Astronomy and Astrophysics – Astrophysics
Scientific paper
2008-11-17
PoS idm2008:030,2008
Astronomy and Astrophysics
Astrophysics
5 pages, 9 figures, to appear in the proceedings of the Identification of Dark Matter conference (IDM 2008), Stockholm, Sweden
Scientific paper
The ROSAT Galactic wind observations confirm that our Galaxy launches supernova driven Galactic winds with wind speeds of about 150 km/s in the Galactic plane. Galactic winds of this strength are incompatible with current isotropic models for Cosmic Ray transport. In order to reproduce our local CRs in the presence of Galactic winds, charged CRs are required to be much more localized than in the standard isotropic GALPROP models. This requires that anisotropic diffusion is the dominant diffusion mode in the interstellar medium, particularly that the diffusion in the disk and in the halo are different. In addition small scale phenomena such as trapping by molecular cloud complexes and the structure of our local environment might influence the secondary CR production rate and our local CR density gradients. We introduce an anisotropic convection driven transport model (aCDM) which is consistent with the Galactic wind observations by ROSAT. This also explains the large bulge/disk ratio as observed by INTEGRAL. Furthermore such models predict an increase in the $e^+/(e^++e^-)$-fraction as observed by PAMELA and HEAT, if the synchrotron constraints in the 408 MHz and WMAP range are taken into account. No additional contribution from Dark Matter is required. The aCDM is able to explain the absence of a positron annihilation signal from molecular clouds as observed by INTEGRAL by virtue of a mechanism which confines and isotropizes CRs between MCs. We find that the EGRET excess of diffuse $\gamma$-rays currently cannot be explained by astrophysical effects in this type of model and that the interpretation of the EGRET excess as Dark Matter annihilation is perfectly consistent with all observational constraints from local CR fluxes and synchrotron radiation.
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