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Kim, Chang-Goo,Ostriker, Eve C.,Kim, Woong-Tae IOP Publishing 2013 The Astrophysical journal Vol.776 No.1
<P>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) alpha Sigma root 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.</P>
Numerical modeling of multiphase, turbulent galactic disks with star formation feedback
Kim, Chang-Goo,Ostriker, Eve C.,Kim, Woong-Tae Cambridge University Press 2012 Proceedings of the International Astronomical Unio Vol.10 No.h16
<B>Abstract</B><P>Star formation is self-regulated by its feedback that drives turbulence and heats the gas. In equilibrium, the star formation rate (SFR) should be directly related to the total (thermal <I>plus</I> turbulent) midplane pressure and hence the total weight of the diffuse gas if energy balance and vertical dynamical equilibrium hold simultaneously. To investigate this quantitatively, we utilize numerical hydrodynamic simulations focused on outer-disk regions where diffuse atomic gas dominates. By analyzing gas properties at saturation, we obtain relationships between the turbulence driving and dissipation rates, heating and cooling rates, the total midplane pressure and the total weight of gas, and the SFR and the total midplane pressure. We find a nearly linear relationship between the SFR and the midplane pressure consistent with the theoretical prediction.</P>