We introduce new analysis methods for studying the star cluster formation processes in Orion A, especially examining the scenario of a cloud-cloud collision. We utilize the CARMA-NRO Orion survey $^{13}$CO (1-0) data to compare molecular gas to the properties of YSOs from the SDSS III IN-SYNC survey. We show that the increase of $v_{\rm 13CO} - v_{\rm YSO}$ and $\Sigma$ scatter of older YSOs can be signals of cloud-cloud collision. SOFIA-upGREAT 158$\mu$m [CII] archival data toward the northern part of Orion A are also compared to the $^{13}$CO data to test whether the position and velocity offsets between the emission from these two transitions resemble those predicted by a cloud-cloud collision model. We find that the northern part of Orion A, including regions ONC-OMC-1, OMC-2, OMC-3 and OMC-4, shows qualitative agreements with the cloud-cloud collision scenario, while in one of the southern regions, NGC1999, there is no indication of such a process in causing the birth of new stars. On the other hand, another southern cluster, L1641N, shows slight tendencies of cloud-cloud collision. Overall, our results support the cloud-cloud collision process as being an important mechanism for star cluster formation in Orion A.

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猎户座 A 中的星团形成

我们介绍了研究猎户座 A 星团形成过程的新分析方法，特别是检查云与云碰撞的场景。我们利用 CARMA-NRO Orion 调查 $^{13}$CO (1-0) 数据将分子气体与来自 SDSS III IN-SYNC 调查的 YSO 的特性进行比较。我们表明，$v_{\rm 13CO} - v_{\rm YSO}$ 和旧 YSO 的 $\Sigma$ 散射的增加可能是云-云碰撞的信号。SOFIA-upGREAT 158$\mu$m [CII] 朝向猎户座 A 北部的档案数据也与 $^{13}$CO 数据进行比较，以测试这两个跃迁的发射之间的位置和速度偏移是否类似于那些由云-云碰撞模型预测的。我们发现猎户座 A 的北部，包括区域 ONC-OMC-1、OMC-2、OMC-3 和 OMC-4，显示与云-云碰撞场景定性一致，而在南部地区之一，NGC1999，没有迹象表明这种过程会导致新恒星的诞生。另一方面，另一个南部星团 L1641N 显示出轻微的云云碰撞趋势。总的来说，我们的结果支持云-云碰撞过程是猎户座 A 星团形成的重要机制。