A partial isotopic decomposition for the Sculptor dSph

Abstract

ABSTRACT All stellar evolution models require an initial isotopic abundance set as input, but these abundances are well known only for the Sun. Yet, input compositions can be estimated by scaling solar abundances using a previously constructed isotopic history model based on astrophysical processes in the Galaxy. This method, however, may not work for obtaining inputs for compositions that have distinct chemical histories from the Galaxy. We thus present a partial isotopic history model for the Sculptor dwarf spheroidal galaxy based on astrophysical processes, which can be used to estimate input isotopic abundances in future nucleosynthesis studies. The model is fitted to observational data, and follows the methodology of the previously constructed isotopic history model for the Galaxy. First, we estimate the isotopic composition of Sculptor’s late-stage evolution (LSE) using the omega chemical evolution code, and then decompose that composition into contributions from various astrophysical sources. Each contribution is then assumed to scale as a function of metallicity. The isotopic abundances are summed into elemental abundances and fit to available observational elemental abundance data to tune the model’s free parameters. The result is an average isotopic history model of Sculptor for massive star, Type Ia SNe, s-process, and r-process contributions that uses elemental data to constrain the isotopic abundances. As an example, our model finds that Type Ia SNe contribute ≈ 87 percent to the LSE Fe abundance, and neutron star mergers contribute ≈ 36 percent to the LSE Eu abundance, in agreement with previous studies.