Hierarchical Phase Space Structure of Dark Matter Haloes: Tidal debris, Caustics, and Dark Matter annihilation

Abstract

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.

12 pages, 7 figures, comments are welcome

References in corpus (4)

• Effects of cold dark matter decoupling and pair annihilation on cosmological perturbations
• The fine-grained phase-space structure of Cold Dark Matter halos
• The Caustic Ring Model of the Milky Way Halo
• Modelling ultra-fine structure in dark matter halos

Cited by in corpus (13)

• A dynamically young and perturbed Milky Way disk
• Tracing the Dark Matter Sheet in Phase Space
• Astrophysical uncertainties on direct detection experiments
• Dependence of direct detection signals on the WIMP velocity distribution
• Caustics in growing Cold Dark Matter Haloes
• Hierarchy in the Phase Space and Dark Matter Astronomy
• Dark matter halo's and self similarity
• Seen and unseen tidal caustics in the Andromeda galaxy
• Resolving infall caustics in dark matter halos
• On general-relativistic Lagrangian perturbation theory and its non-perturbative generalization
• Clustering in the Phase Space of Dark Matter Haloes. I. Results from the Aquarius simulations
• Gravitational Potential from small-scale clustering in action space: Application to Gaia DR2
• Caustics, cold flows, and annual modulation