Numerical Models of the Multiphase Interstellar Matter with Stellar Energy Feedback on a Galactic Scale

High-resolution two-dimensional hydrodynamic simulations for the interstellar matter (ISM) in a galactic disk are enhanced to include explicitly star formation and the feedback effects from supernovae and stellar winds. A globally stable multiphase ISM is formed, in which filamentary and clumpy structure is a characteristic feature. We find a new component of 10⁶-10⁸ K gas that is a direct consequence of the energy input from the feedback. The total supernovae rate in the system varies by an order of magnitude over a timescale of 10⁶ yr. The evolution of the supernovae rate exhibits chaotic behavior because the star formation is triggered by supernovae explosions in the inhomogeneous interstellar medium. We also find that, in spite of its very complicated spatial structure, the multiphase ISM exhibits a one-point probability density function (pdf) that is a perfect lognormal distribution over four decades in density, 10²-10⁶ M_☉ pc^-2. The lognormal pdf is very robust even in regions with frequent bursts of supernovae. Low-density regions or cavities (<10 M_☉ pc^-2), on the other hand, exhibit the normal Gaussian distribution. These characteristic pdf's are achieved over a local dynamical scale. The energy spectra are E(k) ∝ k^-3 without feedback and E(k) ∝ k^-2 including stellar energy feedback.