Supernova blast waves in wind-blown bubbles, turbulent, and power-law ambient media

Abstract

Supernova (SN) blast waves inject energy and momentum into the interstellar medium (ISM), control its turbulent multiphase structure and the launching of galactic outflows. Accurate modelling of the blast wave evolution is therefore essential for ISM and galaxy formation simulations. We present an efficient method to compute the input of momentum, thermal energy, and the velocity distribution of the shock-accelerated gas for ambient media with uniform (and with stellar wind blown bubbles), power-law, and turbulent density distributions. Assuming solar metallicity cooling, the blast wave evolution is followed to the beginning of the momentum conserving snowplough phase. The model recovers previous results for uniform ambient media. The momentum injection in wind-blown bubbles depend on the swept-up mass and the efficiency of cooling, when the blast wave hits the wind shell. For power-law density distributions with $n(r) \sim$ $r^{-2}$ (for $n(r) > n_{_{\rm floor}}$) the amount of momentum injection is solely regulated by the background density $n_{_{\rm floor}}$ and compares to $n_{_{\rm uni}}$ = $n_{_{\rm floor}}$. However, in turbulent ambient media with log-normal density distributions the momentum input can increase by a factor of 2 (compared to the homogeneous case) for high Mach numbers. The average momentum boost can be approximated as $p_{_{\rm turb}}/\mathrm{p_{_{0}}}\ =23.07\, \left(\frac{n_{_{0,\rm turb}}}{1\,{\rm cm}^{-3}}\right)^{-0.12} + 0.82 (\ln(1+b^{2}\mathcal{M}^{2}))^{1.49}\left(\frac{n_{_{0,\rm turb}}}{1\,{\rm cm}^{-3}}\right)^{-1.6}$. The velocity distributions are broad as gas can be accelerated to high velocities in low-density channels. The model values agree with results from recent, computationally expensive, three-dimensional simulations of SN explosions in turbulent media.