The Fundamental Metallicity Relation Reduces Type Ia SN Hubble Residuals More Than Host Mass Alone

TL;DR

This study demonstrates that using the fundamental metallicity relation (FMR) to account for host galaxy metallicity significantly reduces the correlation between Type Ia supernova Hubble residuals and host mass, improving distance measurements.

Contribution

The paper calibrates the FMR for supernova host galaxies using broad-band colors and shows it reduces residual scatter more effectively than host mass alone.

Findings

FMR calibration reduces Hubble residual scatter.

Metallicity is the main factor behind residual-host mass correlation.

FMR provides a robust distance measurement method across redshifts.

Abstract

Type Ia Supernova Hubble residuals have been shown to correlate with host galaxy mass, imposing a major obstacle for their use in measuring dark energy properties. Here, we calibrate the fundamental metallicity relation (FMR) of Mannucci et al. (2010) for host mass and star formation rates measured from broad-band colors alone. We apply the FMR to the large number of hosts from the SDSS-II sample of Gupta et al. (2011) and find that the scatter in the Hubble residuals is significantly reduced when compared with using only stellar mass (or the mass-metallicity relation) as a fit parameter. Our calibration of the FMR is restricted to only star-forming galaxies and in the Hubble residual calculation we include only hosts with log(SFR) > -2. Our results strongly suggest that metallicity is the underlying source of the correlation between Hubble residuals and host galaxy mass. Since the FMR is nearly constant between z = 2 and the present, use of the FMR along with light curve width and color should provide a robust distance measurement method that minimizes systematic errors.