Universal clustering of dark matter in phase space

TL;DR

This paper demonstrates a universal statistical measure of dark matter clustering in phase space, which applies across various halo sizes and enables accurate predictions of the small-scale non-linear power spectrum and dark matter annihilation signals.

Contribution

It introduces and validates the universality of the $P^2SAD$ measure across different environments and scales, providing a new tool for dark matter structure analysis.

Findings

$P^2SAD$ is universal across halo sizes from dwarf to cluster scale.

The measure accurately predicts the small-scale non-linear power spectrum.

Subhalo boost factors for dark matter annihilation are computed across host halo masses.

Abstract

We have recently introduced a novel statistical measure of dark matter clustering in phase space, the particle phase space average density ($P^2SAD$). In a two-paper series, we studied the structure of $P^2SAD$ in the Milky-Way-size Aquarius haloes, constructed a physically motivated model to describe it, and illustrated its potential as a powerful tool to predict signals sensitive to the nanostructure of dark matter haloes. In this letter, we report a remarkable universality of the clustering of dark matter in phase space as measured by $P^2SAD$ within the subhaloes of host haloes across different environments covering a range from dwarf-size to cluster-size haloes ($10^{10}-10^{15}$ M$_\odot$). Simulations show that the universality of $P^2SAD$ holds for more than 7 orders of magnitude, over a 2D phase space, covering over 3 orders of magnitude in distance/velocity, with a simple functional form that can be described by our model. Invoking the universality of $P^2SAD$, we can accurately predict the non-linear power spectrum of dark matter at small scales all the way down to the decoupling mass limit of cold dark matter particles. As an application, we compute the subhalo boost to the annihilation of dark matter in a wide range of host halo masses.