Physical Models for the Clustering of Obscured and Unobscured Quasars
  Clustering measurements of obscured and unobscured quasars show that obscured
quasars reside in more massive dark matter halos than their unobscured
counterparts. These results are inconsistent with simple unified (torus)
scenarios, but might be explained by models in which the distribution of
obscuring material depends on Eddington ratio or galaxy stellar mass. We test
these possibilities by constructing simple physical models to compare to
observed AGN populations. We find that previously observed relationships
between obscuration and Eddington ratio or stellar mass are not sufficient
reproduce the observed quasar clustering results ($\langle \log
M_{\text{halo}}/M_{\odot} \rangle = 12.94 ^{+ 0.10}_{- 0.11}$ and $\langle \log
M_{\text{halo}}/M_{\odot} \rangle = 12.49 ^{+ 0.08}_{- 0.08}$ for obscured and
unobscured populations, respectively) while maintaining the observed fraction
of obscured quasars (30-65$\%$). This work suggests that evolutionary models,
in which obscuration evolves on the typical timescale for black hole growth,
are necessary to understand the observed clustering of mid-IR selected quasars.
