The clumpy torus around type II AGN as revealed by X-ray fluorescent lines

Abstract

The reflection spectrum of the torus around AGN is characterized by X-ray fluorescent lines, which are most prominent for type II AGN. A clumpy torus allows photons reflected from the back-side of the torus to leak through the front free-of-obscuration regions. Therefore, the observed X-ray fluorescent lines are sensitive to the clumpiness of the torus. We analyse a sample of type II AGN observed with Chandra HETGS, and measure the fluxes for the Si Ka and Fe Ka lines. The measured Fe Ka/Si Ka ratios, spanning a range between $5-60$, are far smaller than the ratios predicted from simulations of smooth tori, indicating that the tori of the studied sources have clumpy distributions rather than smooth ones. Compared with simulation results of clumpy tori with a half-opening angle of 60${}^{\circ }$, the Circinus galaxy has a Fe Ka/Si Ka ratio of $\sim 60$, which is close to the simulation results for $N=5$, where $N$ is the average number of clumps along the line of sight. The Fe Ka/Si Ka ratios of the other sources are all below the simulation results for $N=2$. Overall, it shows that the non-Fe fluorescent lines in the soft X-ray band are a potentially powerful probe of the clumpiness of the torus around AGN.

arXiv comment5 pages, 3 figs, accepted by MNRAS

References in corpus (31)

• The chemical composition of the Sun
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• Revisiting the Unified Model of Active Galactic Nuclei
• An X-ray Spectral Model for Compton-Thick Toroidal Reprocessors
• The Chandra High Energy Transmission Grating: Design, Fabrication, Ground Calibration and Five Years in Flight
• Occultation measurement of the size of the X-ray emitting region in the Active Galactic Nucleus of NGC 1365
• First X-ray-Based Statistical Tests for Clumpy-Torus Models: Eclipse Events from 230 Years of Monitoring of Seyfert AGN
• The Nature of the Compton-thick X-ray Reprocessor in NGC 4945
• NuSTAR Spectroscopy of Multi-Component X-ray Reflection from NGC 1068
• Compton Thick AGN: the dark side of the X-ray background
• NuSTAR catches the unveiling nucleus of NGC 1068
• The 2-79 keV X-ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton and Chandra: a Fully Compton-Thick AGN
• The Toroidal Obscuration of Active Galactic Nuclei
• AGN Obscuration and the Unified Model
• The NuSTAR View of Nearby Compton-thick AGN: The Cases of NGC 424, NGC 1320 and IC 2560
• Chandra High Energy Grating Observations of the Fe Ka Line Core in Type 2 Seyfert Galaxies: A Comparison with Type 1 Nuclei
• Iron and Nickel properties in the X-ray reflecting region of the Circinus Galaxy
• The high energy emission line spectrum of NGC 1068
• Extreme X-ray Iron Lines in Active Galactic Nuclei
• Broadband Observations of the Compton-thick Nucleus of NGC 3393
• An X-ray spectral model for clumpy tori in active galactic nuclei
• The NuSTAR view of reflection and absorption in NGC 7582
• A Compton-thin Solution for the Suzaku X-ray Spectrum of the Seyfert 2 Galaxy Mkn 3
• The remarkable X-ray spectrum of the Broad-Line Radio Galaxy 3C 445
• Evidence for a circum-nuclear and ionised absorber in the X-ray obscured BroadLine Radio Galaxy 3C 445
• XMM-Newton unveils the type 2 nature of the BLRG 3C 445
• Monte Carlo simulations of the Nickel K$\alpha$ fluorescent emission line in a toroidal geometry
• X-ray absorption variability in NGC 4507
• X-ray fluorescent lines from the Compton-thick AGN in M51
• On donuts and crumbs: A brief history of torus models
• On the emitting region of X-ray fluorescent lines around Compton-thick AGN

Cited by in corpus (5)

• X-ray signatures of the polar dusty gas in AGN
• The complex infrared dust continuum emission of NGC1068: ground-based N- and Q-band spectroscopy and new radiative transfer models
• Canonical X-Ray Fluorescence Line Intensities as Column Density Indicators
• On the emitting region of X-ray fluorescent lines around Compton-thick AGN
• A near-infrared, optical and ultraviolet polarimetric and timing investigation of complex equatorial dusty structures