If ultra-high energy cosmic rays (UHECRs) are accelerated at astrophysical
point sources, the identification of such sources can be achieved if there is
some kind of radiation at observable wavelengths that may be associated with
the acceleration and/or propagation processes. No radiation of this type has so
far been detected or at least no such connection has been claimed. The process
of photopion production during the propagation of UHECRs from the sources to
the Earth results in the generation of charged and neutral pions. The neutral
(charged) pions in turn decay to gamma quanta and electrons that initiate an
electromagnetic cascade in the universal photon background. We calculate the
flux of this gamma radiation in the GeV-TeV energy range and find that for
source luminosities compatible with those expected from small scale
anisotropies in the directions of arrival of UHECRs, the fluxes can be
detectable by future Cerenkov gamma ray telescopes, such as VERITAS and HESS,
provided the intergalactic magnetic field is not larger than ∼10−10
Gauss and for source distances comparable with the loss length for photopion
production.Comment: accepted for publication on Astroparticle Physic