The fractal structure of the interstellar medium suggests that the interaction of UV radiation with the ISM as described in the context of photon-dominated regions (PDR) dominates most of the physical and chemical conditions, and hence the far-infrared and submm emission from the ISM in the Milky Way. We investigate to what extent the Galactic FIR line emission of the important species CO, C, C+, and O, as observed by the Cosmic Background Explorer (COBE) satellite can be modeled in the framework of a clumpy, UV-penetrated cloud scenario. The far-infrared line emission of the Milky Way is modeled as the emission from an ensemble of clumps with a power law clump mass spectrum and mass-size relation with power-law indices consistent with the observed ISM structure. The individual clump line intensities are calculated using the KOSMA-tau PDR-model for spherical clumps. The model parameters for the cylindrically symmetric Galactic distribution of the mass density and volume filling factor are determined by the observed radial distributions. A constant FUV intensity, in which the clumps are embedded, is assumed. We show that this scenario can explain, without any further assumptions and within a factor of about 2, the absolute FIR-line intensities and their distribution with Galactic longitude as observed by COBE.
目的：本文的目的是了解仙王座B中光子占主导地位的区域的发射，估计仙王座B中大量气体中中性碳的柱密度，并推导出对决定中性碳相对于CO丰度的因素的限制。本文给出了492 GHz CI和12 CO 4-3的15'× 15'全采样图，它们是用KOSMA观测的1'分辨率的。这些新的观测结果与FCRAO 12 CO 1-0、IRAM-30 m 13 CO 2-1和C18 O 1-0数据以及HIRES/IRAS的远红外连续谱数据相结合。KOSMA-tau球形PDR模型已被用于理解仙王座B中PDR的CI和CO发射，并解释了观测到的C^0和CO相对丰度的变化。结果：与仙王座B相关的PDR的发射主要在-14 km s ^-1和-11 km s^-1之间的VLSR处。我们估计约23%的观察到的CII发射的分子热点是由于电离气体在HII区域。尽管CO柱密度变化了一个数量级，但在材料的整体上，C^0柱密度没有显著变化，为2.0+-1.4 x10 ^17 cm^-2。在仙王座B中观测到的\cbyco丰度比在0.06和4之间变化。我们发现所观察到的C/CO丰度比与所观察到的氢柱密度的反相关性，即使包括所有以前的观察提供C/CO比。在这里，我们表明，这种观察到的C/CO丰度与总柱密度的变化可以解释只有由一个合奏团的团块组成的clustrialPDR。在高的H2柱密度，表现出低的C/CO丰度，高质量的团块占主导地位…
Exploring Halo Substructure with Giant Stars: A diffuse star cloud or tidal debris around the Milky Way in Triangulum-Andromeda
我们在这里报告发现了一个明显多余的2 M质量的巨星候选者，其去红0.85 < J-K_S < 1.2，至少在$100\degr < l < 150\degr$和$-20\degr > b > -40\degr$之间的相当大的天球区域，并且覆盖了三角座和仙女座的大部分星座。这种结构似乎并不优先分布在一个清晰的核心周围，而是位于数十千秒差距之外的一个纤细的，cluberous云状结构中。简化的自行图以及子样本的光谱显示这些多余的恒星是真正的巨星，而不是污染的矮星。径向速度测量表明，在这些M巨星的速度色散$σ< 17$ km s $^{-1}$的相干运动学结构的存在。我们的发现支持银河系周围存在相当分散的恒星结构，由于其无核和稀疏的分布，可能是潮汐流或一种新的卫星星系的一部分。
