The dusty torus plays a vital role in unifying active galactic nuclei (AGNs). However, the physical structure of the torus remains largely unclear. Here we present a systematical investigation of the torus mid-infrared (MIR) spectroscopic feature, i.e., the 9.7 um silicate line, of $175$ AGNs selected from the Swift/BAT Spectroscopic Survey (BASS). Our sample is constructed to ensure that each of the $175$ AGNs has Spizter/IRS MIR, optical, and X-ray spectroscopic coverage. Therefore, we can simultaneously measure the silicate strength, optical emission lines, and X-ray properties (e.g., the column density and the intrinsic X-ray luminosity). We show that, consistent with previous works, the silicate strength is weakly correlated with the hydrogen column density ($N_\mathrm{H}^\mathrm{X}$), albeit with large scatters. For X-ray unobscured AGNs, the silicate-strength-derived $V$-band extinction and the broad-H$\alpha$-inferred one are both small; however, for X-ray obscured AGNs, the former is much larger than the latter. In addition, we find that the optical type 1 AGNs with strong X-ray absorption on average show significant silicate absorption, indicating that their X-ray absorption might not be caused by dust-free gas in the broad-line region. Our results suggest that the distribution and structure of the obscuring dusty torus are likely to be very complex. We test our results against the smooth and clumpy torus models and find evidence in favor of the clumpy torus model.

中文翻译：

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X 射线吸收和 9.7 μm 硅酸盐特征作为 AGN 环面结构的探针

尘土飞扬的环面在统一活动星系核 (AGN) 中起着至关重要的作用。然而，环面的物理结构在很大程度上仍不清楚。在这里，我们对从 Swift/BAT 光谱调查 (BASS) 中选择的 175 美元 AGN 的环面中红外 (MIR) 光谱特征（即 9.7 um 硅酸盐线）进行了系统研究。我们的样本旨在确保每个 175 美元的 AGN 都具有 Spizter/IRS MIR、光学和 X 射线光谱覆盖范围。因此，我们可以同时测量硅酸盐强度、光发射线和 X 射线特性（例如，柱密度和本征 X 射线光度）。我们表明，与之前的工作一致，硅酸盐强度与氢柱密度 ($N_\mathrm{H}^\mathrm{X}$) 的相关性较弱，尽管散布很大。对于 X 射线未遮挡 AGN，硅酸盐强度推导的$V$带消光和宽H$\alpha$推导的消光都很小；然而，对于 X 射线遮蔽的 AGN，前者比后者大得多。此外，我们发现具有强X射线吸收的光学1型AGN平均表现出显着的硅酸盐吸收，表明它们的X射线吸收可能不是由宽线区域的无尘气体引起的。我们的结果表明，模糊的尘埃环的分布和结构可能非常复杂。我们针对平滑和块状环面模型测试我们的结果，并找到支持块状环面模型的证据。我们发现具有强X射线吸收的光学1型AGN平均表现出显着的硅酸盐吸收，表明它们的X射线吸收可能不是由宽线区域的无尘气体引起的。我们的结果表明，模糊的尘埃环的分布和结构可能非常复杂。我们针对平滑和块状环面模型测试我们的结果，并找到支持块状环面模型的证据。我们发现具有强X射线吸收的光学1型AGN平均表现出显着的硅酸盐吸收，表明它们的X射线吸收可能不是由宽线区域的无尘气体引起的。我们的结果表明，模糊的尘埃环的分布和结构可能非常复杂。我们针对平滑和块状环面模型测试我们的结果，并找到支持块状环面模型的证据。