  In this paper we study the formation of giant electrons-positron pair halos
around the powerful high energy extragalactic sources. We investigate the
dependence of radiation of pair halos, in particular the spectral and angular
distributions on the energy spectrum of the primary gamma-rays, the redshift of
the source, and the flux of the extragalactic background light.

High Energy Astrophysical Phenomena;Cosmology and Nongalactic Astrophysics