A Compton-thin Solution for the Suzaku X-ray Spectrum of the Seyfert 2
  Galaxy Mkn 3
  Mkn 3 is a Seyfert 2 galaxy that is widely regarded as an exemplary
Compton-thick AGN. We study the Suzaku X-ray spectrum using models of the X-ray
reprocessor that self-consistently account for the Fe K$\alpha$ fluorescent
emission line and the associated Compton-scattered, or reflection, continuum.
We find a solution in which the average global column density,
$0.234^{+0.012}_{-0.010} \times 10^{24} \ \rm cm^{-2}$, is very different to
the line-of-sight column density, $0.902^{+0.012}_{-0.013} \times 10^{24} \ \rm
cm^{-2}$. The global column density is $\sim 5$ times smaller than that
required for the matter distribution to be Compton-thick. Our model accounts
for the profiles of the Fe K$\alpha$ and Fe K$\beta$ lines, and the Fe K edge
remarkably well, with a solar abundance of Fe. The matter distribution could
consist of a clumpy medium with a line-of-sight column density higher than the
global average. A uniform, spherically-symmetric distribution alone cannot
simultaneously produce the correct fluorescent line spectrum and reflection
continuum. Previous works on Mkn 3, and other AGN, that assumed a reflection
continuum from matter with an infinite column density could therefore lead to
erroneous or "puzzling" conclusions if the matter out of the line-of-sight is
really Compton-thin. Whereas studies of samples of AGN have generally only
probed the line-of-sight column density, with simplistic, one-dimensional
models, it is important now to establish the global column densities in AGN. It
is the global properties that affect the energy budget in terms of reprocessing
of X-rays into infrared emission, and that constrain population synthesis
models of the cosmic X-ray background.
