Suzaku Observations of Active Galactic Nuclei Detected in the Swift BAT Survey: Discovery of a “New Type” of Buried Supermassive Black Holes
Suzaku Observations of Active Galactic Nuclei Detected in the Swift BAT Survey: Discovery of a “New Type” of Buried Supermassive Black Holes
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DOI：
10.1086/520576
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发表时间：
2007-06
期刊：
影响因子：
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通讯作者：
Y. Ueda;S. Eguchi;Y. Terashima;R. Mushotzky;J. Tueller;C. Markwardt;N. Gehrels;Y. Hashimoto;S. Potter
中科院分区：
文献类型：
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作者：
Y. Ueda;S. Eguchi;Y. Terashima;R. Mushotzky;J. Tueller;C. Markwardt;N. Gehrels;Y. Hashimoto;S. Potter
本文介绍了Swift BAT硬x射线（bbb15kev）巡天探测到的两个agn （Swift J0601.9-8636和Swift J0138.6-4001）的Suzaku宽带观测结果，这两个agn之前没有x射线数据。Suzaku光谱显示两个物体均具有柱密度为NH≃1023.5-1024 cm-2的重吸收幂律分量，柱密度在10kev以上，并且在冷、光学厚的介质中具有实体角≥2π的强反射分量。我们发现这些agn具有极小的来自原子核的散射光的比例，相对于本征幂律分量来说，仅为小于0.5%。这表明它们被埋在一个几何上非常厚的环面中，开口角很小，并且/或者有异常少量的气体负责散射。在前一种情况下，根据反射分量的小吸收推断，SWIFT J0601.9-8636的几何形状应该是接近正面的。在这个小样本中发现了两个这样的物体，这意味着在当地的宇宙中一定有大量尚未被识别的，非常康普顿厚的agn，以更大的倾角被观察到，即使在目前最灵敏的光学或硬x射线调查中也很难探测到。
We present the Suzaku broadband observations of two AGNs detected by the Swift BAT hard X-ray (>15 keV) survey that did not have previous X-ray data, SWIFT J0601.9-8636 and SWIFT J0138.6-4001. The Suzaku spectra reveal in both objects a heavily absorbed power-law component with a column density of NH ≃ 1023.5-1024 cm-2 that dominates above 10 keV and an intense reflection component with a solid angle ≳2π from a cold, optically thick medium. We find that these AGNs have an extremely small fraction of scattered light from the nucleus, ≲0.5% with respect to the intrinsic power-law component. This indicates that they are buried in a very geometrically thick torus with a small opening angle and/or have an unusually small amount of gas responsible for scattering. In the former case, the geometry of SWIFT J0601.9-8636 should be nearly face-on as inferred from the small absorption for the reflection component. The discovery of two such objects in this small sample implies that there must be a significant number of yet unrecognized, very Compton thick AGNs viewed at larger inclination angles in the local universe, which are difficult to detect even in the currently most sensitive optical or hard X-ray surveys.