ON THE ABSORPTION OF HIGH-ENERGY GAMMA-RAYS BY INTERGALACTIC INFRAREDRADIATION

We present a new calculation of the intergalactic gamma-ray pair-produ ction absorption coefficient as a function of both energy and redshift up to the redshift of 3C 279, z = 0.54. In reexamining this problem, we make use of new observational data on the intergalactic infrared ra diation field (IIRF), together with recent theoretical models of the g alactic, spectral energy distributions of the IIRF from stars and dust reradiation and estimates of the IIRF from galaxy counts and COBE res ults. We present our results for two fairly well defined IIRF spectral energy distributions, one which is within 1 sigma of our previous est imate of the IIRF at similar to 20 mu m. Then we apply our results to the gamma-ray spectrum of Mrk 421 and obtain good agreement with the o bservational data, including the recent results of the HEGRA group.