We present new high resolution numerical simulations of the interstellar medium ( ISM ) in a central R \leq 32 parsecs region around a supermassive black hole ( 1.3 \times 10 ^ { 7 } M _ { \odot } ) 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 ( H _ { 2 } ~ { } ) out of the neutral hydrogen phase as a function of the evolving ambient ISM conditions with a finer spatial resolution ( 0.125 pc ) .
In a quasi equilibrium state , mass fraction of H _ { 2 } ~ { } is about 0.4 ( total H _ { 2 } ~ { } mass is \simeq 1.5 \times 10 ^ { 6 } M _ { \odot } ) of the total gas mass for the uniform far UV ( FUV ) with G _ { 0 } = 10 in Habing unit .
As shown in the previous model , the gas forms an inhomogeneous disk , whose scale-height becomes larger in the outer region .
H _ { 2 } ~ { } forms a thin nuclear disk in the inner \simeq 5 ~ { } { pc } , which is surrounded by molecular clouds swelled up toward h \lesssim 10 ~ { } { pc } .
The velocity field of the disk is highly turbulent in the torus region , whose velocity dispersion is \simeq 20 ~ { } { km } ~ { } { s } ^ { -1 } on average .
Average supernova rate ( SNR ) of \simeq 5 \times 10 ^ { -5 } { yr } ^ { -1 } 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 } \simeq 50 ^ { \circ } 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 H _ { 2 } ~ { } mass in an equillibrium is only slightly smaller ( \simeq 0.35 ) , a testimony to the strong self-shielding nature of H _ { 2 } , and the molecular gas is somewhat more concentrated in a mid-plane .
Other properties of the ISM are not very sensitive either to the FUV intensity and the supernova rate .
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 .