The Gaia-ESO Survey: Calibrating the lithium–age relation with open clusters and associations

I. Cluster age range and initial membership selections^⋆,⋆⋆

¹ Departamento de Física de la Tierra y Astrofísica and IPARCOS-UCM, Instituto de Física de Partículas y del Cosmos de la UCM, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
e-mail: [email protected]
² Observatorio Astronómico Nacional (OAN-IGN), Apdo 112, 28803 Alcalá de Henares, Madrid, Spain
³ Instituto de Astrofísica e Ciências do Espaçø, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
⁴ Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
⁵ Universidad de la Laguna, Dept. Astrofísica, 38206 La Laguna, Tenerife, Spain
⁶ INAF – Osservatorio Astrofisico di Catania, Via S. Sofia, 78 95123 Catania, Italy
⁷ Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, 95123 Catania, Italy
⁸ Institut für Astronomie und Astrophysik, Eberhard Karls Universität, Sand 1, 72076 Tübingen, Germany
⁹ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
¹⁰ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
¹¹ Observational Astrophysics, Division of Astronomy and Space Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
¹² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹³ Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43 221 00 Lund, Sweden
¹⁴ INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento, 1, 90134 Palermo, Italy
¹⁵ Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
¹⁶ Spanish Virtual Observatory, Centro de Astrobiología (INTA-CSIC), PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
¹⁷ Departamento de Ciencias Físicas, Universidad Andrés Bello, Fernández Concha 700, Las Condes, Santiago, Chile
¹⁸ Dipartimento di Fisica “E. Fermi”, Università di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
¹⁹ INAF – Padova Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
²⁰ Instituto de Física y Astronomía, Universidad de Valparaíso, Valparaíso, Chile
²¹ Núcleo Milenio Formación Planetaria – NPF, Universidad de Valparaíso, Valparaíso, Chile
²² Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales (UDP), Santiago, Chile
²³ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
²⁴ Dipartimento di Fisica e Astronomia Galileo Galilei, Vicolo Osservatorio 3, 35122 Padova, Italy

Received: 29 January 2020
Accepted: 29 July 2020

Abstract

Context. Previous studies of open clusters have shown that lithium depletion is not only strongly age dependent but also shows a complex pattern with other parameters that is not yet understood. For pre- and main-sequence late-type stars, these parameters include metallicity, mixing mechanisms, convection structure, rotation, and magnetic activity.

Aims. We perform a thorough membership analysis for a large number of stars observed within the Gaia-ESO survey (GES) in the field of 20 open clusters, ranging in age from young clusters and associations, to intermediate-age and old open clusters.

Methods. Based on the parameters derived from the GES spectroscopic observations, we obtained lists of candidate members for each of the clusters in the sample by deriving radial velocity distributions and studying the position of the kinematic selections in the EW(Li)-versus-T_eff plane to obtain lithium members. We used gravity indicators to discard field contaminants and studied [Fe/H] metallicity to further confirm the membership of the candidates. We also made use of studies using recent data from the Gaia DR1 and DR2 releases to assess our member selections.

Results. We identified likely member candidates for the sample of 20 clusters observed in GES (iDR4) with UVES and GIRAFFE, and conducted a comparative study that allowed us to characterize the properties of these members as well as identify field contaminant stars, both lithium-rich giants and non-giant outliers.

Conclusions. This work is the first step towards the calibration of the lithium–age relation and its dependence on other GES parameters. During this project we aim to use this relation to infer the ages of GES field stars, and identify their potential membership to young associations and stellar kinematic groups of different ages.