8 research outputs found
Kinematic Structure of Molecular Gas around High-mass Star YSO, Papillon Nebula, in N159 East in the Large Magellanic Cloud
We present the ALMA Band 3 and Band 6 results of 12CO(2-1), 13$CO(2-1),
H30alpha recombination line, free-free emission around 98 GHz, and the dust
thermal emission around 230 GHz toward the N159 East Giant Molecular Cloud
(N159E) in the Large Magellanic Cloud (LMC). LMC is the nearest active
high-mass star forming face-on galaxy at a distance of 50 kpc and is the best
target for studing high-mass star formation. ALMA observations show that N159E
is the complex of filamentary clouds with the width and length of ~1 pc and 5
pc - 10 pc, respectively. The total molecular mass is 0.92 x 10^5 Msun from the
13CO(2-1) intensity. N159E harbors the well-known Papillon Nebula, a compact
high-excitation HII region. We found that a YSO associated with the Papillon
Nebula has the mass of 35 Msun and is located at the intersection of three
filamentary clouds. It indicates that the formation of the high-mass YSO was
induced by the collision of filamentary clouds. Fukui et al. 2015 reported a
similar kinematic structure toward a YSO in the N159 West region which is
another YSO that has the mass larger than 35 Msun in these two regions. This
suggests that the collision of filamentary clouds is a primary mechanism of
high-mass star formation. We found a small molecular hole around the YSO in
Papillon Nebula with sub-pc scale. It is filled by free-free and H30alpha
emission. Temperature of the molecular gas around the hole reaches ~ 80 K. It
indicates that this YSO has just started the distruction of parental molecular
cloud.Comment: 28 pages, 7 figures. Submitted to Ap
High-mass star formation triggered by collision between CO filaments in N159 West in the Large Magellanic Cloud
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.Comment: 20 pages, 3 figures, accepted for publication in ApJ