X-ray Spectral Model of Reprocessing by Smooth and Clumpy Molecular Tori in Active Galactic Nuclei with the MONACO framework

TL;DR

This paper develops a detailed X-ray spectral model for AGN tori using Monte Carlo simulations, considering both smooth and clumpy geometries, and explores how various parameters affect the Compton shoulder features.

Contribution

It introduces a comprehensive Monte Carlo model that includes bound electron scattering, Raman, and Reyleigh scattering, and compares smooth and clumpy torus geometries in AGN X-ray spectra.

Findings

Compton shoulder intensity depends on column density, inclination, and metal abundance.

Metal abundance variations influence the strength of the Compton shoulder.

Shape of the Compton shoulder varies with column density and torus clumpiness.

Abstract

We construct an X-ray spectral model of reprocessing by a torus in an active galactic nucleus (AGN) with a Monte Carlo simulation framework MONACO. Two torus geometries of smooth and clumpy cases are considered and compared. In order to reproduce a Compton shoulder accurately, MONACO includes not only free electron scattering but also bound electron scattering. Raman and Reyleigh scattering are also treated, and scattering cross sections dependent on chemical states of hydrogen and helium are included. Doppler broadening by turbulence velocity can be implemented. Our model gives consistent results with other available models, such as MYTorus, except for differences due to different physical parameters and assumptions. We studied the dependence on torus parameters for Compton shoulder, and found that a intensity ratio of Compton shoulder to line core mainly depends on the column density, inclination angle, and metal abundance. For instance, an increase of metal abundance makes the Compton shoulder relatively weak. Also, shape of Compton shoulder depends on the column density. Furthermore, these dependences become different between smooth and clumpy cases. Then, we discuss the possibility of ASTRO-H SXS spectroscopy of Compton shoulder in AGN reflection spectra.