Environmental dependence of SN Ia luminosities

This is accounted for in cosmological studies using a global property of the SN host galaxy, typically the host galaxy stellar mass. However, recent low-redshift studies suggest that this effect manifests itself most strongly when using the local star formation rate (SFR) at the SN location, rather than the global SFR or the stellar mass of the host galaxy.

At high-redshift, such local SFRs are difficult to determine; here, we show that an equivalent local correction can be made by restricting the SN Ia sample in globally star-forming host galaxies to a low-mass host galaxy subset (<=10^10^M_{sun}_). Comparing this sample of SNe Ia (in locally star-forming environments) to those in locally passive host galaxies, we find that SNe Ia in locally star-forming environments are 0.081+/0.018 mag fainter (4.5{sigma}), consistent with the result reported by Rigault+ (2013A&A...560A..66R), but our conclusion is based on a sample ~5 times larger over a wider redshift range.