The vertical metallicity gradient of the Milky Way disk: transitions in [α/Fe] populations
- Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, The Australian National University, Acton, ACT 2611 (Australia)
- Department of Astronomy, The Ohio State University, 140 W 18th Ave, Columbus, OH 43210 (United States)
- UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
- Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States)
- National Optical Astronomy Observatory, Tucson, AZ 85737 (United States)
- Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States)
- Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)
- Department of Physics and Astronomy, Vanderbilt University, 6301 Stevenson Center, Nashville, TN 37235 (United States)
- Rudolf-Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, OX1 3NP, Oxford (United Kingdom)
- Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)
- Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
- Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States)
- Apache Point Observatory, Sunspot, NM 88349 (United States)
Using G dwarfs from the Sloan Extension for Galactic Understanding and Exploration (SEGUE) survey, we have determined the vertical metallicity gradient in the Milky Way's disk and examined how this gradient varies for different [α/Fe] subsamples. Our sample contains over 40,000 stars with low-resolution spectroscopy over 144 lines of sight. It also covers a significant disk volume, between ∼0.3 and 1.6 kpc from the Galactic plane, and allows us to examine the disk in situ, whereas previous analyses were more limited in scope. Furthermore, this work does not presuppose a disk structure, whether composed of a single complex population or distinct thin and thick disk components. We employ the SEGUE Stellar Parameter Pipeline to obtain estimates of stellar parameters, [Fe/H], and [α/Fe] and extract multiple volume-complete subsamples of approximately 1000 stars each. Based on SEGUE's target-selection algorithm, we adjust each subsample to determine an unbiased picture of disk chemistry; consequently, each individual star represents the properties of many. The metallicity gradient is –0.243{sub −0.053}{sup +0.039} dex kpc{sup –1} for the entire sample, which we compare to various literature results. This gradient stems from the different [α/Fe] populations inhabiting different ranges of height above the Galactic plane. Each [α/Fe] subsample shows little change in median [Fe/H] with height. If we associate [α/Fe] with age, the negligible gradients of our [α/Fe] subsamples suggest that stars formed in different epochs exhibit comparable vertical structure, implying similar star formation processes and evolution.
- OSTI ID:
- 22365294
- Journal Information:
- Astrophysical Journal, Vol. 791, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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