论文标题
银河系的边缘
The Edge of the Galaxy
论文作者
论文摘要
我们使用孤立的银河系质量星系以及本地组类似物的宇宙学模拟来定义“边缘”（一种苛性速度，体现在密度或径向速度下降的 - 在暗物质和恒星中。在深色物质中，我们通常识别两种苛性碱：最外面的苛性速度位于〜1.4R_200m，对应于“飞溅”半径，第二个苛性速度位于〜0.6R_200m的第二个苛性碱，可能对应于至少两次可折叠通道的病毒化材料的边缘。飞溅半径在本地组类型环境中定义不明，其中两个星系的光环重叠。但是，第二个苛性碱受到同伴的存在的影响较小，并且是银河系光环的边界的更有用的定义。奇怪的是，恒星分布还具有明确定义的苛性碱，在大多数情况下，这种苛性剂与暗物质的第二个苛性碱相吻合。这可以在径向密度和径向速度曲线中识别，并且应该在未来的观察程序中进行测量。最后，我们表明，在本地组矮星系的相位空间分布中也可以识别第二个苛性碱。使用当前的矮星系种群，我们预测银河系光环的边缘为292 +/- 61 kpc。
We use cosmological simulations of isolated Milky Way-mass galaxies, as well as Local Group analogues, to define the "edge" -- a caustic manifested in a drop in density or radial velocity -- of Galactic-sized haloes, both in dark matter and in stars. In the dark matter, we typically identify two caustics: the outermost caustic located at ~1.4r_200m corresponding to the "splashback" radius, and a second caustic located at ~0.6r_200m which likely corresponds to the edge of the virialized material which has completed at least two pericentric passages. The splashback radius is ill defined in Local Group type environments where the halos of the two galaxies overlap. However, the second caustic is less affected by the presence of a companion, and is a more useful definition for the boundary of the Milky Way halo. Curiously, the stellar distribution also has a clearly defined caustic, which, in most cases, coincides with the second caustic of the dark matter. This can be identified in both radial density and radial velocity profiles, and should be measurable in future observational programmes. Finally, we show that the second caustic can also be identified in the phase-space distribution of dwarf galaxies in the Local Group. Using the current dwarf galaxy population, we predict the edge of the Milky Way halo to be 292 +/- 61 kpc.
