Monte Carlo simulation is one of the best tools to study the complex spectra of Compton-thick active galactic nuclei (AGNs) and to figure out the relation between their nuclear structures and X-ray spectra. We have simulated X-ray spectra of Compton-thick AGNs obscured by an accretion torus whose structure is characterized by a half-opening angle, an inclination angle of the torus relative to the observer, and a column density along the equatorial plane. We divided the simulated spectra into three components: one direct component, an absorbed reflection component, and an unabsorbed reflection component. We then deduced the dependences of these components on the parameters describing the structure of the torus. Our simulation results were applied to fit the wide-band spectrum of the Seyfert 2 galaxy Mrk 3 obtained by Suzaku. The spectral analysis indicates that we observe the nucleus along a line of sight intercepting the torus near its edge, and the column density along the equatorial plane was estimated to be ∼ 10 24 cm −2 . Using this model, we can estimate the luminosities of both the direct emission and the emission irradiating the surrounding matter. This is useful to find the time variability and time lag between the direct and reflected light.

We obtained a wide-band spectrum of the Compton-thick Seyfert 2 galaxy Mrk 3 with Suzaku. The observed spectrum was clearly resolved into weak, soft powerlaw emission, a heavily absorbed power-law component, cold reflection, and many emission lines. The heavily absorbed component, absorbed by gas with a column density of 1.1×10 24 cm −2 , has an intrinsic 2-10 keV luminosity of ∼1.6×10 43 erg 1 s −1 , and is considered to be direct emission from the Mrk 3 nucleus. The reflection component was interpreted as reflection of the direct light off cold, thick material; the reflection fraction R was 1.36±0.20. The cold material is inferred to be located > 1 pc from the central black hole of Mrk 3 due to the low ionization parameter of iron (ξ < 1 erg cm s −1 ) and the narrow iron line width (σ < 22 eV). A Compton shoulder to the iron line was detected, but the intensity of the shoulder component was less than that expected from spherically distributed Compton-thick material. The weak, soft power-law emission is considered to be scattered light by ionized gas. The existence of many highly-ionized lines from O, Ne, Mg, Si, S, and Fe in the observed spectrum indicates that the ionized gas has a broad ionized structure, with ξ=10-1000. The scattering fraction with respect to the direct light was estimated to be 0.9±0.2%, which indicates that the column density of the scattering region is about 3.6 × 10 22 cm −2 . This high-quality spectrum obtained by Suzaku can be considered a template for studies of Seyfert 2 galaxies.

We report on a Suzaku observation of the nearby Seyfert2 galaxy NGC4388. The overall spectrum is well described by the combination of strongly absorbed power-law plus thin thermal plasma emission, as well as previous observations. Thanks to well-calibrated instruments and a low background level, Suzaku measured the broad-band X-ray spectra more precisely than ever, and enabled us to probe the physical structure of the nuclear region. In addition, a time variability having a factor of 1.5 with a half-day time scale was found up to above 10keV. The center energy and the K$\beta$/K$\alpha$ ratio of the narrow Fe-K line, together with less time variability, indicate that the fluorescent material is far from the black hole. A spectral hump around the 30-40keV band, together with a Compton shoulder of the Fe-K line, requires a significant contribution of the reflection component. This is also consistent with a smaller amplitude of time variability in a higher energy band. A large contribution of the reflection component was not observed by the CGRO/OSSE and BeppoSAX, suggesting that NGC4388 had been in a higher flux state, and that Suzaku observed its light echo. A He-like Fe-K$\alpha$ absorption line was also detected, indicating the existence of highly ionized plasma.

We apply three data science techniques, Nonnegative Matrix Factorization (NMF), Principal Component Analysis (PCA) and Independent Component Analysis (ICA), to simulated X-ray energy spectra of a particular class of super-massive black holes. Two competing physical models, one whose variable components are additive and the other whose variable components are multiplicative, are known to successfully describe X-ray spectral variation of these super-massive black holes, within accuracy of the contemporary observation. We hope to utilize these techniques to compare the viability of the models by probing the mathematical structure of the observed spectra, while comparing advantages and disadvantages of each technique. We find that PCA is best to determine the dimensionality of a dataset, while NMF is better suited for interpreting spectral components and comparing them in terms of the physical models in question. ICA is able to reconstruct the parameters responsible for spectral variation. In addition, we find that the results of these techniques are sufficiently different that applying them to observed data may be a useful test in comparing the accuracy of the two spectral models.