The Metallicity Gradient of the Thick Disk Based on Red Horizontal Branch Stars From SDSS DR8
arXiv:1110.1782 · doi:10.1088/0004-6256/142/6/184
Abstract
Based on SDSS DR8, we have selected a sample of 1728 red horizontal branch stars with |Z|<3 kpc by using a color-metallicity relation and stellar parameters. The sample stars clearly trace a typical thick disk population with peaks at |Z|=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 Besancon Galaxy model. The resulting gradient is -0.12+-0.01 dex/kpc for 0.5 <|Z| <3 kpc. The other method is to linearly fit the data based on stars with 1 <|Z| <3 kpc being the main component of the thick disk. Five subgroups are then selected in different directions in the X-|Z| plane to investigate the difference in the vertical metallicity gradient between the Galactocenter and anti-Galactocenter directions. We found that a vertical gradient o-0.22+-0.07 dex/kpc 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 <|Z| <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.
7 pages, 10 figures, accepted by AJ
References in corpus (3)
Cited by in corpus (26)
- Chemodynamical evolution of the Milky Way disk II: Variations with Galactic radius and height above the disk plane
- Chemical Cartography with APOGEE: Large-scale Mean Metallicity Maps of the Milky Way
- Chemical gradients in the Milky Way from the RAVE data. II. Giant stars
- Local stellar kinematics from RAVE data: III. Radial and Vertical Metallicity Gradients based on Red Clump Stars
- Chemical and Kinematic Properties of the Galactic Disk from the LAMOST and Gaia Sample Stars
- The GALAH survey: properties of the Galactic disk(s) in the solar neighbourhood
- Chemical Cartography with LAMOST and Gaia Reveal Azimuthal and Spiral Structure in the Galactic Disk
- The QUEST RR Lyrae Survey: III. The Low Galactic Latitude Catalogue
- Metallicity Gradients of Thick Disk Dwarf Stars
- An Algorithm for Preferential Selection of Spectroscopic Targets in LEGUE
- Origin of the Metallicity Distribution in the Thick Disc
- The Vertical Metallicity Gradient of the Milky Way Disk: Transitions in [a/Fe] Populations
- Milky Way tomography with the SkyMapper Southern Survey: I: Atmospheric parameters and distances of one million red giants
- Through thick and thin: Structure of the Galactic thick disc from extragalactic surveys
- Vertical and radial metallicity gradients in high latitude galactic fields with SDSS
- Effects of the selection function on metallicity trends in spectroscopic surveys of the Milky Way
- Properties of thick discs formed in clumpy galaxies
- Local Stellar Kinematics from RAVE data - VII. Metallicity Gradients from Red Clump Stars
- Numerical Simulation of a possible origin of the positive radial metallicity gradient of the thick disk
- Multiwavelength Campaign on Mrk 509 X. Lower limit on the distance of the absorber from HST COS and STIS spectroscopy
- Red Horizontal Branch stars: an asteroseismic perspective
- Multiwavelength campaign on Mrk 509 IX. The Galactic foreground
- The stellar metallicity distribution of the Milky Way from the BATC survey
- A Spectroscopic Survey of Field Red Horizontal-Branch Stars
- Element abundance analysis of the metal-rich stellar halo and high-velocitythick disk in the galaxy
- Galactic Stellar Populations from Photometric Metallicity Distribution Functions