Differences in the structural properties and star-formation rates of field and cluster galaxies at z~1

Rebecca J. Allen, Glenn G. Kacprzak, Karl Glazebrook, Kim-Vy H. Tran, Lee R. Spitler, Caroline M. S. Straatman, Michael Cowley, Themiya Nanayakkara

Published 2016-05-17Version 1

We investigate the dependance of galaxy sizes and star-formation rates (SFRs) on environment using a mass-limited sample of quiescent and star-forming galaxies with M>10^9.5 at z=0.92 selected from the NMBS survey. Using the GEEC2 spectroscopic cluster catalog and the accurate photometric redshifts from NMBS, we select quiescent and star-forming cluster (sigma=490 km/s) galaxies within two virial radius, Rvir, intervals of 0.5<Rvir<2 and Rvir<0.5. Galaxies residing outside of 2 Rvir of both the cluster centres and additional candidate over-densities are defined as our field sample. Galaxy structural parameters are measured from the COSMOS legacy HST/ACS F814W image. The sizes and Sersic indices of quiescent field and cluster galaxies have the same distribution regardless of Rvir. However, cluster star-forming galaxies within 0.5 Rvir have lower mass-normalised average sizes, by 16${\pm}7\%$, and a higher fraction of Sersic indices with n>1, than field star-forming galaxies. The average SFRs of star-forming cluster galaxies show a trend of decreasing SFR with clustocentric radius. The mass-normalised average SFR of cluster star-forming galaxies is a factor of 2-2.5 (7-9 sigma) lower than that of star-forming galaxies in the field. While we find no significant dependence on environment for quiescent galaxies, the properties of star-forming galaxies are affected, which could be the result of environment acting on their gas content.