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THE METALLICITY GRADIENT OF THE THICK DISK BASED ON RED HORIZONTAL-BRANCH STARS FROM SDSS DR8
Chen, Y. Q.; Zhao, G.; Carrell, K.; Zhao, J. K.
2011-12-01
Source PublicationASTRONOMICAL JOURNAL
Volume142Issue:6
AbstractBased on SDSS DR8, we have selected a sample of 1728 red horizontal-branch (RHB) stars with vertical bar Z vertical bar < 3 kpc by using a color-metallicity relation and stellar parameters. The sample stars clearly trace a typical thick disk population with peaks at vertical bar Z vertical bar = 1.26 kpc and [Fe/H] = -0.54. The vertical metallicity gradient of the thick disk is estimated in two ways. One is a fit to the Gaussian peaks of the metallicity histograms of the thick disk by subtracting minor contributions from the thin disk and the inner halo based on the Besan, con Galaxy Model. The resulting gradient is -0.12 +/- 0.01 dex kpc(-1) for 0.5 < vertical bar Z vertical bar < 3 kpc. The other method is to linearly fit the data based on stars with 1 < vertical bar Z vertical bar < 3 kpc being the main component of the thick disk. Five subgroups are then selected in different directions in the X-vertical bar Z vertical bar plane to investigate the difference in the vertical metallicity gradient between the Galactocenter and anti-Galactocenter directions. We found that a vertical gradient of -0.22 +/- 0.07 dex kpc(-1) is detected for five directions except for one involving the pollution of stars from the bulge. The results indicate that the vertical gradient is dominant, but a radial gradient has a minor contribution for the thick disk population represented by RHB stars with 1 < vertical bar Z vertical bar < 3 kpc. The present work strongly suggests the existence of a metallicity gradient in the thick disk, which is thought to be negligible in most previous works in the literature.
KeywordGalaxy: Disk Galaxy: Kinematics And Dynamics Galaxy: Structure Stars: Horizontal-branch Stars: Late-type
DOI10.1088/0004-6256/142/6/184
Indexed BySCI
Language英语
WOS IDWOS:000297254500006
Citation statistics
Document Type期刊论文
Identifierhttp://ir.bao.ac.cn/handle/114a11/8010
Collection光学天文研究部
AffiliationChinese Acad Sci, Key Lab Opt Astron, Natl Astron Observ, Beijing 100012, Peoples R China
Recommended Citation
GB/T 7714
Chen, Y. Q.,Zhao, G.,Carrell, K.,et al. THE METALLICITY GRADIENT OF THE THICK DISK BASED ON RED HORIZONTAL-BRANCH STARS FROM SDSS DR8[J]. ASTRONOMICAL JOURNAL,2011,142(6).
APA Chen, Y. Q.,Zhao, G.,Carrell, K.,&Zhao, J. K..(2011).THE METALLICITY GRADIENT OF THE THICK DISK BASED ON RED HORIZONTAL-BRANCH STARS FROM SDSS DR8.ASTRONOMICAL JOURNAL,142(6).
MLA Chen, Y. Q.,et al."THE METALLICITY GRADIENT OF THE THICK DISK BASED ON RED HORIZONTAL-BRANCH STARS FROM SDSS DR8".ASTRONOMICAL JOURNAL 142.6(2011).
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