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Scientific paper
Apr 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aipc.1112..101f&link_type=abstract
SCIENCE WITH THE NEW GENERATION OF HIGH ENERGY GAMMA-RAY EXPERIMENTS: Proceedings of the 6th Edition: Bridging the Gap Between G
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Neutrino, Muon, Pion, And Other Elementary Particles, Cosmic Rays, Molecular Clouds, H2 Clouds, Dense Clouds, And Dark Clouds, Distances, Redshifts, Radial Velocities, Spatial Distribution Of Galaxies
Scientific paper
To estimate the opacity of very high-energy photons with the background light, we have modelled the extragalactic optical and infrared diffuse light using available information on cosmic sources in the universe from far-UV to sub-millimeter wavelengths over a wide range of cosmic epochs. To this end we have used number counts, redshift distributions, luminosity functions of extragalactic sources and direct measurements or upper limits to the extragalactic backgrounds by COBE. From the redshift-dependent background spectrum, the photon-photon opacities for sources of high-energy emission at any redshifts were then computed. We have applied our photon-photon opacity estimates to the analysis of spectral data at TeV energies on a few BLAZARs of particular interest (including a z = 0.54 quasar detected by MAGIC, 3C279). We find no evidence in current data for any truly diffuse background components in addition to those from resolved sources. We have tested in particular the effects of a photon background originating at very high redshifts, as would be the emissions by a primeval population of Population III stars at z>=10. We could not identify any opacity features in our studied BLAZAR spectra consistent with such an emission and place a stringent limit on such a diffuse photon intensity of ~6 nW/m2/sr between 1 and 4 μm.
Franceschini Alberto
Rodighiero Giulia
Vaccari Mattia
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