Anisotropy of the Milky Way's Stellar Halo Using K Giants from LAMOST and Gaia
Anisotropy of the Milky Way's Stellar Halo Using K Giants from LAMOST and Gaia
复制标题
使用来自 LAMOST 和盖亚的 K 巨星研究银河系恒星光环的各向异性
DOI：
10.3847/1538-3881/aafd2e
复制
发表时间：
2019-03-01
影响因子：
5.3
通讯作者：
Yang, Chengqun
中科院分区：
文献类型：
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作者：
Bird, Sarah A.;Xue, Xiang-Xiang;Yang, Chengqun
各向异性参数β表征了恒星系统中轨道主要是径向或切向的程度，并可能限制银河系恒星晕的形成和演化。我们测量了来自LAMOST目录的7664颗贫金属（[Fe/H] < -1.3）晕K巨星的β作为银心半径5至100 kpc的函数，其视线速度和距离与第二次盖亚数据发布的自行相匹配。我们为K巨星构造了完整的6D位置和速度，以直接测量速度色散的三个分量（sigma（r），sigma（theta），sigma（phi））（球坐标）。我们发现，在光环的轨道是径向超过我们的整个银河系中心的距离范围达到100千秒差距。各向异性在银心半径约为5-25 kpc时保持显著不变，其幅度取决于恒星的金属丰度，在-1.8 ℃时从β近似下降到0.9。
The anisotropy parameter beta characterizes the extent to which orbits in stellar systems are predominantly radial or tangential and is likely to constrain, for the stellar halo of the Milky Way, scenarios for its formation and evolution. We have measured beta as a function of Galactocentric radius from 5 to 100 kpc for 7664 metal-poor ([Fe/H] < -1.3) halo K giants from the LAMOST catalog with line-of-sight velocities and distances, matched to proper motions from the second Gaia data release. We construct full 6D positions and velocities for the K giants to directly measure the three components of the velocity dispersion (sigma(r), sigma(theta), sigma(phi)) (in spherical coordinates). We find that the orbits in the halo are radial over our full Galactocentric distance range reaching over 100 kpc. The anisotropy remains remarkably unchanged with Galactocentric radius from approximately 5-25 kpc, with an amplitude that depends on the metallicity of the stars, dropping from beta approximate to 0.9 for -1.8