Galaxy Clusters in Formation: Determining the Age of the Red-Sequence in Optical and X-ray Clusters at z~1 with HST

Benjamin P. Koester, Michael D. Gladders, David G. Gilbank +7

Using deep two-band imaging from the Hubble Space Telescope, we measure the color-magnitude relations (CMR) of E/S0 galaxies in a set of 9 optically-selected clusters principally f…