Fermi Gamma-ray Space Telescope

GeV excess electrons upscattering the CMB: a possible resolution to the "Photon Underproduction Crisis"

Tansu Daylan
Stephen K. N. Portillo, Douglas P. Finkbeiner

Abstract:

Recently a gamma-ray excess has been identified in the inner Milky Way, which may be associated with the final state photon shower following DM annihilation to standard model final states. In this scenario $sim$ GeV electrons are also produced and, given their long energy loss timescale ($sim$ Gyr), they can diffuse and escape the galaxy before losing too much energy. If such an electron population exists in the IGM, one observable consequence would be inverse Compton scattering on the CMB, which would produce UV photons that can efficiently ionize the IGM. This may be a possible resolution to the "Photon Underproduction Crisis", recently pointed out by Kollmeier et al. (2014). Regardless of the relevance to this crisis, the existence of a $sim$ GeV electron population in the IGM can put constraints on DM annihilation parameters considering the known X-ray backgrounds.