Point-like gamma ray sources as signatures of distant accelerators of ultra high energy cosmic rays

Abstract

We discuss the possibility of observing distant accelerators of ultra high energy cosmic rays in synchrotron gamma rays. Protons propagating away from their acceleration sites produce extremely energetic electrons during photo-pion interactions with cosmic microwave background photons. If the accelerator is embedded in a magnetized region, these electrons will emit high energy synchrotron radiation. The resulting synchrotron source is expected to be point-like and detectable in the GeV-TeV energy range if the magnetic field is at the nanoGauss level.