Letter to the Editor

Diffuse galactic sub-MeV γ-ray excess from high-energy electrons

¹ 1 Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany e-mail: rsch@tp4.rub.de
² Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany

Received: 22 July 2005
Accepted: 11 September 2005

Abstract

Recent INTEGRAL observations have confirmed the existence of diffuse sub-MeV radiation from the inner Galaxy. We propose a new explanation for the origin of this diffuse component in terms of electrostatic bremsstrahlung radiation from high-energy electrons. This electrostatic bremsstrahlung interpretation requires a very flat power law energy spectrum of high-energy electrons in the inner Galaxy which is reasonable if many point sources with significant spectral dispersion contribute to the injection of high-energy electrons in the Galaxy. The electrostatic bremsstrahlung interpretation avoids the enormous source power problem that previous explanations by radiation from low-energy electrons have.