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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 693835.0, MPI für Astronomie / Publikationen_mpia
Structural evolution of early-type galaxies to z = 2.5 in CANDELS
Authors:Chang, Y.-Y.; van der Wel, A.; Rix, H.-W.; Holden, B.; Bell, E. F.; McGrath, E. J.; Wuyts, S.; Häussler, B.; Barden, M.; Faber, S. M.; Mozena, M.; Ferguson, H. C.; Guo, Y.; Galametz, A.; Grogin, N. A.; Kocevski, D. D.; Koekemoer, A. M.; Dekel, A.; Huang, K.-H.; Hathi, N. P.; Donley, J.
Date of Publication (YYYY-MM-DD):2013
Title of Journal:The Astrophysical Journal
Volume:773
Issue / Number:2
Start Page:id. 149 (13 pp)
Audience:Not Specified
Abstract / Description:Projected axis ratio measurements of 880 early-type galaxies at redshifts 1 < z < 2.5 selected from CANDELS are used to reconstruct and model their intrinsic shapes. The sample is selected on the basis of multiple rest-frame colors to reflect low star-formation activity. We demonstrate that these galaxies as an ensemble are dust-poor and transparent and therefore likely have smooth light profiles, similar to visually classified early-type galaxies. Similar to their present-day counterparts, the z > 1 early-type galaxies show a variety of intrinsic shapes; even at a fixed mass, the projected axis ratio distributions cannot be explained by the random projection of a set of galaxies with very similar intrinsic shapes. However, a two-population model for the intrinsic shapes, consisting of a triaxial, fairly round population, combined with a flat (c/a ~ 0.3) oblate population, adequately describes the projected axis ratio distributions of both present-day and z > 1 early-type galaxies. We find that the proportion of oblate versus triaxial galaxies depends both on the galaxies' stellar mass, and—at a given mass—on redshift. For present-day and z < 1 early-type galaxies the oblate fraction strongly depends on galaxy mass. At z > 1, this trend is much weaker over the mass range explored here (1010 < M */M < 1011), because the oblate fraction among massive (M * ~ 1011 M ) was much higher in the past: 0.59 ± 0.10 at z > 1, compared to 0.20 ± 0.02 at z ~ 0.1. When combined with previous findings that the number density and sizes of early-type galaxies substantially increase over the same redshift range, this can be explained by the gradual emergence of merger-produced elliptical galaxies, at the expense of the destruction of pre-existing disks that were common among their high-redshift progenitors. In contrast, the oblate fraction among low-mass early-type galaxies (log (M */M ) < 10.5) increased toward the present, from z = 0 to 0.38 ± 0.11 at z > 1 to 0.72 ± 0.06 at z = 0. We speculate that this lower incidence of disks at early cosmic times can be attributed to two factors: low-mass, star-forming progenitors at z > 1 were not settled into stable disks to the same degree as at later cosmic times, and the stripping of gas from star-forming disk galaxies in dense environments is an increasingly important process at lower redshifts.
Free Keywords:cosmology: observations; galaxies: elliptical and lenticular; cD; galaxies: evolution; galaxies: formation; galaxies: structure
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.1088/0004-637X/773/2/149
URL:http://cdsads.u-strasbg.fr/abs/2013ApJ...773..149C
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