模拟星系团的径向排列
Radial Alignment in Simulated Clusters
摘要：
在过去几年中，卫星与其暗物质宿主径向对齐的观测证据一直在稳步积累。这种效应在很大范围内都可以看到，从大质量的星系团到星系大小的系统，但基本的物理机制仍然没有建立。为此，我们在高分辨率N体宇宙学模拟中对暗物质子结构的形状和取向进行了详细的分析。我们发现一个强烈的趋势径向对齐的子结构与其主机晕：晕主轴的分布是非常各向异性的，与大多数指向主机的质量质心。一旦亚晕第一次通过宿主的维里半径，排列就会达到峰值，但随后不会被稀释，即使在晕已经通过多达四次的臂间通道之后。这一证据表明，存在一个非常快速的动力学机制作用于这些系统，我们认为，潮汐扭矩在整个轨道是最有可能的候选人。
英文摘要：
Observational evidence for the radial alignment of satellites with their dark matter host has been accumulating steadily in the past few years. The effect is seen over a wide range of scales, from massive clusters of galaxies down to galaxy-sized systems, yet the underlying physical mechanism has still not been established. To this end, we have carried out a detailed analysis of the shapes and orientations of dark matter substructures in high-resolution N-body cosmological simulations. We find a strong tendency for radial alignment of the substructure with its host halo: the distribution of halo major axes is very anisotropic, with the majority pointing towards the center of mass of the host. The alignment peaks once the sub-halo has passed the virial radius of the host for the first time, but is not subsequently diluted, even after the halos have gone through as many as four pericentric passages. This evidence points to the existence of a very rapid dynamical mechanism acting on these systems and we argue that tidal torquing throughout their orbits is the most likely candidate.
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