CANDELS Observations of the Environmental Dependence of the
  Color-Mass-Morphology Relation at z = 1.6
  We study the environmental dependence of color, stellar mass, and morphology
by comparing galaxies in a forming cluster to those in the field at z = 1:6
with Hubble Space Telescope near-infrared imaging in the CANDELS/UDS field. We
quantify the morphology of the galaxies using the effective radius, reff, and
S\'ersic index, n. In both the cluster and field, approximately half of the
bulge-dominated galaxies (n > 2) reside on the red sequence of the
color-magnitude diagram, and most disk-dominated galaxies (n < 2) have colors
expected for star-forming galaxies. There is weak evidence that cluster
galaxies have redder rest-frame U - B colors and higher stellar masses compared
to the field. Star-forming galaxies in both the cluster and field show no
significant differences in their morphologies. In contrast, there is evidence
that quiescent galaxies in the cluster have larger median effective radii and
smaller S\'ersic indices compared to the field with a significance of 2?. These
differences are most pronounced for galaxies at clustercentric distances 1 Mpc
< Rproj < 1.5 Mpc, which have low S\'ersic indices and possibly larger
effective radii, more consistent with star-forming galaxies at this epoch and
in contrast to other quiescent galaxies. We argue that star-forming galaxies
are processed under the influence of the cluster environment at distances
greater than the cluster-halo virial radius. Our results are consistent with
models where gas accretion onto these galaxies is suppressed from processes
associated with the cluster environment.
