Dark Matter Caustics

TL;DR

This paper develops a mathematical framework to identify dark matter caustics and estimate their annihilation radiation in cosmological simulations, accounting for different dark matter thermal velocities.

Contribution

It introduces a method for modeling dark matter caustics in N-body simulations considering hot, warm, and cold initial conditions.

Findings

Method enables detection of caustics in simulations.

Allows estimation of annihilation signals from caustics.

Applicable to various dark matter thermal velocities.

Abstract

Caustics are a generic feature of the nonlinear growth of structure in the dark matter distribution. If the dark matter were absolutely cold, its mass density would diverge at caustics, and the integrated annihilation probability would also diverge for individual particles participating in them. For realistic dark matter candidates, this behaviour is regularised by small but non-zero initial thermal velocities. We present a mathematical treatment of evolution from Hot, Warm or Cold Dark Matter initial conditions which can be directly implemented in cosmological N-body codes. It allows the identification of caustics and the estimation of their annihilation radiation in fully general simulations of structure formation.