Clumpy tori illuminated by the anisotropic radiation of accretion discs
  in active galactic nuclei
  In this paper, we try to explain the observed correlation between the
covering factor (CF) of hot dust and the properties of active galactic nuclei
(AGNs), e.g., the bolometric luminosity ($L_{\rm{bol}}$) and black hole mass
($M_{\rm{BH}}$). Combining the possible dust distribution in the torus, the
angular dependence of the radiation of the accretion disc, and the relation
between the critical angle of torus and the Eddington ratio, there are eight
possible models investigated in our work. We fit the observed CF with these
models to determine the parameters of them. As a result, clumpy torus models
can generally explain the observed correlations of tori, while the smooth
models fail to produce the required CFs. However, there is still significant
scatter even for the best-fitting model, which is the combination of a clumpy
torus illuminated by the anisotropic radiation of accretion disc in an AGN.
Although some of the observed scatter is due to the uncertainties in measuring
$L_{\rm{bol}}$ and $M_{\rm{BH}}$, other factors are required in more realistic
model. The models examined in this paper are not necessary to be the physical
model of tori. However, the reasonable assumptions selected during this process
should be helpful in constructing physical models of tori.
