The Gaia-ESO Survey: the present-day radial metallicity distribution of the Galactic disc probed by pre-main-sequence clusters ^⋆,⋆⋆

¹ Universidade de São Paulo, IAGDepartamento de Astronomia, Rua do Matão 1226, São Paulo, 05509-900 SP, Brazil
e-mail: lspina@usp.br
² INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
³ Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK
⁴ Department of Astronomy, Indiana University, Bloomington, IN, USA
⁵ ASI Science Data Center, via del Politecnico SNC, 00133 Roma, Italy
⁶ Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Università di Catania, via S. Sofia 78, 95123 Catania, Italy
⁷ INAF–Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁸ INAF–Osservatorio Astronomico di Palermo, P.zza del Parlamento 1, 90134 Palermo, Italy
⁹ Dip. di Fisica e Chimica, Università di Palermo, P.zza del Parlamento 1, 90134 Palermo, Italy
¹⁰ Dpto. Astrofísica, Facultad de CC. Fisicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹¹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹² INAF – Padova Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹³ Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, 221 00 Lund, Sweden
¹⁴ INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
¹⁵ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹⁶ Moscow MV Lomonosov State University, Sternberg Astronomical Institute, 119992 Moscow, Russia
¹⁷ Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
¹⁸ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
¹⁹ Instituto de Física y Astronomiía, Universidad de Valparaíso, Chile
²⁰ European Southern Observatory, Alonso de Cordova 3107 Vitacura, Santiago de Chile, Chile
²¹ Instituto de Astrofísica de Andalucía-CSIC, Apdo. 3004, 18080 Granada, Spain
²² Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
²³ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
²⁴ Departamento de Ciencias Fisicas, Universidad Andres Bello, Republica 220, Santiago, Chile
²⁵ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal

Received: 17 November 2016
Accepted: 7 February 2017

Abstract

Context. The radial metallicity distribution in the Galactic thin disc represents a crucial constraint for modelling disc formation and evolution. Open star clusters allow us to derive both the radial metallicity distribution and its evolution over time.

Aims. In this paper we perform the first investigation of the present-day radial metallicity distribution based on [Fe/H] determinations in late type members of pre-main-sequence clusters. Because of their youth, these clusters are therefore essential for tracing the current interstellar medium metallicity.

Methods. We used the products of the Gaia-ESO Survey analysis of 12 young regions (age < 100 Myr), covering Galactocentric distances from 6.67 to 8.70 kpc. For the first time, we derived the metal content of star forming regions farther than 500 pc from the Sun. Median metallicities were determined through samples of reliable cluster members. For ten clusters the membership analysis is discussed in the present paper, while for other two clusters (i.e. Chamaeleon I and Gamma Velorum) we adopted the members identified in our previous works.

Results. All the pre-main-sequence clusters considered in this paper have close-to-solar or slightly sub-solar metallicities. The radial metallicity distribution traced by these clusters is almost flat, with the innermost star forming regions having [Fe/H] values that are 0.10−0.15 dex lower than the majority of the older clusters located at similar Galactocentric radii.

Conclusions. This homogeneous study of the present-day radial metallicity distribution in the Galactic thin disc favours models that predict a flattening of the radial gradient over time. On the other hand, the decrease of the average [Fe/H] at young ages is not easily explained by the models. Our results reveal a complex interplay of several processes (e.g. star formation activity, initial mass function, supernova yields, gas flows) that controlled the recent evolution of the Milky Way.