The Three-Dimensional Structure of a Massive Gas Disk in the Galactic Central Region

Using high-resolution, three-dimensional hydrodynamical simulations, we investigate the structure of the interstellar medium in the central hundred pc region in galaxies, taking into account self-gravity of the gas, radiative cooling from 10 K to $10^8$ K, and energy feedback from supernovae. Similar to the previous two-dimensional results produced by Wada and Norman, we find that a gravitationally and thermally unstable ISM evolves, in a self-stabilizing manner, into a quasi-stable thin disk, which is characterized by a network of cold ($T < 100$ K), dense clumps and filaments, and hot ($T > 10^6$ K), diffuse medium. Supernova explosions blow the diffuse gases from the disk, and as a result, a quasi-steady diffuse halo, which is not uniform but has a plume-like structure, is formed. The density probability distribution function (PDF) in a quasi-steady state is well fitted by a Log-Normal function over about seven orders of magnitude.