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

TL;DR

This study uses 3D hydrodynamic simulations to validate theoretical models of star formation regulation in galactic disks, showing that feedback from stars establishes equilibrium states and influences star formation rates based on local disk properties.

Contribution

First comprehensive 3D simulations confirming theoretical predictions of star formation regulation and equilibrium states in galactic disks with feedback effects.

Findings

Star formation rates scale with gas surface density and stellar disk midplane density.

Equilibrium states are established rapidly in simulations.

Results align with observed properties of the interstellar medium.

Abstract

The energy and momentum feedback from young stars has a profound impact on the interstellar medium (ISM), including heating and driving turbulence in the neutral gas that fuels future star formation. Recent theory has argued that this leads to a quasi-equilibrium self-regulated state, and for outer atomic-dominated disks results in the surface density of star formation $\Sigma_{SFR}$ varying approximately linearly with the weight of the ISM (or midplane turbulent + thermal pressure). We use three-dimensional numerical hydrodynamic simulations to test the theoretical predictions for thermal, turbulent, and vertical dynamical equilibrium, and the implied functional dependence of $\Sigma_{SFR}$ on local disk properties. Our models demonstrate that all equilibria are established rapidly, and that the expected proportionalities 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 surface density and $\rho_{sd}$ is the midplane density of the stellar disk (plus dark matter). This scaling law arises because $\rho_{sd}$ sets the vertical dynamical time in our models (and outer disk regions generally). The coefficient in the star formation law varies inversely with the specific energy and momentum yield from massive stars. We find proportions of warm and cold atomic gas, turbulent-to-thermal pressure, and mean velocity dispersions that are consistent with Solar-neighborhood and other outer-disk observations. This study confirms the conclusions of a previous set of simulations, which incorporated the same physics treatment but was restricted to radial-vertical slices through the ISM.