EXPLORING THE DIVERSITY OF GROUPS AT 0.1 < z < 0.8 WITH X-RAY AND OPTICALLY SELECTED SAMPLES

We present the global group properties of two samples of galaxy groups containing 39 high-quality X-ray-selected systems and 38 optically (spectroscopically) selected systems in coincident spatial regions at 0.12 < z < 0.79. Only nine optical systems are associable with X-ray systems. We discuss the confusion inherent in the matching of both galaxies to extended X-ray emission and of X-ray emission to already identified optical systems. X-ray, dynamical, and total stellar masses of the groups are also derived and presented. We explore the effects of utilizing different centers and applying three different kinds of radial cut to our systems: a constant cut of 1 Mpc and two r[sub 200] cuts, one based on the velocity dispersion of the system and the other on the X-ray emission. Eighty percent of 15 under-luminous groups have less than 40% of their stellar mass in the most massive galaxy which happens in less than 1% of cases with samples matched in stellar mass, taken from the combined group catalog.