了解LMC-30 Dor极端环境下PDR性能的里程碑
A milestone toward understanding PDR properties in the extreme environment of LMC-30Dor
摘要：
更完整的星系演化知识需要了解恒星形成的过程和星际辐射场和星际介质之间的相互作用，在银河系环境穿越广泛的物理参数空间。在这里，我们专注于在大麦云云剑鱼座30周围的低金属丰度ISM的大质量恒星形成的影响。低金属丰度，就像早期宇宙中的一些星系一样，导致形成恒星形成所需的分子气体的紫外线屏蔽减少。该区域的半太阳金属量气体受到超级星团R136的强烈照射，使其成为在极端环境下研究ISM结构的理想实验室。我们的空间分辨研究调查了气体加热和冷却机制，特别是在光解离区域，其中化学和热平衡由远紫外光子（6 eV< hν<13.6 eV）调节。本文介绍了用PACS和SPIRE/FTS获得的远红外精细结构谱线的赫歇尔观测结果。我们结合了原子精细结构线从赫歇尔和斯皮策观测地面CO数据提供诊断的性质和结构的气体建模与Meudon PDR代码。我们导出了光离解气体和分子云的辐射场、压强、尺寸和填充因子的空间分布。通过PDR模型计算，我们发现压力范围为10^5 - 1.7 × 10^6 cm^{-3} K，入射辐射场G_UV范围为10^2 - 2.5 × 10^4。在平行平面几何和均匀介质的假设下，我们得到了1-3等的总消光，对应于0.2 - 3 pc的PDR云，CO深度尺度为0.06 - 0.5pc。我们还确定了气体的三维结构。（节录）
英文摘要：
More complete knowledge of galaxy evolution requires understanding the process of star formation and interaction between the interstellar radiation field and the interstellar medium in galactic environments traversing a wide range of physical parameter space. Here we focus on the impact of massive star formation on the surrounding low metallicity ISM in 30 Doradus in the Large Magellanic Cloud. A low metal abundance, as is the case of some galaxies of the early universe, results in less ultra-violet shielding for the formation of the molecular gas necessary for star formation to proceed. The half-solar metallicity gas in this region is strongly irradiated by the super star cluster R136, making it an ideal laboratory to study the structure of the ISM in an extreme environment. Our spatially resolved study investigates the gas heating and cooling mechanisms, particularly in the photo-dissociation regions where the chemistry and thermal balance are regulated by far-ultraviolet photons (6 eV< hν<13.6 eV). We present Herschel observations of far-infrared fine-structure lines obtained with PACS and SPIRE/FTS. We have combined atomic fine-structure lines from Herschel and Spitzer observations with ground-based CO data to provide diagnostics on the properties and the structure of the gas by modeling it with the Meudon PDR code. We derive the spatial distribution of the radiation field, the pressure, the size, and the filling factor of the photodissociated gas and molecular clouds. We find a range of pressure of ~ 10^5 - 1.7x10^6 cm^{-3} K and a range of incident radiation field G_UV ~ 10^2 - 2.5x10^4 through PDR modeling. Assuming a plane-parallel geometry and a uniform medium, we find a total extinction of 1-3 mag , which correspond to a PDR cloud size of 0.2 to 3pc, with small CO depth scale of 0.06 to 0.5pc. We also determine the three dimensional structure of the gas. (Abridged)
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