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Shape evolution of massive early-type galaxies : confirmation of increased disk prevalence at z > 1

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Abstract
We use high-resolution K-band VLT/HAWK-I imaging over 0.25 deg(2) to study the structural evolution of massive early-type galaxies since z similar to 2. Mass-selected samples, complete down to log(M/M-circle dot) similar to 10.7 such that "typical" (L*) galaxies are included at all redshifts, are drawn from pre-existing photometric redshift surveys. We then separate the samples into different redshift slices and classify them as late-or early-type galaxies on the basis of their specific star formation rate. Axis-ratio measurements for the similar to 400 early-type galaxies in the redshift range 0.6 < z < 1.8 are accurate to 0.1 or better. The projected axis-ratio distributions are then compared with lower redshift samples. We find strong evidence for evolution of the population properties: early-type galaxies at z > 1 are, on average, flatter than at z < 1 and the median projected axis ratio at a fixed mass decreases with redshift. However, we also find that at all epochs z less than or similar to 2, the most massive early-type galaxies (log(M/M-circle dot) > 11.3) are the roundest, with a pronounced lack of galaxies that are flat in projection. Merging is a plausible mechanism that can explain both results: at all epochs, merging is required for early-type galaxies to grow beyond log(M/M-circle dot) similar to 11.3, and all early types over time gradually and partially lose their disk-like characteristics.
Keywords
SIMILAR-TO 2, DIGITAL SKY SURVEY, YALE-CHILE MUSYC, QUIESCENT GALAXIES, ELLIPTIC GALAXIES, SIZE EVOLUTION, MULTIWAVELENGTH SURVEY, STAR-FORMATION, RED SEQUENCE, COMPACT, cosmology: observations, galaxies: elliptical and lenticular, cD, galaxies: evolution, galaxies: formation, galaxies: structure

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Citation

Please use this url to cite or link to this publication:

Chicago
Chang, Yu-Yen, Arjen van der Wel, Hans-Walter Rix, Stijn Wuyts, Stefano Zibetti, Balasubramanian Ramkumar, and Bradford Holden. 2013. “Shape Evolution of Massive Early-type Galaxies : Confirmation of Increased Disk Prevalence at z > 1.” Astrophysical Journal 762 (2).
APA
Chang, Y.-Y., van der Wel, A., Rix, H.-W., Wuyts, S., Zibetti, S., Ramkumar, B., & Holden, B. (2013). Shape evolution of massive early-type galaxies : confirmation of increased disk prevalence at z > 1. ASTROPHYSICAL JOURNAL, 762(2).
Vancouver
1.
Chang Y-Y, van der Wel A, Rix H-W, Wuyts S, Zibetti S, Ramkumar B, et al. Shape evolution of massive early-type galaxies : confirmation of increased disk prevalence at z > 1. ASTROPHYSICAL JOURNAL. 2013;762(2).
MLA
Chang, Yu-Yen, Arjen van der Wel, Hans-Walter Rix, et al. “Shape Evolution of Massive Early-type Galaxies : Confirmation of Increased Disk Prevalence at z > 1.” ASTROPHYSICAL JOURNAL 762.2 (2013): n. pag. Print.
@article{8573745,
  abstract     = {We use high-resolution K-band VLT/HAWK-I imaging over 0.25 deg(2) to study the structural evolution of massive early-type galaxies since z similar to 2. Mass-selected samples, complete down to log(M/M-circle dot) similar to 10.7 such that "typical" (L*) galaxies are included at all redshifts, are drawn from pre-existing photometric redshift surveys. We then separate the samples into different redshift slices and classify them as late-or early-type galaxies on the basis of their specific star formation rate. Axis-ratio measurements for the similar to 400 early-type galaxies in the redshift range 0.6 < z < 1.8 are accurate to 0.1 or better. The projected axis-ratio distributions are then compared with lower redshift samples. We find strong evidence for evolution of the population properties: early-type galaxies at z > 1 are, on average, flatter than at z < 1 and the median projected axis ratio at a fixed mass decreases with redshift. However, we also find that at all epochs z less than or similar to 2, the most massive early-type galaxies (log(M/M-circle dot) > 11.3) are the roundest, with a pronounced lack of galaxies that are flat in projection. Merging is a plausible mechanism that can explain both results: at all epochs, merging is required for early-type galaxies to grow beyond log(M/M-circle dot) similar to 11.3, and all early types over time gradually and partially lose their disk-like characteristics.},
  articleno    = {83},
  author       = {Chang, Yu-Yen and van der Wel, Arjen and Rix, Hans-Walter and Wuyts, Stijn and Zibetti, Stefano and Ramkumar, Balasubramanian and Holden, Bradford},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {SIMILAR-TO 2,DIGITAL SKY SURVEY,YALE-CHILE MUSYC,QUIESCENT GALAXIES,ELLIPTIC GALAXIES,SIZE EVOLUTION,MULTIWAVELENGTH SURVEY,STAR-FORMATION,RED SEQUENCE,COMPACT,cosmology: observations,galaxies: elliptical and lenticular,cD,galaxies: evolution,galaxies: formation,galaxies: structure},
  language     = {eng},
  number       = {2},
  pages        = {9},
  title        = {Shape evolution of massive early-type galaxies : confirmation of increased disk prevalence at z > 1},
  url          = {http://dx.doi.org/10.1088/0004-637X/762/2/83},
  volume       = {762},
  year         = {2013},
}

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