MHz to TeV expectations from scotogenic WIMP dark matter

Particle dark matter (DM) could annihilate into detectable Standard Model particles. Most efforts on the indirect search for DM focus on the high-energy photons directly produced by DM annihilation. However, such prompt signals alone are too weak to be measurable in large astrophysical fore- and backgrounds. Following a multiwavelength approach, the secondary emission from charged annihilation products, including Inverse Compton scattering, bremsstrahlung and synchrotron radiation, should be also taken into account to increase the chances of detecting an unambiguous signal. In our study, we investigate scotogenic DM with a mass around 1 TeV which is consistent with various experimental limits. Scotogenic Weakly Interacting Massive Particles (WIMPs) arise in models where an additional symmetry ensures both the existence of a stable DM candidate and the generation of neutrinos masses through couplings to the dark sector. We present our calculations of the DM photon spectrum in 27 dwarf galaxies of the Milky Way reaching from synchrotron emission in the MHz range to the Inverse Compton peak at MeV energies and to the prompt signature in the GeV up to TeV regime. This unique “triple hump” structure will be easily distinguishable from any other source. We estimate the fore- and background emission from the Milky Way and AGN along the line-of-sight to obtain signal-to-background ratios in different energy bands for each galaxy. We find ratios on the order of 1e-3 between 1 keV and 100 GeV. In the light of upcoming observatories like COSI-SMEX and CTA, the detection of faint DM signals is within reach if a coherent analysis across the MeV to GeV range is applied.