期刊
ASTROPHYSICAL JOURNAL
卷 738, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/738/2/187
关键词
Galaxy: disk; Galaxy: formation; Galaxy: kinematics and dynamics; Galaxy: structure
资金
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- U.S. National Science Foundation [PHY 02-16783, PHY 08-22648]
- NSF [AST-0607482, AST 06-15991, AST-07 07901, AST 05-51161, AST-1009886]
- DFG [SFB 881]
- Max-Planck-Gesellschaft
- Ewha Womans University
- National Research Foundation of Korea
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1009886] Funding Source: National Science Foundation
- National Research Foundation of Korea [2010-0029387] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
We employ measurements of the [alpha/Fe] ratio derived from low-resolution (R similar to 2000) spectra of 17,277 G-type dwarfs from the SEGUE survey to separate them into likely thin-and thick-disk subsamples. Both subsamples exhibit strong gradients of orbital rotational velocity with metallicity, of opposite signs, -20 to -30 km s(-1) dex(-1) for the thin-disk and + 40 to + 50 km s(-1) dex(-1) for the thick-disk population. The rotational velocity is uncorrelated with Galactocentric distance for the thin-disk subsample and exhibits a small trend for the thick-disk subsample. The rotational velocity decreases with distance from the plane for both disk components, with similar slopes (-9.0 +/- 1.0 km s(-1) kpc(-1)). Thick-disk stars exhibit a strong trend of orbital eccentricity with metallicity (about -0.2 dex(-1)), while the eccentricity does not change with metallicity for the thin-disk subsample. The eccentricity is almost independent of Galactocentric radius for the thin-disk population, while a marginal gradient of the eccentricity with radius exists for the thick-disk population. Both subsamples possess similar positive gradients of eccentricity with distance from the Galactic plane. The shapes of the eccentricity distributions for the thin-and thick-disk populations are independent of distance from the plane, and include no significant numbers of stars with eccentricity above 0.6. Among several contemporary models of disk evolution that we consider, radial migration appears to have played an important role in the evolution of the thin-disk population, but possibly less so for the thick disk, relative to the gas-rich merger or disk heating scenarios. We emphasize that more physically realistic models and simulations need to be constructed in order to carry out the detailed quantitative comparisons that our new data enable.
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