Diffuse y-ray emission has long been established as the most prominent feature in the GeV sky. Although the imaging atmospheric Cherenkov technique has been successful in revealing a large population of discrete TeV y-ray sources, a thorough investigation of diffuse emission at TeV energies is still pending. Data from the Galactic Plane Survey (GPS) obtained by the High Energy Stereoscopic System (HESS.) have now achieved a sensitivity and coverage adequate for probing signatures of diffuse emission in the energy range of 100 GeV to a few TeV. y-rays are produced in cosmic-ray interactions with the interstellar medium (aka "sea of cosmic rays") and in inverse Compton scattering on cosmic photon fields. This inevitably leads to guaranteed yray emission related to the gas content along the line-of-sight. Further contributions relate to those y-ray sources that fall below the current detection threshold and the aforementioned inverse Compton emission. Based on the HESS. GPS, we present the first observational assessment of diffuse TeV y-ray emission. The observation is compared with corresponding flux predictions based on the HI (LAB data) and CO (as a tracer of H2, NANTEN data) gas distributions. Consequences for unresolved source contributions and the anticipated level of inverse Compton emission are discussed.
International Cosmic Ray Conference
- Pub Date:
- diffuse y-ray emission;
- imaging atmospheric Cherenkov telescopes;
- Astrophysics - High Energy Astrophysical Phenomena
- 4 pages, 2 figures. In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil)