$γ$-ray flux from Dark Matter Annihilation in Galactic Caustics

Abstract

In the frame of indirect dark matter searches we investigate the flux of high-energy $γ$-ray photons produced by annihilation of dark matter in caustics within our Galaxy under the hypothesis that the bulk of dark matter is composed of the lightest supersymmetric particles. Unfortunately, the detection of the caustics annihilation signal with currently available instruments is rather challenging. Indeed, with realistic assumptions concerning particle physics and cosmology, the $γ$-ray signal from caustics is below the detection threshold of both $\check {\rm C}$erenkov telescopes and satellite-borne experiments. Nevertheless, we find that this signal is more prominent than that expected if annihilation only occurs in the smoothed Galactic halo, with the possible exception of a $\sim 15^{\circ}$ circle around the Galactic center if the mass density profile of our Galaxy exhibits a sharp cusp there. We show that the angular distribution of this $γ$-ray flux changes significantly if DM annihilation preferentially occurs within virialized sub-halos populating our Galaxy rather than in caustics.