A Supernova-regulated Interstellar Medium: Simulations of the Turbulent Multiphase Medium

Abstract

The dynamic state of the interstellar medium, heated and stirred by supernovae (SNe), is simulated using a three-dimensional, nonideal MHD model in a domain extended 0.5 × 0.5 kpc horizontally and 2 kpc vertically, with the gravitational field symmetric about the midplane of the domain, z =0. We include both Type I and Type II SNe, allowing the latter to cluster in regions with enhanced gas density. The system segregates into two main phases: a warm, denser phase and a hot, dilute gas in global pressure equilibrium; there is also dense, cool gas compressed into filaments, shells, and clumps by expanding SN remnants. The filling factor of the hot phase grows with height, so it dominates at | z | ≳0.5 kpc. The multicomponent structure persists throughout the simulation, and its statistical parameters show little time variation. The warm gas is in hydrostatic equilibrium, which is supported by thermal and turbulent pressures. The multiphase gas is in a state of developed turbulence. The rms random velocity is different in the warm and hot phases, 10 and 40 km s -1 , respectively, at | z | ≲1 kpc; the turbulent cell size (twice the velocity correlation scale) is about 60 pc in the warm phase.