TYPE Ia SUPERNOVA RATE MEASUREMENTS TO REDSHIFT 2.5 FROM CANDELS: SEARCHING FOR PROMPT EXPLOSIONS IN THE EARLY UNIVERSE

Within these survey images we discovered 65 supernovae (SNe) of all types, out tot ~ 2.5. We classify -24 of these as Type Ia SNe (SNe Ia) based on host galaxy redshifts and SN photometry (supplemented by grism spectroscopy of six SNe). Here we present a measurement of the volumetric SN la rate as a function of redshift, reaching for the first time beyond z - 2 and putting new constraints on SN Ia progenitor models. Combining the CANDELS rates with all available SN Ia rate measurements in the literature we find that this prompt SN Ia fraction is f sub(p) = (ProQuest: Formulae and/or non-USASCII text omitted), consistent with a delay time distribution that follows a simple t super(-1) power law for all times t > 40 Myr. In both CANDELS and the sister HST program CLASH (Cluster Lensing And Supernova Survey with Hubble), we find a low rate of SNe Ia at z > 1.