THE DIFFERENTIAL SIZE GROWTH OF FIELD AND CLUSTER GALAXIES AT z = 2.1 USING THE ZFOURGE SURVEY

• Published in: The Astrophysical journal Vol. 806; no. 1; pp. 1 - 11
• Main Authors: Allen, Rebecca J, Kacprzak, Glenn G, Spitler, Lee R, Glazebrook, Karl, Labbe, Ivo, Tran, Kim-Vy H, Straatman, Caroline M S, Nanayakkara, Themiya, Brammer, Gabriel B, Quadri, Ryan F
• Format: Journal Article
• Language: English
• Published: 10.06.2015
• Subjects: Galactic clusters; Galactic evolution; Galaxies; Hubble Space Telescope; Photometry; Red shift; Stacks; Star formation
• ISSN: 1538-4357; 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/806/1/3

There is ongoing debate regarding the extent that environment affects galaxy size growth beyond z [> or =, slanted] 1. To investigate the differences in star-forming and quiescent galaxy properties as a function of environment at z = 2.1, we create a mass-complete sample of 59 cluster galaxies and 478 field galaxies with log(M[low *]/M sub([middot in circle])) [> or =, slanted] 9 using photometric redshifts from the ZFOURGE survey. We compare the mass-size relation of field and cluster galaxies using measured galaxy semi-major axis half-light radii (r sub(1/2,maj)) from CANDELS Hubble Space Telescope (HST)/F160W imaging. We find consistent mass-normalized (log(M[low *]/M sub([middot in circle])) = 10.7) sizes for quiescent field galaxies (r sub(1/2,maj) = 1.81 + or - 0.29 kpc) and quiescent cluster galaxies (r sub(1/2,maj) = 2.17 + or - 0.63 kpc). The mass-normalized size of star-forming cluster galaxies (r sub(1/2,maj) = 4.00 + or - 0.26 kpc) is 12% larger (Kolmogorov-Smirnov (KS) test 2.1[sigma]) than star-forming field galaxies (r sub(1/2,maj) = 3.57 + or - 0.10 kpc). From the mass-color relation we find that quiescent field galaxies with 9.7 < log(M[low *]/M sub([middot in circle])) [< or =, slant] 10.4 are slightly redder (KS test 3.6[sigma]) than quiescent cluster galaxies, while cluster and field quiescent galaxies with log(M[low *]/M sub([middot in circle])) > 10.4 have consistent colors. We find that star-forming cluster galaxies are on average 20% redder than star-forming field galaxies at all masses. Furthermore, we stack galaxy images to measure average radial color profiles as a function of mass. Negative color gradients are only present for massive star-forming field and cluster galaxies with log(M[low *]/M sub([middot in circle])) > 10.4; the remaining galaxy masses and types have flat profiles. Our results suggest, given the observed differences in size and color of star-forming field and cluster galaxies, that the environment has begun to influence/accelerate their evolution. However, the lack of differences between field and cluster quiescent galaxies indicates that the environment has not begun to significantly influence their evolution at z ~ 2.