The Fermi Gamma-Ray Haze from Dark Matter Annihilations and Anisotropic
  Diffusion
  Recent full-sky maps of the Galaxy from the Fermi Gamma-Ray Space Telescope
have revealed a diffuse component of emission towards the Galactic center and
extending up to roughly +/-50 degrees in latitude. This Fermi "haze" is the
inverse Compton emission generated by the same electrons which generate the
microwave synchrotron haze at WMAP wavelengths. The gamma-ray haze has two
distinct characteristics: the spectrum is significantly harder than emission
elsewhere in the Galaxy and the morphology is elongated in latitude with
respect to longitude with an axis ratio ~2. If these electrons are generated
through annihilations of dark matter particles in the Galactic halo, this
morphology is difficult to realize with a standard spherical halo and isotropic
cosmic-ray diffusion. However, we show that anisotropic diffusion along ordered
magnetic field lines towards the center of the Galaxy coupled with a prolate
dark matter halo can easily yield the required morphology without making
unrealistic assumptions about diffusion parameters. Furthermore, a Sommerfeld
enhancement to the self annihilation cross-section of ~30 yields a good fit to
the morphology, amplitude, and spectrum of both the gamma-ray and microwave
haze. The model is also consistent with local cosmic-ray measurements as well
as CMB constraints.
