论文标题
Gaia-Sausage-cenceladus对Lamost调查中光环K巨人揭示的银河恒星光环密度形状的影响
Influence of the Gaia-Sausage-Enceladus on the density shape of the Galactic stellar halo revealed by halo K giants from the LAMOST survey
论文作者
论文摘要
我们介绍了Gaia-Sausage-cenceladus（GSE）对Lamost调查中11624 K巨人的银河恒星光环密度形状的影响的研究。每个恒星都根据高斯混合模型，根据其球形速度和金属性，将其分配为GSE成员。我们通过获得的概率将恒星光环划分为两个部分，其中一个由GSE成员组成并定义为与GSE相关的光环，另一个被称为GSE-halo。使用非参数方法，单个功率定律可以很好地描述两个恒星光环的径向数密度曲线，并具有可变的变平$ q $（$ r = \ sqrt {r^2+[（z/q（r）^2}，^2}，^2}，n n = = {ν_0} r^r^r^{ - α} $）。与GSE相关的光环的索引$α$为$ 4.92 \ pm0.12 $，GSE-emem emep halo的指数为$ 4.25 \ pm0.14 $。这两个恒星光环在较小的半径上垂直扁平，但在较大的半径上变得更加球形。我们发现，与GSE相关的光环的垂直平坦程度不如GSE-empered Halo，并且两个恒星光环范围为0.07至0.15之间的$ Q $差异。但是，在考虑偏差之后，被认为在大多数半径内都在0.08之内。最后，我们将结果与两个银河系类似物进行了比较，它们在TNG50模拟中经历了重大合并。对这两个类似物的研究还表明，与主要合并的恒星光环相比，与主要合并相关的恒星光环的椭圆度小。
We present a study of the influence of the Gaia-Sausage-Enceladus (GSE) on the density shape of the Galactic stellar halo using 11624 K giants from the LAMOST survey. Every star is assigned a probability of being a member of the GSE based on its spherical velocities and metallicity by a Gaussian Mixture Model. We divide the stellar halo into two parts by the obtained probabilities, of which one is composed of the GSE members and defined as the GSE-related halo, and the other one is referred to as the GSE-removed halo. Using a non-parametric method, the radial number density profiles of the two stellar halos can be well described by a single power law with a variable flattening $q$ ($r = \sqrt{R^2+[(Z/q(r))]^2}, ν= {ν_0}r^{-α}$). The index $α$ is $4.92\pm0.12$ for the GSE-related halo and $4.25\pm0.14$ for the GSE-removed halo. Both the two stellar halos are vertically flattened at smaller radii but become more spherical at larger radii. We find that the GSE-related halo is less vertically flattened than the GSE-removed halo, and the difference of $q$ between the two stellar halos ranges from 0.07 to 0.15. However, after the consideration of the bias, it is thought to be within 0.08 at most of the radii. Finally, we compare our results with two Milky Way analogues which experience a significant major merger in the TNG50 simulation. The study of the two analogues also shows that the major merger-related stellar halo has a smaller ellipticity than the major merger-removed stellar halo.
