Elemental gas-phase abundances of intermediate redshift type Ia supernova star-forming host galaxies

TL;DR

This study investigates how the oxygen abundance in host galaxies of type Ia supernovae affects their luminosity and the accuracy of cosmic distance measurements, revealing a correlation that supports metallicity's role in supernova brightness.

Contribution

It provides empirical calibration of oxygen abundance in intermediate redshift SN Ia host galaxies and demonstrates its impact on supernova luminosity and distance estimates.

Findings

Oxygen abundance decreases with redshift in massive galaxies.

A negative correlation exists between host galaxy metallicity and SN Ia luminosity residuals.

Metal-rich environments produce intrinsically less luminous SNe Ia.

Abstract

The maximum luminosity of type Ia supernovae (SNe Ia) depends on the oxygen abundance of the regions of the host galaxies where they explode. This metallicity dependence reduces the dispersion in the Hubble diagram (HD) when included with the traditional two-parameter calibration of SN Ia light-curve (LC) parameters and absolute magnitude. In this work, we use empirical calibrations to carefully estimate the oxygen abundance of galaxies hosting SNe Ia from the SDSS-II/SNe Survey at intermediate redshift, by measuring their emission line intensities. We also derive electronic temperature with the direct method for a small fraction of objects for consistency. We find a trend of decreasing oxygen abundance with increasing redshift for the most massive galaxies. Moreover, we study the dependence of the HD residuals (HR) with galaxy oxygen abundance obtaining a correlation in line with those found in other works. In particular, the HR vs oxygen abundance shows a slope of -0.186$\pm$0.123 mag dex$^{-1}$ (1.52$\sigma$), in good agreement with theoretical expectations. This implies smaller distance modulii after corrections for SNe Ia in metal-rich galaxies. Based on our previous results on local SNe Ia, we propose this dependence to be due to the lower luminosity of the SNe Ia produced in more metal-rich environments.