On the theory of mass loss in dwarf galaxies: I - basic equations and the case of wave/thermal driven winds

Abstract

In this work we present a semi-analytical model of galactic wind for dwarf galaxies where thermal and turbulent/momemtum driving mechanisms are studied. The model takes into account wave and internal adiabatic heating mechanisms, as well as radiative and adiabatic cooling. The importance of external sources of energy is discussed. We also studied the role of the spatial distribution of dark matter in the acceleration of the wind and on the mass loss rates. The basic model parameters that regulate the wind mass loss rate and terminal velocity are the gravitational potential profile, the equilibrium temperature of the gas and the amplitude of the turbulent motions of the gas. We found that dwarf galaxies are likely to present quasi-stationary winds with mass loss rates larger than $10^{-3}$M$_{\odot}$yr$^{-1}$ even in the absence of turbulent motions (which is possibly related to the SNe feedback), if the interstellar gas is heated to $T > 10^4 - 10^5$K. We also found that the wind mass loss rate is enhanced for cusped dark matter distributions, such as the NFW-profile, due to the increased pressure gradients at the center of the galaxy. The solutions presented here may serve as benchmarks for numerical simulations, and as inputs for single zone chemical evolution models of dwarf galaxies.