Radio constraints on dark matter annihilation in the galactic halo and its substructures

Abstract

Annihilation of dark matter usually produces together with gamma rays comparable amounts of electrons and positrons. The e(+)e(-) gyrating in the galactic magnetic field then produce secondary synchrotron radiation which thus provides an indirect means to constrain the DM signal itself. To this purpose, we calculate the radio emission from the galactic halo as well as from its expected substructures and we then compare it with the measured diffuse radio background. We employ a multifrequency approach using data in the relevant frequency range 100 MHz-100 GHz, as well as the WMAP haze data at 23 GHz. The derived constraints are of the order <sigma(A)v >=10(-24) cm(3) s(-1) for a DM mass m(chi)=100 GeV sensibly depending, however, on the astrophysical uncertainties, in particular, on the assumption of the galactic magnetic field model. The signal from single bright clumps is instead largely attenuated by diffusion effects and offers only poor detection perspectives.