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Implications of cosmological gamma-ray absorption - I. Evolution of the metagalactic radiation field

2002; EDP Sciences; Volume: 386; Issue: 1 Linguagem: Inglês

1432-0746

T. Kneiske, K. Mannheim, D. H. Hartmann,

Particle Detector Development and Performance

Gamma-ray absorption due to -pair creation on cosmological scales depends on the line-of-sight integral of the evolving density of low-energy photons in the Universe, i.e. on the history of the diuse, isotropic radiation eld. Here we present and discuss a semi-empirical model for this metagalactic radiation eld based on stellar light produced and reprocessed in evolving galaxies. With a minimum of parameters and assumptions, the present-day background intensity is obtained from the far-IR to the ultraviolet band. Predicted model intensities are independent of cosmological parameters, since we require that the comoving emissivity, as a function of redshift, agrees with observed values obtained from deep galaxy surveys. The far-infrared background at present predicted from optical galaxy surveys falls short in explaining the observed one, and we show that this decit can be removed by taking into account (ultra)luminous infrared galaxies with a seperate star formation rate. The accuracy and reliability of the model, out to redshifts of z 5, allow a realistic estimate of the attenuation length of GeV-to-TeV gamma-rays and its uncertainty, which will be the focus of a subsequent paper.