Possible evidence for dark matter annihilations from the excess microwave emission around the center of the Galaxy seen by the Wilkinson Microwave Anisotropy Probe

The Wilkinson Microwave Anisotropy Probe (WMAP) experiment has revealed an excess of microwave emission from the region around the center of our Galaxy. It has been suggested that this signal, known as the “WMAP haze,” could be synchrotron emission from relativistic electrons and positrons generated in dark matter annihilations. In this article, we revisit this possibility. We find that the angular distribution of the WMAP haze matches the prediction for dark matter annihilations with a cusped density profile, ρ(r)∝r^-1.2 in the inner kiloparsecs. Comparing the intensity in different WMAP frequency bands, we find that a wide range of possible weakly interacting massive particle (WIMP) annihilation modes are consistent with the spectrum of the haze for a WIMP with a mass in the 100 GeV to multi-TeV range. Most interestingly, we find that to generate the observed intensity of the haze, the dark matter annihilation cross section is required to be approximately equal to the value needed for a thermal relic, σv∼3×10^-26  cm³/s. No boost factors are required. If dark matter annihilations are in fact responsible for the WMAP haze, and the slope of the halo profile continues into the inner Galaxy, GLAST is expected to detect gamma rays from the dark matter annihilations in the galactic center if the WIMP mass is less than several hundred GeV.