Starburst-driven galactic outflows

Abstract

We propose a model of starburst-driven galactic outflows whose dynamics depend on both radiation and thermal pressure. Standard models of thermal pressure-driven winds fail to explain some key observations of outflows at low- and high-redshift galaxies. We discuss a scenario in which radiation pressure from massive stars in a stellar population drive a shell of gas and dust. Subsequent supernova explosions from the most massive stars in this population then drive stellar ejecta outwards in a rarefied medium, making it collide with the radiation-pressure-driven shell. The collision imparts renewed momentum to the shell, and the resulting re-acceleration makes the shell Rayleigh–Taylor unstable, fragmenting the shell. We show that the speed of these ballistic fragments can explain some recently observed correlations in Lyman break galaxies among wind speed, reddening and star formation rate.