LOSS Revisited - II: The relative rates of different types of supernovae vary between low- and high-mass galaxies

TL;DR

This study compares supernova type rates between low- and high-mass galaxies, revealing significant differences in the occurrence of certain supernova types and implications for understanding galaxy evolution and supernova progenitors.

Contribution

It provides a detailed analysis of supernova type rate variations between galaxy mass ranges using the LOSS sample, confirming and extending previous findings.

Findings

SNe Ib and Ic are underrepresented in low-mass galaxies by a factor of ~3.

Low-mass galaxies host SN 1987A-like SNe and more SN impostors.

Normal SNe Ia are ~30% more common in low-mass galaxies.

Abstract

In Paper I of this series, we showed that the ratio between stripped-envelope (SE) supernova (SN) and Type II SN rates reveals a significant SE SN deficiency in galaxies with stellar masses $\lesssim 10^{10}~{\rm M}_\odot$. Here, we test this result by splitting the volume-limited subsample of the Lick Observatory Supernova Search (LOSS) SN sample into low- and high-mass galaxies and comparing the relative rates of various SN types found in them. The LOSS volume-limited sample contains 180 SNe and SN impostors and is complete for SNe Ia out to 80 Mpc and core-collapse SNe out to 60 Mpc. All of these transients were recently reclassified by us in Shivvers et al. (2017). We find that the relative rates of some types of SNe differ between low- and high-mass galaxies: SNe Ib and Ic are underrepresented by a factor of ~3 in low-mass galaxies. These galaxies also contain the only examples of SN 1987A-like SNe in the sample and host about 9 times as many SN impostors. Normal SNe Ia seem to be ~30\% more common in low-mass galaxies, making these galaxies better sources for homogeneous SN Ia cosmology samples. The relative rates of SNe IIb are consistent in both low- and high-mass galaxies. The same is true for broad-line SNe Ic, although our sample includes only two such objects. The results presented here are in tension with a similar analysis from the Palomar Transient Factory, especially as regards SNe IIb.