The Evolution of Dwarf Galaxies with Star Formation in Outward Propagating Super Shell

Abstract

We simulate the dynamical and chemical evolution of a dwarf galaxy embedded in a dark matter halo, using a three-dimensional N-body/SPH simulation code combined with stellar population synthesis. The initial condition is adopted in accord with a $10^{10}M_\odot$ virialized sphere in a 1-sigma CDM perturbation which contains 10% baryonic mass. A supersonic spherical outflow is driven by the first star burst near the center of the galaxy and produces an expanding super shell in which stars are subsequently formed. Consecutive formation of stars in the expanding shell makes the stellar system settled with the exponential brightness profile, the positive metallicity gradient, and the inverse color gradient in agreement with observed features of dwarf galaxies. We therefore propose that the energy feedback via stellar winds and supernovae is a decisive mechanism for formation of less compact, small systems like dwarf galaxies.