不规则边缘的光晕：回溅半径的重要性
Haloes at the ragged edge: The importance of the splashback radius
摘要：
我们已经探索了暗物质晕的外围维里半径的2.5倍，使用的大样本晕从Illustris绘制，随着一组变焦模拟（MUGS）。在此基础上，对R $_{vir}$以外的形状轮廓进行了系统的探索.在Illustris晕的平均球度分布中，我们确定了接近维里半径的倾角，这在广泛的质量和下降率范围内是稳健的。该特征的内边缘可以与维里半径相关，并且外边缘与回溅半径相关。由于光环之间的差异很大，因此该结果仅在平均值上可见。然而，在四个单独的晕在MUGS样品中，球度的减少和随后的恢复是明显的接近回溅半径。我们发现，这个功能持续了几个陀螺仪，增长的光环。这一特征出现在球形晕密度分布与环境中的沉积结构之间的界面处。形状特征是最强的，当有一个高的速度下降，这意味着效果是由于混合的吸积和virializing材料。在维里半径内的晕区中，惯性速度场变得迅速混合，在这与回溅半径之间的区域作为过渡区。我们还确定了一个长期的和顺利发展的回溅区域的径向密度梯度在许多的MUGS晕。
英文摘要：
We have explored the outskirts of dark matter haloes out to 2.5 times the virial radius using a large sample of halos drawn from Illustris, along with a set of zoom simulations (MUGS). Using these, we make a systematic exploration of the shape profile beyond R$_{vir}$. In the mean sphericity profile of Illustris halos we identify a dip close to the virial radius, which is robust across a broad range of masses and infall rates. The inner edge of this feature may be related to the virial radius and the outer edge with the splashback radius. Due to the high halo-to-halo variation this result is visible only on average. However, in four individual halos in the MUGS sample, a decrease in the sphericity and a subsequent recovery is evident close to the splashback radius. We find that this feature persists for several Gyr, growing with the halo. This feature appears at the interface between the spherical halo density distribution and the filamentary structure in the environment. The shape feature is strongest when there is a high rate of infall, implying that the effect is due to the mixing of accreting and virializing material. The filamentary velocity field becomes rapidly mixed in the halo region inside the virial radius, with the area between this and the splashback radius serving as the transition region. We also identify a long-lasting and smoothly evolving splashback region in the radial density gradient in many of the MUGS halos.
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