Seyfert星系中秒差距尺度的尘埃分布--MIDI AGN快照巡天的结果
Parsec-scale dust distributions in Seyfert galaxies - Results of the MIDI AGN snapshot survey
摘要：
活动星系核（AGN）的中红外光谱主要是由暖尘埃辐射所决定的。只有干涉观测提供了必要的角分辨率来分辨核尘埃并研究其分布和性质。因此，对活动星系核中尘埃的研究是VLTI中红外干涉仪的主要科学目标之一。作为第一步，验证了活动星系核观测的可行性，并确定了最有希望进行详细研究的源。这是在一个“快照调查”中进行的，使用了保证时间的观测。在调查中，试图观测13个在中红外线中最明亮的活动星系核，这些活动星系核在帕拉纳尔可见。三个最明亮，研究最好的来源的结果已在单独的论文中发表。在这里，我们提出的干涉观测其余10个，较暗的活动星系核。对于其中8个，可以进行干涉测量。根据7个活动星系核的干涉测量数据，对活动星系核加热尘埃的空间范围进行了大小估计或限制。这表明尘埃的分布是紧凑的，大小在几个秒差距的数量级。导出的大小大致与中红外线的光度的平方根S ~ sqrt（L）成比例，在类型1和类型2对象之间没有明确的区别。这与加热到T ~ 300 K的近光学厚尘埃结构模型一致。对于三个源，由于硅酸盐的10微米的功能是暂时检测到无论是在发射或吸收。根据迄今为止使用ARM-A研究的所有活动星系核的结果，我们得出结论，在中红外线中，单个星系核之间的差异大于1型和2型物体之间的一般差异。
英文摘要：
The emission of warm dust dominates the mid-infrared spectra of active galactic nuclei (AGN). Only interferometric observations provide the necessary angular resolution to resolve the nuclear dust and to study its distribution and properties. The investigation of dust in AGN cores is hence one of the main science goals for the MID-infrared Interferometric instrument MIDI at the VLTI. As the first step, the feasibility of AGN observations was verified and the most promising sources for detailed studies were identified. This was carried out in a "snapshot survey" with MIDI using Guaranteed Time Observations. In the survey, observations were attempted for 13 of the brightest AGN in the mid-infrared which are visible from Paranal. The results of the three brightest, best studied sources have been published in separate papers. Here we present the interferometric observations for the remaining 10, fainter AGN. For 8 of these, interferometric measurements could be carried out. Size estimates or limits on the spatial extent of the AGN-heated dust were derived from the interferometric data of 7 AGN. These indicate that the dust distributions are compact, with sizes on the order of a few parsec. The derived sizes roughly scale with the square root of the luminosity in the mid-infrared, s ~ sqrt(L), with no clear distinction between type 1 and type 2 objects. This is in agreement with a model of nearly optically thick dust structures heated to T ~ 300 K. For three sources, the 10 micron feature due to silicates is tentatively detected either in emission or in absorption. Based on the results for all AGN studied with MIDI so far, we conclude that in the mid-infrared the differences between individual galactic nuclei are greater than the generic differences between type 1 and type 2 objects.
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