2020ApJ...897...66L -
Astrophys. J., 897, 66-66 (2020/July-1)
The variable and non-variable X-ray absorbers in Compton-thin Type II active galactic nuclei.
LAHA S., MARKOWITZ A.G., KRUMPE M., NIKUTTA R., ROTHSCHILD R. and SAHA T.
Abstract (from CDS):
We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broadband 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 NH ∼ 1020.5–24 cm–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 to 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 over-dense regions should account for line-of-sight column densities as low as ∼a few x1021 cm–2. However, 13/20 sources yielded no detection of significant variability in the full-covering obscurer, with upper limits of ΔNH spanning 1021–23 cm–2. The dominant absorbing media in these systems could be distant, such as kiloparsec-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.
Abstract Copyright:
© 2020. The American Astronomical Society. All rights reserved.
Journal keyword(s):
Active galaxies - Supermassive black holes - Quasar absorption line spectroscopy - Interstellar medium
Simbad objects:
23
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