THE EVOLVING RELATIONS BETWEEN SIZE, MASS, SURFACE DENSITY, AND STAR FORMATION IN 3 × 10⁴GALAXIES SINCE<i>z</i>= 2

Abstract

The presence of massive, compact, quiescent galaxies at z&gt;2 presents a major\nchallenge for theoretical models of galaxy formation and evolution. Using one\nof the deepest large public near-IR surveys to date, we investigate in detail\nthe correlations between star formation and galaxy structural parameters (size,\nstellar mass, and surface density) from z=2 to the present. At all redshifts,\nmassive quiescent galaxies (i.e. those with little or no star formation) occupy\nthe extreme high end of the surface density distribution and follow a tight\nmass-size correlation, while star-forming galaxies show a broad range of both\ndensities and sizes. Conversely, galaxies with the highest surface densities\ncomprise a nearly-homogeneous population with little or no ongoing star\nformation, while less dense galaxies exhibit high star-formation rates and\nvarying levels of dust obscuration. Both the sizes and surface densities of\nquiescent galaxies evolve strongly from z=2-0; we parameterize this evolution\nfor both populations with simple power law functions and present best-fit\nparameters for comparison to future theoretical models. Higher-mass quiescent\ngalaxies undergo faster structural evolution, consistent with previous results.\nInterestingly, star-forming galaxies' sizes and densities evolve at rates\nsimilar to those of quiescent galaxies. It is therefore possible that the same\nphysical processes drive the structural evolution of both populations,\nsuggesting that "dry mergers" may not be the sole culprit in this size\nevolution.\n