A multi-epoch X-ray study of the nearby Seyfert 2 galaxy NGC 7479: Linking column density variability to the torus geometry

• Main Authors: Pizzetti, Andrealuna, Torres-Alba, Nuria, Marchesi, Stefano, Ajello, Marco, Silver, Ross, Zhao, Xiurui
• Format: Journal Article
• Language: English
• Published: 22-06-2022
• Subjects: Physics - Astrophysics of Galaxies; Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.2206.10946

ApJ 936, 149 - September 8 2022 Active galactic nuclei (AGN) are powered by accreting supermassive black
holes, surrounded by a torus of obscuring material. Recent studies have shown
how the torus structure, formerly thought to be homogeneous, appears to be
'patchy': the detection of variability in the line-of-sight hydrogen column
density, in fact, matches the description of an obscurer with a complex
structure made of clouds with different column density. In this work, we
perform a multi-epoch analysis of the X-ray spectra of the Seyfert 2 galaxy NGC
7479 in order to estimate its torus properties, such as the average column
density and the covering factor. The measurement of the line-of-sight hydrogen
column density variability of the torus allows us to obtain an upper limit on
the cloud distance from the central engine. In addition, using the X-ray
luminosity of the source, we estimate the Eddington ratio to be in a range of
Edd=0.04-0.05 over all epochs.