Optimal angular window for observing Dark Matter annihilation from the Galactic Center region: the case of gamma-ray lines

Understand

Although the emission of radiation from dark matter annihilation is expected to be maximized at the Galactic Center, geometric factors and the presence of point-like and diffuse backgrounds make the choice of the angular window size to optimize the chance of a signal detection a non-trivial problem.

• Contrarily to what is often assumed, we find that the best strategy is to focus on a window size around the Galactic Center of ~ 1 deg to >~ 30 deg, where the optimal size depends on the angular distribution of the signal and the backgrounds.
• Although our conclusions are general, we illustrate this point in the particular case of annihilation into two monochromatic photons in the phenomenologically most interesting range of energy 45 GeV < E < 80 GeV, which is of great interest for the GLAST satellite.
• We find for example that Dark Matter models with sufficiently strong line annihilation signals, like the Inert Doublet Model, may be detectable without or with very moderate boost factors.