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NGC 1068的3-5微米高角分辨率谱：连续谱源发射和吸收特征的分布

The 3-5 micron Spectrum of NGC 1068 at High Angular Resolution: Distribution of Emission and Absorption Features across the Nuclear Continuum Source

T. R. Geballe, R. E. Mason, A. Rodríguez-Ardila, D. J. Axon

备注：
42 pages, incl. 2 tables and 5 figures. Accepted by ApJ on 22 June 2009. Typos fixed, references changed/removed
发表信息：
Astrophys.J.701:1710-1720,2009
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摘要：

我们报告中等分辨率的3-5微米光谱的NGC 1068的核在0.3弧秒（20 pc）的分辨率与摄谱仪狭缝对准近似沿电离锥的活动星系核。在这个方向上的核连续源的去卷积半高宽是0.3角秒。探测到了四条日冕线，它们的激发有很大的不同;每个峰值的强度都在无线电结C附近，大约在红外连续峰以北0.3弧秒，无线电喷流改变方向。加上在该位置附近观察到的加宽的谱线轮廓，这表明冲击电离是日冕谱线的主要激发机制。3.4微米碳氢化合物吸收的深度在连续峰的正南方最大，类似于10微米硅酸盐吸收。这一点以及两个特征在整个原子核中的光学深度的相似和快速变化表明，两者的大部分都出现在连续源前面的尘埃环境中。对CO的柱密度设定了一个新的更严格的限制。虽然尘埃屏的clueries模型可能解释硅酸盐特征的浅度，但3.4微米特征的存在和CO的缺乏强烈地让人想起银河系弥漫云环境，如果所有三种现象都发生在这样的环境中，那么对它们和观察到的硅酸盐特征的解释是一致的，离中央引擎只有10个百分点

英文摘要：

We report moderate resolution 3-5 micron spectroscopy of the nucleus of NGC 1068 obtained at 0.3 arcsec (20 pc) resolution with the spectrograph slit aligned approximately along the ionization cones of the AGN. The deconvolved FWHM of the nuclear continuum source in this direction is 0.3 arcsec. Four coronal lines of widely different excitations were detected; the intensity of each peaks near radio knot C, approximately 0.3 arcsec north of the infrared continuum peak, where the radio jet changes direction. Together with the broadened line profiles observed near that location, this suggests that shock-ionization is the dominant excitation mechanism of the coronal lines. The depth of the 3.4 micron hydrocarbon absorption is maximum at and just south of the continuum peak, similar to the 10 micron silicate absorption. That and the similar and rapid variations of the optical depths of both features across the nucleus suggest that substantial portions of both arise in a dusty environment just in front of the continuum source(s). A new and tighter limit is set on the column density of CO. Although clumpy models of the dust screen might explain the shallowness of the silicate feature, the presence of the 3.4 micron feature and the absence of CO are strongly reminiscent of Galactic diffuse cloud environments and a consistent explanation for them and the observed silicate feature is found if all three phenomena occur in such an environment, existing as close as 10 pc from the central engine.

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