Giant Molecular Clouds in M33. I. BIMA All-Disk Survey
Giant Molecular Clouds in M33. I. BIMA All-Disk Survey
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M33 中的巨型分子云。
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
L. Blitz
中科院分区：
文献类型：
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作者：
G. Engargiola;R. Plambeck;E. Rosolowsky;L. Blitz
我们首次给出了M33的整个Hα盘的~（12）CO（J = 1 → 0）干涉图。13″直径的合成光束对应于50 pc的线性分辨率，足以区分单个的巨分子云（GMC）。从这些数据中，我们生成了一个包含148个GMC的目录，预计不超过15个来源是虚假的。该星表完整到GMC质量为1.5 × 105 M，总质量为2.3 × 107 M。在选定的领域CO的单碟观测意味着，我们的调查检测到的CO流量的50%，因此，M33的总分子量为4.5 × 107 M，约2%的H I质量。在我们的目录中的GMC主要局限于中心区域（R < 4 kpc）。他们表现出显着的空间和运动学相关性与过密H I丝的几何形状表明，GMCs的形成如下的长丝。大麦哲伦星系的质谱dN/dM = 2.6±0.3，比银河系和大麦哲伦星系的质谱陡很多。结合总质量，这个陡峭的函数意味着M33中的GMC形式的特征质量为1.77 × 104 M。2/3以上的GMC具有H Ⅱ区，提示GMC具有较短的静止期。我们的研究结果表明，快速组装的分子云从原子气体，并迅速开始大规模的星星的形成。
We present the first interferometric 12CO (J = 1 → 0) map of the entire Hα disk of M33. The 13″ diameter synthesized beam corresponds to a linear resolution of 50 pc, sufficient to distinguish individual giant molecular clouds (GMCs). From these data we generated a catalog of 148 GMCs with an expectation that no more than 15 of the sources are spurious. The catalog is complete down to GMC masses of 1.5 × 105 M⊙ and contains a total mass of 2.3 × 107 M⊙. Single-dish observations of CO in selected fields imply that our survey detects ∼50% of the CO flux, hence that the total molecular mass of M33 is 4.5 × 107 M⊙, approximately 2% of the H I mass. The GMCs in our catalog are confined largely to the central region (R < 4 kpc). They show a remarkable spatial and kinematic correlation with overdense H I filaments; the geometry suggests that the formation of GMCs follows that of the filaments. The GMCs exhibit a mass spectrum dN/dM ∝ M-2.6±0.3, considerably steeper than that found in the Milky Way and in the LMC. Combined with the total mass, this steep function implies that the GMCs in M33 form with a characteristic mass of ∼7 × 104 M⊙. More than 2/3 of the GMCs have associated H II regions, implying that the GMCs have a short quiescent period. Our results suggest the rapid assembly of molecular clouds from atomic gas, with prompt onset of massive star formation.