Herein , we present results from observations of the ^ { 12 } CO ( J =1–0 ) , ^ { 13 } CO ( J =1–0 ) , and ^ { 12 } CO ( J =2–1 ) emission lines toward the Carina nebula complex ( CNC ) obtained with the Mopra and NANTEN2 telescopes .
We focused on massive-star-forming regions associated with the CNC including the three star clusters Tr 14 , Tr 15 , and Tr 16 , and the isolated WR-star HD 92740 .
We found that the molecular clouds in the CNC are separated into mainly four clouds at velocities -27 , -20 , -14 , and -8 km s ^ { -1 } .
Their masses are 0.7 \times 10 ^ { 4 } M _ { \odot } , 5.0 \times 10 ^ { 4 } M _ { \odot } , 1.6 \times 10 ^ { 4 } M _ { \odot } , and 0.7 \times 10 ^ { 4 } M _ { \odot } , respectively .
Most are likely associated with the star clusters , because of their high ^ { 12 } CO ( J =2–1 ) / ^ { 12 } CO ( J =1–0 ) intensity ratios and their correspondence to the Spitzer 8 \mu m distributions .
In addition , these clouds show the observational signatures of cloud–cloud collisions .
In particular , there is a V-shaped structure in the position–velocity diagram and a complementary spatial distribution between the -20 km s ^ { -1 } cloud and the -14 km s ^ { -1 } cloud .
Based on these observational signatures , we propose a scenario wherein the formation of massive stars in the clusters was triggered by a collision between the two clouds .
By using the path length of the collision and the assumed velocity separation , we estimate the timescale of the collision to be \sim 1 Myr .
This is comparable to the ages of the clusters estimated in previous studies .