A high resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy

TL;DR

This study provides a detailed chemical evolution history of the Fornax dwarf spheroidal galaxy by analyzing high-resolution spectra of 81 stars, revealing unique abundance patterns and the role of AGB stars in element formation.

Contribution

First detailed high-resolution chemical abundance analysis of stars in the Fornax dwarf galaxy's center, highlighting its unique chemical evolution and s-process element contributions.

Findings

Fornax stars show low [$ ext{α}$/Fe], [Ni/Fe], and [Na/Fe] compared to Milky Way stars.

High [Ba/Y] indicates significant s-process contribution from low metallicity AGB stars.

Evidence of s-process contribution to Eu abundance.

Abstract

For the first time we show the detailed late-stage chemical evolution history of small nearby dwarf spheroidal galaxy in the Local Group. We present the results of a high resolution (R$\sim$20000) FLAMES/GIRAFFE abundance study at ESO/VLT of 81 photometrically selected red giant branch stars in the central 25$'$ of the Fornax dwarf spheroidal galaxy. We present abundances of \alfe\ (Mg, Si, Ca and Ti), iron-peak elements (Fe, Ni and Cr) and heavy elements (Y, Ba, La, Nd and Eu). Our sample was randomly selected, and is clearly dominated by the younger and more metal rich component of Fornax which represents the major fraction of stars in the central region. This means that the majority of our stars are 1$-$4 Gyr old, and thus represent the end phase of chemical evolution in this system. Our sample of stars has unusually low [$\alpha$/Fe], [Ni/Fe] and [Na/Fe] compared to the Milky Way stellar populations at the same [Fe/H]. The particularly important role of stellar winds from low metallicity AGB stars in the creation of s-process elements is clearly seen from the high [Ba/Y]. Furthermore, we present evidence for an s-process contribution to Eu.