Michael Childress
LBNL
Abstract:
Type Ia Supernovae (SNe Ia) are excellent standardizable candles for measuring cosmological distances to map out the expansion history of the Universe, but the precise nature of their stellar progenitors remains unclear. The study of the environments in which SNe Ia are found can yield insight into the nature of their progenitors and provide a critical cross-check on the impartiality of corrected SN Ia luminosities with progenitor properties. Using a sample of SNe Ia and their host galaxies from the Nearby Supernova Factory (SNfactory), we investigate the global properties of SN Ia environments as well as the relationship of SN Ia luminosities to the properties of their host galaxies. We show that the galaxies hosting SNe Ia are extremely normal, and their statistical properties indicate that over two thirds of SNe Ia arise from young (< 500 Myr) progenitors. Hubble residuals of SNfactory SNe Ia show a dependence on the mass, metallicity, and star-formation intensity of their host galaxies, consistent with results of other recent studies. We explore several possible explanations for the origin of this Hubble residual host bias.