AGN Feedback: Does it work?

TL;DR

This paper investigates the effectiveness of AGN feedback mechanisms, particularly jets and outflows, in regulating galaxy and black hole growth, finding that observed outflows are generally insufficient for significant feedback.

Contribution

It introduces a novel measurement technique for AGN outflows and assesses their potential role in feedback across different AGN types.

Findings

Outflows in NGC 4051 are 4-5 orders of magnitude below feedback thresholds.

Most Seyferts have outflow velocities less than escape velocities, indicating weak feedback.

Jet-related feedback is limited to a small fraction of quasars.

Abstract

While feedback is important in theoretical models, we do not really know if it works in reality. Feedback from jets appears to be sufficient to keep the cooling flows in clusters from cooling too much and it may be sufficient to regulate black hole growth in dominant cluster galaxies. Only about 10% of all quasars, however, have powerful radio jets, so jet-related feedback cannot be generic. The outflows could potentially be a more common form of AGN feedback, but measuring mass and energy outflow rates is a challenging task, the main unknown being the location and geometry of the absorbing medium. Using a novel technique, we made first such measurement in NGC 4051 using XMM data and found the mass and energy outflow rates to be 4 to 5 orders of magnitude below those required for efficient feedback. To test whether the outflow velocity in NGC 4051 is unusually low, we compared the ratio of outflow velocity to escape velocity in a sample of AGNs and found it to be generally less than one. It is thus possible that in most Seyferts the feedback is not sufficient and may not be necessary.