AGN Feedback: Does it work?
  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.
