Effects of inhomogeneity and anisotropy of radiation field on production and absorption of high-energy radiation

ABSTRACT We investigate the geometrical effects affecting the production and absorption of gamma-ray radiation emitted in inverse Compton scattering in the synchrotron self-Compton process. We evaluate the effect of the anisotropy of the radiation field seen by the scattering electrons, homogeneously distributed in the emission region. Next, we also consider the inhomogeneous distribution of electrons and investigate its effect in the spherically symmetric emission region. We also study the cylindrical shape of the emission region and its effect on the isotropy of the emitted radiation. We obtain simple numerical factors that scale the emission for different assumptions about the geometry of the emission region and the distribution of the emitting electrons. For a 3D Gaussian spatial distribution of the electrons, we obtain 0.222 times lower flux than for a homogeneous emission region. Finally, we also evaluate the absorption of the radiation produced in the different scenarios, and compare the full calculations with the two most commonly assumed simplifications. We find that for cases when the absorption is less than by one order of magnitude, the full calculations for a homogeneous sphere can be well approximated with a homogeneously emitting slab, while the absorption in the case of a 3D Gaussian distribution of electrons is significantly weaker.