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arXiv 2005.10778astro-ph.GAastro-ph.SR
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M17 SWex中的云结构：可能的云-云碰撞

Cloud structures in M17 SWex : Possible cloud-cloud collision

Shinichi W. Kinoshita, Fumitaka Nakamura, Quang Nguyen-Luong, Benjamin Wu, Tomomi Shimoikura, Koji Sugitani, Kazuhito Dobashi, Hideaki Takemura, Patricio Sanhue… 展开作者

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, Cassandra Fallscheer

备注：
34 pages, 13 figures, Accepted for publication in PASJ
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摘要：

利用野边山45米望远镜的宽视场$^{13}$ CO（$J=1-0$）资料，利用SCIMES研究了M17红外暗云复合体的云结构。总共，我们确定了118个云，其中包含11个半径大于1 pc的大云。云主要分布在10 $-$ 20 km s $^{-1}$和30 $-$ 40 km s $^{-1}$两个代表性速度范围内。通过与ATLASGAL星表的比较，我们发现大多数具有10个20 km s $^{-1}$和30个40 km s $-$ CO云可能分别位于2 kpc（人马座臂）和3 kpc（盾牌臂）的距离上。通过对识别出的云的空间结构和速度结构的分析，试图揭示该地区云结构的成因。这里我们讨论三种可能性：（1）不同速度的重叠，（2）云的振荡，（3）云-云碰撞。从位置-速度图上，我们发现了$\sim$ 20 km s $^{-1}$和$\sim$ 35 km s $^{-1}$之间的空间扩展的微弱发射，主要分布在云层的空间重叠区。我们还发现，在某些地区，不同速度的云重叠，磁场的方向突然改变。散射辐射在位置-位置-速度空间中的分布和弯曲磁场的存在有利于云-云碰撞的发生。在云-云碰撞的情况下，我们建议，两个$\sim$ 35公里的$^{-1}$前景云碰撞的云在$\sim$ 20公里的$^{-1}$与15公里的s $^{-1}$的相对速度。这些云可能是速度分别为$\sim$ 35 km s $^{-1}$（$\gtrsim 10^3 $ M $_{\odot}$）和$\sim$ 20 km s $^{-1}$（$\gtrsim 10^4 $ M $_{\odot}$）的两个较大云的子结构。

英文摘要：

Using wide-field $^{13}$CO ($J=1-0$) data taken with the Nobeyama 45-m telescope, we investigate cloud structures of the infrared dark cloud complex in M17 with SCIMES. In total, we identified 118 clouds that contain 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$^{-1}$ and 30 $-$ 40 km s$^{-1}$. By comparing with the ATLASGAL catalog, we found that the majority of the $^{13}$CO clouds with 10 $-$ 20 km s$^{-1}$ and 30 $-$ 40 km s$^{-1}$ are 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. From the position-velocity diagrams, we found spatially-extended faint emission between $\sim$ 20 km s$^{-1}$ and $\sim$ 35 km s$^{-1}$, which is mainly distributed in the spatially-overlapped areas of the clouds. 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 $\sim$35 km s$^{-1}$ foreground clouds are colliding with clouds at $\sim$20 km s$^{-1}$ with a relative velocity of 15 km s$^{-1}$. These clouds may be substructures of two larger clouds having velocities of $\sim$ 35 km s$^{-1}$ ($\gtrsim 10^3 $ M$_{\odot}$) and $\sim$ 20 km s$^{-1}$ ($\gtrsim 10^4 $ M$_{\odot}$), respectively.

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