The early days of the Sculptor dwarf spheroidal galaxy

TL;DR

This study analyzes the chemical composition of five metal-poor stars in the Sculptor dwarf galaxy, revealing similarities to the Milky Way's early stars and providing insights into galaxy formation and nucleosynthesis.

Contribution

It doubles the number of high-resolution spectroscopic observations of metal-poor stars in Sculptor and compares their chemical abundances with those of the Milky Way and ultra faint dwarfs.

Findings

Most Sculptor metal-poor stars follow Milky Way abundance trends.

Identification of an outlier missing products of massive Type II supernovae.

Evidence of s-process contribution in some stars' neutron capture elements.

Abstract

We present the high resolution spectroscopic study of five -3.9<=[Fe/H]<=-2.5 stars in the Local Group dwarf spheroidal, Sculptor, thereby doubling the number of stars with comparable observations in this metallicity range. We carry out a detailed analysis of the chemical abundances of alpha, iron peak, light and heavy elements, and draw comparisons with the Milky Way halo and the ultra faint dwarf stellar populations. We show that the bulk of the Sculptor metal-poor stars follows the same trends in abundance ratios versus metallicity as the Milky Way stars. This suggests similar early conditions of star formation and a high degree of homogeneity of the interstellar medium. We find an outlier to this main regime, which seems to miss the products of the most massive of the TypeII supernovae. In addition to its value to help refining galaxy formation models, this star provides clues to the production of cobalt and zinc. Two of our sample stars have low odd-to-even barium isotope abundance ratios, suggestive of a fair proportion of s-process; we discuss the implication for the nucleosynthetic origin of the neutron capture elements.