On the metallicity of star-forming dwarf galaxies

We construct three extremely different scenarios of the star formation hist ories applicable to a sample of dwarf galaxies, based on either their prese nt metallicity or their luminosity. The three possible scenarios imply diff erent mechanical energy input rates, and these we compare with the theoreti cal lower limits established for the ejection of processed matter out of dw arf galaxies. The comparison strongly points to the existence of extended g aseous halos in these galaxies acting as the barrier that allows galaxies t o retain their metals and enhance their abundance. At the same time, our fi ndings strongly point to a continuous star-forming process, rather than to coeval bursts, as the main contributor to the overall metallicity in our ga laxy sample.