Metallicity and Kinematics of the Galactic Halo from the LAMOST Sample Stars

作者：Shuai Liu, Cuihua Du, Heidi Jo Newberg, Yuqin Chen, Zhenyu Wu, Jun Ma, Xu Zhou, Zihuang Cao, Yonghui Hou, Yuefei Wang, Yong Zhang · 发表于：The Astrophysical Journal · 年份：2018 · DOI：10.3847/1538-4357/aacf91 · 被引用次数：19 · 研究领域：Stellar, planetary, and galactic studies、Astrophysics and Star Formation Studies、Astronomy and Astrophysical Research

Abstract We study the metallicity distribution and kinematic properties of 4680 A/F/G/K-type giant stars with 5 kpc selected from the LAMOST spectroscopic survey. The metallicity distribution of giant stars with kpc can be described by a three-peak Gaussian model with peaks at [Fe/H] ∼ −0.6 ± 0.1, −1.2 ± 0.3 and −2.0 ± 0.2, corresponding to the ratio of 19%, 74%, and 7%, respectively. The [ α /Fe] is used to associate the three peaks with the thick-disk, inner-halo and outer-halo components of the Galaxy. The metallicity distribution of these giant stars, which is fit with Gaussians corresponding to the three components, show a growing fraction of inner-halo components and declining fraction of the thick-disk components with increasing distance from the Galactic plane. Adopting a galaxy potential model, we also derive the orbital parameters of the sample stars, such as orbit eccentricity and rotation velocity. The peak values of derived orbital eccentricity for stars covering different metallicity regions maintain e ∼ 0.75, independent of height above the plane, within the range 15 kpc. By comparing the MDFs of stars in different rotation velocity intervals, we find that the majority of the retrograde stars are more metal-poor than the prograde stars.