Simultaneous Constraints on the Star Formation History and Nucleosynthesis of Sculptor dSph

TL;DR

This study uses stellar abundance ratios and a chemical evolution model to constrain the star formation history and nucleosynthesis processes of the Sculptor dwarf spheroidal galaxy, revealing a short, ancient star formation period and insights into supernova and AGB element production.

Contribution

It introduces a method combining multiple abundance ratios with a chemical evolution model to simultaneously constrain SFH and nucleosynthesis in dwarf galaxies, providing new insights into their evolutionary history.

Findings

Sculptor dSph has an ancient SFH with a duration of about 0.9 Gyr.

Observed [Mn/Fe] and [Ni/Fe] trends favor sub-Chandrasekhar mass Type Ia supernova models.

A combination of prompt and delayed r-process events is needed to explain certain element ratios.

Abstract

We demonstrate that using up to seven stellar abundance ratios can place observational constraints on the star formation histories (SFHs) of Local Group dSphs, using the Sculptor dSph as a test case. We use a one-zone chemical evolution model to fit the overall abundance patterns of $\alpha$ elements (which probe the core-collapse supernovae that occur shortly after star formation), $s$-process elements (which probe AGB nucleosynthesis at intermediate delay times), and iron-peak elements (which probe delayed Type Ia supernovae). Our best-fit model indicates that Sculptor dSph has an ancient SFH, consistent with previous estimates from deep photometry. However, we derive a total star formation duration of $\sim0.9$ Gyr, which is shorter than photometrically-derived SFHs. We explore the effect of various model assumptions on our measurement and find that modifications to these assumptions still produce relatively short SFHs of duration $\lesssim1.4$ Gyr. Our model is also able to compare sets of predicted nucleosynthetic yields for supernovae and AGB stars, and can provide insight into the nucleosynthesis of individual elements in Sculptor dSph. We find that observed [Mn/Fe] and [Ni/Fe] trends are most consistent with sub-$M_{\mathrm{Ch}}$ Type Ia supernova models, and that a combination of "prompt" (delay times similar to core-collapse supernovae) and "delayed" (minimum delay times $\gtrsim50$ Myr) $r$-process events may be required to reproduce observed [Ba/Mg] and [Eu/Mg] trends.