TORUS AND ACTIVE GALACTIC NUCLEUS PROPERTIES OF NEARBY SEYFERT GALAXIES: RESULTS FROM FITTING INFRARED SPECTRAL ENERGY DISTRIBUTIONS AND SPECTROSCOPY
TORUS AND ACTIVE GALACTIC NUCLEUS PROPERTIES OF NEARBY SEYFERT GALAXIES: RESULTS FROM FITTING INFRARED SPECTRAL ENERGY DISTRIBUTIONS AND SPECTROSCOPY
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DOI：
10.1088/0004-637x/736/2/82
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发表时间：
2011-05
期刊：
影响因子：
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通讯作者：
A. Alonso-Herrero;C. Ramos Almeida;R. Mason;A. Asensio Ramos;P. Roche;N. Levenson;M. Elitzur;C. Packham;J. M. Rodríguez Espinosa;S. Young;T. Díaz-Santos;A. Pérez-García
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作者：
A. Alonso-Herrero;C. Ramos Almeida;R. Mason;A. Asensio Ramos;P. Roche;N. Levenson;M. Elitzur;C. Packham;J. M. Rodríguez Espinosa;S. Young;T. Díaz-Santos;A. Pérez-García
我们使用了CLUMPY环面模型和贝叶斯方法拟合了13个附近Seyfert星系的红外光谱能量分布和地面高角分辨率中红外光谱。这使我们能够对环面模型参数施加严格的约束，如观测角度i、环面径向厚度Y、云分布的角尺寸σ环面，以及沿径向赤道射线N0的平均云数。我们发现，观测角度i并不是控制星系分类为1型或2型的唯一参数。原则上，只要在视线上有一片云，就可以在任何视角下观察到2s型。对于团块介质来说，一个更相关的量是活动星系核（AGN）光子不被吸收而逃逸的概率。在我们的样本中，类型1具有相对较高的逃逸概率，为Pesc ~ 12%-44%，而类型2，如预期的那样，往往具有非常低的逃逸概率。我们的拟合也证实了塞弗特星系的环面是紧密的，环面模型半径在1 - 6pc之间。模型对数据的缩放也提供了AGN的放热光度Lbol(AGN)，这与文献中的估计非常一致。当我们将Seyfert星系的样本与文献中的PG类星体样本结合起来，跨越Lbol(AGN) ~ 1043-1047 erg s−1的范围时，我们发现了环面后退的可信证据。也就是说，在高AGN光度下，环面几何覆盖因子（f2 ~ 0.1 ~ 0.3）比在低AGN光度下（f2 ~ 0.9 ~ 1，在~ 1043 ~ 1044 erg s−1）有更低的趋势。这是因为在低AGN光度下，环面看起来有更宽的角尺寸（更大的σ环面）和更多的沿径向赤道射线的云。然而，我们不能排除这种可能性，即这是由于在低AGN亮度下与尘埃环面无关的扩展尘埃结构污染所致，因为我们样本中的大多数尘埃结构都位于高度倾斜的星系中。
We used the CLUMPY torus models and a Bayesian approach to fit the infrared spectral energy distributions and ground-based high angular resolution mid-infrared spectroscopy of 13 nearby Seyfert galaxies. This allowed us to put tight constraints on torus model parameters such as the viewing angle i, the radial thickness of the torus Y, the angular size of the cloud distribution σtorus, and the average number of clouds along radial equatorial rays N0. We found that the viewing angle i is not the only parameter controlling the classification of a galaxy into type 1 or type 2. In principle, type 2s could be viewed at any viewing angle i as long as there is one cloud along the line of sight. A more relevant quantity for clumpy media is the probability for an active galactic nucleus (AGN) photon to escape unabsorbed. In our sample, type 1s have relatively high escape probabilities, Pesc ∼ 12%–44%, while type 2s, as expected, tend to have very low escape probabilities. Our fits also confirmed that the tori of Seyfert galaxies are compact with torus model radii in the range 1–6 pc. The scaling of the models to the data also provided the AGN bolometric luminosities Lbol(AGN), which were found to be in good agreement with estimates from the literature. When we combined our sample of Seyfert galaxies with a sample of PG quasars from the literature to span a range of Lbol(AGN) ∼ 1043–1047 erg s−1, we found plausible evidence of the receding torus. That is, there is a tendency for the torus geometrical covering factor to be lower (f2 ∼ 0.1–0.3) at high AGN luminosities than at low AGN luminosities (f2 ∼ 0.9–1 at ∼1043–1044 erg s−1). This is because at low AGN luminosities the tori appear to have wider angular sizes (larger σtorus) and more clouds along radial equatorial rays. We cannot, however, rule out the possibility that this is due to contamination by extended dust structures not associated with the dusty torus at low AGN luminosities, since most of these in our sample are hosted in highly inclined galaxies.