It was shown several years ago that dark matter halo outskirts are characterized by very steep density profiles in a very small radial range. This feature has been interpreted as a pile-up of different particle orbits at a similar location, namely, splashback material at half an orbit after collapse. Adhikari et al. (2014) obtained the location of the splashback radius through a very simple model by calculating a dark matter shell trajectory in the secondary infall model while it crosses a growing NFW profile-shaped dark matter halo. Because they imposed a halo profile instead of calculating it from the trajectories of the shells of dark matter, they were not able to find the dark matter profile around the splashback radius. In the present paper, we use an improved spherical infall model taking into account shell crossing as well as several physical effects such as ordered and random angular momentum, dynamical friction, adiabatic contraction, etc. This allows us to determine the density profile from the inner to the outer region and to study the behavior of the outer density profile. We compare the density profiles and their logarithmic slope of with the simulation results of Diemer and Kravtsov (2014), finding a good agreement between the prediction of the model and the simulations.

中文翻译：

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球面塌陷模型中的飞溅半径

几年前的研究表明，暗物质晕外围的特征是在非常小的径向范围内具有非常陡峭的密度分布。这一特征被解释为不同粒子轨道在相似位置的堆积，即坍缩后半个轨道上的飞溅物质。阿迪卡里等人。（2014 年）通过一个非常简单的模型，通过计算二次流入模型中的暗物质壳轨迹，当它穿过一个不断增长的 NFW 剖面形暗物质晕时，获得了飞溅半径的位置。因为他们强加了一个光晕轮廓，而不是根据暗物质壳的轨迹计算它，所以他们无法找到飞溅半径周围的暗物质轮廓。在本论文中，我们使用改进的球形流入模型，考虑到壳交叉以及一些物理效应，如有序和随机角动量、动态摩擦、绝热收缩等。这使我们能够确定从内部到外部区域的密度分布和研究外部密度分布的行为。我们将密度分布及其对数斜率与 Diemer 和 Kravtsov (2014) 的模拟结果进行比较，发现模型的预测与模拟之间存在良好的一致性。