The Relative Specific Type Ia Supernovae Rate From Three Years of ASAS-SN

TL;DR

This study analyzes three years of ASAS-SN data to measure how the rate of Type Ia supernovae varies with host galaxy luminosity and mass, revealing higher relative rates in lower-mass galaxies.

Contribution

It extends previous supernova rate studies to lower-mass galaxies and quantifies the dependence of SN Ia rates on host galaxy properties.

Findings

SN Ia rate scales as (M*/10^10 M_sun)^-0.5

Rate increases by factor of 10-20 in galaxies with log(M*/M_sun) < 7

Luminosity distribution follows a Schechter function with alpha ≈ 1.5

Abstract

We analyze the 476 SN Ia host galaxies from the All-Sky Automated Survey for Supernova (ASAS-SN) Bright Supernova Catalogs to determine the observed relative Type Ia supernova (SN) rates as a function of luminosity and host galaxy properties. We find that the luminosity distribution of the SNe Ia in our sample is reasonably well described by a Schechter function with a faint-end slope $\alpha \approx 1.5$ and a knee $M_{\star} \approx -18.0$. Our specific SN Ia rates are consistent with previous results but extend to far lower host galaxy masses. We find an overall rate that scales as $(M_{\star}/10^{10} M_{\odot})^{\alpha}$ with $\alpha \approx -0.5$. This shows that the specific SN Ia rate continues rising towards lower masses even in galaxies as small as $\log(M_{\star} / M_{\odot}) \lesssim 7.0$, where it is enhanced by a factor of $\sim10-20$ relative to host galaxies with stellar masses $\sim10^{10}M_{\odot}$. We find no strong dependence of the specific SN Ia rate on the star formation activity of the host galaxies, but additional observations are required to improve the constraints on the star formation rates.