Gamma-ray evidences of the dark matter clumps

TL;DR

This paper investigates gamma-ray signals from small dark matter clumps in our galaxy, analyzing how annihilation processes could produce detectable point-like or extended gamma-ray sources, and constrains dark matter models using Fermi/LAT data.

Contribution

It introduces a parameterized velocity-dependent annihilation cross section model and applies it to gamma-ray data to constrain dark matter clump properties and candidates.

Findings

Constraints on dark matter annihilation cross sections from Fermi/LAT data.

Potential to identify dark matter clumps as point-like or extended gamma-ray sources.

Sensitivity to dark matter density profiles in clumps.

Abstract

We discuss the possibility of identification of point-like gamma-ray sources (PGS) with small scale dark matter (DM) clumps in our Galaxy. Gamma-rays are supposed to originate from annihilation of DM particles in the clumps, where annihilation rate is supposed to be enhanced, besides higher density, due to smaller relative velocities $v$ of DM particles. We parameterized the annihilation cross section $\sigma_\text{ann}(v)$ in the form of an arbitrary power law dependence on the relative velocity $v$ with/without factor of Sommerfeld-Gamow-Sakharov, implying existence of a new Coulomb-like interaction. Adopting different parameters of cross section and clump, satisfying condition $\Omega\lesssim 0.2$ on density of DM particles of question, they are constrained from comparison with Fermi/LAT data on unidentified PGS as well as on diffuse $\gamma$-radiation; results are applied to concrete DM candidates. Such analysis is found to be sensitive enough to existing uncertainty in the density profiles of DM in the clump what can provide a tool for their test. Also we discuss possibilities when gamma-radiating clump changes visibly its position on celestial sphere and it is seen as a spatially extended gamma-source (EGS), what can be probed in future experiments like Gamma-400.