Probing the Radio Loud/Quiet AGN dichotomy with quasar clustering
  We investigate the clustering properties of 45441 radio-quiet quasars (RQQs)
and 3493 radio-loud quasars (RLQs) drawn from a joint use of the Sloan Digital
Sky Survey (SDSS) and Faint Images of the Radio Sky at 20 cm (FIRST) surveys in
the range $0.3<z<2.3$. This large spectroscopic quasar sample allow us to
investigate the clustering signal dependence on radio-loudness and black hole
(BH) virial mass. We find that RLQs are clustered more strongly than RQQs in
all the redshift bins considered. We find a real-space correlation length of
$r_{0}=6.59_{-0.24}^{+0.33}\,h^{-1}\,\textrm{Mpc}$ and
$r_{0}=10.95_{-1.58}^{+1.22}\,h^{-1}\,\textrm{Mpc}$ {\normalsize{}for} RQQs and
RLQs, respectively, for the full redshift range. This implies that RLQs are
found in more massive host haloes than RQQs in our samples, with mean host halo
masses of $\sim4.9\times10^{13}\,h^{-1}\,M_{\odot}$ and
$\sim1.9\times10^{12}\,h^{-1}\,M_{\odot}$, respectively. Comparison with
clustering studies of different radio source samples indicates that this mass
scale of $\gtrsim1\times10^{13}\,h^{-1}\,M_{\odot}$ is characteristic for the
bright radio-population, which corresponds to the typical mass of galaxy groups
and galaxy clusters. The similarity we find in correlation lengths and host
halo masses for RLQs, radio galaxies and flat-spectrum radio quasars agrees
with orientation-driven unification models. Additionally, the clustering signal
shows a dependence on black hole (BH) mass, with the quasars powered by the
most massive BHs clustering more strongly than quasars having less massive BHs.
We suggest that the current virial BH mass estimates may be a valid BH proxies
for studying quasar clustering. We compare our results to a previous
theoretical model that assumes that quasar activity
