The Gaia-ESO Survey: Lithium enrichment histories of the Galactic thick and thin disc^★

¹ Dipartimento di Fisica & Astronomia, Università degli Studi di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
² INAF–Osservatorio Astronomico di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
e-mail: xiaoting.fu@oabo.inaf.it
³ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ Instituto de Astrofísica e Cências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
⁵ INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Florence, Italy
⁶ SISSA–International School for Advanced Studies, via Bonomea 265, 34136 Trieste, Italy
⁷ European Southern Observatory, Alonso de Cordova 3107 Vitacura, Santiago de Chile, Chile
⁸ University of New South Wales Sydney, Australia 2052
⁹ Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
¹⁰ Dpto. Física Teǿrica y del Cosmos, Universidad de Granada, 18071 Granada, Spain
¹¹ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
¹² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹³ Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio av. 3, 10257 Vilnius, Lithuania
¹⁴ Departamento de Astronomia, Universidad de Concepcion, 3349001 Concepcion, Chile
¹⁵ Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Universitá di Catania, via S. Sofia 78, 95123 Catania, Italy
¹⁶ Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo Osservatorio 3, 35122 Padova, Italy
¹⁷ Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, 221 00 Lund, Sweden
¹⁸ INAF–Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
¹⁹ Instituto de Astrofísica de Andalucía-CSIC, Apdo. 3004, 18080 Granada, Spain
²⁰ INAF–Padova Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
²¹ Laboratoire d’astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
²² Departamento de Ciencias Fisicas, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago, Chile
²³ Instituto de Física y Astronomiía, Universidad de Valparaiíso, Chile
²⁴ Observatoire de la Côte d’Azur, Laboratoire Lagrange, CNRS UMR 7293, Nice Cedex 04, France
²⁵ Nucleo de Astronomia, Universidad Diego Portales, Ejercito 441, Santiago, Chile

Received: 30 July 2017
Accepted: 9 November 2017

Abstract

Lithium abundance in most of the warm metal-poor main sequence stars shows a constarnt plateau (A(Li) ~ 2.2 dex) and then the upper envelope of the lithium vs. metallicity distribution increases as we approach solar metallicity. Meteorites, which carry information about the chemical composition of the interstellar medium (ISM) at the solar system formation time, show a lithium abundance A(Li) ~ 3.26 dex. This pattern reflects the Li enrichment history of the ISM during the Galaxy lifetime. After the initial Li production in big bang nucleosynthesis, the sources of the enrichment include asymptotic giant branch (AGB) stars, low-mass red giants, novae, type II supernovae, and Galactic cosmic rays. The total amount of enriched Li is sensitive to the relative contribution of these sources. Thus different Li enrichment histories are expected in the Galactic thick and thin disc. We investigate the main sequence stars observed with UVES in Gaia-ESO Survey iDR4 catalogue and find a Li- [α/Fe] anticorrelation independent of [Fe/H], T_eff, and log (g). Since in stellar evolution different α enhancements at the same metallicity do not lead to a measurable Li abundance change, the anticorrelation indicates that more Li is produced during the Galactic thin disc phase than during the Galactic thick disc phase. We also find a correlation between the abundance of Li and s-process elements Ba and Y, and they both decrease above the solar metallicity, which can be explained in the framework of the adopted Galactic chemical evolution models.