论文标题
[CII]158μm自我吸收和光学深度效应
[CII] 158 μm self-absorption and optical depth effects
论文作者
论文摘要
语境。 [CII]158μm远红外（FIR）精细结构线是星形星际介质（ISM）的最重要的冷却线之一。高光谱分辨率观察结果显示了[CII]发射的线谱中的复杂结构。目标。我们的目的是确定在[^{12} CII]中观察到的复杂曲线是由于沿视线沿线速度成分还是基于[^{^{12} CII]和同位素[^{13} CII]线的比较而引起的。方法。与M43，Horsehead〜Pdr，Monoceros〜R2和M17〜SW中的Sofia/up-Great 7像素阵列接收器进行深入整合，允许检测光学薄[^{13} CII]发射线，以及[^{12} CII]发射线，具有高信号到noise noise速率。我们首先从单个组件模型得出[^{12} CII]光学深度和[CII]柱密度。但是，观察到的复杂线轮廓需要具有发射背景和吸收前景的双层模型。多组分速度拟合使我们能够得出[CII]气体的物理条件：色谱柱密度和激发温度。结果。我们在所有四个来源中发现了中度至高[^{12} CII]光学深度，并且在Mon R2和M17 SW中发现了[^{12} CII]的自我吸收。温暖背景发射的高柱密度对应于高达41 mag的等效AV。前景的吸收需要大量的冷和致密[CII]气体密度，同等的AV范围约为13 mag。结论。温暖背景材料的柱密度需要沿视线和速度堆叠的多个光子主导区域（PDR）表面。在吸收中检测到的密集和冷前景的巨大柱密度不能用任何已知的情况来解释，我们只能推测其起源
Context. The [CII] 158 μm far-infrared (FIR) fine-structure line is one of the most important cooling lines of the star-forming interstellar medium (ISM). High spectral resolution observations have shown complex structures in the line profiles of the [CII] emission. Aims. Our aim is to determine whether the complex profiles observed in [^{12}CII] are due to individual velocity components along the line-of-sight or to self-absorption based on a comparison of the [^{12}CII] and isotopic [^{13}CII] line profiles. Methods. Deep integrations with the SOFIA/upGREAT 7-pixel array receiver in M43, Horsehead~PDR, Monoceros~R2, and M17~SW allow for the detection of optically thin [^{13}CII] emission lines, along with the [^{12}CII] emission lines, with a high signal-to-noise ratio. We first derived the [^{12}CII] optical depth and the [CII] column density from a single component model. However, the complex line profiles observed require a double layer model with an emitting background and an absorbing foreground. A multi-component velocity fit allows us to derive the physical conditions of the [CII] gas: column density and excitation temperature. Results. We find moderate to high [^{12}CII] optical depths in all four sources and self-absorption of [^{12}CII] in Mon R2 and M17 SW. The high column density of the warm background emission corresponds to an equivalent Av of up to 41 mag. The foreground absorption requires substantial column densities of cold and dense [CII] gas, with an equivalent Av ranging up to about 13 mag. Conclusions. The column density of the warm background material requires multiple photon-dominated region (PDR) surfaces stacked along the line of sight and in velocity. The substantial column density of dense and cold foreground [CII] gas detected in absorption cannot be explained with any known scenario and we can only speculate on its origins
