Cloud-cloud collisions in the common foot point of molecular loops 1 and 2 in the Galactic Center

摘要

Recent large-area, deep CO surveys in the Galactic disk have revealed the formation of similar to 50 high-mass stars or clusters triggered by cloud-cloud collisions (CCCs). Although the Galactic Center (GC)-which contains the highest volume density of molecular gas-is the most favorable place for cloud collisions, systematic studies of CCCs in that region are still untouched. Here we report for the first time evidence of CCCs in the common foot point of molecular loops 1 and 2 in the GC. We have investigated the distribution of molecular gas toward the foot point by using a methodology for identifying CCCs, and we have discovered clear signatures of CCCs. Using the estimated displacements and relative velocities of the clouds, we find the elapsed time since the beginnings of the collisions to be 10(5)-10(6) yr. We consider possible origins for previously reported peculiar velocity features in the foot point and discuss star formation triggered by CCCs in the GC.