Constraints on the Extragalactic infrared background from gamma-ray observations of Markarian 501

摘要

We use the new results of the HEGRA detector on the TeV γ-ray emission from Mrk 501 to set upper limits on the energy density of the cosmic infrared background (CIRB). Contrary to previous interpretations of the γ- ray spectrum of Mrk 421 as showing an intergalactic absorption cutoff at 5 TeV, the observed spectrum of Mrk 501 extends beyond 10 TeV and appears to be unattenuated by γ-γ collisions with the low-energy CIRB photons. The upper limits on the CIRB intensity-derived both assuming an a priori shape for the CIRB spectrum and Without model-dependent assumptions - are thus quite strong and almost come into conflict with the observational Evaluations based on deep surveys of extragalactic sources in the near -and mid-infrared.