The galactic center arc as source of high energy #gamma#-rays

Abstract

In this paper we discuss the radio arc at the galactic center to be the counterpart of the high-energy #gamma#-ray source 2EG J1746-2852. Thought 2EG J1746-2852 must be regarded as true source in excess of the diffuse background, its position can not be determined to better than 0.3 . The observed flux is constant within the statistical limits and the spectrum is very hard. The lack of variability makes it highly unlikely that any of the compact sources in the vicinity of the Galactic Center is the counterpart of 2EG J1746-2852. This includes the peculiar source Sgr A* at the very center of the Galaxy, which is often discussed to harbour a black holes of 10"6 M_sun. Existing radio data on the arc support the view that its synchrotron emission originates from cooling, initially monoenergetic electrons which diffuse and convect from their sources to the outer extensions of the arc. If the source of high-energy electrons coincides with the sickle region (G0.18-0.04), as indicated by the radio data, then the ambient far-infrared (FIR) photons can be up-scattered to #gamma#-rays by inverse-Compton interaction with the young high-energy electrons. We solve the continuity equation for the electrons including terms for diffusion, convection, monoenergetic injection, and the full energy loss. With that we show that the predicted #gamma#-ray emission depends mainly on the magnetic field strength in the arc and that both the flux and the spectrum of 2EG J1746-2852 can be well explained. Our model shall be tested on radio data at frequencies beyond 10 GHz in future work. (orig.)Available from TIB Hannover: RN 9303(364) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman