The dark connection between the EGRET excess of diffuse Galactic gamma rays, the Canis Major dwarf, the Monoceros ring, the INTEGRAL 511 keV annihilation line, the gas flaring and the Galactic rotation curve

摘要

The EGRET excess of diffuse Galactic gamma rays shows all the key features ofdark matter annihilation (DMA) for a WIMP mass in the range 50-100 GeV,especially the distribution of the excess is compatible with a standard haloprofile with some additional ringlike substructures at 4 and 13 kpc from theGalactic centre. These substructures coincide with the gravitational potentialwell expected from the ring of dust at 4 kpc and the tidal stream of darkmatter from the Canis Major satellite galaxy at 13 kpc, as deduced from N-bodysimulations fitting to the Monoceros ring of stars. Strong independent supportfor this substructure is given by the gas flaring in our Galaxy. The gamma rays from DMA are originating predominantly from the hadronizationof mono-energetic quarks, which should produce also a small, but known fractionof protons and antiprotons. Bergstrom et al. an antiproton flux far above theobserved antiproton flux and they conclude that the DMA interpretation of theEGRET excess can therefore be excluded. However, they used an isotropicpropagation model, i.e. the same diffusive propagation in the disk and thehalo. It is shown that an anisotropic propagation model is consistent with theEGRET gamma ray excess, the antiproton flux and the ratios of secondary/primaryand unstable/stable cosmic ray particles. Such an anisotropic propagation issupported by the large bulge/disk ratio of the positron annihilation line, asobserved by the INTEGRAL satellite. In this case no need for new sourcesspecific to the bulge are needed, so the claimed evidence for strong DMA in thebulge from these observations is strongly propagation model dependent.