Journal
ASTRONOMICAL JOURNAL
Volume 147, Issue 5, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/0004-6256/147/5/116
Keywords
Galaxy: abundances; Galaxy: disk; Galaxy: stellar content; Galaxy: structure
Categories
Funding
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy Office of Science
- University of Arizona
- Brazilian Participation Group
- Brookhaven National Laboratory
- Carnegie Mellon University
- University of Florida
- French Participation Group
- German Participation Group
- Harvard University
- Michigan State/Notre Dame/JINA Participation Group
- Johns Hopkins University
- Lawrence Berkeley National Laboratory
- Max Planck Institute for Astrophysics
- Max Planck Institute for Extraterrestrial Physics
- New Mexico State University
- New York University
- Ohio State University
- Pennsylvania State University
- University of Portsmouth
- Princeton University
- Spanish Participation Group
- University of Tokyo
- University of Utah
- Vanderbilt University
- University of Virginia
- University of Washington
- Yale University
- National Science Foundation [AST-1109178, AST-0907873]
- NASA through Hubble Fellowship from the Space Telescope Science Institute [HST-HF-51285.01]
- NASA [NAS5-26555]
- NSF Astronomy and Astrophysics Postdoctoral Fellowship [AST-1203017]
- Physics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA) [PHY 08-22648]
- US National Science Foundation
- Instituto de Astrofisica de Canarias
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1109888] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1109178] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Physics [1430152] Funding Source: National Science Foundation
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We present Galactic mean metallicity maps derived from the first year of the SDSS-III APOGEE experiment. Mean abundances in different zones of projected Galactocentric radius (0 < R < 15 kpc) at a range of heights above the plane (0 < vertical bar z vertical bar < 3 kpc), are derived from a sample of nearly 20,000 giant stars with unprecedented coverage, including stars in the Galactic mid-plane at large distances. We also split the sample into subsamples of stars with low- and high-[alpha/M] abundance ratios. We assess possible biases in deriving the mean abundances, and find that they are likely to be small except in the inner regions of the Galaxy. A negative radial metallicity gradient exists over much of the Galaxy; however, the gradient appears to flatten for R < 6 kpc, in particular near the Galactic mid-plane and for low-[alpha/M] stars. At R > 6 kpc, the gradient flattens as one moves off the plane, and is flatter at all heights for high-[alpha/M] stars than for low-[alpha/M] stars. Alternatively, these gradients can be described as vertical gradients that flatten at larger Galactocentric radius; these vertical gradients are similar for both low- and high-[alpha/M] populations. Stars with higher [alpha/M] appear to have a flatter radial gradient than stars with lower [alpha/M]. This could suggest that the metallicity gradient has grown steeper with time or, alternatively, that gradients are washed out over time by migration of stars.
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