Galactic chimney sweeping: the effect of ‘gradual’ stellar feedback mechanisms on the evolution of dwarf galaxies

Abstract

ABSTRACT We investigate the impact of time-resolved ‘gradual’ stellar feedback processes in high redshift dwarf spheroidal galaxies. Here ‘gradual’ feedback refers to individual stellar feedback events which deposit energy over a period of time. We conduct high-resolution hydrodynamical simulations of dwarf spheroidal galaxies with halo masses of 107–108 M⊙, based on z = 6 progenitors of the Milky Way’s dwarf spheroidal galaxies. We also include a novel feedback prescription for individual massive stars, which includes stellar winds and an HMXB (high mass X-ray binary) phase, on top of supernovae. We find the mass of gas unbound across a 1 Gyr starburst is uniformly lowered if gradual feedback mechanisms are included across the range of metallicities, halo concentration parameters, and galaxy masses studied here. Furthermore, we find including gradual feedback in the smallest galaxies delays the unbinding of the majority of the gas and facilitates the production of ‘chimneys’ in the dense shell surrounding the feedback generated hot, pressurized ‘superbubble’. These ‘chimneys’ vent hot gas from the galaxy interior, lowering the temperature of the central 10 kpc of the gaseous halo. Additionally, we find radiative cooling has little effect on the energetics of simulations that include a short, violent starburst compared with those that have a longer, less concentrated starburst. Finally, we investigate the relative impact of HMXB feedback and stellar winds on our results, finding the ubiquity of stellar winds throughout each starburst makes them a defining factor in the final state of the interstellar medium.