MINCE II. Neutron capture elements

TL;DR

This study measures neutron-capture element abundances in giant stars from different galactic sub-components, revealing distinct nucleosynthetic histories and chemical evolution patterns, especially for the Gaia Sausage Enceladus and Sequoia groups.

Contribution

It provides detailed neutron-capture element abundances in 33 stars across galactic sub-components and compares these with stochastic chemical evolution models, highlighting differences in their nucleosynthetic histories.

Findings

GSE stars show a tight anti-correlation of [Sr/Ba] vs [Ba/H].

Sequoia stars exhibit higher [Sr/Ba] ratios at given [Ba/H], indicating different nucleosynthesis.

GSE chemical evolution resembles that of a dwarf galaxy with winds and inefficient star formation.

Abstract

The MINCE (Measuring at Intermediate metallicity Neutron-Capture Elements) project aims to gather the abundances of neutron-capture elements but also of light elements and iron peak elements in a large sample of giant stars in this metallicity range. T The aim of this work is to study the chemical evolution of galactic sub-components recently identified (i.e. Gaia Sausage Enceladus (GSE), Sequoia). We used high signal-to-noise ratios, high-resolution spectra and standard 1D LTE spectrum synthesis to determine the detailed abundances. We could determine the abundances for up to 10 neutron-capture elements (Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm and Eu) in 33 stars. The general trends of abundance ratios [n-capture element/Fe] versus [Fe/H] are in agreement with the results found in the literature. When our sample is divided in sub-groups depending on their kinematics, we found that the run of [Sr/Ba] vs [Ba/H] for the stars belonging to the GSE accretion event shows a tight anti-correlation. The results for the Sequoia stars, although based on a very limited sample, shows a [Sr/Ba] systematically higher than the [Sr/Ba] found in the GSE stars at a given [Ba/H] hinting at a different nucleosynthetic history. Stochastic chemical evolution models have been computed to understand the evolution of the GSE chemical composition of Sr and Ba. The first conclusions are that the GSE chemical evolution is similar to the evolution of a dwarf galaxy with galactic winds and inefficient star formation. Detailed abundances of neutron-capture elements have been measured in high-resolution, high signal-to-noise spectra of intermediate metal-poor stars, the metallicity range covered by the MINCE project. These abundances have been compared to detailed stochastic models of galactic chemical evolution.