Fermi Gamma-ray Space Telescope

The Density of Blazars above 100 MeV and the Origin of the Extragalactic Gamma-ray Background v.2.0

Lea Marcotulli
(Mattia di Mauro, Marco Ajello on behalf of the Fermi-LAT collaboration.)


The origin of the extragalactic gamma-ray background (EGB) has been investigated since its discovery but has remained elusive all this time. Resolving the different gamma-ray emitting populations is key to unveil its composition and the Fermi-Large Area Telescope has played a major role towards this goal. Relying on 8 years of data, we obtained the most sensitive source count distribution of blazars >100 MeV. This has enabled us to derive the contribution of blazars to the EGB, highlighting the fact that they can not reproduce the entire EGB and that indeed another component, either a source class or an exotic diffuse component such as interaction of dark matter particles, is required to explain the residual emission. In this talk we will present the results of our analysis as well as discuss alternatives for the origin of the missing EGB component.