标题： 使用凯克I望远镜的LWS以衍射极限分辨率获得的NGC 1068的第一组空间分辨中红外光谱 显示英文标题

标题： The First Spatially Resolved Mid-IR Spectra of NGC 1068 Obtained at Diffraction-limited Resolution with LWS at Keck I Telescope

摘要： 我们利用凯克I望远镜的长波长光谱仪（LWS）以0.25\arcsec 的衍射极限分辨率，展示了NGC 1068的空间分辨中红外光谱。NGC 1068的中红外图像沿南北方向延伸。先前的成像研究表明，这些扩展区域位于电离锥内部，表明中红外辐射可能来自窄线云的内部区域，而非原本假设的尘埃环本身。在中红外的拉长区域，我们获得了两个不同狭缝位置角度（+8.0度和-13.0度）下的空间分辨中红外光谱。从这些光谱中，我们在北部扩展区域只发现了微弱的硅酸盐吸收，但在核区和南部扩展区域则发现强烈吸收。这与一个略微倾斜的冷致密遮蔽环模型一致，该模型覆盖了大部分南部区域，但位于北部扩展区域之后。尽管详细的光谱分析需要辐射转移模型，但北部扩展区域缺乏硅酸盐发射促使我们考虑双尘埃群体模型作为可能的解释之一，在这一模型中，电离锥内的尘埃群体与尘埃环中的尘埃群体存在差异。电离锥内的尘埃可能缺少小的硅酸盐颗粒，导致北部扩展区域只有无特征的连续谱，而尘埃环中的尘埃含有大量的小硅酸盐颗粒，从而在核区和南部扩展区域产生强烈的硅酸盐吸收线。 显示英文摘要

摘要： We present spatially resolved mid-IR spectra of NGC 1068 with a diffraction-limited resolution of 0.25\arcsec using the Long Wavelength Spectrometer (LWS) at the Keck I telescope. The mid-infrared image of NGC 1068 is extended along the N-S direction. Previous imaging studies have shown the extended regions are located inside the ionization cones indicating that the mid-infrared emission arises perhaps from the inner regions of the narrow-line clouds instead of the proposed dusty torus itself. The spatially resolved mid-IR spectra were obtained at two different slit position angles, +8.0 and -13.0 degrees across the elongated regions in the mid-IR. From these spectra, we found only weak silicate absorption toward the northern extended regions but strong in the nucleus and the southern extended regions. This is consistent with a model of a slightly inclined cold obscuring torus which covers much of the southern regions but is behind the northern extension. While a detailed analysis of the spectra requires a radiative transfer model, the lack of silicate emission from the northern extended regions prompts us to consider a dual dust population model as one of the possible explanations in which a different dust population exists in the ionization cones compared to that in the dusty torus. Dust inside the ionization cones may lack small silicate grains giving rise to only a featureless continuum in the northern extended regions while dust in the dusty torus has plenty of small silicate grains to produce the strong silicate absorption lines towards the nucleus and the southern extended regions.