A first constraint on the thick disk scale length: Differential radial abundances in K giants at galactocentric radii 4, 8, and 12 kpc

T. Bensby*, A. Alves-Brito, M. S. Oey, D. Yong, J. Meléndez

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    164 Citations (Scopus)

    Abstract

    Based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan telescopes, we present detailed elemental abundances for 20 red giant stars in the outer Galactic disk, located at Galactocentric distances between 9 and 13kpc. The outer disk sample is complemented with samples of red giants from the inner Galactic disk and the solar neighborhood, analyzed using identical methods. For Galactocentric distances beyond 10kpc, we only find chemical patterns associated with the local thin disk, even for stars far above the Galactic plane. Our results show that the relative densities of the thick and thin disks are dramatically different from the solar neighborhood, and we therefore suggest that the radial scale length of the thick disk is much shorter than that of the thin disk. We make a first estimate of the thick disk scale length of L thick = 2.0kpc, assuming L thin = 3.8kpc for the thin disk. We suggest that radial migration may explain the lack of radial age, metallicity, and abundance gradients in the thick disk, possibly also explaining the link between the thick disk and the metal-poor bulge.

    Original languageEnglish
    Article numberL46
    JournalAstrophysical Journal Letters
    Volume735
    Issue number2
    DOIs
    Publication statusPublished - 10 Jul 2011

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