Absorption and Scattering in Thomson-Thick Media
Pawel Magdziarz
Astronomical Observatory, Jagiellonian University, Cracow, Poland
Andrzej A. Zdziarski
Copernicus Astronomical Center, Warsaw, Poland
Using a Monte Carlo method, we study Compton scattering and absorption of
X-rays and gamma-rays in cold media. We consider both reflection and
transmission of X-rays and gamma-rays. First, we consider reflection from a
slab of large optical depth, for which we derive analytic approximations to
energy and angle-dependent Green's functions. Second, we consider transmission
of X-rays and gamma-rays through a spherical shell of an arbitrary optical
depth, for which we derive energy-dependent Green's functions. The Green's
functions take into account Compton scattering with Klein-Nishina effects as
well as absorption with an arbitrary dependence on energy (which allows to
treat media with an arbitrary ionization state and chemical composition).
Our treatment of reflection takes into account the angular dependence, which
is crucial in the hard X-ray and soft gamma-ray range. The effect is
especially important for modeling spectra of Seyfert 1's and galactic black
hole sources, in which Compton reflection occurs commonly. On the other hand,
our transmission Green's functions allow to treat Thomson-thick plasmas, which
commonly occur in Seyfert 2's.