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arXiv 1201.4240astro-ph.CO
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AGN统一模型的红外测试

Testing the AGN Unification Model in the Infrared

Cristina Ramos Almeida, N. A. Levenson, A. Alonso-Herrero, A. Asensio Ramos, J. M. Rodriguez Espinosa, A. M. Perez Garcia, C. Packham, R. Mason, J. T. Radomski, T. Diaz-Santos

摘要:

我们提出了近中红外光谱能量分布(SED)的21个塞弗特星系,使用亚角秒分辨率成像数据。我们的目的是比较性质的Seyfert 1(Sy 1)和Seyfert 2(Sy 2)环面使用cluttertorus模型和贝叶斯方法,以适应红外(IR)核SED。这些尘土飞扬的环面的物理尺寸小于6 pc半径,从我们的配合。活动星系核(AGN)的统一计划的各种观测差异的观察几何。然而,我们发现的证据表明,强统一可能不成立,并立即尘埃周围的Sy 1和Sy 2核本质上是不同的。这里研究的2型环面更广泛,有更多的团块,这些团块具有较低的光学深度比1型环面。环面的覆盖因子越大,直接观测活动星系核的概率越小,反之亦然。在我们的样本中,Sy 2环面具有比Sy 1环面更大的覆盖因子(C_T=0.95+/-0.02)和更小的逃逸概率(C_T=0.5+/-0.1)。因此,在这里提出的结果的基础上,塞弗特星系的分类可能更多地取决于环面的内在性质,而不是仅仅依赖于它的倾角,这与最简单的统一模型相矛盾。

英文摘要:

We present near-to-mid-infrared spectral energy distributions (SEDs) for 21 Seyfert galaxies, using subarcsecond resolution imaging data. Our aim is to compare the properties Seyfert 1 (Sy1) and Seyfert 2 (Sy2) tori using clumpy torus models and a Bayesian approach to fit the infrared (IR) nuclear SEDs. These dusty tori have physical sizes smaller than 6 pc radius, as derived from our fits. Active galactic nuclei (AGN) unification schemes account for a variety of observational differences in terms of viewing geometry. However, we find evidence that strong unification may not hold, and that the immediate dusty surroundings of Sy1 and Sy2 nuclei are intrinsically different. The Type 2 tori studied here are broader, have more clumps, and these clumps have lower optical depths than those of Type 1 tori. The larger the covering factor of the torus, the smaller the probability of having direct view of the AGN, and vice-versa. In our sample, Sy2 tori have larger covering factors (C_T=0.95+/-0.02) and smaller escape probabilities than those of Sy1 (C_T=0.5+/-0.1). Thus, on the basis of the results presented here, the classification of a Seyfert galaxy may depend more on the intrinsic properties of the torus rather than on its mere inclination, in contradiction with the simplest unification model.

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