Obscuring fraction of active galactic nuclei implied by supernova and
  radiative feedbacks
  We study the obscuring structure of circumnuclear disks (CNDs) by considering
supernova (SN) feedbacks from nuclear starburst and the effect of anisotropic
radiative pressure from AGNs. We suppose that the mass accretion onto a central
supermassive black hole (SMBH) is triggered by SN-driven turbulence within
CNDs, and we explore how the structures of CNDs depend on the BH mass ($M_{\rm
BH}$) and AGN luminosity ($L_{\rm AGN}$). We find that the obscuring fraction
($f_{\rm obs}$) peaks at $\sim10\%$ of the Eddington luminosity ($L_{\rm
Edd}$), and its maximal value is $f_\mathrm{obs} \sim 0.6$ for less massive
SMBHs (e.g., $M_{\rm BH} < 10^{8}M_{\odot}$). This is because the scale height
of CNDs is determined by the SN-driven accretion for a smaller $L_{\rm AGN}$,
while the dusty molecular gas in CNDs is blown away by the radiation pressure
from AGNs beyond the critical luminosity. On the other hand, for massive SMBHs
(e.g., $M_{\rm BH} > 10^{8}M_{\odot}$), $f_{\rm obs}$ is always smaller than
$0.2$, and it is almost independent of $L_{\rm AGN}$ because the scale height
of CNDs is mainly controlled by the maximal star-formation efficiency ($C_{\rm
*, max}$) in CNDs. By comparison with the obscuring fractions suggested from
the mid-infrared observations of nearby AGNs, the SN plus radiative feedback
model with $C_{\rm *, max} = 10^{-7}\, {\rm yr}^{-1}$ well reproduces the
observations for $M_\mathrm{BH} = 10^8 M_\odot$. We also find that the intense
starburst or the existence of dust-free absorbers inside CNDs are necessary, to
explain X-ray observations.
