Chasing Type Ia Supernovae in the Early Universe with the Hubble Space Telescope

Steve Rodney

Johns Hopkins University

Type Ia Supernovae (SNIa) are a cornerstone of modern cosmology. They provided the first direct evidence for the accelerating expansion of the universe, and are among the most promising tools for unveiling the nature of the "dark energy" driving that acceleration. It is widely accepted that SNIa are generated by the thermonuclear explosion of a white dwarf in a binary system. Beyond that basic picture, however, there is very little certainty about their progenitor star systems. An important test of SNIa progenitor models is measurement of the time between star formation and supernova explosion: the Delay Time Distribution (DTD). The DTD can be derived indirectly from measurements of the cosmic SNIa rate. This test has the most leverage at high redshift, where progenitor models significantly diverge. I will present early results from two ongoing HST treasury programs, CANDELS and CLASH, in which we have for the first time extended SNIa rate measurements to z~2, introducing new challenges for SNIa progenitor models.