The tale of the tail - disentangling the high transverse velocity stars in Gaia DR2
The tale of the tail - disentangling the high transverse velocity stars in Gaia DR2
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尾巴的故事 - 解开盖亚 DR2 中的高横向速度恒星
DOI：
10.1093/mnras/staa077
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发表时间：
2020
影响因子：
4.8
通讯作者：
Boeche Corrado
中科院分区：
文献类型：
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作者：
Amarante Joao A. S.;Smith Martin C.;Boeche Corrado
虽然恒星晕仅占银河系恒星总质量的1.1%，但晕星的运动学编码了有关银河系起源和演化的宝贵信息。结果表明，GaiaDR 2中的高横速星在Hertzsprung-Russell（HR）图上显示出双重序列，表明在1 kpc内局部星晕中存在分叉。我们通过更新流行的Besançon/Galaxia模型来拟合这些恒星，将最新的恒星晕观测结果和Schönrich & Binney对厚盘的改进运动学描述结合起来。我们能够获得一个很好的匹配theGaiplane和银河系盘和恒星晕的属性提供新的约束。特别是，我们表明，运动学定义的厚盘的贡献，这种高速尾。我们使用LAMOST DR 5的化学物质进行了更详细的研究，确定了具有厚盘化学物质的逆行恒星群。我们的厚盘运动学模型不能解释这个人口，所以我们得出结论，有可能是一个来自太阳附近的加热或吸积恒星的贡献。我们还研究了这个样本中的动力学子结构，得出的结论是，它们可能是由于共振轨道，而不是吸积人口。最后，我们提供了新的见解的性质的两个序列和它们的关系与过去的吸积事件和原始的银河系盘。
Although the stellar halo accounts for just ∼1 per cent of the total stellar mass of the Milky Way, the kinematics of halo stars encode valuable information about the origins and evolution of our Galaxy. It has been shown that the high transverse velocity stars inGaiaDR2 reveal a double sequence in the Hertzsprung–Russell (HR) diagram, indicating a bifurcation in the local stellar halo within 1 kpc. We fit these stars by updating the popular Besançon/Galaxia model, incorporating the latest observational results for the stellar halo and an improved kinematic description for the thick disc from Schönrich & Binney . We are able to obtain a good match to theGaiadata and provide new constraints on the properties of the Galactic disc and stellar halo. In particular, we show that the kinematically defined thick-disc contribution to this high velocity tail is. We look in greater detail using chemistry from LAMOST DR5, identifying a population of retrograde stars with thick-disc chemistry. Our thick-disc kinematic model cannot account for this population and so we conclude there is likely to be a contribution from heated or accreted stars in the Solar Neighbourhood. We also investigate proposed dynamical substructures in this sample, concluding that they are probably due to resonant orbits rather than accreted populations. Finally, we provide new insights on the nature of the two sequences and their relation with past accretion events and the primordial Galactic disc.