Detailed abundances in stars belonging to ultra-faint dwarf spheroidal galaxies

TL;DR

This study analyzes the chemical compositions of stars in ultra-faint dwarf spheroidal galaxies using high-resolution spectra, revealing slightly lower abundance ratios than in field halo stars and insights into early nucleosynthesis processes.

Contribution

It provides the first detailed chemical abundance analysis of stars in ultra-faint dwarf galaxies using X-Shooter spectra, highlighting differences from field halo stars.

Findings

Stars in ultra-faint dwarf galaxies have slightly lower abundance ratios than field halo stars.

No extreme abundance patterns were observed in Hercules stars.

Neutron capture element synthesis suggests a common early nucleosynthetic process.

Abstract

We report preliminary results concerning the detailed chemical composition of metal poor stars belonging to close ultra-faint dwarf galaxies (hereafter UfDSphs). The abundances have been determined thanks to spectra obtained with X-Shooter, a high efficiency spectrograph installed on one of the ESO VLT units. The sample of ultra-faint dwarf spheroidal stars have abundance ratios slightly lower to what is measured in field halo star of the same metallicity.We did not find extreme abundances in our Hercules stars as the one found by Koch for his 2 Hercules stars. The synthesis of the neutron capture elements Ba and Sr seems to originate from the same nucleosynthetic process in operation during the early stages of the galactic evolution.