Homogeneity in the early chemical evolution of the Sextans dwarf spheroidal galaxy

Lucchesi, R.; Lardo, C.; Primas, F.; Jablonka, P.; North, P.; Battaglia, G.; Starkenburg, E.; Hill, V.; Irwin, M.; Francois, P.; Shetrone, M.; Tolstoy, E.; Venn, K.
Bibliographical reference

Astronomy and Astrophysics

Advertised on:
12
2020
Number of authors
13
IAC number of authors
1
Citations
13
Refereed citations
11
Description
We present the high-resolution spectroscopic analysis of two new extremely metal-poor star (EMPS) candidates in the dwarf spheroidal galaxy Sextans. These targets were preselected from medium-resolution spectra centered around the Ca II triplet in the near-infrared and were followed-up at higher resolution with VLT/UVES. We confirm their low metallicities with [Fe/H] = -2.95 and [Fe/H] = -3.01, which place them among the most metal-poor stars known in Sextans. The abundances of 18 elements, including C, Na, the α, Fe-peak, and neutron-capture elements, are determined. In particular, we present the first unambiguous detection of Zn in a classical dwarf at extremely low metallicity. Previous indications were made of a large scatter in the abundance ratios of the Sextans stellar population around [Fe/H] ∼ - 3 when compared to other galaxies, particularly with very low observed [α/Fe] ratios. We took the opportunity of reanalyzing the full sample of EMPS in Sextans and find a [α/Fe] Milky Way-like plateau and a ∼0.2 dex dispersion at fixed metallicity.

Based on UVES observations collected at the ESO, proposal 093.D-0311.
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