We carried out observations toward the giant molecular cloud W 37 with the J = 1 - 0 transitions of ^ { 12 } CO , ^ { 13 } CO , and C ^ { 18 } O using the 13.7 m single-dish telescope at the Delingha station of Purple Mountain Observatory .
Based on the three CO lines , we calculated the column densities , cloud masses for the molecular clouds with radial velocities at around +20 \mathrm { km s } ^ { -1 } .
The gas mass of W 37 , calculated from ^ { 13 } CO emission , is 1.7 \times 10 ^ { 5 } M _ { \odot } , above the criteria of giant molecular cloud .
The dense ridge of W 37 is a dense filament , which is supercritical in linear mass ratio .
Dense clumps found by C ^ { 18 } O emission are aligned along the dense ridge with a regular interval about 2.8 pc , similar to the clump separation caused by large-scale ‘ sausage instability ’ .
We confirm the identification of the giant molecular filament ( GMF ) G 18.0-16.8 by and find a new giant filament , G 16.5-15.8 , located in the west \sim 0.8 \degr of G 18.0-16.8 .
Both GMFs are not gravitationally bound , as indicated by their low linear mass ratio ( \sim 80 M _ { \odot } \mathrm { pc } ^ { -1 } ) .
We compared the gas temperature map with the dust temperature map from Herschel images , and find similar structures .
The spatial distributions of class I objects and the dense clumps is reminiscent of triggered star formation occurring in the northwestern part of W 37 , which is close to NGC 6611 .