Co-authors' Institutions: Gemini Observatory, Nottingham University, Oxford University, University of Hawaii at Manoa, University of Hawaii at Hilo, Oxford University, SUNY Stonybrook, Dominion Astrophysical Observatory

Abstract:

The Gemini/HST Galaxy Cluster Project combines very deep GMOS multi-object spectroscopy and multi-color imaging with HST high resolution imaging to study the evolution of cluster galaxies from redshift z=1 to the present. For each of the 15 massive, x-ray selected galaxy clusters in our sample, we have obtained spectroscopy of 30-60 galaxies with sufficient S/N to measure galaxy central velocity dispersions (a mass measurement) to an accuracy of 15% or better. Relative metallicity, alpha-to-iron ratios, and relative luminosity-weighted mean ages are derived from the spectroscopy to an accuracy of 0.15 dex. >From the HST imaging we derive quantitative morphological parameters, such as the effective radius, mean surface brightness, and bulge-to-disk ratios, and analyse these together with the spectroscopic indicators in the form of very tight scaling relations such as the Fundamental Plane. This allows us to place the tightest constraints on the evolution of galaxies, as a function of galaxy mass, versus both redshift and macroscopic cluster properties such as x-ray temperature and x-ray morphology. This talk will cover the most recent results from our survey, which include: 1) The detection of a change in both the zeropoint and the slope/tilt of the Fundamental Plane as a function of redshift revealing a mass-dependance in the evolution of cluster galaxies; 2) Cluster-wide differences in the mean alpha-to-iron ratio of galaxy stellar populations which show that the galaxies in some galaxy clusters cannot possibly evolve passively into the galaxies seen in clusters today; 3) spatially segregated properties of galaxies within individual galaxy clusters and their relation to, e.g., x-ray shock fronts, the cluster center, and infalling clumps.