Publ. Astron. Soc. Jap., 74, 128-151 (2022/February-1)
Star burst in W 49 N presumably induced by cloud-cloud collision.
MIYAWAKI R., HAYASHI M. and HASEGAWA T.
Abstract (from CDS):
We present high-resolution observations of CS (J = 1-0), H13CO+ (J = 1-0), and SiO (v = 0: J = 1-0) lines, together with the 49 GHz and 86 GHz continuum emissions, toward W 49 N carried out with the Nobeyama Millimeter Array. We identified 11 CS, eight H13CO+, and six SiO clumps with radii of 0.1-0.5 pc. The CS and H13CO+ clumps are mainly divided into two velocity components, one at 4 km s–1 and the other at 12 km s–1, while the SiO clumps have velocities between the two components. The SiO emission is distributed toward the ultracompact H II (UCHII) ring, where the 4 km s–1 component clumps of CS and H13CO+ also exist. The 12 km s–1 component clumps of CS are detected at the east and west of the UCHII ring with an apparent hole toward the ring. The clump masses vary from 4.4 x 102 M☉ to 4.9 x 104 M☉ with the mean values of 0.94 x 104 M☉, 0.88 x 104 M☉, and 2.2 x 104 M☉ for the CS, H13CO+, and SiO clumps, respectively. The total masses derived from CS, H13CO+, and SiO clumps are 1.0 x 105 M☉, 0.70 x 105 M☉, and 1.3 x 105 M☉, respectively, which agree well with the corresponding virial masses of 0.71 x 105 M☉, 1.3 x 105 M☉, and 0.88 x 105 M☉, respectively. The average molecular hydrogen densities of the clumps are 0.90 x 106 cm–3, 1.4 x 106 cm–3, and 7.6 x 106 cm–3 for the CS, H13CO+, and SiO clumps, respectively. The density derived from the SiO clumps seems significantly higher than those from the others, probably because the SiO emission is produced in high-density shocked regions. The free-fall time scale of the clumps is estimated to be ∼3 x 104 yr, which gives an accretion rate of 3 x 10–3-1 M☉ yr–1 on to a stellar core. The observed clumps are, if they are undergoing free-fall, capable of producing dozens of massive stars in the next 105 yr. We propose a view that two pre-existing clouds with radial velocities of 4 km s–1 and 12 km s–1 collided with each other almost face-on to produce the observed clumps with intermediate velocities and triggered the burst of massive star formation in W 49 N.
© The Author(s) 2021. Published by Oxford University Press on behalf of the Astronomical Society of Japan.
ISM: clouds - ISM: individual objects (W 49 A Molecular Cloud) - ISM - stars: massive - stars: formation
Status at CDS
Objects in title, abstract, text, figures, and all or part of small table(s) being processed in SIMBAD. // Examining the need for a new acronym.
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