Astrophys. J., 869, 94-94 (2018/December-3)
Metal mixing and ejection in dwarf galaxies are dependent on nucleosynthetic source.
EMERICK A., BRYAN G.L., LOW M.-M.M., COTE B., JOHNSTON K.V. and O'SHEA B.W.
Abstract (from CDS):
Using a high-resolution simulation of an isolated dwarf galaxy, accounting for multichannel stellar feedback and chemical evolution on a star-by-star basis, we investigate how each of 15 metal species is distributed within our multiphase interstellar medium (ISM) and ejected from our galaxy by galactic winds. For the first time, we demonstrate that the mass fraction probability distribution functions (PDFs) of individual metal species in the ISM are well described by a piecewise log-normal and power-law distribution. The PDF properties vary within each ISM phase. Hot gas is dominated by recent enrichment, with a significant power-law tail to high metal fractions, while cold gas is predominantly log-normal. In addition, elements dominated by asymptotic giant branch (AGB) wind enrichment (e.g., N and Ba) mix less efficiently than elements dominated by supernova enrichment (e.g., α elements and Fe). This result is driven by the differences in source energetics and source locations, particularly the higher chance compared to massive stars for AGB stars to eject material into cold gas. Nearly all of the produced metals are ejected from the galaxy (only 4% are retained), but over 20% of metals dominated by AGB enrichment are retained. In dwarf galaxies, therefore, elements synthesized predominantly through AGB winds should be both overabundant and have a larger spread compared to elements synthesized in either core-collapse or Type Ia supernovae. We discuss the observational implications of these results, their potential use in developing improved models of galactic chemical evolution, and their generalization to more massive galaxies.
© 2018. The American Astronomical Society. All rights reserved.
galaxies: evolution - hydrodynamics - ISM: abundances - stars: abundances
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