Volume 644, December 2020
|Number of page(s)||14|
|Published online||02 December 2020|
Homogeneity in the early chemical evolution of the Sextans dwarf spheroidal galaxy⋆
European Southern Observatory, Karl-Schwarzschild-str. 2, 85748 Garching bei München, Germany
2 Physics Institute, Laboratoire d’astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, 1290 Versoix, Switzerland
3 GEPI, Observatoire de Paris, CNRS, Université de Paris Diderot, 92195 Meudon Cedex, France
4 Instituto de Astrofísica de Canarias (IAC), Calle Via Láctea, s/n, 38205 San Cristóbal de la Laguna, Tenerife, Spain
5 Departamento de Astrofísica, Universidad de La Laguna, 38206 San Cristóbal de la Laguna, Tenerife, Spain
6 Leibniz-Institut fur Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
7 Laboratoire Lagrange, Université de Nice Sophia-Antipolis, Observatoire de la Côte d’Azur, France
8 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
9 McDonald Observatory, University of Texas at Austin, Fort David, TX, USA
10 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
11 Department of Physics and Astronomy, University of Victoria, PO Box 3055, STN CSC, Victoria, BC V8W 3P6, Canada
Accepted: 20 August 2020
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.
Key words: stars: abundances / Local Group / galaxies: dwarf / galaxies: formation
© ESO 2020
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