论文标题
降低的适当运动选定的光环：目录的方法和描述
The Reduced Proper Motion selected halo: methods and description of the catalogue
论文作者
论文摘要
盖亚任务提供了有史以来最大的银河系图表。使用它来绘制银河系光环有助于解开其合并历史记录。具有可靠距离估计的Gaia DR2中光晕恒星的鉴定需要特殊的方法，因为这些恒星通常距离较远且稀缺。我们应用了降低的运动（RPM）方法，以基于GAIA光度法和适当的运动来识别光环主序列星。使用这种类型的恒星的颜色 - 吸收量的关系，我们计算了光度距离。我们的选择导致一组$ \ sim10^7 $暂定的主序列光环恒星，典型的距离不确定性为$ 7 \％$，中位速度误差为20 km/s。我们样本的中间距离为$ \ sim 4.4 $ kpc，最微弱的星星位于$ \ sim 16 $ kpc。我们样品中恒星的空间分布是集中浓缩的。对天空中恒星平均速度的目视检查显示出大规模的图案以及GD-1流的清晰烙印以及Jhelum和Leiptr流的暂定暗示。不完整和选择效果限制了我们可靠地解释模式以及识别新子结构的能力。我们通过将样品恒星的视线速度设置为零来定义伪速度空间。在这个空间中，我们恢复了几个已知的结构，例如Gaia-ceceladus（即Gaia-sausage）的足迹以及Helmi流和其他一些逆行子结构（红杉，Thamnos）。我们表明，两点速度相关函数揭示了小于100 km/s的尺度上的明显聚类，其幅度与6D Gaia Halo样品相似。这种聚类表明附近的溪流的存在主要是相结合的。
The Gaia mission has provided the largest ever astrometric chart of the Milky Way. Using it to map the Galactic halo is helpful for disentangling its merger history. The identification of halo stars in Gaia DR2 with reliable distance estimates requires special methods because such stars are typically farther away and scarce. We apply the reduced proper motion (RPM) method to identify halo main sequence stars on the basis of Gaia photometry and proper motions. Using the colour-absolute-magnitude relation for this type of stars, we calculate photometric distances. Our selection results in a set of $\sim10^7$ tentative main sequence halo stars with typical distance uncertainties of $7\%$ and with median velocity errors of 20 km/s. The median distance of our sample is $\sim 4.4$ kpc, with the faintest stars located at $\sim 16$ kpc. The spatial distribution of the stars in our sample is centrally concentrated. Visual inspection of the mean velocities of stars on the sky reveals large-scale patterns as well as clear imprints of the GD-1 stream and tentative hints of the Jhelum and Leiptr streams. Incompleteness and selection effects limit our ability to interpret the patterns reliably as well as to identify new substructures. We define a pseudo-velocity space by setting to zero the line-of-sight velocities of our sample stars. In this space, we recover several known structures such as the footprint of Gaia-Enceladus (i.e. the Gaia-Sausage) as well as the Helmi streams and some other retrograde substructures (Sequoia, Thamnos). We show that the two-point velocity correlation function reveals significant clustering on scales smaller than 100 km/s, of similar amplitude as found for the 6D Gaia halo sample. This clustering indicates the presence of nearby streams that are predominantly phase-mixed.
