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

Abstract

Feedback from active galactic nuclei (AGN) is widely considered to be the main driver inregulating 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 massesand star formation rates (SFRs) and investigate the relationships between AGN luminosities, specific star formation rates (sSFRs) and outflow strengths W90 - the 90 per cent velocity width of the [O III]λ 5007Å line power and a proxy for the AGN-driven outflow speed. Outflowstrength 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 observedionized gas outflows which have to be powered by AGN activity. More importantly, we find anegative correlation between W90 and sSFR in the AGN hosts with the highest SFRs, i.e. withthe highest gas content, where presumably the coupling of the AGN-driven wind to the gasis strongest. This implies that AGN with strong outflow signatures are hosted in galaxies thatare 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.