Celestial-Body Focused Dark Matter Annihilation Throughout the Galaxy

TL;DR

This paper proposes a novel dark matter detection method focusing on celestial bodies capturing and annihilating DM, leading to distinctive signals that can be constrained using gamma-ray data, significantly improving existing limits.

Contribution

It introduces a new scenario where celestial bodies enhance DM annihilation signals, providing a different morphology and stronger constraints from gamma-ray observations.

Findings

Constraints on DM-nucleon cross section down to 10^{-39} cm^2 for sub-GeV DM.

Neutron stars set limits for TeV-scale DM down to 10^{-47} cm^2.

Signal dominance over halo annihilation in specific astrophysical environments.

Abstract

Indirect detection experiments typically measure the flux of annihilating dark matter (DM) particles propagating freely through galactic halos. We consider a new scenario where celestial bodies "focus" DM annihilation events, increasing the efficiency of halo annihilation. In this setup, DM is first captured by celestial bodies, such as neutron stars or brown dwarfs, and then annihilates within them. If DM annihilates to sufficiently long-lived particles, they can escape and subsequently decay into detectable radiation. This produces a distinctive annihilation morphology, which scales as the product of the DM and celestial body densities, rather than as DM density squared. We show that this signal can dominate over the halo annihilation rate in $\gamma$-ray observations in both the Milky Way Galactic center and globular clusters. We use \textit{Fermi} and H.E.S.S. data to constrain the DM-nucleon scattering cross section, setting powerful new limits down to $\sim10^{-39}~$cm$^2$ for sub-GeV DM using brown dwarfs, which is up to nine orders of magnitude stronger than existing limits. We demonstrate that neutron stars can set limits for TeV-scale DM down to about $10^{-47}~$cm$^2$.