METALLICITY AND KINEMATIC DISTRIBUTIONS OF RED HORIZONTAL-BRANCH STARS FROM THE SDSS SURVEY
- Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
On the basis of a recently derived color-metallicity relation and stellar parameters from the Sloan Digital Sky Survey Data Release 7 spectroscopic survey, a large sample of red horizontal-branch (RHB) candidates have been selected to serve as standard candles. The metallicity and kinematic distributions of these stars indicate that they mainly originate from the thick-disk and the halo populations. The typical thick disk is characterized by the first group peaking at [Fe/H] {approx} -0.6, V{sub rot} {approx} 170 km s{sup -1} with a vertical scale height around |Z| {approx} 1.2 kpc, while stars with [Fe/H] < -0.9 are dominated by the halo population. Two sub-populations of the halo are suggested by the RHB stars peaking at [Fe/H] {approx} -1.3: one component with V{sub rot} > 0 km s{sup -1} (Halo I) shows a sign of metallicity gradient in the [Fe/H] versus |Z| diagram, while the other with V{sub rot} < 0 km s{sup -1} (Halo II) does not. The Halo I mainly clumps at the inner halo with R < 10 kpc and the Halo II comes both from the inner halo with R < 10 kpc and the outer halo with R > 10 kpc based on the star distribution in the R versus |Z| diagram.
- OSTI ID:
- 21443267
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 140, Issue 2; Other Information: DOI: 10.1088/0004-6256/140/2/500; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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