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.

中文翻译：

---

M 17 SWex 中的云结构：可能的云-云碰撞

使用 Nobeyama 45 米望远镜拍摄的宽视场 $^{13}$CO ($J=1-0$) 数据，我们使用 SCIMES 研究了 M17 中红外暗云复合体的云结构。我们总共确定了 118 个云，其中包含 11 个半径大于 1 pc 的大云。云层主要分布在 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 目录比较，我们发现大部分 $^{13}$CO 云具有 10 $-$ 20 km s$^{-1}$ 和 30 $-$ 40 km s$^{-1 }$ 可能分别位于 2 kpc（射手臂）和 3 kpc（盾牌臂）的距离处。分析识别出的云的空间配置及其速度结构，我们试图揭示该区域云结构的起源。这里我们讨论三种可能性：(1) 不同速度重叠，(2) 云振荡，(3) 云与云碰撞。从位置速度图中，我们发现 $\sim$ 20 km s$^{-1}$ 和 $\sim$ 35 km s$^{-1}$ 之间的空间扩展微弱发射，主要分布在云的空间重叠区域。我们还发现，在一些不同速度的云层重叠的区域，磁场方向发生了突变。与其他场景相比，位置-位置-速度空间中漫射发射的分布和弯曲磁场似乎有利于云-云碰撞场景。在云-云碰撞场景中，我们提出两个 $\sim$35 km s$^{-1}$ 前景云以 $\sim$20 km s$^{-1}$ 的相对速度与云碰撞15 公里 s$^{-1}$。