Star Cluster Formation in Orion A
  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.
