Survey for supernovae in massive high-redshift clusters

We describe our ongoing program designed to measure the SN‐Ia rate in a sample of massive z=0.5–0.9 galaxy clusters. The SN‐Ia rate is a poorly known observable, especially at high z, and in cluster environments. The SN rate and its redshift dependence can serve as powerful discrimiminants for a number of key issues in astrophysics and cosmology. Our observations will put clear constraints on the characteristic SN‐Ia “delay time”, the typical time between the formation of a stellar population and the explosion of some of its members as SNe‐Ia. Such constraints can exclude entire categories of SN‐Ia progenitor models, since different models predict different delays. These data will also help to resolve the question of the dominant source of the high metallicity in the intracluster medium (ICM) — SNe‐Ia, or core‐collapse SNe from an early stellar population with a top‐heavy IMF, perhaps those population III stars responsible for the early re‐ionization of the Universe. Since clusters are excellent laborator...