Speaker
Dr
Ilias Cholis
(SISSA/ISAS)
Description
The Fermi haze is a diffuse component of gamma-ray emission
centered towards the galactic center, extending up to approximately $\pm$50
degrees in latitude,
recently revealed after analysis of full-sky map data from the Fermi LAT instrument.
The Fermi ``haze'' is the gamma-ray counterpart generated by inverse Compton
emission
from the same population of electrons which generate the microwave synchrotron
haze
observed at WMAP wavelengths, with two distinct characteristics: its
significantly harder spectrum than the emission elsewhere in the Galaxy and its
morphology that is elongated along the latitude with respect to the longitude with an
axis
ratio ~2. If dark matter annihilation, in the
Galactic halo, is responsible for producing those electrons, the standard spherical halo
and isotropic diffusion of cosmic rays in the
Galaxy can not explain the elongated morphology of the signal.
Yet, the presence of ordered magnetic field towards the center of the Galaxy
can cause cosmic rays to diffuse anisotropically along the ordered field lines. Also
dark matter halos have been shown to be generically triaxial by cosmological
simulations.
The combination of a prolate dark matter halo and anisotropic diffusion can easily
yield the required
morphology of the signal without making unrealistic assumptions about the galactic
magnetic field
while also being consistent with local cosmic-ray measurements as well as CMB
constraints. A
Sommerfeld enhancement to the annihilation cross-section of ~30 yields a good fit
to the morphology, amplitude, and spectrum of both the gamma-ray and microwave
haze.
Finally, such DM models, can give a very different neutrino signal as compared to
astrophysical
models suggested in order to explain the Fermi haze signal.
Primary authors
Dr
Gregory Dobler
(KITP/UCSB)
Dr
Ilias Cholis
(SISSA/ISAS)
Co-author
Prof.
Neal Weiner
(NYU/IAS)
