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

Abstract

We present the results of Atacama Large Millimeter/submillimeter Array observations in 12 CO(1–0) emission at 0.58 × 0.52 pc 2 resolution toward the brightest H ii region N66 of the Small Magellanic Cloud (SMC). The 12 CO(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 ⊙ galaxy, the SMC, with similar kinematics as in N159W-South and N159E of the Large Magellanic Cloud.