EGRET excess of diffuse galactic gamma rays as tracer of dark matter

Abstract

The public data from the EGRET space telescope on diffuse Galactic gamma rays in the energy range from 0.1 to 10 GeV are reanalyzed with the purpose of searching for signals of Dark Matter annihilation (DMA). The analysis confirms the previously observed excess for energies above 1 GeV in comparison with the expectations from conventional Galactic models. In addition, the excess was found to show all the key features of a signal from Dark Matter Annihilation (DMA): a) the excess is observable in all sky directions and has the same shape everywhere, thus pointing to a common source; b) the shape corresponds to the expected spectrum of the annihilation of non-relativistic massive particles into -among others -neutral π 0 mesons, which decay into photons. From the energy spectrum of the excess we deduce a WIMP mass between 50 and 100 GeV, while from the intensity of the excess in all sky directions the shape of the halo could be reconstructed. The DM halo is consistent with an almost spherical isothermal profile with substructure in the Galactic plane in the form of toroidal rings at 4 and 14 kpc from the center. These rings lead to a peculiar shape of the rotation curve, in agreement with the data, which proves that the EGRET excess traces the Dark Matter.

Indirect Dark Matter Signals from EGRET and PAMELA compared

“…The excess shows all the features of DMA for a WIMP mass between 50 and 70 GeV, as shown in Fig. 1 [4]. In addition, the results are perfectly consistent with the expectations from Supersymmetry [7].…”

“…The effect is so large that visible matter cannot explain this peculiar shape, simply because there is not much visible matter above 10 kpc. Also the peculiar change in the slope of the rotation curve at a Galactic radius around 10 kpc can only be explained by a ringlike structure [4]. A similar ring in the outer disk has been discovered in a nearby galaxy, indicating that such infalls may shape the disk and its warps [22].…”

“…1400 data points is around 1, indicating that the errors are correctly estimated. But above all such a good χ 2 implies that the main conditions for a signal of DMA are fulfilled, namely i) the shape of the excess corresponds to the fragmentation of mono-energetic quarks with the same energy in all sky directions and ii) it was found that the intensity distribution of the excess agrees with the mass distribution, as deduced from the rotation curve [4] iii) the background distribution agrees within errors with the expectation from GALPROP, the most up-to-date Galactic propagation model [15], as can be seen from Fig. 3 in Ref.…”

The minimal non-minimal standard model

“…From the analysis one can conclude, that the Källén-Lehmann density integral ds ρ(s) is small below roughly √ s < 90 GeV , the exact limits depending on the detailed model. Recent results from the EGRET experiment can be interpreted as providing evidence of the annihilation of dark matter pairs [21]. For this mechanism to work cosmologically it is necessary that the dark matter particles are stable by themselves through some preserved symmetry.…”

AMS-02 on the International Space Station

“…Existing measurements of the positron fraction (see figure 2) have in some cases shown deviations from standard model expectations which are consistent with supersymmetric dark matter, but controversial within the available statistics [8,9]. Thanks to its excellent particle identification capabilities, AMS-02 is able to measure the positron spectrum in particular, but in general all the interesting fluxes, simultaneously and independently, thus enhancing the reliability of a potential discovery, with substantially improved precision for background and signal.…”