期刊
ASTRONOMICAL JOURNAL
卷 141, 期 3, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-6256/141/3/90
关键词
methods: data analysis; stars: abundances; stars: fundamental parameters; surveys; techniques: imaging spectroscopy
资金
- Physics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA)
- U.S. National Science Foundation
- National Science Foundation through the NSF [AST-0802292]
- NSF
- [PHY 02-16783]
- [PHY 08-22648]
- [AST-0607518]
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1009886] Funding Source: National Science Foundation
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 Teff = [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] similar to -2.5; preliminary tests indicate that a metallicity limit as low as [Fe/H] similar to -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 themetallicity range for the method may extend to similar to + 0.5.
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