Star formation, gas cycles and the chemical evolution of dwarf irregular galaxies

Because of their low gravitational energies dwarf galaxies are greatly exposed to energetical influences from internal and external sources. In gas-rich dwarf irregular galaxies not only that star formation regulates itself due to the stellar energy release, but also supernova-driven galactic winds are accepted as a general explanation for their low metallicities.
Chemodynamical models of dIrrs that take the dynamics of different gas phases and the stars as well as their energetical and materialistic interactions into account can show that strong evaporation of interstellar clouds embedded in the hot supernova gas leads to an almost perfect mixing of the interstellar gas.
If circumgalactic HI envelops exist as it is observed with growing evidence around actively star-forming dIrrs, infalling gas clouds are poluted by metal-enriched hot outflows by means of condensation. This leads to a large range of timescales for the self-enrichment of the interstellar medium in dIrrs. In addition, the infalling gas feeds the formation of a gaseous disk until the star formation rate reaches a level of stellar energy release that compensates the gas accumulation. By this, also peculiar element abundances, like their low N/O ratios at also low O, that are difficult to understand otherwise, are self-consistently reproduced.