Star Formation Regulation, Gas Cycles and the chemical evolution of dwarf irregular galaxies

¹ Institute of Astronomy, Vienna University, Türkenschanzstrasse 17, 1180 Vienna, Austria
² INAF – Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy

Abstract

Due to their low gravitational energies, dwarf galaxies are greatly exposed to energetical influences from internal and external sources. By means of chemodynamical models we show that their star formation is inherently self-regulated, that peculiar abundance ratios can only be achieved assuming different star-formation episodes and that evaporation of interstellar clouds embedded in a hot phase can lead to a fast mixing of the interstellar gas. Metal-enriched hot outflows can accrete onto infalling clouds by means of condensation leading to a large range of timescales for the self-enrichment of the ISM from local scales within a few tens of Myr up to a few Gyr for the large-range circulation. Infall of clouds is also required to explain abundance ratios of metal-poor galaxies at evolved stages because it reduces the metallicity altering only marginally the abundance ratios.