NIHAO XXII: Introducing black hole formation, accretion and feedback
  into the NIHAO simulation suite
  We introduce algorithms for black hole physics, i.e., black hole formation,
accretion and feedback, into the NIHAO (Numerical Investigation of a Hundred
Astrophysical Objects) project of galaxy simulations. This enables us to study
high mass, elliptical galaxies, where feedback from the central black hole is
generally thought to have a significant effect on their evolution. We
furthermore extend the NIHAO suite by 45 simulations that encompass $z=0$ halo
masses from $1 \times 10^{12}$ to $4 \times 10^{13}\,\mathrm{M}_{\odot}$, and
resimulate five galaxies from the original NIHAO sample with black hole
physics, which have $z=0$ halo masses from $8 \times 10^{11}$ to $3 \times
10^{12}\,\mathrm{M}_{\odot}$. Now NIHAO contains 144 different galaxies and
thus has the largest sample of zoom-in simulations of galaxies, spanning $z=0$
halo masses from $9 \times 10^{8}$ to $4 \times 10^{13}\,\mathrm{M}_{\odot}$.
In this paper we focus on testing the algorithms and calibrating their free
parameters against the stellar mass versus halo mass relation and the black
hole mass versus stellar mass relation. We also investigate the scatter of
these relations, which we find is a decreasing function with time and thus in
agreement with observations. For our fiducial choice of parameters we
successfully quench star formation in objects above a $z=0$ halo mass of
$10^{12}\,\mathrm{M}_{\odot}$, thus transforming them into red and dead
galaxies.
