Nobeyama 45-m CO survey for Cygnus-X: possible evidences for formation of DR21 and W75N by cloud-cloud collision

We present 12CO(J=1-0), 13CO(J=1-0), C18O(J=1-0) and CN(N=1-0) images of the Cygnus-X region taken with Nobeyama 45-m telescope and FOREST receiver. Cygnus-X is one of the most active high-mass star formation site in the Galaxy, therefore, its understandings are important to reveal evolution of the Galaxy. The observations cover the almost entire area of Cygnus-X North and South clouds at the angular resolution of ~19" which corresponds to ~0.13 pc at the distance of 1.4 kpc. 
We find possible evidences for formation of DR21 and W75N high-mass star clusters by cloud-cloud collision. The region consists of two different velocity components, blue-shifted cloud (-7 -- 0 km/s) and red-shifted cloud (6 -- 15 km/s) also reported by Schneider et al. (2006), those are distributed complementary each other. The bridge features are detected between the two velocities around the clusters position. The position relation of the two clouds along the line-of-sight supports collision event. The colliding velocity ~10 km/s and column density ~1e23 cm-2 are explainable the formation of high-mass stars clusters in the region.