Cloud structures in M 17 SWex : Possible cloud-cloud collision
Cloud structures in M 17 SWex : Possible cloud-cloud collision
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M 17 SWex 中的云结构：可能的云与云碰撞
DOI：
10.1093/pasj/psaa053
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发表时间：
2021
影响因子：
2.3
通讯作者：
and Cassandra Fallscheer
中科院分区：
文献类型：
--
作者：
Shinichi W. Kinoshita;Fumitaka Nakamura;Quang Nguyen-Luong;Benjamin Wu;Tomomi Shimoikura;Koji Sugitani;Kazuhito Dobashi;Hideaki Takemura;Patricio Sanhueza;Kee-Tae Kim;Hyunwoo Kang;Neal J Evans;Glenn J White;and Cassandra Fallscheer
Using wide-field13CO (J= 1−0) data taken with the Nobeyama 45 m telescope, we investigate cloud structures of the infrared dark cloud complex in M 17 with Spectral Clustering for Interstellar Molecular Emission Segmentation. In total, we identified 118 clouds that include 11 large clouds with radii larger than 1 pc. The clouds are mainly distributed in the two representative velocity ranges of 10–20 km s−1and 30–40 km s−1. By comparing this with the ATLASGAL catalog, we found that the majority of the13CO clouds with 10–20 km s−1and 30–40 km s−1are likely located at distances of 2 kpc (Sagittarius arm) and 3 kpc (Scutum arm), respectively. Analyzing the spatial configuration of the identified clouds and their velocity structures, we attempt to reveal the origin of the cloud structure in this region. Here we discuss three possibilities: (1) overlapping with different velocities, (2) cloud oscillation, and (3) cloud–cloud collision. In the position–velocity diagrams, we found spatially extended faint emission between ∼20 km s−1and ∼35 km s−1, which is mainly distributed in the spatially overlapped areas of the clouds. Additionally, the cloud complex system is unlikely to be gravitationally bound. We also found that in some areas where clouds with different velocities overlapped, the magnetic field orientation changes abruptly. The distribution of the diffuse emission in the position–position–velocity space and the bending magnetic fields appear to favor the cloud–cloud collision scenario compared to other scenarios. In the cloud–cloud collision scenario, we propose that two ∼35 km s−1foreground clouds are colliding with clouds at ∼20 km s−1with a relative velocity of 15 km s−1. These clouds may be substructures of two larger clouds having velocities of ∼35 km s−1(≳103M⊙) and ∼20 km s−1(≳104M⊙), respectively.
