Molecular Gas Disk Structures around AGNs
  We present new high resolution numerical simulations of the ISM in a central
R ~32 parsecs region around a supermassive black hole at a galactic center.
Three-dimensional hydrodynamic modeling of the ISM (Wada & Norman 2002) with
the nuclear starburst now includes tracking of the formation of molecular
hydrogen out of the neutral hydrogen phase. In a quasi equilibrium state, mass
fraction of H2 is about 0.4 (total H2 mass is ~1.5 10^6 Msun) of the total gas
mass for the uniform far UV (FUV) with G_0 = 10. The gas forms an inhomogeneous
disk, whose scale-height becomes larger in the outer region. H2 forms a thin
nuclear disk in the inner ~ 5 pc, which is surrounded by molecular clouds
swelled up toward h < 10 pc. The velocity field of the disk is highly turbulent
in the torus region, whose velocity dispersion is ~ 20 km/s on average. Average
supernova rate (SNR) of ~ 5 10^-5/yr is large enough to energize these
structures. Gas column densities toward the nucleus larger than 10^22 cm^-2 are
observed if the viewing angle is smaller than \theta_v ~ 50 deg from the
edge-on. However, the column densities are distributed over almost two orders
of magnitude around the average for any given viewing angle due to the clumpy
nature of the torus. For a stronger FUV (G_0 =100), the total H2 mass in an
equillibrium is only slightly smaller (~ 0.35). Finally the morphology and
kinematics of the circumnuclear molecular gas disks emerging from our models is
similar to that revealed by recent near infrared observations using VLTI/Keck.
