Existence of the Metal-rich Stellar Halo and High-velocity Thick Disk in the Galaxy
Existence of the Metal-rich Stellar Halo and High-velocity Thick Disk in the Galaxy
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DOI：
10.3847/1538-4357/abbd3d
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
Yepeng Yan;C. Du;Hefan Li;Jian-rong Shi;Jun Ma;H. Newberg
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文献类型：
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作者：
Yepeng Yan;C. Du;Hefan Li;Jian-rong Shi;Jun Ma;H. Newberg
基于第二次GAIA数据发布(DR2)，结合LAMOST和远地点光谱测量，我们研究了相对于银河系局部静止标准相对速度至少为220的高速恒星的运动学和金属丰度分布。具有[Fe/H]Dex的高速恒星的自转速度分布可以用双高斯模型很好地描述，峰值分别位于厚盘和晕处。这意味着银河系中应该存在高速厚盘(HVTD)和富金属星晕(MRSH)。HVTD恒星在Toomre图中的位置与晕相同，但其自转速度和金属丰度与正则厚盘相同。MRSH恒星的自转速度、轨道偏心率和在Lindblad和Toomre图中的位置与标准晕星基本相同，但它们的金属含量更高。此外，我们的样本恒星的金属丰度分布函数用四个高斯模型很好地拟合，分别与外晕、内晕、MRSH和HVTD有关。化学和运动学性质以及年龄表明，MRSH和HVTD恒星可能是在原地形成的。
Based on the second Gaia data release (DR2), combined with the LAMOST and APOGEE spectroscopic surveys, we study the kinematics and metallicity distribution of the high-velocity stars that have a relative speed of at least 220 with respect to the local standard of rest in the Galaxy. The rotational velocity distribution of the high-velocity stars with [Fe/H] dex can be well described by a two-Gaussian model, with peaks at and , associated with the thick disk and halo, respectively. This implies that there should exist a high-velocity thick disk (HVTD) and a metal-rich stellar halo (MRSH) in the Galaxy. The HVTD stars have the same position as the halo in the Toomre diagram but show the same rotational velocity and metallicity as the canonical thick disk. The MRSH stars have basically the same rotational velocity, orbital eccentricity, and position in the Lindblad and Toomre diagram as the canonical halo stars, but they are more metal-rich. Furthermore, the metallicity distribution function of our sample stars are well fitted by a four-Gaussian model, associated with the outer halo, inner halo, MRSH, and HVTD, respectively. Chemical and kinematic properties and age imply that the MRSH and HVTD stars may form in situ.