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

R. Lucchesi , C. Lardo , Francesca Primas , P. Jablonka , P. North , G. Battaglia , E. Starkenburg , Vanessa Hill (1) , M. Irwin , P. Francois , M. Shetrone , E. Tolstoy , K. Venn

1 LAGRANGE - Joseph Louis LAGRANGE

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.

Mots clés: Astrophysics - Astrophysics of Galaxies; Astrophysics - Solar and Stellar Astrophysics

Domaines: Astrophysique [astro-ph]; Astrophysique galactique [astro-ph.GA]; Astrophysique stellaire et solaire [astro-ph.SR]; Instrumentation et méthodes pour l'astrophysique [astro-ph.IM]

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, 2020, ⟨10.1051/0004-6361/202037534⟩. ⟨insu-03001956⟩