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J. Gallagher, P. Garnavich (University of Notre Dame), P. Berlind (F. L. Whipple Observatory), S. Jha (University of California, Berkeley), P. Challis, R. P. Kirshner (Harvard-Smithsonian CfA)
We study the effect of environment on the properties of type Ia supernovae by analyzing the integrated spectra of 57 host galaxies. Integrated spectra of galaxies best represent the global properties of the host and can be used to directly compare with spectra of high-redshift galaxies. We deduce from the spectra the metallicity, current star-formation rate, and star-formation history of the hosts and compare these to the supernova decline rate which is an indicator of the luminosity. We also compare the magnitude residuals of each SNe Ia from the best fit Hubble law to test for systematic effects that are uncorrected by the light curve shape. Our results indicate a smaller than 2\sigma correlation between spiral host galaxy metallicity and SN Ia light curve decline rate. We do not see a correlation between SN Ia decline rate and host galaxy absolute B magnitude, nor do we find evidence of a significant relationship between decline rate and current host galaxy star formation rate. A less than 2\sigma correlation is present between the SN Ia Hubble residuals and both host galaxy absolute B magnitude and star formation history. Furthermore, we characterize the environmental property distributions for type Ia SN host galaxies through a comparison with the general galactic population using Kolmogorov-Smirnov tests. The results show the host galaxy metallicity distribution to be similar to the galactic metallicity distributions found in the NFGS and SDSS galaxy samples. Significant differences are observed between the SN Ia distributions of absolute B magnitude and star formation histories and the corresponding distributions of galaxies in the NFGS and SDSS. The discrepancies are investigated and the effects on SN Ia properties are discussed.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.