The Chemical Evolution of Star-Forming Galaxies Over the Last 11 Billion Years

TL;DR

This study examines how the relationship between stellar mass and metallicity in star-forming galaxies has evolved over the last 11 billion years, revealing a flattening trend and an upper metallicity limit.

Contribution

It provides a detailed analysis of the evolution of the mass-metallicity relation across five cosmic epochs, highlighting the flattening and saturation effects over time.

Findings

The mass-metallicity relation flattens at late times.

An empirical upper limit to gas-phase oxygen abundance exists regardless of redshift.

The stellar mass at which metallicities saturate decreases from z~0.8 to the present.

Abstract

We calculate the stellar mass-metallicity relation at five epochs ranging to z~2.3. We quantify evolution in the shape of the mass-metallicity relation as a function of redshift; the mass-metallicity relation flattens at late times. There is an empirical upper limit to the gas-phase oxygen abundance in star-forming galaxies that is independent of redshift. From examination of the mass-metallicity relation and its observed scatter we show that the flattening at late times is a consequence of evolution in the stellar mass where galaxies enrich to this empirical upper metallicity limit; there is also evolution in the fraction of galaxies at a fixed stellar mass that enrich to this limit. The stellar mass where metallicities begin to saturate is ~0.7 dex smaller in the local universe than it is at z~0.8.