Possible indications of a clumpy dark matter halo

Abstract

We investigate if the gamma ray halo, for which recent evidence has been found in EGRET data, can be explained by neutralino annihilations in a clumpy halo. We find that the measured excess gamma ray flux can be explained through a moderate amount of clumping in the halo. The required amount of clumping implies also a measurable excess of antiprotons at low energies, which may be suggested by recent measurements by the BESS Collaboration. The predicted antiproton fluxes resulting from neutralino annihilations in a clumpy halo are high enough to give an excess over cosmic-ray produced antiprotons also at moderately high energies (above a few GeV). This prediction, as well as that of one or two sharp gamma lines coming from annihilations into \ensuremath{\gamma}\ensuremath{\gamma} or $Z\ensuremath{\gamma},$ can be tested in upcoming space-borne experiments such as AMS and GLAST.