A Model of Supernovae Feedback in Galaxy Formation

Abstract

A model of supernovae feedback during disc galaxy formation is developed. The model incorporates infall of cooling gas from a halo and outflow of hot gas from a multiphase interstellar medium and a self-regulated model for star formation. Hot gas is created by thermal evaporation of cold gas clouds in supernovae remnants, and criteria are derived to estimate the characteristic temperature and density of the hot component and hence the net mass outflow rate. A number of refinements of the model are investigated, including a simple model of a galactic fountain, the response of the cold component to the pressure of the hot gas, pressure induced star formation and chemical evolution. The main conclusion of this paper is that low rates of star formation can expel a large fraction of the gas from a dwarf galaxy. Effective feedback can therefore take place in a quiescent mode and does not require strong bursts of star formation. Consequences for galaxy formation and damped Ly alpha systems are discussed.