Gas Mixing, Gas Cycles and the Chemical Evolution of Dwarf Irregular Galaxies

Abstract

Abstract. Dwarf galaxies are ideal laboratories to study influential effects on galaxy evolution. In particular, their gas-rich variant with very active star formation, starbursting dwarf irregulars, shows chemical and structural signatures that lead unambiguously to the conclusion that they are standing in a vital contact with their surroundings. Gas infall cannot only trigger star formation but also allows for a reduction of the metal content. On the other hand, active star formation ignites numerous supernovae type II which accumulate and can produce a galactic wind. This again depletes the metals pushing them into a gas mixing cycle with different timescales, locally of about 10 Myrs, but an galactic scales of at least 1 Gyr. This paper illuminates the different processes like gas infall and outflow and their effects on the chemical evolution, the star formation, and the gas mixing in dwarf irregular galaxies.

Cosmological Implications of Dwarf Spheroidal Chemical Evolution

“…The escape fraction of SNe II and SNe Ia ejecta increases linearly with their respective SNe rates, but the overall efficiency is inversely proportional to the depth of the galactic potential well, as measured by the total galaxy mass, m tot . We do not allow more than 90% of the SNe ejecta to escape at each timestep, based on the prediction by Hensler et al (2004) that up to 25% of SNe material gets mixed into the local ISM on short timescales rather than being carried away by an expanding superbubble. We note that the main conclusions of this paper are robust to the implementation of feedback.…”

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

“…Since the vast majority of dIrrs contains old stellar populations, the problem exists how to reach these low abundance values from an evolved state that is reached on the secondary production track of N. Under the assumption that dIrrs are young systems several authors allowed for starburst-driven galactic winds with selective element depletion, while others presented models that follow the assumption of abundance self-enrichment of the observed Hii regions. For a comprehensive discussion see Hensler et al (2004).…”

Internal chemo-dynamical Modeling of Gas Exchange within Galaxies and with their Environment

“…those in the combined SWB/Hii complexes) contribute to the observations by the enhancement or, respectively, dilution of metals. Since gas infall is not only affecting the chemistry but also SF (Hensler et al 2004) and dynamics of outflows we have extended the former models (Recchi et al 2004 by infalling clouds (Recchi & Hensler 2007). In these models, two kinds of cloud contributions are considered, only initially existing and continuously formed, respectively.…”