A study of AGN and supernova feedback in simulations of isolated and
  merging disc galaxies
  We perform high resolution N-body+SPH simulations of isolated Milky-Way-like
galaxies and major mergers between them, to investigate the effect of feedback
from both an active galactic nucleus (AGN) and supernovae on the galaxy's
evolution. Several AGN methods from the literature are used independently and
in conjunction with supernova feedback to isolate the most important factors of
these feedback processes. We find that in isolated galaxies, supernovae
dominate the suppression of star formation but the star formation rate is
unaffected by the presence of an AGN. In mergers the converse is true when
models with strong AGN feedback are considered, shutting off star formation
before a starburst can occur. AGN and supernovae simulated together suppress
star formation only slightly more than if they acted independently. This
low-level interaction between the feedback processes is due to AGN feedback
maintaining the temperature of a hot halo of gas formed by supernovae. For each
of the feedback processes the heating temperature is the dominant parameter
rather than the overall energy budget or timing of heating events. Finally, we
find that the black hole mass is highly resolution dependent, with more massive
black holes found in lower resolution simulations.
