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The chemical evolution of the Galactic thick and thin disks

Published online by Cambridge University Press:  01 June 2008

Cristina Chiappini
Cristina Chiappini*
Affiliation:
Geneva Observatory, Geneva University, 51 Chemin des Mailletes, Sauverny, CH1290, Switzerland, email: Cristina.Chiappini@obs.unige.ch Osservatorio Astronomico di Trieste - INAF, Via G. B. Tiepolo 11, Trieste, Italy
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Abstract

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Recent data have revealed a clear distinction between the abundance patterns of the Milky Way (MW) thick and thin disks, suggesting a different origin for each of these components. In this work we first review the main ideas on the formation of the thin disk. From chemical evolution arguments we show that the thin disk should have formed on a long timescale. We also show clear signs that the local stellar samples are contaminated by stars coming from inner radii. We then check what would have to be changed in such a model in order to explain the observables in the thick disk. We find that a model in which the thick disk forms on a much shorter timescale than thin disk and with a star formation efficiency of around a factor of 10 larger than that in the thin disk can account for the observed abundance ratio shifts of several elements between thick and thin disk stars. Moreover, the lack of scatter in the abundance ratio patterns of both the thick and thin disks suggest both components to have been formed in situ by gas accretion and not by mergers of smaller stellar systems. Especially for the thick disk, this last constraint becomes a strong one if its metallicity distribution extends to, at least, solar. Finally, we briefly discuss the interplay between present deuterium abundance and present infall rates in connection with the thin disk evolution.

Keywords

Galaxy: abundancesGalaxy: diskGalaxy: evolutionstars: abundances
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Issue S254: The Galaxy Disk in Cosmological Context , June 2008 , pp. 191 - 196
Copyright
Copyright © International Astronomical Union 2009

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