We construct a new sample of 32 obscured active galactic nuclei (AGNs) selected from the Second XMM-Newton Serendipitous Source Catalogue to investigate their multiwavelength properties in relation to the "scattering fraction", the ratio of the soft X-ray flux to the absorption-corrected direct emission. The sample covers a broad range of the scattering fraction (0.1%-10%). A quarter of the 32 AGNs have a very low scattering fraction (smaller than 0.5%), which suggests that they are buried in a geometrically thick torus with a very small opening angle. We investigate correlations between the scattering fraction and multiwavelength properties. We find that AGNs with a small scattering fraction tend to have low [O III]lambda5007/X-ray luminosity ratios. This result agrees with the expectation that the extent of the narrow-line region is small because of the small opening angle of the torus. There is no significant correlation between scattering fraction and far-infrared luminosity. This implies that a scale height of the torus is not primarily determined by starburst activity. We also compare scattering fraction with black hole mass or Eddington ratio and find a weak anti-correlation between the Eddington ratio and scattering fraction. This implies that more rapidly growing supermassive black holes tend to have thicker tori.
@article{arxiv.1002.0909,
title = {Scattered X-rays in Obscured Active Galactic Nuclei and their Implications for Geometrical Structure and Evolution},
author = {Kazuhisa Noguchi and Yuichi Terashima and Yukiko Ishino and Yasuhiro Hashimoto and Michael Koss and Yoshihiro Ueda and Hisamitsu Awaki},
journal= {arXiv preprint arXiv:1002.0909},
year = {2015}
}
Comments
13 pages, 10 figures, accepted for publication in ApJ