Multiwavelength Observation of WIMP Annihilation

Abstract

The annihilation of neutralino dark matter may result in observable signals in different wavelength. In the present paper we will discuss the effect of neutralino annihilation in the halo of our Galaxy and in its center. According to high resolution cold dark matter simulations, large virialized halos are formed through the constant merging of smaller halos appeared at previous times. At each epoch, dark matter halos have then a clumpy component which is made of these merging subhalos. The annihilation of dark matter in these clumps, always present in the halo of our Galaxy, may be responsible for appreciable fluxes of $γ$-rays, potentially detectable. We find that, depending on the fundamental parameters of the clump density profile and on the distribution of clumps in the Galactic halo, the contribution to the diffuse $γ$-ray background from clumps could be used to obtain constraints on the neutralino properties such as mass and annihilation cross section. On the other hand the annihilation of neutralino dark matter in the galactic center may result in radio signals. At the galactic center, infact, the accretion flow onto the central black hole sustains strong magnetic fields that can induce synchrotron emission, in the radio wavelength, by electrons and positrons generated in neutralino annihilations during advection onto the black hole. We find that the observed emission from the galactic center is consistent with neutralinos following a Navarro Frenk and White density profile at the galactic center while it is inconsistent with the presence of a spike density profile, supposed to be generated by the formation history of the central black hole.