The Gaia-ESO Survey: radial distribution of abundances in the Galactic disc from open clusters and young-field stars^⋆

¹ INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
e-mail: laura@arcetri.astro.it
² Leibniz-Institut fur Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
³ Institut d’Astrophysique de Paris; Université Pierre et Marie Curie, 75014 Paris, France
⁴ INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁵ INAF, Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133 Roma, Italy
⁶ INAF, Osservatorio Astronomico di Roma, via Frascati 33, 00078 Roma, Italy
⁷ Paris-Meudon Observatory, 61 avenue de l’Observatoire, 75014 Paris, France
⁸ ASI Science Data Center, via del Politecnico snc, 00133 Roma, Italy
⁹ Department of Astronomy, Indiana University, Bloomington, IN 47405, USA
¹⁰ Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio al. 3, 10222 Vilnius, Lithuania
¹¹ Universidade de Sao Paulo, IAG Departamento de Astronomia, Rua do Matao 1226, 05509-900 Sao Paulo, Brasil
¹² Dipartimento di Fisica e Astronomia, Università di Padova, vicolo Osservatorio 3, 35122 Padova, Italy
¹³ Centro de Astrobiología (INTA-CSIC), Departamento de Astrofísica, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
¹⁴ Suffolk University, Madrid Campus, C/Valle de la Viña 3, 28003 Madrid, Spain
¹⁵ Departamento de Astronomía, Casilla, 160-C, Universidad de Concepción, Concepción, Chile
¹⁶ Instituto de Astrofisica e Ciencias do espaço -CAUP, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁷ Millennium Institute of Astrophysics, Santiago, Chile
¹⁸ Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile
¹⁹ Institute of Astronomy, Madingley Road, University of Cambridge, CB3 0HA, UK
²⁰ Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
²¹ Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, 221 00 Lund, Sweden
²² Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, 18008 Granada, Spain
²³ INAF–Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
²⁴ Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Universitá di Catania, via S. Sofia 78, 95123 Catania, Italy
²⁵ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
²⁶ Facultad de Ciencias, Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretana 1111, 5030 Casilla, Valparaíso, Chile
²⁷ Max Planck Institut fur Astronomie, Koenigstuhl 17, 69117 Heidelberg, Germany
²⁸ ESO, Alonso de Cordova 3107, 19001 Santiago de Chile, Chile
²⁹ Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
³⁰ Departamento de Ciencias Físicas, Universidad Andres Bello, República 220, Santiago, Chile

Received: 20 December 2016
Accepted: 1 March 2017

Abstract

Context. The spatial distribution of elemental abundances in the disc of our Galaxy gives insights both on its assembly process and subsequent evolution, and on the stellar nucleogenesis of the different elements. Gradients can be traced using several types of objects as, for instance, (young and old) stars, open clusters, HII regions, planetary nebulae.

Aims. We aim to trace the radial distributions of abundances of elements produced through different nucleosynthetic channels – the α-elements O, Mg, Si, Ca and Ti, and the iron-peak elements Fe, Cr, Ni and Sc – by use of the Gaia-ESO IDR4 results for open clusters and young-field stars.

Methods. From the UVES spectra of member stars, we have determined the average composition of clusters with ages > 0.1 Gyr. We derived statistical ages and distances of field stars. We traced the abundance gradients using the cluster and field populations and compared them with a chemo-dynamical Galactic evolutionary model.

Results. The adopted chemo-dynamical model, with the new generation of metallicity-dependent stellar yields for massive stars, is able to reproduce the observed spatial distributions of abundance ratios, in particular the abundance ratios of [O/Fe] and [Mg/Fe] in the inner disc (5 kpc <R_GC< 7 kpc), with their differences, that were usually poorly explained by chemical evolution models.

Conclusions. Oxygen and magnesium are often considered to be equivalent in tracing α-element abundances and in deducing, for example, the formation timescales of different Galactic stellar populations. In addition, often [α/Fe] is computed combining several α-elements. Our results indicate, as expected, a complex and diverse nucleosynthesis of the various α-elements, in particular in the high metallicity regimes, pointing towards a different origin of these elements and highlighting the risk of considering them as a single class with common features.