红外暗云中分子气体团块的性质研究

Study on the Properties of Molecular Gas Clumps in IRDCs

利用^(12)CO(1-0)、^(13)CO(1-0)与C^(18)O(1-0)分子谱线成图观测数据,并结合ATLASGAL(The APEX(Atacama Pathfinder Experiment)Telescope Large Area Survey of the Galaxy)尘埃连续谱巡天观测结果详细地研究了9个红外暗云(Infrared Dark Clouds,IRDCs)中团块的物理性质与运动学特征.给出了红外暗云的速度区间,以及在红外暗云所对应的Spitzer(Spitzer Space Telescope)8μm辐射背景上叠加了与红外暗云轮廓基本吻合的^(13)CO和C^(18)O积分强度分布图.9个红外暗云中有8个呈纤维状结构.在这些红外暗云中共找出51个致密团块,质量偏大的团块大部分聚集在红外暗云的枢纽位置.质量统计直方图中表现出明显的双峰结构,进一步证实纤维状分子云物质输送的图景.^(12)CO(1-0)计算所得的典型激发温度T_(ex)在这些团块中的分布为10-15 K之间.证认出3个蓝轮廓的团块和5个红轮廓的团块,发现有17个处于不同演化阶段的团块与外流候选体位置重叠,这表明外流活动可能普遍存在于不同演化阶段的团块中.在MSF(Massive Star-Forming)团块和YSO(Young Stellar Object)团块中较高的外流探测率表明吸积率随着团块中恒星形成的演化阶段而增加.这些都是引力束缚的团块,并有可能进一步塌缩.所有团块都满足形成大质量恒星的基本物理条件.这些处在不同演化阶段的早期大质量恒星形成团块是研究大质量恒星形成的理想候选体.

Using the observation data of ^(12)CO(1-0),^(13)CO(1-0)and C^(18)O(1-0)lines,and combined with the observation results of ATLASGAL(The APEX(Atacama Pathfinder Experiment)Telescope Large Area Survey of the Galaxy)dust continuum survey,the physical properties and kinematic characteristics of clumps have been studied in nine infrared dark clouds(IRDCs)in detail.Velocity range of infrared dark clouds are given.It is showed that the Spitzer 8μm radiation background corresponding to the infrared dark cloud is superimposed with the ^(13)CO(1-0)and C^(18)O(1-0)integral intensity distribution map basically consistent with the outline of the infrared dark cloud.Eight of the nine IRDCs present the filamentary structure.Totally,with 51 identified dense clumps in these infrared dark clouds,most of these clumps with large masses gather at the hub of infrared dark clouds.The obvious bimodal structure is shown in the mass statistical histogram,which further confirms the picture of matter transport in a fibrous molecular cloud.The typical excitation temperature distribution of CO in these clumps is between 10 K and 15 K.We find three clumps with blue profiles and five clumps with red profiles.There are 17 in different evolution stages associated with outflow candidates,so outflow should be common in clumps.The higher detection rate of outflow in MSF(Massive Star-Forming)and YSO(Young Stellar Object)clumps may indicate that the accretion in the process of star formation may increase with the evolution stage of star formation in the clumps.All of these clumps are gravitationally bound and tend to collapse.All clumps meet the basic physical conditions for the formation of massive stars.These early stage massive star-forming clumps at different evolution stages are ideal targets to study the massive star formation.