The chemical case for no winds in dwarf irregular galaxies

Abstract

We argue that isolated gas-rich dwarf galaxies - in particular, dwarf irregular (dIrr) galaxies - do not necessarily undergo significant gas loss. Our aim is to investigate whether the observed properties of isolated, gas-rich dwarf galaxies, not affected by external environmental processes, can be reproduced by self-consistent chemophotometric infall models with continuous star formation histories and no mass or metal loss. Themodel is characterized by the total mass of primordial gas available to the object, its characteristic collapse time-scale, and a constant star formation efficiency. A grid of 144 such models has been computed by varying these parameters, and their predictions (elemental abundances, stellar and gas masses, photometric colours) have been compared with a set of observations of dIrr galaxies obtained from the literature. It is found that the models with moderate to low efficiency are able to reproduce most of the observational data, including the relative abundances of nitrogen and oxygen. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.