0 Assigned ID: 2026 ----- Attempting Submission 1 (Sat Mar 02 00:28:28 GMT 2013) ----- A variety of observations now indicate that the progenitors of today's massive early-type galaxies were very compact at z ~ 2, suggesting that they must have undergone significant size growth over the past 10 Gyr. Studies of galaxy environment offer a unique probe of the physical mechanisms driving this size evolution, allowing us to distinguish the effects of environment-dependent processes (such as mergers) from those of secular processes. Here, we propose a comprehensive analysis of the HST imaging data from multiple large programs, including the new Frontier Fields initiative, with the ultimate goals of [1] measuring the minor-merger rate as a function of environment at z ~ 0.5 and [2] constraining the size-density relation across a broad range of overdensity, from isolated field galaxies to the centers of rich clusters. Through comparison with simulations, we will determine whether minor mergers are sufficient to explain the observed size evolution as a function of environment. In addition to valuable constraints on the physical mechanisms driving size growth at z < 2, our analysis will yield a wealth of legacy data products, including quantitative morphology and size measurements, photometric redshift and stellar mass catalogs, as well as environment statistics across multiple legacy HST fields. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE Default Medium false false false false false SUPPORTED