ALMA reveals a cloud-cloud collision that triggers star formation in N66N of the Small Magellanic Cloud

Abstract

We present the results of Atacama Large Millimeter/submillimeter Array (ALMA) observation in ${}^{12}$CO(1-0) emission at 0.58 $\times$ 0.52 pc${}^2$ resolution toward the brightest HII region N66 of the Small Magellanic Cloud (SMC). The ${}^{12}$CO(1-0) emission toward the north of N66 reveals the clumpy filaments with multiple velocity components. Our analysis shows that a blueshifted filament at a velocity range 154.4-158.6 km s${}^{-1}$ interacts with a redshifted filament at a velocity 158.0-161.8 km s${}^{-1}$. A third velocity component in a velocity range 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 $\sim$ 0.2 Myr using the relative velocity ($\sim$ 5.1 km s${}^{-1}$) and displacement ($\sim$ 1.1 pc) of those interacting filaments. These results suggest that the event occurred at 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 $\sim$0.2 Z${}_{\odot }$ galaxy, the SMC, with similar kinematics as in N159W-South and N159E of the Large Magellanic Cloud.

arXiv comment9 pages, 5 figures. Accepted for publication in Astrophysical Journal Letters (ApJL)

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• An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. I. Overview: CO Cloud Distributions
• An ALMA Glimpse of Dense Molecular Filaments Associated with High-mass Protostellar Systems in the Large Magellanic Cloud
• An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. II. CO Cloud Catalog
• The First Detection of a Protostellar CO Outflow in the Small Magellanic Cloud with ALMA
• The internal proper motion kinematics of NGC346: past formation and future evolution
• Towards the impact of GMC collisions on the star formation rate
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• CO Observations of the SMC-N66 Hii Region with ALMA: Properties of Clumps along Filamentary Molecular Clouds and Possible Expansion Motion