Early-stage star-forming cloud cores in Galactic Legacy Infrared Mid-Plane Survey (GLIMPSE) extended green objects (EGOs) as traced by organic species
Early-stage star-forming cloud cores in Galactic Legacy Infrared Mid-Plane Survey (GLIMPSE) extended green objects (EGOs) as traced by organic species
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DOI：
10.1093/mnras/stu1758
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发表时间：
2014-08
影响因子：
4.8
通讯作者：
J. Ge;Jinhua He;Xi Chen;S. Takahashi
中科院分区：
文献类型：
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作者：
J. Ge;Jinhua He;Xi Chen;S. Takahashi
为了研究大质量恒星形成早期核的物理和化学性质，我们分析了CH 3OH、CH 3 OCH 3、HCOOCH 3和CH 3CH 2CN四种有机物对我们以前单碟谱线观测到的29个扩展绿色天体（EGO）云核的激发和丰度。发现EGO云核具有相似的甲醇J（3）-J（2）旋转温度，约为44 K，典型的线性尺寸约为0.036pc，典型的束流平均甲醇丰度约为10（-9）（束流校正值可达10（-7））。后三个物种的丰度，归一化的甲醇，也被发现是相关的各种各样的云，如EGO云核，热corinos，大规模的热核心和银河系中心云。EGO云核的化学性质介于热核和热可里诺之间。然而，这四个物种的丰度和丰度比不能令人满意的解释最近的化学模型，无论是在EGO云核或从文献中的各种类型的云核。
In order to investigate the physical and chemical properties of massive star-forming cores in the early stages, we analyse the excitation and abundance of four organic species, CH3OH, CH3OCH3, HCOOCH3 and CH3CH2CN, towards 29 extended green object (EGO) cloud cores that were observed by our previous single-dish spectral line survey. The EGO cloud cores are found to have similar methanol J(3)-J(2) rotation temperatures of similar to 44 K, a typical linear size of similar to 0.036 pc and a typical beam-averaged methanol abundance of several 10(-9) (the beam-corrected value could reach several 10(-7)). The abundances of the latter three species, normalized by that of methanol, are also found to be correlated across a large variety of clouds such as EGO cloud cores, hot corinos, massive hot cores and Galactic Centre clouds. The chemical properties of the EGO cloud cores lie between those of hot cores and hot corinos. However, the abundances and abundance ratios of the four species cannot be explained satisfactorily by recent chemical models, either among EGO cloud cores or among the various types of cloud core from literature.