THE SEGUE STELLAR PARAMETER PIPELINE. V. ESTIMATION OF ALPHA-ELEMENT ABUNDANCE RATIOS FROM LOW-RESOLUTION SDSS/SEGUE STELLAR SPECTRA
- Department of Physics and Astronomy and JINA (Joint Institute for Nuclear Astrophysics), Michigan State University, East Lansing, MI 48824 (United States)
- Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)
- UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
- Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States)
- Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States)
- Department of Science Education, Ewha Womans University, Seoul 120-750 (Korea, Republic of)
- Indian Institute of Astrophysics, 2nd block Koramangala, Bangalore 560034 (India)
- Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)
We present a method for the determination of [{alpha}/Fe] ratios from low-resolution (R = 2000) SDSS/SEGUE stellar spectra. By means of a star-by-star comparison with degraded spectra from the ELODIE spectral library and with a set of moderately high-resolution (R = 15, 000) and medium-resolution (R = 6000) spectra of SDSS/SEGUE stars, we demonstrate that we are able to measure [{alpha}/Fe] from SDSS/SEGUE spectra (with S/N>20/1) to a precision of better than 0.1 dex, for stars with atmospheric parameters in the range T{sub eff} = [4500, 7000] K, log g = [1.5, 5.0], and [Fe/H] = [-1.4, +0.3], over the range [{alpha}/Fe] = [-0.1, +0.6]. For stars with [Fe/H] <-1.4, our method requires spectra with slightly higher signal-to-noise to achieve this precision (S/N>25/1). Over the full temperature range considered, the lowest metallicity star for which a confident estimate of [{alpha}/Fe] can be obtained from our approach is [Fe/H] {approx}-2.5; preliminary tests indicate that a metallicity limit as low as [Fe/H] {approx}-3.0 may apply to cooler stars. As a further validation of this approach, weighted averages of [{alpha}/Fe] obtained for SEGUE spectra of likely member stars of Galactic globular clusters (M15, M13, and M71) and open clusters (NGC 2420, M67, and NGC 6791) exhibit good agreement with the values of [{alpha}/Fe] from previous studies. The results of the comparison with NGC 6791 imply that the metallicity range for the method may extend to {approx}+0.5.
- OSTI ID:
- 21583204
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 141, Issue 3; Other Information: DOI: 10.1088/0004-6256/141/3/90; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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