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Confirming chemical clocks: asteroseismic age dissection of the Milky Way disk(s)

Aguirre, VS, Bojsen-Hansen, M, Slumstrup, D, Casagrande, L, Kawata, D, Ciuca, I, Handberg, R, Lund, MN, Mosumgaard, JR, Huber, D, Johnson, JA, Pinsonneault, MH, Serenelli, AM, Stello, D, Tayar, J, Bird, JC, Cassisi, S, Hon, M, Martig, M, Nissen, PE , Rix, HW, Schönrich, R, Sahlholdt, C, Trick, WH and Yu, J (2018) Confirming chemical clocks: asteroseismic age dissection of the Milky Way disk(s). Monthly Notices of the Royal Astronomical Society. ISSN 0035-8711

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Abstract

Investigations of the origin and evolution of the Milky Way disk have long relied on chemical and kinematic identification of its components to reconstruct our Galactic past. Difficulties in determining precise stellar ages have restricted most studies to small samples, normally confined to the solar neighbourhood. Here we break this impasse with the help of asteroseismic inference and perform a chronology of the evolution of the disk throughout the age of the Galaxy. We chemically dissect the Milky Way disk population using a sample of red giant stars spanning out to 2~kpc in the solar annulus observed by the {\it Kepler} satellite, with the added dimension of asteroseismic ages. Our results reveal a clear difference in age between the low- and high-$\alpha$ populations, which also show distinct velocity dispersions in the $V$ and $W$ components. We find no tight correlation between age and metallicity nor [$\alpha$/Fe] for the high-$\alpha$ disk stars. Our results indicate that this component formed over a period of more than 2~Gyr with a wide range of [M/H] and [$\alpha$/Fe] independent of time. Our findings show that the kinematic properties of young $\alpha$-rich stars are consistent with the rest of the high-$\alpha$ population and different from the low-$\alpha$ stars of similar age, rendering support to their origin being old stars that went through a mass transfer or stellar merger event, making them appear younger, instead of migration of truly young stars formed close to the Galactic bar.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record V Silva Aguirre, M Bojsen-Hansen, D Slumstrup, L Casagrande, D Kawata, I Ciucá, R Handberg, M N Lund, J R Mosumgaard, D Huber, J A Johnson, M H Pinsonneault, A M Serenelli, D Stello, J Tayar, J C Bird, S Cassisi, M Hon, M Martig, P E Nissen, H W Rix, R Schönrich, C Sahlholdt, W H Trick, J Yu; Confirming chemical clocks: asteroseismic age dissection of the Milky Way disk(s), Monthly Notices of the Royal Astronomical Society, , sty150, is available online at: https://doi.org/10.1093/mnras/sty150
Uncontrolled Keywords: astro-ph.GA; astro-ph.GA; astro-ph.SR
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 25 Jan 2018 10:27
Last Modified: 25 Jan 2018 10:27
DOI or Identification number: 10.1093/mnras/sty150
URI: http://researchonline.ljmu.ac.uk/id/eprint/7893

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