Deep Extragalactic VIsible Legacy Survey (DEVILS): The sSFR-M$_{\star}$ plane part II: Starbursts, SFHs and AGN Feedback

TL;DR

This study investigates how different physical processes, including stochastic star formation and AGN feedback, influence galaxy evolution across the star formation rate-stellar mass plane, revealing mass-dependent mechanisms driving galaxy quenching.

Contribution

It provides observational evidence linking AGN activity to rapid star formation decline in massive galaxies, expanding understanding of galaxy quenching mechanisms.

Findings

Low-mass galaxies show flat SFHs with high SFR dispersion due to stochastic processes.

High-mass galaxies with high SFR dispersion are associated with AGN-driven quenching.

AGN feedback is identified as the main driver of rapid star formation decline in massive galaxies.

Abstract

In part I of this series we discussed the variation of star-formation histories (SFHs) across the specific star formation rate - stellar mass plane (sSFR-M$_{\star}$) using the Deep Extragalactic VIsible Legacy Survey (DEVILS). Here we explore the physical mechanisms that are likely driving these observational trends, by comparing the properties of galaxies with common recent SFH shapes. Overall, we find that the processes shaping the movement of galaxies through the sSFR-M$_{\star}$ plane can be be largely split into two stellar mass regimes, bounded by the minimum SFR dispersion ($\sigma_{SFR}$) point. At lower stellar masses we find that large $\sigma_{SFR}$ values are likely observed due to a combination of stochastic star-formation processes and a large variety in absolute sSFR values, but relatively constant/flat SFHs. While at higher stellar masses we see strong observational evidence that Active Galactic Nuclei (AGN) are associated with rapidly declining SFHs, and that these galaxies reside in the high $\sigma_{SFR}$ region of the plane. As such, we suggest that AGN feedback, leading to galaxy quenching, is the primary driver of the high $\sigma_{SFR}$ values. These results are consistent with previous theoretical interpretations of the $\sigma_{SFR}$-M$_{\star}$ relation.