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VLBA Imaging of 12.2 GHz Methanol Masers

Published online by Cambridge University Press:  12 April 2016

S. P. Ellingsen ,
P.M. McCulloch ,
P. J. Diamond  and
R. P. Norris
S. P. Ellingsen
Affiliation:
University of Tasmania, Hobart, TAS, Australia
P.M. McCulloch
Affiliation:
University of Tasmania, Hobart, TAS, Australia
P. J. Diamond
Affiliation:
National Radio Astronomy Observatory, Socorro, NM, USA
R. P. Norris
Affiliation:
Australia Telescope National Facility, Epping, NSW, Australia

Abstract

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We have used the VLBA to image the 12.2 GHz (20-3−1 E) masing transition of methanol toward the massive star formation region G345.01+1.79. The maser spots are distributed in a curved structure with a near monotonic velocity distribution along the curve. The cluster of maser emission covers an area of approximately 200 milli-arcseconds in right ascension and 70 milli-arcseconds in declination.

Comparison of the positions of the 12.2 GHz methanol maser spots in G345.01+1.79 as determined from the 1995 VLBA observations with 1988 Parkes-Tidbinbilla Interferometer observations shows that the relative positions of the maser spots detected in both epochs has changed by less than 5 milli-arcseconds during that interval. Assuming a distance of 2.3 kpc to G345.01+1.79 implies an upper limit on the relative tangential velocities of the maser spots of 7 km s−1.

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 164: Radio Emission from Galactic and Extragalactic Compact Sources , 1998 , pp. 375 - 376
Copyright
Copyright © Astronomical Society of the Pacific 1998

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