The DEEP3 Galaxy Redshift Survey: The Impact of Environment on the Size
  Evolution of Massive Early-type Galaxies at Intermediate Redshift
  Using data drawn from the DEEP2 and DEEP3 Galaxy Redshift Surveys, we
investigate the relationship between the environment and the structure of
galaxies residing on the red sequence at intermediate redshift. Within the
massive (10 < log(M*/Msun) < 11) early-type population at 0.4 < z <1.2, we find
a significant correlation between local galaxy overdensity (or environment) and
galaxy size, such that early-type systems in higher-density regions tend to
have larger effective radii (by ~0.5 kpc or 25% larger) than their counterparts
of equal stellar mass and Sersic index in lower-density environments. This
observed size-density relation is consistent with a model of galaxy formation
in which the evolution of early-type systems at z < 2 is accelerated in
high-density environments such as groups and clusters and in which dry, minor
mergers (versus mechanisms such as quasar feedback) play a central role in the
structural evolution of the massive, early-type galaxy population.
