An Empirical Determination of the Intergalactic Background Light Using   NIR Deep Galaxy Survey Data out to 5 microns and the Gamma-ray Opacity of the   Universe
  We extend our previous model-independent determination of the intergalactic background light (IBL), based purely on galaxy survey data, out to a wavelength of 5 microns. Our approach enables us to constrain the range of photon densities, based on the uncertainties from observationally determined luminosity densities and colors. We further determine a 68% confidence upper and lower limit on the opacity of the universe to gamma-rays up to energies of 1.6/(1+z) TeV. A comparison of our lower limit redshift-dependent opacity curves to the opacity limits derived from the results of both ground-based air Cherenkov telescope and Fermi-LAT observations of PKS 1424+240 allows us to place a new upper limit on the redshift of this source, independent of IBL modeling. 
Sean T. Scully, Matthew A. Malkan and Floyd W. Stecker
astro-ph.HE astro-ph.CO astro-ph.GA