暗物质晕的分级相空间结构：潮汐碎片、焦散线和暗物质湮灭
Hierarchical Phase Space Structure of Dark Matter Haloes: Tidal debris, Caustics, and Dark Matter annihilation
摘要：
大部分质量含量的暗物质晕预计是在潮汐碎片的形式。碎片的密度不是恒定的，而是由于在轨道远心和近心处形成焦散而增加，或由于相位混合而衰减。在相空间中，碎片聚集在一个被暗物质的原始温度截断的层次中。了解这种相位结构对于解释许多天体物理观测，特别是暗物质探测实验具有重要意义。考虑到这一目的，我们开发了一个通用的理论框架来描述冷暗物质晕相空间的层次结构。我们不做任何假设球对称和/或光滑和连续的吸积。相反，在作用角空间中使用关联函数，我们可以完全解释分层结构（预测作用空间中的两点关联函数~（ΔJ）^{-1.6}），以及相空间的原始离散性。作为一个应用程序，我们估计提升的暗物质湮灭信号由于维里半径内的相空间的结构：由于层次潮汐碎片的提升是为了统一，而原始的相结构的离散性可以提高总湮灭信号的数量级。后者主要由超过维里半径的20%的区域，并且对于最近形成的具有最小程度的相混合的晕是最大的。
英文摘要：
Most of the mass content of dark matter haloes is expected to be in the form of tidal debris. The density of debris is not constant, but rather can grow due to formation of caustics at the apocenters and pericenters of the orbit, or decay as a result of phase mixing. In the phase space, the debris assemble in a hierarchy which is truncated by the primordial temperature of dark matter. Understanding this phase structure can be of significant importance for the interpretation of many astrophysical observations and in particular dark matter detection experiments. With this purpose in mind, we develop a general theoretical framework to describe the hierarchical structure of the phase space of cold dark matter haloes. We do not make any assumption of spherical symmetry and/or smooth and continuous accretion. Instead, working with correlation functions in the action-angle space, we can fully account for the hierarchical structure (predicting a two-point correlation function ~ (ΔJ)^{-1.6} in the action space), as well as the primordial discreteness of the phase space. As an application, we estimate the boost to the dark matter annihilation signal due to the structure of the phase space within virial radius: the boost due to the hierarchical tidal debris is of order unity, whereas the primordial discreteness of the phase structure can boost the total annihilation signal by up to an order of magnitude. The latter is dominated by the regions beyond 20% of the virial radius, and is largest for the recently formed haloes with the least degree of phase mixing.
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