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

Abstract : We present the high-resolution spectroscopic analysis of two new extremely metal-poor stars (EMPS) candidates in the dwarf spheroidal galaxy Sextans. These targets were pre-selected from medium resolution spectra centered around the Ca II triplet in the near-infrared and followed-up at higher resolution with VLT/UVES. We confirm their low metallicities with [Fe/H]=-2.95 and [Fe/H]=-3.01, placing them among the most metal-poor stars known in Sextans. The abundances of 18 elements, including C, Na, the alpha-elements, Fe-peak, and neutron capture elements, are determined. In particular, we present the first measurements of Zn in a classical dwarf at extremely low metallicity. There has been previous hints of a large scatter in the abundance ratios of the Sextans stellar population around [Fe/H] -3 when compared to other galaxies. We took the opportunity of this work to re-analyse the full sample of EMPS and find a Milky-Way -like plateau and a normal dispersion at fixed metallicity.
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https://hal-insu.archives-ouvertes.fr/insu-03001956
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R. Lucchesi, C. Lardo, Francesca Primas, P. Jablonka, P. North, et al.. Homogeneity in the early chemical evolution of the Sextans dwarf Spheroidal galaxy. Astronomy and Astrophysics - A&A, EDP Sciences, 2020, ⟨10.1051/0004-6361/202037534⟩. ⟨insu-03001956⟩

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