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Thomas Bensby. Profile photo.

Thomas Bensby

Senior lecturer

Thomas Bensby. Profile photo.

The Gaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk

Author

  • M. Bergemann
  • Gregory Ruchti
  • A. Serenelli
  • Sofia Feltzing
  • A. Alves-Brito
  • M. Asplund
  • Thomas Bensby
  • P. Gruiters
  • U. Heiter
  • A. Hourihane
  • A. Korn
  • K. Lind
  • A. Marino
  • P. Jofre
  • T. Nordlander
  • Nils Ryde
  • C. C. Worley
  • G. Gilmore
  • S. Randich
  • A. M. N. Ferguson
  • R. D. Jeffries
  • G. Micela
  • I. Negueruela
  • T. Prusti
  • H. -W. Rix
  • A. Vallenari
  • E. J. Alfaro
  • C. Allende Prieto
  • A. Bragaglia
  • S. E. Koposov
  • A. C. Lanzafame
  • E. Pancino
  • A. Recio-Blanco
  • R. Smiljanic
  • N. Walton
  • M. T. Costado
  • E. Franciosini
  • V. Hill
  • C. Lardo
  • P. de Laverny
  • L. Magrini
  • E. Maiorca
  • T. Masseron
  • L. Morbidelli
  • G. Sacco
  • G. Kordopatis
  • G. Tautvaisiene

Summary, in English

We study the relationship between age, metallicity, and alpha-enhancement of FGK stars in the Galactic disk. The results are based upon the analysis of high-resolution UVES spectra from the Gaia-ESO large stellar survey. We explore the limitations of the observed dataset, i.e. the accuracy of stellar parameters and the selection effects that are caused by the photometric target preselection. We find that the colour and magnitude cuts in the survey suppress old metal-rich stars and young metal-poor stars. This suppression may be as high as 97% in some regions of the age-metallicity relationship. The dataset consists of 144 stars with a wide range of ages from 0.5 Gyr to 13.5 Gyr, Galactocentric distances from 6 kpc to 9.5 kpc, and vertical distances from the plane 0 < vertical bar Z vertical bar < 1.5 kpc. On this basis, we find that i) the observed age-metallicity relation is nearly flat in the range of ages between 0 Gyr and 8 Gyr; ii) at ages older than 9 Gyr, we see a decrease in [Fe/H] and a clear absence of metal-rich stars; this cannot be explained by the survey selection functions; iii) there is a significant scatter of [Fe/H] at any age; and iv) [Mg/Fe] increases with age, but the dispersion of [Mg/Fe] at ages > 9 Gyr is not as small as advocated by some other studies. In agreement with earlier work, we find that radial abundance gradients change as a function of vertical distance from the plane. The [Mg/Fe] gradient steepens and becomes negative. In addition, we show that the inner disk is not only more alpha-rich compared to the outer disk, but also older, as traced independently by the ages and Mg abundances of stars.

Department/s

  • Lund Observatory

Publishing year

2014

Language

English

Publication/Series

Astronomy & Astrophysics

Volume

565

Document type

Journal article

Publisher

EDP Sciences

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • stars: abundances
  • stars: fundamental parameters
  • solar neighborhood
  • Galaxy: disk
  • Galaxy: formation
  • surveys

Status

Published

Project

  • Gaia-ESO Survey

ISBN/ISSN/Other

  • ISSN: 0004-6361