The Gaia-ESO Survey: Galactic evolution of lithium from iDR6^⋆,⋆⋆

¹ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, 40129 Bologna, Italy
e-mail: donatella.romano@inaf.it
² INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
³ Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
⁴ GEPI, Observatoire de Paris, Université PSL, CNRS, Place Jules Janssen, 92190 Meudon, France
⁵ Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK
⁶ Dipartimento di Fisica, Sezione di Astronomia, Università di Trieste, Via Tiepolo 11, 34131 Trieste, Italy
⁷ INAF, Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34131 Trieste, Italy
⁸ INFN, Sezione di Trieste, Via Valerio 2, 34127 Trieste, Italy
⁹ INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹⁰ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
¹¹ Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
¹² INAF, Osservatorio Astronomico di Roma, Via Frascati 33, 00077 Monte Porzio Catone, Roma, Italy
¹³ SISSA, Via Bonomea 265, 34136 Trieste, Italy
¹⁴ Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, 221 00 Lund, Sweden
¹⁵ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
¹⁶ Observational Astrophysics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
¹⁷ School of Physics, UNSW, Sydney, NSW 2052, Australia
¹⁸ Centre of Excellence for All-Sky Astrophysics in Three Dimensions (ASTRO 3D), Australia
¹⁹ Institute of Theoretical Physics and Astronomy, Vilnius University, Sauletekio Av. 3, 10257 Vilnius, Lithuania
²⁰ Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
²¹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
²² Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
²³ Space Science Data Center-ASI, Via del Politecnico SNC, 00133 Roma, Italy
²⁴ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
²⁵ The Kavli Institute for Astronomy and Astrophysics at Peking University, 100871 Beijing, PR China
²⁶ Departamento de Física de la Tierra y Astrofísica and IPARCOSUCM, Instituto de Física de Partículas y del Cosmos de la UCM, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
²⁷ Departmento de Astrofísica, Centro de Astrobiología (INTA-CSIC), ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
²⁸ INAF, Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
²⁹ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Received: 18 May 2021
Accepted: 18 June 2021

Abstract

Context. After more than 50 years, astronomical research still struggles to reconstruct the history of lithium enrichment in the Galaxy and to establish the relative importance of the various ⁷Li sources in enriching the interstellar medium (ISM) with this fragile element.

Aims. To better trace the evolution of lithium in the Milky Way discs, we exploit the unique characteristics of a sample of open clusters (OCs) and field stars for which high-precision ⁷Li abundances and stellar parameters are homogeneously derived by the Gaia-ESO Survey (GES).

Methods. We derive possibly un-depleted ⁷Li abundances for 26 OCs and star forming regions with ages from young (∼3 Myr) to old (∼4.5 Gyr), spanning a large range of galactocentric distances, 5 < R_GC/kpc < 15, which allows us to reconstruct the local late Galactic evolution of lithium as well as its current abundance gradient along the disc. Field stars are added to look further back in time and to constrain ⁷Li evolution in other Galactic components. The data are then compared to theoretical tracks from chemical evolution models that implement different ⁷Li forges.

Results. Thanks to the homogeneity of the GES analysis, we can combine the maximum average ⁷Li abundances derived for the clusters with ⁷Li measurements in field stars. We find that the upper envelope of the ⁷Li abundances measured in field stars of nearly solar metallicities (−0.3 < [Fe/H]/dex < +0.3) traces very well the level of lithium enrichment attained by the ISM as inferred from observations of cluster stars in the same metallicity range. We confirm previous findings that the abundance of ⁷Li in the solar neighbourhood does not decrease at super-solar metallicity. The comparison of the data with the chemical evolution model predictions favours a scenario in which the majority of the ⁷Li abundance in meteorites comes from novae. Current data also seem to suggest that the nova rate flattens out at later times. This requirement might have implications for the masses of the white dwarf nova progenitors and deserves further investigation. Neutrino-induced reactions taking place in core-collapse supernovae also produce some fresh lithium. This likely makes a negligible contribution to the meteoritic abundance, but could be responsible for a mild increase in the ⁷Li abundance in the ISM of low-metallicity systems that would counterbalance the astration processes.