On the dependence of the type Ia SNe luminosities on the metallicity of their host galaxies

TL;DR

This study investigates the relationship between type Ia supernova luminosities and host galaxy metallicity, finding that lower metallicity galaxies tend to host brighter supernovae, which could impact cosmological measurements.

Contribution

It provides observational evidence linking supernova brightness to host galaxy metallicity, supporting theoretical predictions and highlighting potential systematic errors in cosmology.

Findings

Brighter SNe Ia are associated with lower metallicity host galaxies.

80% confidence that the observed trend is not due to chance.

The metallicity dependence could affect cosmological distance estimates.

Abstract

The metallicity of the progenitor system producing a type Ia supernova (SN Ia) could play a role in its maximum luminosity, as suggested by theoretical predictions. We present an observational study to investigate if such a relationship there exists. Using the 4.2m WHT we have obtained intermediate-resolution spectroscopy data of a sample of 28 local galaxies hosting SNe Ia, for which distances have been derived using methods independent to those based on the own SN Ia parameters. From the emission lines observed in their optical spectrum, we derived the gas-phase oxygen abundance in the region where each SN Ia exploded. Our data show a trend, with a 80% of chance not to be due to random fluctuation, between SNe Ia absolute magnitudes and the oxygen abundances of the host galaxies, in the sense that luminosities tend to be higher for galaxies with lower metallicities. This result seems like to be in agreement with both the theoretically expected behavior, and with other observational results. This dependence $M_{B}$-Z might induce to systematic errors when is not considered in deriving SNe Ia luminosities and then using them to derive cosmological distances.