The Extragalactic Gamma-Ray Background from Core Dominated Radio
  Galaxies
  Recent radio surveys have discovered a large number of low luminosity core
dominated radio galaxies that are much more abundant than those at higher
luminosities. These objects will be too faint in gamma-rays to be detected
individually by Fermi. Nevertheless, they may contribute significantly to the
unresolved extragalactic gamma-ray background. We consider here the possible
contribution of these core dominated radio galaxies to the diffuse
extragalactic gamma-ray background. Using published data available for all 45
of the radiogalaxies listed as detected counterparts in the Fermi FL8Y source
list update to the 3FGL catalog, we have searched for radio maps which can
resolve the core flux from the total source flux. Using high resolution radio
maps we were able to obtain core fluxes for virtually every source. We then
derived a relation between core radio flux and gamma-ray flux that we
extrapolated to sources with low radio luminosities that are known to be highly
core dominated. We then employed a very recent determination of the luminosity
function for core dominated radio galaxies in order to obtain the contribution
of all possible gamma-ray emitting radio galaxies to the unresolved
extragalactic gamma-ray background. We find this contribution to be a possibly
non-negligible, 4% - 18% of the background.
