A Dynamical Model of Supernova Feedback: Gas Outflows from the Interstellar Medium

Abstract

AbstractIn this Chapter, a dynamical model of supernova feedback which follows the evolution of bubbles driven by supernovae in a multi-phase interstellar medium (ISM) is presented. Bubbles are followed until the point of break-out into the halo, starting from an initial adiabatic phase to a radiative phase. This detailed hydrodynamical model shows that a key property which sets the fate of bubbles in the ISM its the gas surface density, through the work done by the expansion of bubbles and its role in setting the gas scaleheight. The multi-phase description of the ISM is essential, and neglecting it leads to order of magnitude differences in the predicted outflow rates. The predicted mass loading and outflow velocities are compared to observations of local and high-redshift galaxies and find good agreement. With the aim of analysing the dependence of the mass loading of the outflow, \(\beta \) (i.e. the ratio between the outflow and star formation rates), on galaxy properties, I embed the dynamical supernovae feedback model in the galaxy formation simulation, GALFORM. The dependence of \(\beta \) solely on the circular velocity, as it is widely assumed in the literature, is actually a poor description of the outflow rate. A more fundamental relation is that between \(\beta \) and the gas surface density and gas fraction. The use of the new mass loading model leads to a shallower faint-end slope in the predicted optical and near-infrared galaxy luminosity functions.KeywordsStar FormationOutflow RateStellar MassStar Formation RateDiffuse MediumThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.