The Clustering of X-ray Luminous Quasars
  The clustering of active galactic nuclei (AGN) sheds light on their typical
large (Mpc-scale) environments, which can constrain the growth and evolution of
supermassive black holes. Here we measure the clustering of luminous
X-ray-selected AGN in the Stripe 82X and XMM-XXL-North surveys around the peak
epoch of black hole growth, in order to investigate the dependence of
luminosity on large-scale AGN environment. We compute the auto-correlation
function of AGN in two luminosity bins, $10^{43}\leq L_X<10^{44.5}$ erg
s$^{-1}$ at $z\sim 0.8$ and $L_X\geq 10^{44.5}$ erg s$^{-1}$ at $z\sim 1.8$,
and calculate the AGN bias taking into account the redshift distribution of the
sources using three different methods. Our results show that while the less
luminous sample has an inferred typical halo mass that is smaller than for the
more luminous AGN, the host halo mass may be less dependent on luminosity than
suggested in previous work. Focusing on the luminous sample, we calculate a
typical host halo mass of $\sim 10^{13}$ M$_{\odot}~h^{-1}$, which is similar
to previous measurements of moderate-luminosity X-ray AGN and significantly
larger than the values found for optical quasars of similar luminosities and
redshifts. We suggest that the clustering differences between different AGN
selection techniques are dominated by selection biases, and not due to a
dependence on AGN luminosity. We discuss the limitations of inferring AGN
triggering mechanisms from halo masses derived by large-scale bias.
