Differential Rotation of the Halo Traced by K-giant Stars
Differential Rotation of the Halo Traced by K-giant Stars
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K巨星追踪的光环的差分旋转
DOI：
10.3847/1538-4357/aba1ec
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发表时间：
2020-07
影响因子：
4.9
通讯作者：
Xue Xiang-Xiang
中科院分区：
文献类型：
--
作者：
Tian Hao;Liu Chao;Wang Yougang;Xu Yan;Yang Chengqun;Zhang Bo;Xue Xiang-Xiang
我们利用LAMOST DR5中选取的k巨星，研究了银晕在不同空间位置上的旋转速度变化。对光晕和盘的旋转速度分布进行建模，我们发现在固定的星系中心半径r下，随着与银盘平面Z的垂直距离的增加，晕群的旋转速度几乎呈线性下降。我们得出两个子样本沿Z轴的衰减率分别为- 3.07±0.63和- 1.89±0.37 km s - 1 kpc - 1。通过与TNG模拟的比较，我们认为这种趋势是由圆盘和光晕之间的相互作用引起的。模拟结果表明，只有扁晕的旋转速度随z的增加而减小，这表明银晕是扁的，其星系中心半径是扁的。另一方面，本研究清楚地追踪了圆盘组件（主要是厚盘）的耀斑；当R在12 ~ 20kpc之间时，磁盘可以垂直延伸到磁盘平面上方。更有趣的是，我们发现盖亚-恩克拉多斯-香肠组分仅在光环中有显著的贡献，即23%-47%的分数，而在外部子样本中，贡献太低，无法很好地约束。
We use K-giant stars selected from the LAMOST DR5 to study the variation of the rotational velocity of the Galactic halo at different space positions. Modeling the rotational velocity distribution with both the halo and disk components, we find that the rotational velocity of the halo population decreases almost linearly with increasing vertical distance to the Galactic disk plane, Z, at fixed galactocentric radius, R. The samples are separated into two parts with and . We derive that the decreasing rates along Z for the two subsamples are −3.07 ± 0.63 and −1.89 ± 0.37 km s−1 kpc−1, respectively. Comparing with the TNG simulations, we suggest that this trend is caused by the interaction between the disk and halo. The results from the simulations show that only an oblate halo can provide a decreasing rotational velocity with increasing Z. This indicates that the Galactic halo is oblate with galactocentric radius . On the other hand, the flaring of the disk component (mainly the thick disk) is clearly traced by this study; with R between 12 and 20 kpc, the disk can vertically extend to above the disk plane. What is more interesting is that we find the Gaia–Enceladus–Sausage component has a significant contribution only in the halo with , i.e., a fraction of 23%–47%, while in the outer subsample, the contribution is too low to be well constrained.
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影响因子：
4.8
作者：
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通讯作者：
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影响因子：
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作者：
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影响因子：
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作者：
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DOI：
10.1051/0004-6361/201425455
发表时间：
2015-03
期刊：
arXiv: Solar and Stellar Astrophysics
影响因子：
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作者：
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通讯作者：
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影响因子：
4.8
作者：
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通讯作者：
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