Progenitor Evolution and Dark Energy Time Variation from CLASH SNe Ia

Abstract

The nature and timescales behind the growth of the white dwarf toward the Chandrasekhar mass are not known. The two leading competing scenarios for Type Ia supernovae (SNe Ia) are accretion from a companion [single degenerate (SD)] or merger with another white dwarf [double degenerate (DD)]. Measurement of the SNe Ia delay time distribution could distinguish between these scenarios. Possibly both channels operate, on short (SD) and long (DD) time scales. A supernova search in parallel with our Cluster Lensing And Supernova survey with Hubble extends the Hubble diagram of SNe Ia to z > 1.5, probing progenitor evolution and testing the constancy of dark energy (DE) with time. We use HST ACS to detect SNe Ia at 1 < z < 1.5 and WFC3 to find SNe Ia at 1.5 < z < 2.5, thus providing constraints for the variation in the DE equation of state. This redshift epoch provides the unique chance to test SNe Ia distance measurements for the deleterious effects of evolution independent of our ignorance of dark energy. Our program provides the first measurement of the SNe Ia rate at z ~ 2.