Observing Cluster Galaxies and their Progenitors with JDEM

The Joint Dark Energy Mission (JDEM) is expected to have a field-of-view that is several orders of magnitude larger than that of current instruments on the Hubble Space Telescope, with only slightly reduced sensitivity and resolution. This contribution gives a brief discussion of the impact that JDEM would have on studies of galaxies in clusters at 0.5<z<2 and of the most massive galaxies at higher redshift. Of particular importance is JDEMs unique wide-field near-IR capability, enabling the selection and morphological study of high redshift galaxies in the rest-frame optical rather than the rest-frame ultra-violet.