Different regulation of stellar metallicities between star-forming and quiescent galaxies -- Insights into galaxy quenching

TL;DR

This study reveals that stellar metallicity in star-forming and quiescent galaxies is governed by different factors, linking black hole feedback and galaxy quenching through metallicity evolution and galaxy properties.

Contribution

It uncovers the distinct dependencies of stellar metallicity on galaxy properties for star-forming versus quiescent galaxies, connecting black hole feedback to galaxy quenching.

Findings

Stellar metallicity in star-forming galaxies is mainly driven by stellar mass.

In passive galaxies, stellar metallicity is primarily influenced by stellar velocity dispersion.

Black hole feedback is linked to rapid chemical enrichment and galaxy quenching.

Abstract

One of the most important questions in astrophysics is what causes galaxies to stop forming stars. Previous studies have shown a tight link between quiescence and black hole mass. Other studies have revealed that quiescence is also associated with 'starvation', the halting of gas inflows, which results in the remaining gas being used up by star formation and in rapid chemical enrichment. In this work, we find the missing link between these two findings. Using a large sample of galaxies, we uncover the intrinsic dependencies of the stellar metallicity on galaxy properties. In the case of star-forming galaxies, stellar metallicity is primarily driven by stellar mass. However, for passive galaxies, the stellar metallicity is primarily driven by the stellar velocity dispersion. The latter is known to be tightly correlated with black hole mass. This result can be seen as connecting previous studies, where the integrated effect of black hole feedback (i.e. black hole mass, traced by the velocity dispersion) prevents gas inflows, starving the galaxy, which is seen by the rapid increase in the stellar metallicity, and leading to the galaxy becoming passive.