The influence of Host Galaxies in Type Ia Supernova Cosmology

TL;DR

This study analyzes how host galaxy properties influence Type Ia Supernova brightness and decline rates, confirming significant correlations and finding no impact on cosmological parameters, with implications for supernova standardization.

Contribution

It provides the first comprehensive analysis of host galaxy effects on SNe Ia using a large, diverse sample, confirming correlations with host mass and star formation rate with high statistical significance.

Findings

SNe Ia are more luminous in massive hosts

SNe Ia decline faster in massive and low star formation hosts

No evolution of host effects with redshift

Abstract

We use a sample of 1338 spectroscopically confirmed and photometrically classified Type Ia Supernovae (SNe Ia), sourced from the CSP, CfA, SDSS-II, and SNLS supernova samples, to examine the relationships between SNe Ia and the galaxies that host them. Our results provide confirmation with improved statistical significance that SNe Ia, after standardization, are on average more luminous in massive hosts (significance $\rm > 5 \sigma$), and decline more rapidly in massive hosts (significance $\rm > 9\sigma$) and in hosts with low specific star formation rates (significance $\rm > 8\sigma$). We study the variation of these relationships with redshift and detect no evolution. We split SNe Ia into pairs of subsets that are based on the properties of the hosts, and fit cosmological models to each subset. Including both systematic and statistical uncertainties, we do not find any significant shift in the best-fit cosmological parameters between the subsets. Among different SN Ia subsets, we find that SNe Ia in hosts with high specific star formation rates have the least intrinsic scatter ($\rm \sigma_{int}=0.08\pm0.01$) in luminosity after standardization.