Kiloparsec‐Scale Jets in FR I Radio Galaxies and the γ‐Ray Background

We discuss the contribution of kiloparsec-scale jets in FR I radio galaxiesto the diffuse gamma-ray background radiation. The analyzed gamma-ray emissioncomes from inverse-Compton scattering of starlight photon fields by theultrarelativistic electrons whose synchrotron radiation is detected from suchsources at radio, optical and X-ray energies. We find that these objects, underthe minimum-power hypothesis (corresponding to a magnetic field of 300 muG inthe brightest knots of these jets), can contribute about one percent to theextragalactic gamma-ray background measured by EGRET. We point out that thisresult already indicates that the magnetic fields in kpc-scale jets oflow-power radio galaxies are not likely to be smaller than 10 muG on average,as otherwise the extragalactic gamma-ray background would be overproduced.Comment: 18 pages, 3 figures included. ApJ accepte