Issue |
A&A
Volume 600, April 2017
|
|
---|---|---|
Article Number | A70 | |
Number of page(s) | 16 | |
Section | Galactic structure, stellar clusters and populations | |
DOI | https://doi.org/10.1051/0004-6361/201629363 | |
Published online | 31 March 2017 |
Red giants observed by CoRoT and APOGEE: The evolution of the Milky Way’s radial metallicity gradient
1 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: fanders@aip.de
2 Laboratório Interinstitucional de e-Astronomia, – LIneA, Rua Gal. José Cristino 77, 20921-400 Rio de Janeiro, Brazil
3 School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
4 Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
5 LESIA, Université Pierre et Marie Curie, Université Denis Diderot, Obs. de Paris, 92195 Meudon Cedex, France
6 Osservatorio Astronomico di Padova – INAF, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
7 Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-970 Porto Alegre, Brazil
8 Institut dÁstrophysique Spatiale, UMR8617, CNRS, Université Paris XI, Bâtiment 121, 91405 Orsay Cedex, France
9 Dept. of Physics and JINA-CEE (Joint Institute for Nuclear Astrophysics – Center for the Evolution of the Elements), Univ. of Notre Dame, Notre Dame, IN 46530, USA
10 Observatório Nacional, Rua Gal. José Cristino 77, 20921-400 Rio de Janeiro, Brazil
11 Laboratoire AIM, CEA/DSM – CNRS – Univ. Paris Diderot – IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette Cedex, France
12 Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
13 Universidad de La Laguna, Departamento de Astrofísica, 38206 La Laguna, Tenerife, Spain
14 New Mexico State University, Las Cruces, NM 88003, USA
15 Department of Astronomy, University of Virginia, PO Box 400325, Charlottesville VA 22904-4325, USA
16 Space Science Institute, 4750 Walnut Street Suite 205, Boulder CO 80301, USA
17 Institut d’Astrophysique et de Géophysique, Allée du 6 août, 17 – Bât. B5c, 4000 Liège 1 (Sart-Tilman), Belgium
18 Apache Point Observatory PO Box 59, Sunspot, NM 88349, USA
19 Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
20 Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
21 Observatoire de la Côte d’Azur, Laboratoire Lagrange, CNRS UMR 7923, BP 4229, 06304 Nice Cedex, France
Received: 21 July 2016
Accepted: 19 December 2016
Using combined asteroseismic and spectroscopic observations of 418 red-giant stars close to the Galactic disc plane (6 kpc < RGal ≲ 13 kpc, | ZGal| < 0.3 kpc), we measure the age dependence of the radial metallicity distribution in the Milky Way’s thin disc over cosmic time. The slope of the radial iron gradient of the young red-giant population (−0.058 ± 0.008 [stat.] ±0.003 [syst.] dex/kpc) is consistent with recent Cepheid measurements. For stellar populations with ages of 1−4 Gyr the gradient is slightly steeper, at a value of −0.066 ± 0.007 ± 0.002 dex/kpc, and then flattens again to reach a value of ~−0.03 dex/kpc for stars with ages between 6 and 10 Gyr. Our results are in good agreement with a state-of-the-art chemo-dynamical Milky-Way model in which the evolution of the abundance gradient and its scatter can be entirely explained by a non-varying negative metallicity gradient in the interstellar medium, together with stellar radial heating and migration. We also offer an explanation for why intermediate-age open clusters in the solar neighbourhood can be more metal-rich, and why their radial metallicity gradient seems to be much steeper than that of the youngest clusters. Already within 2 Gyr, radial mixing can bring metal-rich clusters from the innermost regions of the disc to Galactocentric radii of 5 to 8 kpc. We suggest that these outward-migrating clusters may be less prone to tidal disruption and therefore steepen the local intermediate-age cluster metallicity gradient. Our scenario also explains why the strong steepening of the local iron gradient with age is not seen in field stars. In the near future, asteroseismic data from the K2 mission will allow for improved statistics and a better coverage of the inner-disc regions, thereby providing tighter constraints on theevolution of the central parts of the Milky Way.
Key words: Galaxy: general / Galaxy: evolution / Galaxy: disk / Galaxy: stellar content / Galaxy: abundances / stars: abundances
© ESO, 2017
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