Gravitational and mass distribution effects on stationary superwinds

Abstract

Here, we model the effect of non-uniform dynamical mass distributions and their associated gravitational fields on the stationary galactic superwind solution. We do this by considering an analogue injection of mass and energy from stellar winds and SNe. We consider both compact dark-matter and baryonic haloes that does not extend further from the galaxies optical radii $R_{\rm opt}$ as well as extended gravitationally-interacting ones. We consider halo profiles that emulate the results of recent cosmological simulations and coincide also with observational estimations from galaxy surveys. This allows to compare the analytical superwind solution with outflows from different kinds of galaxies. We give analytical formulae that establish when an outflow is possible and also characterize distinct flow regimes and enrichment scenarios. We also constraint the parameter space by giving approximate limits above which gravitation, self-gravitation and radiative cooling can inhibit the stationary flow. We obtain analytical expressions for the free superwind hydrodynamical profiles. We find that the existence or inhibition of the superwind solution highly depends on the steepness and concentration of the dynamical mass and the mass and energy injection rates. We compare our results with observational data and a recent numerical work. We put our results in the context of the mass-metallicity relationship to discuss observational evidence related to the selective loss of metals from the least massive galaxies and also discuss the case of massive galaxies.