Assigned ID: 491 ----- Attempting Submission 1 (Fri Feb 24 17:14:17 GMT 2012) ----- Although groups are the most common environment experienced by galaxies, we still know surprisingly little about the mechanisms that drive galaxy evolution in these systems. While galaxy-galaxy encounters and mergers are thought to be common in groups, recent observations and simulations suggest encounters with the hot intragroup medium may also be important. To help distinguish between these possibilities, groups with and without a hot intragroup medium must be studied over a range of redshifts. Such studies have been limited because groups tend to be very faint in X-rays and difficult to detect at even moderate redshifts. Fortunately, the recently completed 4 Msec Chandra observation of the CDFS now allows the hot intragroup gas to be detected in ordinary groups out to z=1 and beyond. Here, we propose to use archival HST images from GEMS, GOODS and CANDELS to study the galaxy populations in a unique sample of 40 X-ray groups and approximately 100 non-X-ray groups in the CDFS in the redshift range z=0.5 to z=1.6. The ACS and WFC3 images will be used to search for signs of interactions and disturbances in these galaxies which will allow a detailed analysis of the effects of interactions as a function of group mass and redshift. Since the depth of the Chandra exposure in the CDFS is unlikely to be matched for any other fields, our group sample will be the only one with sufficient X-ray data to allow such a study for the forseeable future. COSMOLOGY 12 Small false 0.0 0.0 false false false false SUPPORTED