High Redshift Optically-Selected Galaxy Clusters

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AST-0206154Ellingson, EricaGalaxy clusters at redshift approximately one offer a unique opportunity to study evolution, ranging from individual galaxies to the largest cosmic structures. However, current samples of clusters at these high redshifts are still small. This work involves the Red Cluster Sequence (RCS) Survey, a new optical cluster survey which has been designed to discover clusters at high redshift while minimizing many of the contamination sources that have plagued earlier optical surveys for clusters. The spectroscopic and optical/near-infrared imaging campaign represents the first detailed follow-up observations of the RCS sample. The primary goal is to confirm the cluster redshifts, evaluate success rates, and calibrate photometric estimates of cluster richness. Observations of this first subsample will calibrate the entire RCS survey, which is expected to contain 200 clusters at z 0.8. Further detailed measurements of cluster blue fractions, population gradients within clusters and the star formation histories of cluster galaxies will trace the infall of star forming field galaxies into clusters, and their eventual transformation into a red, passively-evolving cluster populations. Related programs using the Hubble Space Telescope, Chandra, XMM, and BIMA will provide additional information on cluster masses, the intra-cluster medium and galaxy morphologies. Together with previous results for lower redshift clusters, this program will trace in detail the evolution of clusters over a large fraction of the age of the universe.***