The Differential Size Growth of Field and Cluster Galaxies at z=2.1
  Using the ZFOURGE Survey
  There is ongoing debate regarding the extent that environment affects galaxy
size growth beyond z>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 Spitler et al. (2012) and 478 field
galaxies with log(M)>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 ($r_{1/2,maj}$) from CANDELS HST/F160W
imaging. We find consistent mass normalized (log(M)=10.7) sizes for quiescent
field galaxies ($r_{1/2,maj}=1.81\pm0.29$ kpc) and quiescent cluster galaxies
($r_{1/2,maj}=2.17\pm0.63$ kpc). The mass normalized size of star-forming
cluster galaxies ($r_{1/2,maj}=4.00\pm0.26$ kpc ) is 12% larger (KS test
$2.1\sigma$) than star-forming field galaxies ($r_{1/2,maj}=3.57\pm0.10$ kpc).
From the mass-color relation we find that quiescent field galaxies with
9.7<log(M)<10.4 are slightly redder (KS test $3.6\sigma$) than quiescent
cluster galaxies, while cluster and field quiescent galaxies with log(M)>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)>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.
