Cosmological implications of dwarf spheroidal chemical evolution

Abstract

The chemical properties of dwarf spheroidals in the local group are shown to be inconsistent with star formation being truncated after the reionization epoch (z~8). Enhanced levels of [Ba/Y] in stars in dwarf spheroidals like Sculptor indicate strong s-process production from low-mass stars whose lifetimes are comparable with the duration of the pre-reionization epoch. The chemical evolution of Sculptor is followed using a model with SNeII and SNeIa feedback and mass- and metallicity-dependent nucleosynthetic yields for elements from H to Pb. We are unable to reproduce the Ba/Y ratio unless stars formed over an interval long enough for the low-mass stars to pollute the interstellar medium with s-elements. This robust result challenges the suggestion that most of the local group dwarf spheroidals are fossils of reionization and supports the case for large initial dark matter halos.

7 pages, 4 figures. Accepted for publication in ApJ. Minor changes following referee report

References in corpus (2)

• Star formation feedback and metal enrichment by SN Ia and SN II in dwarf spheroidal galaxies: the case of Draco
• Star Formation Histories of Local Group Dwarf Galaxies

Cited by in corpus (7)

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• Life and times of dwarf spheroidal galaxies
• The Chemical Evolution of Dwarf Spheroidal Galaxies: Dissecting the Inner Regions and their Stellar Populations
• Effects of the galactic winds on the stellar metallicity distribution of dwarf spheroidal galaxies
• The evolution of the photometric properties of Local Group dwarf spheroidal galaxies
• The Chemistry of the Local Group
• About the Chemical Evolution of dSphs (and the peculiar Globular Cluster Omega Cen)