Infrared Spectroscopy of Seyfert 2 Galaxies: A Look through the Obscuring Torus? II.
Infrared Spectroscopy of Seyfert 2 Galaxies: A Look through the Obscuring Torus? II.
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DOI：
10.1086/303735
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发表时间：
1994-02
期刊：
影响因子：
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通讯作者：
S. Veilleux;R. Goodrich;G. Hill
中科院分区：
文献类型：
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作者：
S. Veilleux;R. Goodrich;G. Hill
本文给出了33个Seyfert 2星系的高分辨J带和K带光谱。其中两个星系也在L波段被观测到。这些数据被用来寻找宽的Paβ、Brγ和Brα线，以寻找在可见光波段被尘埃隐藏的宽线区域（BLR）。模糊的BLR被确认为三个先前报告的发现，新的数据表明可能在多达六个额外的塞弗特2的BLR检测。我们的结果与标准的环面模型是一致的，如果过渡区之间的光学薄的“喉”的环面和光学厚的核心是相当延长。柯尼格尔和卡特耶的沙尘风模型也可以解释这些数据。宽线区和窄线区的比较表明，BLR比窄线区（NLR）更加模糊。这一结果与环面和尘埃风模型的预测一致，尘埃位于NLR和BLR之间。的列深度的BLR与从X射线数据确定的列深度的比较表明，具有检测到的宽复合线的对象具有较低的X射线列的一般趋势。然而，在红外和X射线柱深度之间存在大的散射。核气体性质的波动（例如，金属丰度或气尘比）或电离和中性气体成分的分布差异可以很容易地解释这种散射。对于Seyfert 1星系，宽Paβ和Brγ的宽度位于分布的窄端。由宽红外线预测的去红宽Hβ光度与正常Seyfert 1的宽Hβ光度相似，硬X射线通量与预测的宽Hα通量的比值也相似。在通过红外光谱和分光偏振法检测到的具有BLR的物体中，宽红外线通常比散射通量预期的值强一个数量级。红外光谱也被用来评估Seyfert 2星系中[Fe II]和H2发射的起源。目前的数据排除的可能性，[Fe II]排放产生的仅仅是从一个环核星暴。与核外流相关的冲击是[Fe II]和H2的可能来源，尽管核连续体的光电离也可能有助于[Fe II]发射，X射线加热可能在产生H2发射中发挥作用。
High-resolution J-band and K-band spectra of a sample of 33 Seyfert 2 galaxies are presented. Two of these galaxies were also observed in the L band. These data are used to look for broad Paβ, Brγ, and Brα lines, in search of broad-line regions (BLRs) that are hidden by dust at optical wavelengths. Obscured BLRs are confirmed for three previously reported discoveries, and the new data suggest possible BLR detections in as many as six additional Seyfert 2's. Our results are consistent with the standard torus model if the transition zone located between the optically thin “throat” of the torus and the optically thick core is rather extended. The dusty wind model of Königl & Kartje can also explain the data. Comparisons of the broad-line and narrow-line extinctions indicate that the BLRs are considerably more obscured than the narrow-line regions (NLRs). This result agrees with the predictions of both the torus and dusty wind models, where the dust is located between the NLR and the BLR. Comparisons of the column depths to the BLRs with the column depths determined from X-ray data show a general tendency for the objects with detected broad recombination lines to have lower X-ray columns. A large scatter exists between the infrared and X-ray columns depths, however. Fluctuations in the properties of the nuclear gas (e.g., metallicity or gas-to-dust ratio) or differences in the distributions of the ionized and neutral gas components can easily account for this scatter. The widths of broad Paβ and Brγ lie on the narrow end of the distribution for Seyfert 1 galaxies. The dereddened broad Hβ luminosities predicted from the broad infrared lines are similar to the broad Hβ luminosities of normal Seyfert 1's, and so are the ratios of the hard X-ray flux to the predicted broad Hα flux. In objects with a BLR detected through both infrared spectroscopy and spectropolarimetry, the broad infrared lines often are an order of magnitude stronger than the values expected from the scattered flux. The infrared spectra were also used to assess the origin of the [Fe II] and H2 emission in Seyfert 2 galaxies. The present data rule out the possibility that the [Fe II] emission is produced solely from a circumnuclear starburst. Shocks associated with nuclear outflows are a likely source of both [Fe II] and H2, although photoionization by the nuclear continuum may also contribute to the [Fe II] emission, and X-ray heating may play a role in producing the H2 emission.