Scattered X-rays in Obscured Active Galactic Nuclei and Their Implications for Geometrical Structure and Evolution
Abstract
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 (<= 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]λ5007/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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2010
- DOI:
- 10.1088/0004-637X/711/1/144
- arXiv:
- arXiv:1002.0909
- Bibcode:
- 2010ApJ...711..144N
- Keywords:
-
- galaxies: active;
- galaxies: Seyfert;
- X-rays: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 13 pages, 10 figures, accepted for publication in ApJ