Program: GN-2005A-C-7

Most galaxies in the universe, including the Milky Way, are members of groups of galaxies. Therefore, studies of the group environment are important for understanding galaxy evolution. Optical and X-ray observations of nearby groups have revealed strong trends between the morphologies of the member galaxies and global group properties, such as velocity dispersion and X-ray emission, but little is known about these important systems at higher redshifts. To better understand evolution in the group environment, we have embarked on a multiwavelength study of 11 X-ray selected groups at $z=0.2-0.5$. The proposed spectroscopic survey with GMOS-N will enable us to confirm membership for 20-30 galaxies per group, measure accurate group velocity dispersions, and study the star formation properties of group galaxies. Combined with our existing HST and XMM data, the proposed observations will allow us to study how the galaxy population in groups has evolved in time and to better understand the mechanisms that drive galaxy evolution in the group environment.