Chemical cartography with apogee: Large-scale mean metallicity maps of the Milky Way disk
- New Mexico State University, Las Cruces, NM 88003 (United States)
- Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)
- Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States)
- Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States)
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)
- Department of Physics and Astronomy and JINA, Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI 48824 (United States)
- Observatório Nacional, São Cristóvão, Rio de Janeiro (Brazil)
- Texas Christian University, Fort Worth, TX 76129 (United States)
- Osservatorio Astronomico di Padova-INAF, Vicolo dell'Osservatorio 5, I-35122 Padova (Italy)
- Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
- Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
- Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 ILD (United Kingdom)
- Research School of Astronomy and Astrophysics, Australian National University, Mt. Stromlo Observatory, Cotter Road, Weston, ACT 2611 (Australia)
- Laboratório Interinstitucional de e-Astronomia-LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400 (Brazil)
- Observatoire de la Cote d'Azur, Boulevard de l'Observatoire, B.P. 4229, F-06304 NICE Cedex 4 (France)
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 < |z| < 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-[α/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-[α/M] stars. At R > 6 kpc, the gradient flattens as one moves off the plane, and is flatter at all heights for high-[α/M] stars than for low-[α/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-[α/M] populations. Stars with higher [α/M] appear to have a flatter radial gradient than stars with lower [α/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.
- OSTI ID:
- 22340256
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 147, Issue 5; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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