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Soft gamma-ray background and light Dark Matter annihilation | | Yann Rasera
; Romain Teyssier
; Patrick Sizun
; Michel Casse
; Pierre Fayet
; Bertrand Cordier
; Jacques Paul
; | | Date: |
29 Jul 2005 | | Subject: | astro-ph hep-ph | | Abstract: | The bulk of the extragalactic background between 10 keV and 10 GeV is likely to be explained by the emission of Seyfert galaxies, type Ia supernovae, and blazars. However, as revealed by the INTEGRAL satellite, the bulge of our galaxy is an intense source of a 511 keV gamma-ray line, indicating the production of a large number of annihilating positrons. The origin of the latter is debated, and they could be produced, in particular, by the (S- or P-wave) annihilations of light Dark Matter particles into e+e-. In any case, the cumulated effect of similar sources at all redshifts could lead to a new background of hard X-ray and soft gamma-ray photons. On the basis of the hierarchical model of galaxy formation, we compute analytically the SNIa contribution to the background, and add it to Seyfert and blazars emission models. We find that any extra contribution to this unresolved background at 511 keV should be lower than about 4 keV/cm^2/s/sr. Using the same model of galaxy formation, we also compute the extragalactic background due to Dark Matter annihilation. We obtain a new estimate which is one order of magnitude lower than previous works, because we consider that positrons cannot annihilate in very low mass dark matter halos that are unable to host galaxies. As a result, the hypothesis of light Dark Matter particles remains compatible with the observed extragalactic background. | | Source: | arXiv, astro-ph/0507707 | | Services: | Forum | Review | PDF | Favorites | |
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