A FIRST CONSTRAINT ON THE THICK DISK SCALE LENGTH: DIFFERENTIAL RADIAL ABUNDANCES IN K GIANTS AT GALACTOCENTRIC RADII 4, 8, AND 12 kpc
- Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-221 00 Lund (Sweden)
- Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Santiago (Chile)
- Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1042 (United States)
- Research School of Astronomy and Astrophysics, Australian National University, Weston, ACT 2611 (Australia)
- Departamento de Astronomia do IAG/USP, Universidade de Sao Paulo, Rua do Matao 1226, Sao Paulo, 05508-900 SP (Brazil)
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 13 kpc. 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 10 kpc, 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{sub thick} = 2.0 kpc, assuming L{sub thin} = 3.8 kpc 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.
- OSTI ID:
- 21562550
- Journal Information:
- Astrophysical Journal Letters, Vol. 735, Issue 2; Other Information: DOI: 10.1088/2041-8205/735/2/L46; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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