Three Dimensional Hydrodynamic Simulations of Multiphase Galactic Disks with Star Formation Feedback: I. Regulation of Star Formation Rates

摘要

The energy and momentum feedback from young stars has a profound impact onthe interstellar medium (ISM), including heating and driving turbulence in theneutral gas that fuels future star formation. Recent theory has argued thatthis leads to a quasi-equilibrium self-regulated state, and for outeratomic-dominated disks results in the surface density of star formation$\Sigma_{SFR}$ varying approximately linearly with the weight of the ISM (ormidplane turbulent + thermal pressure). We use three-dimensional numericalhydrodynamic simulations to test the theoretical predictions for thermal,turbulent, and vertical dynamical equilibrium, and the implied functionaldependence of $\Sigma_{SFR}$ on local disk properties. Our models demonstratethat all equilibria are established rapidly, and that the expectedproportionalities between mean thermal and turbulent pressures and$\Sigma_{SFR}$ apply. For outer disk regions, this results in $\Sigma_{SFR}\propto \Sigma \sqrt{\rho_{sd}}$, where $\Sigma$ is the total gas surfacedensity and $\rho_{sd}$ is the midplane density of the stellar disk (plus darkmatter). This scaling law arises because $\rho_{sd}$ sets the verticaldynamical time in our models (and outer disk regions generally). Thecoefficient in the star formation law varies inversely with the specific energyand momentum yield from massive stars. We find proportions of warm and coldatomic gas, turbulent-to-thermal pressure, and mean velocity dispersions thatare consistent with Solar-neighborhood and other outer-disk observations. Thisstudy confirms the conclusions of a previous set of simulations, whichincorporated the same physics treatment but was restricted to radial-verticalslices through the ISM.