Using the NANTEN2 Observatory, we carried out a molecular line study of high-mass star forming regions with reflection nebulae, NGC 2068 and NGC 2071, in Orion in the 13CO(J=2-1) transition. The 13CO distribution shows that there are two velocity components at 9.0 and 10.5 km/s . The blue-shifted component is in the northeast associated with NGC 2071, whereas the red-shifted component is in the southwest associated with NGC 2068. The total intensity distribution of the two clouds shows a gap of ~1 pc, suggesting that they are detached at present. A detailed spatial comparison indicates that the two show complementary distributions. The blue-shifted component lies toward an intensity depression to the northwest of the red-shifted component, where we find that a displacement of 0.8 pc makes the two clouds fit well with each other. Furthermore, a new simulation of non-frontal collisions shows that observations from 60 degrees off the collisional axis agreed well with the velocity structure in this region. On the basis of these results, we hypothesize that the two components collided with each other at a projected relative velocity 3.0 km/s estimated to be 0.3 Myr for an assumed axis of the relative motion 60 degrees off the line of sight. We assume that the two most massive early B-type stars in the cloud, illuminating stars of the two reflection nebulae, were formed by collisional triggering at the interfaces between the two clouds. Given the other young high-mass star forming regions, namely, M42, M43, and NGC 2024 (Fukui et al. 2018b; Ohama et al. 2017a), it seems possible that collisional triggering has been independently working to form O-type and early B-type stars in Orion in the last Myr over a projected distance of ~80 pc.

中文翻译：

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猎户座的大质量恒星形成可能是由云-云碰撞引发的。三、NGC 2068 和 NGC 2071

使用 NANTEN2 天文台，我们对猎户座 13CO(J=2-1) 跃迁中具有反射星云 NGC 2068 和 NGC 2071 的大质量恒星形成区域进行了分子线研究。13CO 分布显示在 9.0 和 10.5 km/s 处有两个速度分量。蓝移分量在与 NGC 2071 相关的东北部，而红移分量在与 NGC 2068 相关的西南部。两团云的总强度分布显示出~1 pc 的差距，表明它们是分离的目前。详细的空间比较表明两者显示出互补的分布。蓝移分量位于红移分量西北部的强度降低处，我们发现 0.8 pc 的位移使两朵云相互吻合。此外，非正面碰撞的新模拟表明，从碰撞轴偏离 60 度的观测结果与该区域的速度结构非常吻合。基于这些结果，我们假设两个组件以 3.0 km/s 的预计相对速度相互碰撞，对于偏离视线 60 度的相对运动的假定轴估计为 0.3 Myr。我们假设云中两颗质量最大的早期 B 型恒星，照亮了两个反射星云的恒星，是通过在两个云之间的界面处碰撞触发而形成的。鉴于其他年轻的大质量恒星形成区，即 M42、M43 和 NGC 2024（Fukui 等人 2018b；Ohama 等人 2017a），