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arXiv 1002.0909astro-ph.GA
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活动星系核的散射X射线及其对几何结构和演化的意义

Scattered X-rays in Obscured Active Galactic Nuclei and their Implications for Geometrical Structure and Evolution

Kazuhisa Noguchi, Yuichi Terashima, Yukiko Ishino, Yasuhiro Hashimoto, Michael Koss, Yoshihiro Ueda, Hisamitsu Awaki

备注：
13 pages, 10 figures, accepted for publication in ApJ
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摘要：

我们构建了一个新的样本的32个模糊的活动星系核（AGN）从第二XMM-牛顿偶发源目录中选择，调查他们的多波长特性的“散射分数”，软X射线通量的吸收校正的直接发射的比率。样品覆盖了宽范围的散射分数（0.1%-10%）。四分之一的32 AGN有一个非常低的散射分数（小于0.5%），这表明他们被埋在一个几何厚环面与一个非常小的开口角。我们调查的散射分数和多波长特性之间的相关性。我们发现，活动星系核与一个小的散射分数往往有较低的[O III] A5007/X射线光度比。这一结果与窄线区域的范围小的预期一致，这是因为环面的开度角小。散射分数与远红外光度之间没有显著的相关性。这意味着环面的尺度高度并不主要由星暴活动决定。我们还比较了散射分数与黑洞质量和爱丁顿比的关系，发现它们之间存在弱的反相关关系。这意味着成长更快的超大质量黑洞往往有更厚的环面。

英文摘要：

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.

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