ALMA Reveals a Cloud-Cloud Collision that Triggers Star Formation in the Small Magellanic Cloud

We present the results of Atacama Large Millimeter/submillimeter Array observations in 12CO(1-0) emission at 0.58 × 0.52 pc2 resolution toward the brightest H ii region N66 of the Small Magellanic Cloud (SMC). The 12CO(1-0) emission toward the north of N66 reveals clumpy filaments with multiple velocity components. Our analysis shows that a blueshifted filament at a velocity range of 154.4-158.6 km s-1 interacts with a redshifted filament at a velocity of 158.0-161.8 km s-1. A third velocity component at a velocity range of 161-165.0 km s-1 constitutes hub-filaments. An intermediate-mass young stellar object (YSO) and a young pre-main-sequence star cluster have hitherto been reported in the intersection of these filaments. We find a V-shape distribution in the position-velocity diagram at the intersection of two filaments. This indicates the physical association of those filaments due to a cloud-cloud collision. We determine the collision timescale 0.2 Myr using the relative velocity (5.1 km s-1) and displacement (1.1 pc) of those interacting filaments. These results suggest that the event occurred about 0.2 Myr ago and triggered the star formation, possibly an intermediate-mass YSO. We report the first observational evidence for a cloud-cloud collision that triggers star formation in N66N of the low metallicity 0.2 Z o galaxy, the SMC, with similar kinematics as in N159W-South and N159E of the Large Magellanic Cloud.