Chemistry and Star Formation in the Host Galaxies of Type Ia Supernovae

We study the effect of environment on the properties of type Ia supernovae byanalyzing the integrated spectra of 57 local type Ia supernova host galaxies.We deduce from the spectra the metallicity, current star formation rate, andstar formation history of the host and compare these to the supernova declinerates. Additionally, we compare the host properties to the Hubble residuals foreach SN. Our results indicate a statistically insignificant correlation in thedirection higher metallicity spiral galaxies host fainter type Ia supernovae.However, we present qualitative evidence suggesting progenitor age is morelikely than metallicity to be the source of variability in supernova peakluminosities. We do not find a correlation between the supernova decline rateand both host galaxy absolute B magnitude and current/past host galaxy starformation rate. A tenuous correlation is observed between the supernova Hubbleresiduals and host galaxy metallicities. Finally, we characterize theenvironmental property distributions for type Ia supernova host galaxiesthrough a comparison with two larger, more general galaxy distributions usingKolmogorov-Smirnov tests. The results show the host galaxy metallicitydistribution to be similar to the metallicity distributions of the galaxies ofthe NFGS and SDSS. Significant differences are observed between the SN Iadistributions of absolute B magnitude and star formation histories and thecorresponding distributions of galaxies in the NFGS and SDSS. Among these is anabrupt upper limit observed in the distribution of star formation histories ofthe host galaxy sample suggesting a type Ia supernovae characteristic delaytime lower limit of approximately 2.0 Gyrs. Other distribution discrepanciesare investigated and the effect on the supernova properties are discussed.Comment: 28 pages, 15 figures, accepted for publication in Ap