用Herschel观测到的恒星形成的最早阶段（EPoS）：B68的尘埃温度和密度分布
The Earliest Phases of Star formation observed with Herschel (EPoS): The dust temperature and density distributions of B68
摘要：
在赫歇尔GTKP“恒星形成的最早阶段”的框架内，我们拍摄了100至500 μ m之间的B68。将辅助（亚）mm数据、12/13 CO（2-1）跃迁的谱线图以及NIR消光图添加到分析中。我们采用了射线跟踪算法来获得二维中平面尘埃温度和体积密度分布，而不遭受损失的平均效果简单的SED拟合程序。额外的3D辐射转移计算被用来研究外部辐射和FIR图中发现的特殊新月形形态之间的联系。首次空间解析了B68的尘埃温度和密度分布。我们发现T_dust从边缘的16.7 K下降到中心的8.2 K，这比简单的SED拟合方法的结果低约4 K。中心的N_H峰位于4.3x10^22 cm^-2，n_H峰位于3.4x10^5 cm^-3。B68的材料质量为3.1兆太阳，假设距离为150秒差距，A_K > 0.2等。我们在东南树干中探测到一个致密源，这在消光和CO中也可以看到。我们发现从内部高原边缘向外的径向密度分布为n_H ~ r^-3.5。这种陡峭的轮廓可以由以下任一种或两种原因引起：具有显著UV贡献的外部照射或晶体结构的碎裂。我们的三维辐射转移模型的外部照射的核心各向异性ISRF再现新月形态。我们的一氧化碳观测表明，B68在空间和速度上都是一串小球的一部分，这可能表明它曾经是一个分散的细丝的一部分。我们还解决了一个新的紧凑的源在东南干线，并发现它是轻微的质心速度从B68，贷款定性支持核心碰撞的情况。
英文摘要：
(Abriged) In the framework of the Herschel GTKP "The earliest phases of star formation", we have imaged B68 between 100 and 500 um. Ancillary (sub)mm data, spectral line maps of the 12/13CO(2-1) transitions as well as a NIR extinction map were added to the analysis. We employed a ray-tracing algorithm to derive the 2D mid-plane dust temperature and volume density distribution without suffering from LoS averaging effects of simple SED fitting procedures. Additional 3D radiative transfer calculations were employed to investigate the connection between the external irradiation and the peculiar crescent shaped morphology found in the FIR maps. For the first time, we spatially resolve the dust temperature and density distribution of B68. We find T_dust dropping from 16.7 K at the edge to 8.2 K in the centre, which is about 4 K lower than the result of the simple SED fitting approach. N_H peaks at 4.3x10^22 cm^-2 and n_H at 3.4x10^5 cm^-3 in the centre. B68 has a mass of 3.1 M_sun of material with A_K > 0.2 mag for an assumed distance of 150 pc. We detect a compact source in the southeastern trunk, which is also seen in extinction and CO. We find the radial density distribution from the edge of the inner plateau outward to be n_H ~ r^-3.5. Such a steep profile can arise from either or both of the following: external irradiation with a significant UV contribution or the fragmentation of filamentary structures. Our 3D radiative transfer model of an externally irradiated core by an anisotropic ISRF reproduces the crescent morphology. Our CO observations show that B68 is part of a chain of globules in both space and velocity, which may indicate that it was once part of a filament which dispersed. We also resolve a new compact source in the SE trunk and find that it is slightly shifted in centroid velocity from B68, lending qualitative support to core collision scenarios.
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