CANDELS Observations of the Environmental Dependence of the Color-Mass-Morphology Relation at z = 1.6

TL;DR

This study investigates how galaxy properties like color, mass, and shape depend on environment at redshift 1.6, revealing environmental effects on quiescent galaxy sizes and morphologies in forming clusters versus the field.

Contribution

It provides new insights into the environmental influence on galaxy morphology and size at high redshift, especially the processing of star-forming galaxies in cluster outskirts.

Findings

Cluster galaxies are slightly redder and more massive than field galaxies.

Quiescent cluster galaxies have larger sizes and lower Sersic indices than field counterparts.

Environmental effects extend beyond the cluster virial radius, affecting galaxy evolution.

Abstract

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.