A refined sub-grid model for black hole accretion and AGN feedback in
  large cosmological simulations
  In large scale cosmological hydrodynamic simulations simplified sub-grid
models for gas accretion onto black holes and AGN feedback are commonly used.
Such models typically depend on various free parameters, which are not well
constrained. We present a new advanced model containing a more detailed
description of AGN feedback, where those parameters reflect the results of
recent observations. The model takes the dependency of these parameters on the
black hole properties into account and describes a continuous transition
between the feedback processes acting in the so-called radio-mode and
quasar-mode. In addition, we implement a more detailed description of the
accretion of gas onto black holes by distinguishing between hot and cold gas
accretion. Our new implementations prevent black holes from gaining too much
mass, particularly at low redshifts so that our simulations are now very
successful in reproducing the observed present-day black hole mass function.
Our new model also suppresses star formation in massive galaxies slightly more
efficiently than many state-of-the-art models. Therefore, the simulations that
include our new implementations produce a more realistic population of
quiescent and star-forming galaxies compared to recent observations, even if
some discrepancies remain. In addition, the baryon conversion efficiencies in
our simulation are - except for the high mass end - consistent with
observations presented in literature over the mass range resolved by our
simulations. Finally, we discuss the significant impact of the feedback model
on the low-luminous end of the AGN luminosity function.
