Diffuse γ - Rays from Galactic Halos
Abstract
Here we review our current knowledge on diffuse gamma-rays from galactic halos. Estimates of the relative contribution of the various emission processes at low and high latitudes are compared to the data over 6 decades in energy. The observed spectral shape differs from what was expected, especially at ver low and very high energies. In the latter case, above 1 GeV, the sky emission related to gas exceeds the expected pi^0 decay spectrum. At energies below 1 MeV the relatively high gamma-ray intensity indicates at high density of nearly relativistic electrons which would have a strong influence on the energy and ionisation balance of the interstellar medium. Given the EGRET results for the Magellanic Clouds the gamma-ray emissivity in the outer halo is probably small, so that a substantial amount of baryonic dark matter may be hidden at 20-50 kpc radius without inducing observable gamma-ray emission.
- Publication:
-
The Physics of Galactic Halos
- Pub Date:
- 1997
- DOI:
- 10.48550/arXiv.astro-ph/9603046
- arXiv:
- arXiv:astro-ph/9603046
- Bibcode:
- 1997pgh..conf..279P
- Keywords:
-
- Astrophysics
- E-Print:
- 12 pages, invited Review at 156th Heraeus Workshop "The Physics of Galactic Halos", Bad Honnef, February 1996