ISO-SWS Spectroscopy of NGC 1068
ISO-SWS Spectroscopy of NGC 1068
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NGC 1068 的 ISO-SWS 光谱
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
A. Sternberg
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作者：
D. Lutz;E. Sturm;R. Genzel;A. Moorwood;T. Alexander;H. Netzer;A. Sternberg
我们展示 NGC 1068 的红外空间天文台短波光谱仪 (ISO-SWS) 光谱，其分辨率可达 2.4-45 μm 的完整波长范围，分辨率约为 1500。已在更高的灵敏度和全分辨率~2000 下观察到选定的子范围。我们总共检测到 36 条发射线，并得出 13 条额外跃迁的上限。大多数观察到的跃迁是源自窄线区域（NLR）和扩展发射线区域内部的精细结构和重组线。我们比较了光学线和红化不敏感的红外线的线轮廓，以约束 NLR 的动态结构和消光特性。对于所发现的巨大差异，最可能的解释是两种效应的组合：(1) NGC 1068 NLR 的空间结构是高度电离的流出锥体和较低激发扩展发射的组合。 (2) NLR 的部分，主要是速度高于系统速度的后退部分，会受到消光的影响，从而显着抑制这些云的光发射。然而，即使对于几乎没有遮挡的红外精细结构线，线不对称和净蓝移仍然存在。这可能是由于 NLR 的固有不对称性（也许也由不对称射电连续谱发射所暗示），或者是由于非常高的列密度模糊组件，即使从红外视图中也隐藏了部分 NLR。我们提出了氢分子 (H2) 11 条旋转和振动发射线的检测和限制。它们出现在温度为几百开尔文的致密分子介质中，这很可能与近红外 H2 振动跃迁以及分子气体的毫米波示踪剂（CO、HCN）中看到的温暖而致密的成分密切相关。假定的秒差距尺度分子环面的任何发射都可能被这种更大规模的发射所淹没。在配套论文中，我们使用 SWS 数据推导了 NGC 1068 活动核发射的光谱能量分布，对模糊的宽线区域的红外发射进行了限制，并结合其他星系的 SWS 光谱讨论了连续谱及其特征。
We present Infrared Space Observatory-Short Wave Spectrometer (ISO-SWS) spectroscopy of NGC 1068 for the complete wavelength range 2.4-45 μm at resolving power ~1500. Selected subranges have been observed at higher sensitivity and full resolving power ~2000. We detect a total of 36 emission lines and derive upper limits for 13 additional transitions. Most of the observed transitions are fine-structure and recombination lines originating in the narrow-line region (NLR) and the inner part of the extended emission-line region. We compare the line profiles of optical lines and reddening-insensitive infrared lines to constrain the dynamical structure and extinction properties of the NLR. The most likely explanation of the considerable differences found is a combination of two effects: (1) The spatial structure of the NGC 1068 NLR is a combination of a highly ionized outflow cone and lower excitation extended emission. (2) Parts of the NLR, mainly in the receding part at velocities above systemic, are subject to extinction that is significantly suppressing optical emission from these clouds. Line asymmetries and net blueshifts remain, however, even for infrared fine-structure lines suffering very little obscuration. This may be either due to an intrinsic asymmetry of the NLR, as perhaps also suggested by the asymmetric radio continuum emission or due to a very high column density obscuring component which is hiding part of the NLR even from infrared view. We present detections and limits for 11 rotational and rovibrational emission lines of molecular hydrogen (H2). They arise in a dense molecular medium at temperatures of a few hundred kelvins that is most likely closely related to the warm and dense components seen in the near-infrared H2 rovibrational transitions, and in millimeter-wave tracers (CO, HCN) of molecular gas. Any emission of the putative parsec-scale molecular torus is likely overwhelmed by this larger scale emission. In companion papers we use the SWS data to derive the spectral energy distribution emitted by the active nucleus of NGC 1068, to put limits on infrared emission from the obscured broad-line region, and discuss the continuum and its features in conjunction with SWS spectra of other galaxies.