Quasar feedback: accelerated star formation and chaotic accretion
  Growing Supermassive Black Holes (SMBH) are believed to influence their
parent galaxies in a negative way, terminating their growth by ejecting gas out
before it could turn into stars. Here we present some of the most sophisticated
SMBH feedback simulations to date showing that quasar's effects on galaxies are
not always negative. We find that when the ambient shocked gas cools rapidly,
the shocked gas is compressed into thin cold dense shells, filaments and
clumps. Driving these high density features out is much more difficult than
analytical models predict since dense filaments are resilient to the feedback.
However, in this regime quasars have another way of affecting the host -- by
triggering a massive star formation burst in the cold gas by over-pressurising
it. Under these conditions SMBHs actually accelerate star formation in the
host, having a positive rather than negative effect on their host galaxies. The
relationship between SMBH and galaxies is thus even more complex and symbiotic
than currently believed. We also suggest that the instabilities found here may
encourage the chaotic AGN feeding mode.
