Galactic archaeology with asteroseismology and spectroscopy: Red giants observed by CoRoT and APOGEE^⋆

¹ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: fanders@aip.de;cristina.chiappini@aip.de
² Laboratório Interinstitucional de e-Astronomia, − LIneA, Rua Gal. José Cristino 77, 20921-400 Rio de Janeiro, Brazil
³ Osservatorio Astronomico di Padova – INAF, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
e-mail: thaise.rodrigues@oapd.inaf.it
⁴ Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio 2, 35122 Padova, Italy
⁵ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
⁶ LESIA, Observatoire de Paris, PSL Research University, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, 92195 Meudon, France
⁷ Institut d’Astrophysique et de Géophysique, Allée du 6 aout, 17 − Bat. B5c, 4000 Liège 1 ( Sart-Tilman), Belgium
⁸ The Ohio State University, Department of Astronomy, 4055 McPherson Laboratory, 140 West 18th Ave., Columbus, OH 43210-1173, USA
⁹ Observatoire de la Côte d’Azur, Laboratoire Lagrange, CNRS UMR 7923, BP 4229, 06304 Nice Cedex, France
¹⁰ Institut d’Astrophysique Spatiale, CNRS, Université Paris XI, 91405 Orsay Cedex, France
¹¹ Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
¹² Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
¹³ Institut für Astronomie, Universität Wien, Türkenschanzstr. 17, Wien, Austria
¹⁴ Laboratoire AIM, CEA/DRF – CNRS – Univ. Paris Diderot – IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette Cedex, France
¹⁵ Space Science Institute, 4750 Walnut Street Suite 205, Boulder CO 80301, USA
¹⁶ Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, 91501-970 Porto Alegre, Brazil
¹⁷ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁸ Observatório Nacional, Rua Gal. José Cristino 77, 20921-400 Rio de Janeiro, Brazil
¹⁹ Instituto de Astrofisica de Canarias, C/ Vía Láctea, s/n, 38205 La Laguna, Tenerife, Spain
²⁰ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
²¹ 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
²² Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106, USA
²³ New Mexico State University, Las Cruces, NM 88003, USA
²⁴ Department of Astronomy, University of Virginia, PO Box 400325, Charlottesville VA 22904-4325, USA
²⁵ ELTE Gothard Astrophysical Observatory, Szent Imre herceg st. 112, 9704 Szombathely, Hungary
²⁶ Department of Astronomy, Indiana University, Bloomington, IN 47405, USA
²⁷ Dept. of Astronomy, University of Michigan, Ann Arbor, MI, 48104, USA
²⁸ Apache Point Observatory, PO Box 59, Sunspot, NM 88349, USA
²⁹ Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park 146 Brownlow Hill Liverpool L3 5RF, UK
³⁰ Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
³¹ Institute for Gravitationand the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
³² Mcdonald Observatory, University of Texas at Austin, HC75 Box 1337-MCD, Fort Davis, TX 79734, USA
³³ Vanderbilt University, Dept. of Physics & Astronomy, VU Station B 1807, Nashville, TN 37235, USA
³⁴ Johns Hopkins University, Dept. of Physics and Astronomy, 3701 San Martin Drive, Baltimore, MD 21210, USA

Received: 17 August 2015
Accepted: 3 August 2016

Abstract

With the advent of the space missions CoRoT and Kepler, it has recently become feasible to determine precise asteroseismic masses and relative ages for large samples of red giant stars. We present the CoRoGEE dataset, obtained from CoRoT light curves for 606 red giants in two fields of the Galactic disc that have been co-observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). We used the Bayesian parameter estimation code PARAM to calculate distances, extinctions, masses, and ages for these stars in a homogeneous analysis, resulting in relative statistical uncertainties of ≲2% in distance, ~4% in radius, ~9% in mass and ~25% in age. We also assessed systematic age uncertainties stemming from different input physics and mass loss. We discuss the correlation between ages and chemical abundance patterns of field stars over a broad radial range of the Milky Way disc (5 kpc <R_Gal< 14 kpc), focussing on the [α/Fe]-[Fe/H]-age plane in five radial bins of the Galactic disc. We find an overall agreement with the expectations of pure chemical-evolution models computed before the present data were available, especially for the outer regions. However, our data also indicate that a significant fraction of stars now observed near and beyond the solar neighbourhood migrated from inner regions. Mock CoRoGEE observations of a chemodynamical Milky Way disc model indicate that the number of high-metallicity stars in the outer disc is too high to be accounted for even by the strong radial mixing present in the model. The mock observations also show that the age distribution of the [α/Fe]-enhanced sequence in the CoRoGEE inner-disc field is much broader than expected from a combination of radial mixing and observational errors. We suggest that a thick-disc/bulge component that formed stars for more than 3 Gyr may account for these discrepancies. Our results are subject to future improvements due to (a) the still low statistics, because our sample had to be sliced into bins of Galactocentric distances and ages; (b) large uncertainties in proper motions (and therefore guiding radii); and (c) corrections to the asteroseismic mass-scaling relation. The situation will improve not only upon the upcoming Gaia data releases, but also with the foreseen increase in the number of stars with both seismic and spectroscopic information.