The variable and non-variable X-ray absorbers in Compton-thin type-II Active Galactic Nuclei

Abstract

We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broad band spectra from XMM-Newton, Chandra, and Suzaku. The aim is to study the variability of the neutral intrinsic X-ray obscuration along the line of sight and investigate the properties and location of the dominant component of the X-ray-obscuring gas. The observations are sensitive to absorption columns of $N_{\mathrm{H}}\sim 10^{20.5-24}\mathrm{c}{\mathrm{m}}^{-2}$ of fully- and partially-covering neutral and/or lowly-ionized gas on timescales spanning days to well over a decade. We detected variability in the column density of the full-covering absorber in 7/20 sources, on timescales of months-years, indicating a component of compact-scale X-ray-obscuring gas lying along the line of sight of each of these objects. Our results imply that torus models incorporating clouds or overdense regions should account for line of sight column densities as low as $\sim$ a few $\times 10^{21}$ cm${}^{-2}$. However, 13/20 sources yielded no detection of significant variability in the full-covering obscurer, with upper limits to $\Delta N_{\mathrm{H}}$ spanning $10^{21-23}$ cm${}^{-2}$. The dominant absorbing media in these systems could be distant, such as kpc-scale dusty structures associated with the host galaxy, or a homogeneous medium along the line of sight. Thus, we find that overall, strong variability in full-covering obscurers is not highly prevalent in Compton-thin type IIs, at least for our sample, in contrast to previous results in the literature. Finally, 11/20 sources required a partial-covering, obscuring component in all or some of their observations, consistent with clumpy near-Compton-thick compact-scale gas.

Accepted for publication in ApJ

References in corpus (26)

• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• The close environments of accreting massive black holes are shaped by radiative feedback
• Occultation measurement of the size of the X-ray emitting region in the Active Galactic Nucleus of NGC 1365
• The Millennium Galaxy Catalogue: the B-band attenuation of bulge and disc light and the implied cosmic dust and stellar mass densities
• Resolving the obscuring torus in NGC 1068 with the power of infrared interferometry: Revealing the inner funnel of dust
• On the origin of soft X-rays in obscured AGN: answers from high-resolution spectroscopy with XMM-Newton
• Suzaku Observations of Active Galactic Nuclei Detected in the Swift/BAT Survey: Discovery of "New Type" of Buried Supermassive Black Holes
• Dust inflated accretion disc as the origin of the Broad Line Region in Active Galactic Nuclei
• The mass of the black hole in Centaurus A from SINFONI AO-assisted integral-field observations of stellar kinematics
• High-Velocity Bipolar Molecular Emission from an AGN Torus
• Parsec-scale dust distributions in Seyfert galaxies - Results of the MIDI AGN snapshot survey
• Rapid N_H changes in NGC 4151
• Galaxy gas as obscurer: II. Separating the galaxy-scale and nuclear obscurers of Active Galactic Nuclei
• The hard X-ray spectrum of NGC 5506 as seen by NuSTAR
• The Suzaku Observation of the Nucleus of the Radio-Loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material
• X-ray spectral variability of Seyfert 2 galaxies
• The central parsecs of active galactic nuclei: challenges to the torus
• A Long Look At MCG-5-23-16 With NuSTAR: I- Relativistic Reflection And Coronal Properties
• A multiwavelength map of the nuclear region of NGC7582
• Emission Line Properties of Seyfert Galaxies in the 12 Micron Sample
• The Seyfert 2 galaxy NGC 2110: hard X-ray emission observed by NuSTAR and variability of the iron K$\alpha$ line
• A Low-Flux State in IRAS 00521-7054 seen with NuSTAR and XMM-Newton: Relativistic Reflection and an Ultrafast Outflow
• Transient and Highly Polarized Double-Peaked H-alpha Emission in the Seyfert 2 Nucleus of NGC 2110
• Evidence for Relativistic Disk Reflection in the Seyfert 1h Galaxy/ULIRG IRAS 05189-2524 Observed by NuSTAR and XMM-Newton
• Evidence for Non-Hydrostatic Gas Motions in the Hot ISM of Centaurus A
• Suzaku observation of IRAS 00521-7054, a peculiar type-II AGN with a very broad feature at 6 keV

Cited by in corpus (2)

• Extreme ultra-soft X-ray variability in an eROSITA observation of the Narrow-Line Seyfert 1 Galaxy 1H 0707-495
• An X-ray spectral study of the origin of reflection features in bare Seyfert 1 galaxy ESO 511--G030