REVISING THE KINEMATICS OF 12 GHz CH{sub 3}OH MASERS TOWARD W3(OH)

Journal Article · Sun Jun 20 04:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/716/2/1356· OSTI ID:21452922

Moscadelli, L ^[1]; Xu, Y ^[2]; Chen, X ^[3]

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1. INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze (Italy)
2. Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)
3. Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

We derive accurate proper motions of the CH{sub 3}OH 12 GHz masers toward the W3(OH) ultra-compact (UC) H II region, employing seven epochs of VLBA observations spanning a time interval of about 10 yr. The achieved velocity accuracy is of the order of 0.1 km s{sup -1}, adequate to precisely measure the relative velocities of most of the 12 GHz masers in W3(OH), with amplitude varying in the range 0.3-3 km s{sup -1}. Toward W3(OH), the most intense 12 GHz masers concentrate in a small area toward the north (the northern clump) of the UC H II region. We have compared the proper motions of the CH{sub 3}OH 12 GHz masers with those (derived from literature data) of the OH 6035 MHz masers, emitting from the same region of the methanol masers. In the northern clump, the two maser emissions emerge from nearby (but likely distinct) cloudlets of masing gas with, in general, a rather smooth variation of line-of-sight and sky-projected velocities, which suggests some connection of the environments and kinematics traced by both maser types. The conical outflow model, previously proposed to account for the 12 GHz maser kinematics in the northern clump, does not reproduce the new, accurate measurements of 12 GHz maser proper motions and has to be rejected. We focus on the subset of 12 GHz masers of the northern clump belonging to the 'linear structure at P.A. = 130{sup 0}-140{sup 0}', whose regular variation of LSR velocities with position presents evidence for some ordered motion. We show that the three-dimensional velocities of this 'linear distribution' of 12 GHz masers can be well fitted considering a flat, rotating disk, seen almost edge-on.

• OSTI ID: 21452922
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 716; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ALCOHOLS
AMPLIFIERS
ASTROPHYSICS
ELECTRONIC EQUIPMENT
EQUIPMENT
FREQUENCY RANGE
GHZ RANGE
GHZ RANGE 01-100
HYDROXY COMPOUNDS
MASERS
METHANOL
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
MOTION
ORGANIC COMPOUNDS
PHYSICS
PROPER MOTION