SUPERNOVAE AND THEIR HOST GALAXIES

We study the correlations between the distance of a supernova (SN) fro m the center of the host galaxy and measurable properties such as SN s pectral types and luminosity at maximum light for Type Ia supernovae ( SNe Ia). The rate of SNe Ia within 1 kpc of the center of spiral galax ies is significantly lower than outside this region. The rates of Type II (SNe II) and Type Ib/c (SNe Ib/c) supernovae in the central 1 kpc region of spiral galaxies are at least as high as, and perhaps higher than, those in the outer regions. This is the first direct evidence th at stellar bulges in spiral galaxies are not efficient SNe Ia producer s and that novae and nova-like systems in the bulges are therefore not efficient producers of SNe Ia. The radial distribution of all types o f supernovae are, within errors, the same beyond similar to 7 kpc. So SNe Ia are also unlikely to come from a halo population. We also analy ze a subsample of SNe Ia including the Calan/Tololo sample and 11 near by well-observed SNe Ia for which accurate photometry is available. Su pernovae at more than 7.5 kpc from the galactic center show 3-4 times smaller scatter in brightness than those closer to the center. This be havior represents an important new constraint on evolutionary models o f SNe Ia and their correlation with the underlying stellar population. SNe Ia at larger galactocentric distances may define a more homogeneo us group for measuring cosmological distances. The B-max, V-max, and I -max magnitudes for SNe Ia beyond 7.5 kpc from the center of the host galaxies were found to be -19.05 +/- 0.20, -19.07 +/- 0.18, and -18.81 +/- 0.18, respectively.