A new determination of the extragalactic background of diffuse gamma rays taking into account dark matter annihilation

Institut für Experimentelle Kernphysik, Universität Karlsruhe (TH), PO Box 6980, 76128 Karlsruhe, Germany e-mail: Wim.de.Boer@cern.ch, [sander;zhukov]@ekp.uni-karlsruhe.de

Received: 30 November 2006
Accepted: 2 May 2007

Abstract

The extragalactic background (EGB) of diffuse gamma rays can be determined by subtracting the Galactic contribution from the data. This requires a Galactic model (GM) and we include for the first time the contribution of dark matter annihilation (DMA), which was previously proposed as an explanation for the EGRET excess of diffuse Galactic gamma rays above 1 GeV. In this paper it is shown that the newly determined EGB shows a characteristic high energy bump on top of a steeply falling soft contribution. The bump is shown to be compatible with a contribution from an extragalactic DMA signal from weakly interacting massive particles (WIMPs) with a mass between 50 and 100 GeV in agreement with the EGRET excess of the Galactic diffuse gamma rays and in disagreement with earlier analysis. The remaining soft contribution of the EGB is shown to resemble the spectra of the observed point sources in our Galaxy.