Galaxy metallicity near and far

TL;DR

This paper explores galaxy metallicity relations across different redshifts, revealing a consistent fundamental metallicity relation up to z~2.5 and metallicity gradients linked to star formation, explained by gas infall dynamics.

Contribution

It demonstrates the invariance of the Fundamental Metallicity Relation up to z~2.5 and links metallicity gradients to gas infall and star formation in high-redshift galaxies.

Findings

Metallicity tightly related to stellar mass and SFR in local galaxies.

High-redshift galaxies follow the same FMR as local galaxies up to z~2.5.

Metallicity evolution observed at z>2.5, with lower metallicities.

Abstract

Metallicity appears to be one the most important tool to study formation and evolution of galaxies. Recently, we have shown that metallicity of local galaxies is tightly related not only to stellar mass, but also to star formation rate (SFR). At low stellar mass, metallicity decreases sharply with increasing SFR, while at high stellar mass, metallicity does not depend on SFR. The residual metallicity dispersion across this Fundamental Metallicity Relation (FMR) is very small, about 0.05dex. High redshift galaxies, up to z~2.5, are found to follow the same FMR defined by local SDSS galaxies, with no indication of evolution. At z>2.5, evolution of about 0.6dex off the FMR is observed, with high-redshift galaxies showing lower metallicities. This result can be combined with our recent discover of metallicity gradients in three high redshift galaxies showing disk dynamics. In these galaxies, the regions with higher SFR also show lower metallicities. Both these evidences can be explained by the effect of smooth infall of gas into previously enriched galaxies, with the star-formation activity triggered by the infalling gas.