高线性动态范围谱线成像揭示金牛座分子气体的大尺度结构
Large-Scale Structure of the Molecular Gas in Taurus Revealed by High Linear Dynamic Range Spectral Line Mapping
摘要：
我们报告的金牛座分子云区域的J = 1-0过渡的12 CO和13 CO的100平方度的调查结果。每个速度通道中的云的图像包括在20”网格上的约300万奈奎斯特采样像素。这两种同位素的高灵敏度和大的线性动态范围的地图揭示了一个非常复杂的，高度结构化的云形态。在13 CO发射中有明显的大尺度相关结构，具有非常精细的尺寸，包括细丝、空腔和环。12 CO的排放显示了一个完全不同的结构，特别是复杂的界面之间的区域的更大和更小的柱密度定义的最大规模的云结构的边界。从相对扩散的气体中的12 CO发射中看到的条纹的轴与磁场的方向对齐。使用一个列密度依赖模型的CO分数丰度，我们推导出的质量映射到24,000太阳质量的区域，一个因素的三个大于将获得与规范CO丰度限制在高列密度区域。我们确定云的一半质量是在柱密度低于2.1x10^{21}每平方厘米的区域。年轻恒星在覆盖区域的分布是高度不均匀的，当N（H2）= 6 × 10 ^{21} cm^{-2}时，在一个像素中找到一颗特定列密度恒星的概率急剧上升。我们确定了一个相对较低的恒星形成效率（年轻恒星质量/分子气体质量），在0.3%和1.2%之间，以及过去300万年的平均恒星形成率为8x 10 ^{-5}星/年^{-1}。
英文摘要：
We report the results of a 100 square degree survey of the Taurus Molecular Cloud region in the J = 1-0 transition of 12CO and 13CO. The image of the cloud in each velocity channel includes ~ 3 million Nyquist sampled pixels on a 20" grid. The high sensitivity and large linear dynamic range of the maps in both isotopologues reveal a very complex, highly structured cloud morphology. There are large scale correlated structures evident in 13CO emission having very fine dimensions, including filaments, cavities, and rings. The 12CO emission shows a quite different structure, with particularly complex interfaces between regions of greater and smaller column density defining the boundaries of the largest-scale cloud structures. The axes of the striations seen in the 12CO emission from relatively diffuse gas are aligned with the direction of the magnetic field. Using a column density-dependent model for the CO fractional abundance, we derive the mass of the region mapped to be 24,000 solar masses, a factor of three greater than would be obtained with canonical CO abundance restricted to the high column density regions. We determine that half the mass of the cloud is in regions having column density below 2.1x10^{21} per square cm. The distribution of young stars in the region covered is highly nonuniform, with the probability of finding a star in a pixel with a specified column density rising sharply for N(H2) = 6x10^{21} cm^{-2}. We determine a relatively low star formation efficiency (mass of young stars/mass of molecular gas), between 0.3 and 1.2 %, and an average star formation rate during the past 3 Myr of 8x10^{-5} stars yr^{-1}.
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