Evolution of the Stellar Mass-Metallicity Relation. II. Constraints on Galactic Outflows from the Mg Abundances of Quiescent Galaxies

TL;DR

This study investigates the evolution of the stellar mass-metallicity relation in quiescent galaxies across redshifts, revealing that iron abundance evolves while magnesium abundance remains constant, and constrains galactic outflows using chemical evolution models.

Contribution

It provides new constraints on galactic outflows by analyzing Mg and Fe abundances in quiescent galaxies at different redshifts, and models the mass-loading factor's dependence on galaxy mass.

Findings

Mass-[Fe/H] relation evolves with redshift, lower normalization at higher z.

Mass-[Mg/H] relation shows no significant evolution over the observed redshift range.

Average outflow mass-loading factor scales as M_*^{-0.21}.

Abstract

We present the stellar mass-[Fe/H] and mass-[Mg/H] relation of quiescent galaxies in two galaxy clusters at $z\sim0.39$ and $z\sim0.54$. We derive the age, [Fe/H], and [Mg/Fe] for each individual galaxy using a full-spectrum fitting technique. By comparing with the relations for $z\sim0$ SDSS galaxies, we confirm our previous finding that the mass-[Fe/H] relation evolves with redshift. The mass-[Fe/H] relation at higher redshift has lower normalization and possibly steeper slope. However, based on our sample, the mass-[Mg/H] relation does not evolve over the observed redshift range. We use a simple analytic chemical evolution model to constrain average outflow that these galaxies experience over their lifetime, via the calculation of mass-loading factor. We find that the average mass-loading factor $\eta$ is a power-law function of galaxy stellar mass, $\eta \propto M_*^{-0.21\pm0.09}$. The measured mass-loading factors are consistent with the results of other observational methods for outflow measurements and with the predictions where outflow is caused by star formation feedback in turbulent disks.