Weidong Li
UC Berkeley
Abstract:
In this talk I will present new measurements of the observed rates
of supernovae (SNe) in the local Universe, determined from the Lick
Observatory Supernova Search (LOSS). We have obtained 2.3 million
observations of ~15,000 sample galaxies over an interval of 11 years
(March 1998 through Dec. 2008). We considered 1036 SNe detected
in our sample and used an optimal subsample of 726 SNe (274 SNe Ia,
116 SNe Ibc, 324 SNe II) to determine our SN rates. This is the
largest and most homogeneous set of nearby SNe ever assembled for
this purpose, and ours is the first local SN rate analysis based on
CCD imaging and modern image-subtraction techniques. I will talk
about the properties of our sample galaxies, the derivation of the
luminosity function of SNe Ia from a complete sample to help with
the rate calculations, and the correlations between SN rates and
their host galaxy properties. We find that there is a significant
rate-size relation: the galaxies of smaller sizes (luminosities or
masses) have bigger SN rates (after normalized by its size).
I will discuss the implication of this relation and whether it
is connected to the star formation histories of the sample galaxies.
I will also discuss the popular two-component ("prompt" and "delayed")
model for the SN Ia rates and what we have learned from our search.