A model of the egret source at the galactic center: Inverse compton scattering within sagittarius a east and its halo

Continuum low-frequency radio observations of the Galactic center reveal the presence of two prominent radio sources, Sgr A East and its surrounding halo, containing nonthermal particle distributions with power-law indexes ∼ 2.5-3.3 and ∼2.4, respectively. The central 1-2 pc region is also a source of intense (stellar) UV and (dust-reprocessed) far-IR radiation that bathes these extended synchrotronemitting structures. A recent detection of γ-rays (2EG J1746-2852) from within ∼1° of the Galactic center by EGRET onboard the Compton Gamma Ray Observatory (CGRO) shows that the emission from this environment extends to very high energies. We suggest that inverse Compton scattering between the power-law electrons inferred from the radio properties of Sgr A East and its halo and the UV and IR photons from the nucleus may account for the possibly diffuse γ-ray source as well. We show that both particle distributions may be contributing to the γ-ray emission, although their relevant strength depends on the actual physical properties (such as the magnetic field intensity) in each source. If this picture is correct, the high-energy source at the Galactic center is extended over several arcminutes, which can be tested with the next generation of γ-ray and hard X-ray missions.