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

Using high-resolution, three-dimensional hydrodynamical simulations, weinvestigate the structure of the interstellar medium in the central hundred pcregion in galaxies, taking into account self-gravity of the gas, radiativecooling from 10 K to $10^8$ K, and energy feedback from supernovae. Similar tothe previous two-dimensional results produced by Wada and Norman, we find thata gravitationally and thermally unstable ISM evolves, in a self-stabilizingmanner, into a quasi-stable thin disk, which is characterized by a network ofcold ($T < 100$ K), dense clumps and filaments, and hot ($T > 10^6$ K), diffusemedium. Supernova explosions blow the diffuse gases from the disk, and as aresult, a quasi-steady diffuse halo, which is not uniform but has a plume-likestructure, is formed. The density probability distribution function (PDF) in aquasi-steady state is well fitted by a Log-Normal function over about sevenorders of magnitude.