Jet-induced star formation in gas-rich galaxies
  Feedback from active galactic nuclei (AGN) has become a major component in
simulations of galaxy evolution, in particular for massive galaxies. AGN jets
have been shown to provide a large amount of energy and are capable of
quenching cooling flows. Their impact on the host galaxy, however, is still not
understood. Subgrid models of AGN activity in a galaxy evolution context so far
have been mostly focused on the quenching of star formation. To shed more light
on the actual physics of the "radio mode" part of AGN activity, we have
performed simulations of the interaction of a powerful AGN jet with the massive
gaseous disc (10^11 solar masses) of a high-redshift galaxy. We spatially
resolve both the jet and the clumpy, multi-phase interstellar medium (ISM) and
include an explicit star formation model in the simulation. Following the
system over more than 10^7 years, we find that the jet activity excavates the
central region, but overall causes a significant change to the shape of the
density probability distribution function and hence the star formation rate due
to the formation of a blast wave with strong compression and cooling in the
ISM. This results in a ring- or disc-shaped population of young stars. At later
times, the increase in star formation rate also occurs in the disc regions
further out since the jet cocoon pressurizes the ISM. The total mass of the
additionally formed stars may be up to 10^10 solar masses for one duty cycle.
We discuss the details of this jet-induced star formation (positive feedback)
and its potential consequences for galaxy evolution and observable signatures.
