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Structural evolution of early-type galaxies to z=2.5 in CANDELS

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Abstract
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 similar to 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 (10(10) < M*/M-circle dot < 10(11)), because the oblate fraction among massive (M* similar to 10(11) M-circle dot) was much higher in the past: 0.59 +/- 0.10 at z > 1, compared to 0.20 +/- 0.02 at z similar to 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-circle dot) < 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.
Keywords
STAR-FORMING GALAXIES, SIMILAR-TO 1, DIGITAL SKY SURVEY, EXTRAGALACTIC, LEGACY SURVEY, HUBBLE-SPACE-TELESCOPE, GREATER-THAN 1, ELLIPTIC, GALAXIES, QUIESCENT GALAXIES, MASSIVE GALAXIES, INTRINSIC SHAPES, cosmology: observations, galaxies: elliptical and lenticular, cD, galaxies: evolution, galaxies: formation, galaxies: structure

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MLA
Chang, Yu-Yen, Arjen van der Wel, Hans-Walter Rix, et al. “Structural Evolution of Early-type Galaxies to Z=2.5 in CANDELS.” ASTROPHYSICAL JOURNAL 773.2 (2013): n. pag. Print.
APA
Chang, Y.-Y., van der Wel, A., Rix, H.-W., Holden, B., Bell, E. F., McGrath, E. J., Wuyts, S., et al. (2013). Structural evolution of early-type galaxies to z=2.5 in CANDELS. ASTROPHYSICAL JOURNAL, 773(2).
Chicago author-date
Chang, Yu-Yen, Arjen van der Wel, Hans-Walter Rix, Bradford Holden, Eric F Bell, Elizabeth J McGrath, Stijn Wuyts, et al. 2013. “Structural Evolution of Early-type Galaxies to Z=2.5 in CANDELS.” Astrophysical Journal 773 (2).
Chicago author-date (all authors)
Chang, Yu-Yen, Arjen van der Wel, Hans-Walter Rix, Bradford Holden, Eric F Bell, Elizabeth J McGrath, Stijn Wuyts, Boris Haeussler, Marco Barden, SM Faber, Mark Mozena, Henry C Ferguson, Yicheng Guo, Audrey Galametz, Norman A Grogin, Dale D Kocevski, Anton M Koekemoer, Avishai Dekel, Kuang-Han Huang, Nimish P Hathi, and Jennifer Donley. 2013. “Structural Evolution of Early-type Galaxies to Z=2.5 in CANDELS.” Astrophysical Journal 773 (2).
Vancouver
1.
Chang Y-Y, van der Wel A, Rix H-W, Holden B, Bell EF, McGrath EJ, et al. Structural evolution of early-type galaxies to z=2.5 in CANDELS. ASTROPHYSICAL JOURNAL. 2013;773(2).
IEEE
[1]
Y.-Y. Chang et al., “Structural evolution of early-type galaxies to z=2.5 in CANDELS,” ASTROPHYSICAL JOURNAL, vol. 773, no. 2, 2013.
@article{8572988,
  abstract     = {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 similar to 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 (10(10) < M*/M-circle dot < 10(11)), because the oblate fraction among massive (M* similar to 10(11) M-circle dot) was much higher in the past: 0.59 +/- 0.10 at z > 1, compared to 0.20 +/- 0.02 at z similar to 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-circle dot) < 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.},
  articleno    = {149},
  author       = {Chang, Yu-Yen and van der Wel, Arjen and Rix, Hans-Walter and Holden, Bradford and Bell, Eric F and McGrath, Elizabeth J and Wuyts, Stijn and Haeussler, Boris and Barden, Marco and Faber, SM and Mozena, Mark and Ferguson, Henry C and Guo, Yicheng and Galametz, Audrey and Grogin, Norman A and Kocevski, Dale D and Koekemoer, Anton M and Dekel, Avishai and Huang, Kuang-Han and Hathi, Nimish P and Donley, Jennifer},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {STAR-FORMING GALAXIES,SIMILAR-TO 1,DIGITAL SKY SURVEY,EXTRAGALACTIC,LEGACY SURVEY,HUBBLE-SPACE-TELESCOPE,GREATER-THAN 1,ELLIPTIC,GALAXIES,QUIESCENT GALAXIES,MASSIVE GALAXIES,INTRINSIC SHAPES,cosmology: observations,galaxies: elliptical and lenticular,cD,galaxies: evolution,galaxies: formation,galaxies: structure},
  language     = {eng},
  number       = {2},
  pages        = {13},
  title        = {Structural evolution of early-type galaxies to z=2.5 in CANDELS},
  url          = {http://dx.doi.org/10.1088/0004-637X/773/2/149},
  volume       = {773},
  year         = {2013},
}

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