The Luminosity function, Rate, and Distance of Supernova

Weidong Li
UC Berkeley


The Lick Observatory Supernova Search (LOSS), conducted with a 30-in robotic telescope, is one of the most successful nearby SN search engines in the past decade. Over 15,000 galaxies have been monitored in the course of the search, yielding more than 1,000 SN discoveries. Our database of images and log files allow us to construct a complete SN sample to derive the observed luminosity functions (LFs) for the different SN types. These LFs, together with other improvements in the analysis, allow us to derive the most accurate rates for the nearby SNe to date. We find a surprising correlation between the SN rates and the host galaxy sizes. I will also discuss the two-component model for the SN Ia rates. In the second part of my talk, I will discuss a method to improve the accuracy of the distance measurements toward SNe Ia, by dividing the SN Ia sample into two subclasses according to the expansion velocity measurements from their spectra. We find that the so called "high-expansion velocity" events seem to have either a different reddening law, or a different color/luminosity correlation, from the "normal-expansion velocity" events. Implications of this method will be discussed.