Browsing by Subject "quiescent galaxies"
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Item CANDELS Observations Of The Environmental Dependence Of The Color-Mass-Morphology Relation At Z=1.6(2013-06) Bassett, Robert; Papovich, Casey; Lotz, Jennifer M.; Bell, Eric F.; Finkelstein, Steven L.; Newman, Jeffrey A.; Tran, Kim-Vy; Almaini, Omar; Lani, Caterina; Cooper, Michael; Croton, Darren; Dekel, Avishai; Ferguson, Henry C.; Kocevski, Dale D.; Koekemoer, Anton M.; Koo, David C.; McGrath, Elizabeth J.; McIntosh, Daniel H.; Wechsler, Risa; Finkelstein, Steven L.We study the environmental dependence of color, stellar mass, and morphology by comparing galaxies in a forming cluster to those in the field at z = 1.6 with Hubble Space Telescope near-infrared imaging in the CANDELS/UDS field. We quantify the morphology of the galaxies using the effective radius, r(eff), and Sersic index, n. In both the cluster and field, approximately half of the bulge-dominated galaxies (n > 2) reside on the red sequence of the color-magnitude diagram, and most disk-dominated galaxies (n < 2) have colors expected for star-forming galaxies. There is weak evidence that cluster galaxies have redder rest-frame U - B colors and higher stellar masses compared to the field. Star-forming galaxies in both the cluster and field show no significant differences in their morphologies. In contrast, there is evidence that quiescent galaxies in the cluster have larger median effective radii and smaller Sersic indices compared to the field with a significance of 2 sigma. These differences are most pronounced for galaxies at clustercentric distances 1 Mpc < R-proj < 1.5 Mpc, which have low Sersic indices and possibly larger effective radii, more consistent with star-forming galaxies at this epoch and in contrast to other quiescent galaxies. We argue that star-forming galaxies are processed under the influence of the cluster environment at distances greater than the cluster-halo virial radius. Our results are consistent with models where gas accretion onto these galaxies is suppressed from processes associated with the cluster environment.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 A WFC3 Grism Emission Line Redshift Catalog In The GOODS-South Field(2015-06) Morris, Aaron M.; Kocevski, Dale D.; Trump, Jonathan R.; Weiner, Benjamin J.; Hathi, Nimish P.; Barro, Guillermo; Dahlen, Tomas; Faber, Sandra M.; Finkelstein, Steven L.; Fontana, Adriano; Ferguson, Henry C.; Grogin, Norman A.; Grutzbauch, Ruth; Guo, Yicheng C.; Hsu, Li-Ting; Koekemoer, Anton M.; Koo, David C.; Mobasher, Bahram; Pforr, Janine; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn; Finkelstein, Steven L.We combine Hubble Space Telescope (HST)/Wide Field Camera3 (WFC3) imaging and G141 grism observations from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and 3D-HST surveys to produce a catalog of grism spectroscopic redshifts for galaxies in the CANDELS/GOODS-South field. The WFC3/G141 grism spectra cover a wavelength range of 1.1 <= lambda <= 1.7 mu m with a resolving power of R similar to 130 for point sources, thus providing rest-frame optical spectra for galaxies out to z similar to 3.5. The catalog is selected in the H-band (F160W) and includes both galaxies with and without previously published spectroscopic redshifts. Grism spectra are extracted for all H-band detected galaxies with H <= 24 and a CANDELS photometric redshift z(phot) >= 0.6. The resulting spectra are visually inspected to identify emission lines, and redshifts are determined using cross-correlation with empirical spectral templates. To establish the accuracy of our redshifts, we compare our results against high-quality spectroscopic redshifts from the literature. Using a sample of 411 control galaxies, this analysis yields a precision of sigma(NMAD) = 0.0028 for the grism-derived redshifts, which is consistent with the accuracy reported by the 3D-HST team. Our final catalog covers an area of 153 arcmin(2) and contains 1019 redshifts for galaxies in GOODS-S. Roughly 60% (608/1019) of these redshifts are for galaxies with no previously published spectroscopic redshift. These new redshifts span a range of 0.677 <= z <= 3.456 and have a median redshift of z = 1.282. The catalog contains a total of 234 new redshifts for galaxies at z > 1.5. In addition, we present 20 galaxy pair candidates identified for the first time using the grism redshifts in our catalog, including four new galaxy pairs at z similar to 2, nearly doubling the number of such pairs previously identified.