Evidence of suppression of star formation by quasar-driven winds in gas-rich host galaxies at z<1?

TL;DR

This study provides observational evidence that AGN-driven winds can suppress star formation in gas-rich galaxies at redshifts below 1, supporting the feedback hypothesis in galaxy evolution.

Contribution

It presents a large sample analysis showing that strong AGN outflows are linked to reduced star formation in high-gas-content galaxies, highlighting AGN feedback's role.

Findings

AGN outflow strength is independent of sSFR for mid-IR selected AGN.

Negative correlation between outflow velocity and sSFR in high-SFR galaxies.

AGN-driven winds are not caused by star formation but by the AGN activity.

Abstract

Feedback from active galactic nuclei (AGN) is widely considered to be the main driver in regulating the growth of massive galaxies through heating or driving gas out of the galaxy, preventing further increase in stellar mass. Observational proof for this scenario has, however, been scarce. We have assembled a sample of 132 radio-quiet type-2 and red AGN at 0.1<z<1. We measure the kinematics of the AGN-ionized gas, the host galaxies' stellar masses and star formation rates and investigate the relationships between AGN luminosities, specific star formation rates (sSFR) and outflow strengths W90 -- the 90\% velocity width of the [OIII]5007 line power and a proxy for the AGN-driven outflow speed. Outflow strength is independent of sSFR for AGN selected on their mid-IR luminosity, in agreement with previous work demonstrating that star formation is not sufficient to produce the observed ionized gas outflows which have to be powered by AGN activity. More importantly, we find a negative correlation between W90 and sSFR in the AGN hosts with the highest SFRs, i.e., with the highest gas content, where presumably the coupling of the AGN-driven wind to the gas is strongest. This implies that AGN with strong outflow signatures are hosted in galaxies that are more `quenched' than galaxies with weaker outflow signatures. Despite the galaxies' high SFRs, we demonstrate that the outflows are not star-formation driven but indeed due to AGN-powering. This observation is consistent with the AGN having a net suppression, `negative' impact, through feedback on the galaxies' star formation history.