Quasar clustering in a galaxy and quasar formation model based on ultra
  high-resolution N-body simulations
  We investigate clustering properties of quasars using a new version of our
semi-analytic model of galaxy and quasar formation with state-of-the-art
cosmological N-body simulations. In this study, we assume that a major merger
of galaxies triggers cold gas accretion on to a supermassive black hole and
quasar activity. Our model can reproduce the downsizing trend of the evolution
of quasars. We find that the median mass of quasar host dark matter haloes
increases with cosmic time by an order of magnitude from z=4 (a few 1e+11 Msun)
to z=1 (a few 1e+12 Msun), and depends only weakly on the quasar luminosity.
Deriving the quasar bias through the quasar--galaxy cross-correlation function
in the model, we find that the quasar bias does not depend on the quasar
luminosity, similar to observed trends. This result reflects the fact that
quasars with a fixed luminosity have various Eddington ratios and thus have
various host halo masses that primarily determine the quasar bias. We also show
that the quasar bias increases with redshift, which is in qualitative agreement
with observations. Our bias value is lower than the observed values at high
redshifts, implying that we need some mechanisms that make quasars inactive in
low-mass haloes and/or that make them more active in high-mass haloes.
