Propagation of Highly Efficient Star Formation in the North American Nebula (NGC 7000)

We mapped the molecular cloud associated with the North American Nebula in the NH₃ lines and the H₂O maser using the Kashima 34-m telescope. The line ratio shows the molecular gas is cold. For the clumps and subclumps in the cloud we also estimate the star forming efficiency (SFE). The east end of the cloud shows the highest SEF, 0.62, and the other end is the lowest, 0.06. The 3 dimensional structure derived using the published Hα map suggests the east end is in the HII region and it should be a reason why the SFE is high there.