Hierarchy in the Phase Space and Dark Matter Astronomy

TL;DR

This paper presents a theoretical framework for the hierarchical phase space structure of cold dark matter haloes, revealing potential signals for dark matter detection and implications for understanding dark matter distribution.

Contribution

It introduces a novel hierarchical phase space model for dark matter haloes, applying the stable clustering hypothesis to small-scale structures, and explores implications for dark matter detection signals.

Findings

Dark matter annihilation signal could be up to 100 times larger than smooth halo predictions.

Local boost in detection signals is inversely proportional to smooth halo density.

Temporal and directional uncertainties in dark matter detection could be significant.

Abstract

We develop a theoretical framework for describing the hierarchical structure of the phase space of cold dark matter haloes, due to gravitationally bound substructures. Because it includes the full hierarchy of the cold dark matter initial conditions and is hence complementary to the halo model, the stable clustering hypothesis is applied for the first time here to the small-scale phase space structure. As an application, we show that the particle dark matter annihilation signal could be up to two orders of magnitude larger than that of the smooth halo within the Galactic virial radius. The local boost is inversely proportional to the smooth halo density, and thus is O(1) within the solar radius, which could translate into interesting signatures for dark matter direct detection experiments: The temporal correlation of dark matter detection can change by a factor of 2 in the span of 10 years, while there will be significant correlations in the velocity space of dark matter particles. This can introduce O(1) uncertainty in the direction of local dark matter wind, which was believed to be a benchmark of directional dark matter searches or the annual modulation signal.