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تسجيل مستخدم جديدHigh-mass star formation triggered by collision between CO filaments in N159 West in the Large Magellanic Cloud
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We have carried out 13CO(J=2-1) observations of the active star-forming region N159 West in the LMC with ALMA. We have found that the CO distribution at a sub-pc scale is highly elongated with a small width. These elongated clouds called filaments show straight or curved distributions with a typical width of 0.5-1.0pc and a length of 5-10pc. All the known infrared YSOs 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 ~10^4 yrs. 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 ~10^5 yrs ago and triggered formation of the high-mass star having ~37 Mo. 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 magneto-hydro-dynamical numerical simulations (Inoue & Fukui 2013). This turbulence increases the mass accretion rate to ~6x10^-4 Mo yr^-1, which is required to overcome the stellar feedback to form the high-mass star.
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We report a possibility that the high-mass star located in the HII region RCW 34 was formed by a triggering induced by a collision of molecular clouds. Molecular gas distributions of the $^{12}$CO and $^{13}$CO $J=$2-1, and $^{12}$CO $J=$3-2 lines to
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We present the ALMA observations of CO isotopes and 1.3 mm continuum emission toward the N159E-Papillon Nebula in the Large Magellanic Cloud (LMC). The spatial resolution is 025-028 (0.06-0.07 pc), which is a factor of 3 higher than the previous ALMA
observations in this region. The high resolution allowed us to resolve highly filamentary CO distributions with typical widths of $sim$0.1 pc (full width half maximum) and line masses of a few 100 $M_{odot}$ pc$^{-1}$. The filaments (more than ten in number) show an outstanding hub-filament structure emanating from the nebular center toward the north. We identified for the first time two massive protostellar outflows of $sim$10$^4$ yr dynamical age along one of the most massive filaments. The observations also revealed several pillar-like CO features around the Nebula. The H II region and the pillars have a complementary spatial distribution and the column density of the pillars is an order of magnitude higher than that of the pillars in the Eagle nebula (M16) in the Galaxy, suggesting an early stage of pillar formation with an age younger than $sim$10$^5$ yr. We suggest that a cloud-cloud collision triggered the formation of the filaments and protostar within the last $sim$2 Myr. It is possible that the collision is more recent, as part of the kpc-scale H I flows come from the tidal interaction resulting from the close encounter between the LMC and SMC $sim$200 Myr ago as suggested for R136 by Fukui et al.
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