HIGH-MASS STAR FORMATION TRIGGERED BY COLLISION BETWEEN CO FILAMENTS IN N159 WEST IN THE LARGE MAGELLANIC CLOUD

Abstract

We have carried out 13CO(J = 2–1) observations of the active star-forming region N159 west in the Large Magellanic Cloud with ALMA. We have found that the CO distribution at a sub-parsec scale is highly elongated with a small width. These elongated clouds called "filaments" show straight or curved distributions with a typical width of 0.5–1.0 pc and a length of 5–10 pc. All the known infrared young stellar objects are located toward the filaments. We have found broad CO wings of two molecular outflows toward young high-mass stars in N159W-N and N159W-S, whose dynamical timescale is ∼104 years. This is the first discovery of protostellar outflow in external galaxies. For N159W-S, which is located toward an intersection of two filaments, we set up a hypothesis that the two filaments collided with each other ∼105 years ago and triggered the formation of the high-mass star having ∼37 . The colliding clouds show significant enhancement in linewidth in the intersection, suggesting excitation of turbulence in the shocked interface layer between them, as is consistent with the magnetohydrodynamical numerical simulations. This turbulence increases the mass accretion rate to yr−1, which is required to overcome the stellar feedback to form the high-mass star.