguson, H. C.; Castellano, M.; Amorin, R.; Ashby, M. L. N.; Barro, G.; Behroozi, P.; Boutsia, K.; Caputi, K. I.; Chary, R. R.; Dekel, A.; Dickinson, M. E.; Faber, S. M.; Fazio, G. G.; Finkelstein, S. L.; Galametz, A.; Giallongo, E.; Giavalisco, M.; Grogin, N. A.; Guo, Y.; Kocevski, D.; Koekemoer, A. M.; Koo, D. C.; Lee, K. S.; Lu, Y.; Merlin, E.; Mobasher, B.; Nonino, M.; Papovich, C.; Paris, D.; Pentericci, L.; Reddy, N.; Renzini, A.; Salmon, B.; Salvato, M.; Sommariva, V.; Song, M.; Vanzella, E.; Finkelstein, S. L.; Song, M.Context. The form and evolution of the galaxy stellar mass function (GSMF) at high redshifts provide crucial information on star formation history and mass assembly in the young Universe, close or even prior to the epoch of reionization. Aims. We used the unique combination of deep optical/near-infrared/mid-infrared imaging provided by HST, Spitzer, and the VLT in the CANDELS-UDS. GOODS-South, and HUDF fields to determine the GSMF over the redshift range 3.5 <= z <= 7.5. Methods. We used the LIST WEC3/IR near-infrared imaging from CANDELS and HUDF09, reaching H similar or equal to 27-28.5 over a total area of 369 arcmin(2), in combination with associated deep usT ACS optical data, deep Spitzer IRAC imaging from the SEDS programme, and deep Y and K-band VI l Hawk-I images from the ElliGS programme, to select a galaxy sample with high-quality photometric redshifts. These have been calibrated with more than 150 spectroscopic redshifts in the range 3.5 <= z <= 7.5, resulting in an overall precision of sigma(z)/(1 + z) similar to 0.037. With this database we have determined the low-mass end of the high-redshift GSMF with unprecedented precision, reaching down to masses as low as M* similar to 10(9) M-circle dot at z = 4 and similar to 6 x 10(9) M-circle dot at z = 7. Results. We find that the GSMF at 3.5 <= z <= 7.5 depends only slightly on the recipes adopted to measure the stellar masses, namely the photometric redshifts, the star formation histories, the nebular contribution, or the presence of AGN in the parent sample. The low-mass end of the GSMF is steeper than has been found at lower redshifts, but appears to be unchanged over the redshift range probed here. Meanwhile the high-mass end of the GSMF appears to evolve primarily in density, although there is also some evidence of evolution in characteristic mass. Our results are very different from previous mass function estimates based on converting UV galaxy luminosity functions into mass functions via tight mass-to-light relations. Integrating our evolving GSMF over mass, we find that the growth of stellar mass density is barely consistent with the time-integral of the star formation rate (lensity over cosmic time at z > 4. Conclusions. These results confirm the unique synergy of the CANDELS+HUDF, and SIDS surveys for the discovery and study of moderate/low-mass galaxies at high iredshifts, and reaffirm the importance of space-based infrared selection for the unbiased measurement of the evolving GSMF in the young Universe.Item The HETDEX Pilot Survey. IV. The Evolution Of O II Emitting Galaxies From Z Similar To 0.5 To Z Similar To 0(2013-05) Ciardullo, Robin; Gronwall, Caryl; Adams, Joshua J.; Blanc, Guillermo A.; Gebhardt, Karl; Finkelstein, Steven L.; Jogee, Shardha; Hill, Gary J.; Drory, Niv; Hopp, Ulrich; Schneider, Donald P.; Zeimann, Gregory R.; Dalton, Gavin B.; Adams, Joshua J.; Blanc, Guillermo A.; Gebhardt, Karl; Finkelstein, Steven L.; Jogee, ShardhaWe present an analysis of the luminosities and equivalent widths of the 284 z < 0.56 [O II]-emitting galaxies found in the 169 arcmin(2) pilot survey for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). By combining emission-line fluxes obtained from the Mitchell spectrograph on the McDonald 2.7 m telescope with deep broadband photometry from archival data, we derive each galaxy's dereddened [O II] lambda 3727 luminosity and calculate its total star formation rate. We show that over the last similar to 5Gyr of cosmic time, there has been substantial evolution in the [O II] emission-line luminosity function, with L* decreasing by similar to 0.6 +/- 0.2 dex in the observed function, and by similar to 0.9 +/- 0.2 dex in the dereddened relation. Accompanying this decline is a significant shift in the distribution of [O II] equivalent widths, with the fraction of high equivalent-width emitters declining dramatically with time. Overall, the data imply that the relative intensity of star formation within galaxies has decreased over the past similar to 5Gyr, and that the star formation rate density of the universe has declined by a factor of similar to 2.5 between z similar to 0.5 and z similar to 0. These observations represent the first [O II]-based star formation rate density measurements in this redshift range, and foreshadow the advancements which will be generated by the main HETDEX survey.Item Hubble Space Telescope Emission Line Galaxies At Z Similar To 2: The Ly Alpha Escape Fraction(2014-11) Ciardullo, Robin; Zeimann, Gregory R.; Gronwall, Caryl; Gebhardt, Henry; Schneider, Donald P.; Hagen, Alex; Malz, A. I.; Blanc, Guillermo A.; Hill, Gary J.; Drory, Niv; Gawiser, Eric; Hill, Gary J.; Drory, NivWe compare the H beta line strengths of 1.90 < z < 2.35 star-forming galaxies observed with the near-IR grism of the Hubble Space Telescope with ground-based measurements of Ly alpha from the HETDEX Pilot Survey and narrow-band imaging. By examining the line ratios of 73 galaxies, we show that most star-forming systems at this epoch have a Ly alpha escape fraction below similar to 6%. We confirm this result by using stellar reddening to estimate the effective logarithmic extinction of the H beta emission line (c(H beta) = 0.5) and measuring both the H beta and Ly alpha luminosity functions in a similar to 100,000 Mpc(3) volume of space. We show that in our redshift window, the volumetric Ly alpha escape fraction is at most 4.4(-1.2)(+2.1)%, with an additional systematic similar to 25% uncertainty associated with our estimate of extinction. Finally, we demonstrate that the bulk of the epoch's star-forming galaxies have Ly alpha emission line optical depths that are significantly greater than that for the underlying UV continuum. In our predominantly [O-III] lambda 5007- selected sample of galaxies, resonant scattering must be important for the escape of Ly alpha photons.Item Luminous And High Stellar Mass Candidate Galaxies At Z Approximate To 8 Discovered In The Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey(2012-12) Yan, Haojing; Finkelstein, Steven L.; Huang, Kuang-Han; Ryan, Russell E.; Ferguson, Henry C.; Koekemoer, Anton M.; Grogin, Norman A.; Dickinson, Mark; Newman, Jeffrey A.; Somerville, Rachel S.; Dave, Romeel; Faber, S. M.; Papovich, Casey; Guo, Yicheng; Giavalisco, Mauro; Lee, Kyoung-soo; Reddy, Naveen; Cooray, Asantha R.; Siana, Brian D.; Hathi, Nimish P.; Fazio, Giovanni G.; Ashby, Matthew; Weiner, Benjamin J.; Lucas, Ray A.; Dekel, Avishai; Pentericci, Laura; Conselice, Christopher J.; Kocevski, Dale D.; Lai, Kamson; Finkelstein, Steven L.One key goal of the Hubble Space Telescope Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey is to track galaxy evolution back to z approximate to 8. Its two-tiered "wide and deep" strategy bridges significant gaps in existing near-infrared surveys. Here we report on z approximate to 8 galaxy candidates selected as F105W-band dropouts in one of its deep fields, which covers 50.1 arcmin(2) to 4 ks depth in each of three near-infrared bands in the Great Observatories Origins Deep Survey southern field. Two of our candidates have J < 26.2 mag, and are >1 mag brighter than any previously known F105W-dropouts. We derive constraints on the bright end of the rest-frame ultraviolet luminosity function of galaxies at z approximate to 8, and show that the number density of such very bright objects is higher than expected from the previous Schechter luminosity function estimates at this redshift. Another two candidates are securely detected in Spitzer Infrared Array Camera images, which are the first such individual detections at z approximate to 8. Their derived stellar masses are on the order of a few x 10(9) M-circle dot, from which we obtain the first measurement of the high-mass end of the galaxy stellar mass function at z approximate to 8. The high number density of very luminous and very massive galaxies at z approximate to 8, if real, could imply a large stellar-to-halo mass ratio and an efficient conversion of baryons to stars at such an early time.