Molecular Flows in Contemporary Active Galaxies and the Efficacy of Radio-Mechanical Feedback

TL;DR

This study compares molecular gas flows in brightest cluster galaxies with those in other active galaxies, revealing that radio feedback in BCGs is more extensive and effective at lifting gas, but less efficient at accelerating it, with implications for star formation suppression.

Contribution

It provides a comparative analysis of molecular flows driven by radio feedback in BCGs versus quasars and starbursts, highlighting the greater efficacy of radio feedback in massive cluster galaxies.

Findings

Radio feedback in BCGs produces larger molecular flows than in other active galaxies.

Molecular flows in BCGs have higher mass but lower velocities compared to quasars and starbursts.

Star formation appears suppressed in BCGs, possibly due to feedback effects.

Abstract

Molecular gas flows are analyzed in 14 cluster galaxies (BCGs) centered in cooling hot atmospheres. The BCGs contain $10^{9}-10^{11}~\rm M_\odot$ of molecular gas, much of which is being moved by radio jets and lobes. The molecular flows and radio jet powers are compared to molecular outflows in 45 active galaxies within $z<0.2$. We seek to understand the relative efficacy of radio, quasar, and starburst feedback over a range of active galaxy types. Molecular flows powered by radio feedback in BCGs are $\sim$10--1000 times larger in extent compared to contemporary galaxies hosting quasar nuclei and starbursts. Radio feedback yields lower flow velocities but higher momenta compared to quasar nuclei, as the molecular gas flows in BCGs are usually $\sim$10--100 times more massive. The product of the molecular gas mass and lifting altitude divided by the AGN or starburst power -- a parameter referred to as the lifting factor -- exceeds starbursts and quasar nuclei by two to three orders of magnitude, respectively. When active, radio feedback is generally more effective at lifting gas in galaxies compared to quasars and starburst winds. The kinetic energy flux of molecular clouds generally lies below and often substantially below a few percent of the driving power. We find tentatively that star formation is suppressed in BCGs relative to other active galaxies, perhaps because these systems rarely form molecular disks that are more impervious to feedback and are better able to promote star formation.