THE LICK/SDSS LIBRARY. II. [Ca/Fe] AND [Mg/Fe] IN F, G, AND K STARS FROM SDSS-DR7

被引：10
作者：
Franchini, M. [1 ]
Morossi, C. [1 ]
Di Marcantonio, P. [1 ]
Malagnini, M. L. [1 ,2 ]
Chavez, M. [3 ]
机构：
[1] INAF Osservatorio Astron Trieste, I-34131 Trieste, Italy
[2] Univ Trieste, Dipartimento Fis, Sez Astron, I-34131 Trieste, Italy
[3] Inst Nacl Astrofis Opt & Electr, Puebla 72840, Mexico
来源：
ASTROPHYSICAL JOURNAL | 2011年 / 730卷 / 02期
基金：
美国国家科学基金会; 美国国家航空航天局;
关键词：
Galaxy: stellar content; stars: abundances; stars: fundamental parameters; stars: late-type; ALPHA-ENHANCED STARS; SYNTHETIC LICK INDEXES; DIGITAL SKY SURVEY; ABUNDANCE RATIOS; CHEMICAL EVOLUTION; SOLAR NEIGHBORHOOD; THICK DISK; MILKY-WAY; G-DWARF; SPECTRA;
D O I：
10.1088/0004-637X/730/2/117
中图分类号：
P1 [天文学];
学科分类号：
0704 ;
摘要：
We analyzed the spectra of 17,600 F, G, and K stars extracted from the seventh Sloan Digital Sky Survey Data Release (SDSS-DR7) database in order to derive <[alpha/Fe]>, [Ca/Fe], and [Mg/Fe] ratios. Particular attention has been devoted to estimating homogeneous and self-consistent atmospheric parameter values, T-eff, log g, and [Fe/H], by comparing synthetic and observational Lick/SDSS indices. We present results for the sub-sample of more than 4000 spectra whose overall quality allowed us to derive fairly accurate stellar atmospheric parameter values and, therefore, reliable abundance ratios. A Monte Carlo approach was adopted to evaluate both the errors in the observational Lick/SDSS indices and in the derived parameter estimates. The analysis of the trends of [Ca/Fe] and [Mg/Fe] versus [Fe/H] pointed out that (1) the [Ca/Fe] and [Mg/Fe] ratios increase with decreasing [Fe/H] with different slopes reaching maximum average levels of +0.25 and +0.40 dex at [Fe/H] similar or equal to -1.75, respectively; (2) our sample contains, at a given [Fe/H], stars characterized by significantly different amounts of alpha-enhancement, thus belonging to different Galactic populations; and (3) the analyzed sample shows a predominance of thick disk stars for [Fe/H] > -0.5 and the presence of stars belonging to the "high-alpha" halo population for -2.0 < [Fe/H] < -0.5.
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页数：12
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