论文标题
使用恒星流测量银河盘的物质密度
Measuring the Matter Density of the Galactic Disk Using Stellar Streams
论文作者
论文摘要
我们提出了一种新的方法，用于通过分析通过或接近银河平面的动态冷恒星流的运动学来确定银河盘的总物质表面密度。该方法依赖于这样的溪流恒星的垂直成分大约恒定的事实，因此它们的垂直位置和垂直速度通过银河磁盘的物质密度相互关联。通过在模拟数据恒星流上测试我们的方法，具有逼真的相空分散和GAIA的不确定性，我们证明它适用于小流到几公斤的距离，并且磁盘的表面密度可以确定为6％的精度。此方法与其他质量测量值互补。特别是，它不依赖于银河磁盘中恒星的任何平衡假设，也可以使表面密度在距离太阳大距离处良好精度测量。这样的测量结果将为我们提供了银河磁盘的物质组成及其空间变化，对深色磁盘子结构的限制更强，甚至诊断出可能的非平衡效应，从而使其他类型的动态质量测量偏见。
We present a novel method for determining the total matter surface density of the Galactic disk by analysing the kinematics of a dynamically cold stellar stream that passes through or close to the Galactic plane. The method relies on the fact that the vertical component of energy for such stream stars is approximately constant, such that their vertical positions and vertical velocities are interrelated via the matter density of the Galactic disk. By testing our method on mock data stellar streams, with realistic phase-space dispersions and Gaia uncertainties, we demonstrate that it is applicable to small streams out to a distance of a few kilo-parsec, and that the surface density of the disk can be determined to a precision of 6 %. This method is complementary to other mass measurements. In particular, it does not rely on any equilibrium assumption for stars in the Galactic disk, and also makes it possible to measure the surface density to good precision at large distances from the Sun. Such measurements would inform us of the matter composition of the Galactic disk and its spatial variation, place stronger constraints on dark disk sub-structure, and even diagnose possible non-equilibrium effects that bias other types of dynamical mass measurements.
