论文标题
用Gaia数据释放2探测银河系中的轴向对称性破裂2
Probing Axial Symmetry Breaking in the Galaxy with Gaia Data Release 2
论文作者
论文摘要
我们研究了Gaia Data Release 2中的一组太阳能社区（$ d <3 $ kpc）的星星，以确定方位角恒星计数差异，即从银河中心到太阳的线的左右和右差异 - 并比较北方和南方的这些差异。在这份伴侣论文中，Gardner等人。 （2020年），我们描述了从采样效果，不完整和/或Interloper种群中删除错误不对称的程序，因为这对于轴对称的测试至关重要。特别是，我们已经小心翼翼地选择了适当的幅度，颜色，面式的半乳化半径和银河$ | b | $和$ | z | $。我们发现，需要高精度的视差确定会引起采样偏见，因此我们避免了这种要求并排除在外，例如，视线周围的区域与麦哲伦云的视线以及其镜像的视线线，以确保匹配良好的数据集。在进行保守的削减之后，我们证明了方位角不对称的存在，并在北方和南部发现了差异。这些不对称性给出了对银河系扰动的性质和起源的关键见解，从而使我们能够评估麦哲伦云（LMC＆SMC），银河棒和其他质量对银河质量分布的相对影响，如Gardner等人所述。 （2020）。不对称的径向依赖性揭示了我们归因于银河条的变化，并且它以$（0.95 \ pm 0.03）R_0 $的半径更改符号，其中$ r_0 $ r_0 $ the Sun-galactic-Center（GC）距离，以使我们对外部Lindblad Resonant Resonant Readant Radius进行了首次直接评估。
We study a set of solar neighborhood ($d < 3$ kpc) stars from Gaia Data Release 2 to determine azimuthal star count differences, i.e., left and right of the line from the Galactic center through the sun - and compare these differences north and south. In this companion paper to Gardner et al. (2020), we delineate our procedures to remove false asymmetries from sampling effects, incompleteness, and/or interloper populations, as this is crucial to tests of axisymmetry. Particularly, we have taken care to make appropriate selections of magnitude, color, in-plane Galactocentric radius and Galactic $|b|$ and $|z|$. We find that requiring parallax determinations of high precision induces sampling biases, so that we eschew such requirements and exclude, e.g., regions around the lines of sight to the Magellanic clouds, along with their mirror-image lines of sight, to ensure well-matched data sets. After making conservative cuts, we demonstrate the existence of azimuthal asymmetries, and find differences in those, north and south. These asymmetries give key insights into the nature and origins of the perturbations on Galactic matter, allowing us to assess the relative influence of the Magellanic Clouds (LMC & SMC), the Galactic bar, and other masses on the Galactic mass distribution, as described in Gardner et al. (2020). The asymmetry's radial dependence reveals variations that we attribute to the Galactic bar, and it changes sign at a radius of $(0.95 \pm 0.03) R_0$, with $R_0$ the Sun-Galactic-Center (GC) distance, to give us the first direct assessment of the outer Lindblad resonant radius.
