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Voronkov M.A.,CSIRO | Voronkov M.A.,Astro Space Center | Caswell J.L.,CSIRO | Britton T.R.,CSIRO | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

The Australia Telescope Compact Array (ATCA) has been used to map class I methanol masers at 36 and 44GHz in G309.38-0.13. Maser spots are found at nine locations in an area of 50 × 30 arcsec2, with both transitions reliably detected at only two locations. The brightest spot is associated with shocked gas traced by 4.5-μm emission. The data allowed us to make a serendipitous discovery of a high-velocity 36-GHz spectral feature, which is blueshifted by about 30kms-1 from the peak velocity at this frequency, but spatially located close to (within a few arcseconds of) the brightest maser spot. We interpret this as indicating an outflow parallel to the line of sight. Such a high-velocity spread of maser features, which has not been previously reported in the class I methanol masers associated with a single molecular cloud, suggests that the outflow most likely interacts with a moving parcel of gas. © 2010 CSIRO. Journal compilation © 2010 RAS. Source


Voronkov M.A.,CSIRO | Voronkov M.A.,Astro Space Center | Caswell J.L.,CSIRO | Ellingsen S.P.,University of Tasmania | Sobolev A.M.,Ural Federal University
Monthly Notices of the Royal Astronomical Society | Year: 2010

The Australia Telescope Compact Array has been used to make the first extensive search for the class I methanol masers at 9.9 GHz. In total, 48 regions of high-mass star formation were observed. In addition to masers in W33-Met (G12.80. -0.19) and G343.12. -0.06 (IRAS 16547. -4247) which have already been reported in the literature, two new 9.9-GHz masers have been found towards G331.13. -0.24 and G19.61. -0.23. We have determined absolute positions (accurate to roughly a second of arc) for all the detected masers and suggest that some class I masers may be associated with shocks driven into molecular clouds by expanding H ii regions. Our observations also imply that the evolutionary stage of a high-mass star-forming region when the class I masers are present can outlast the stage when the class II masers at 6.7-GHz are detectable, and overlaps significantly with the stage when OH masers are active. © 2010 CSIRO. Journal compilation © 2010 RAS. Source


Kalinina N.D.,Ural Federal University | Sobolev A.M.,Ural Federal University | Kalenskii S.V.,Astro Space Center
New Astronomy | Year: 2010

Results of a spectral survey of molecular cores NGC 6334I and NGC 6334I(N) in a number of spectral intervals with widths of about 1000 MHz are presented. Observations were carried out with the SEST radiotelescope. Number of the intervals for NGC 6334I was 11. 209 spectral features were detected towards molecular core NGC 6334I, out of which 203 features were assigned to 25 species. Number of the intervals for NGC 6334I(N) was 6. They represent a subset of the intervals used for the NGC 6334I. The spectrum of NGC 6334I(N) appears to be considerably more poor with the features: 63 features were detected, out of which 55 were assigned to 13 species. Catalogues of assigned features for both sources are presented. They contain the notation of corresponding molecular transition, frequency, and the following observational data: integrated intensity, Vlsr velocity, FWHM and antenna temperature. © 2010 Elsevier B.V. All rights reserved. Source


Voronkov M.A.,CSIRO | Voronkov M.A.,Astro Space Center | Caswell J.L.,CSIRO | Ellingsen S.P.,University of Tasmania | And 6 more authors.
Proceedings of the International Astronomical Union | Year: 2012

We review properties of all known collisionally pumped (class I) methanol maser series based on observations with the Australia Telescope Compact Array (ATCA) and the Mopra radio telescope. Masers at 36, 84, 44 and 95 GHz are most widespread, while 9.9, 25, 23.4 and 104 GHz masers are much rarer, tracing the most energetic shocks. A survey of many southern masers at 36 and 44 GHz suggests that these two transitions are highly complementary. The 23.4 GHz maser is a new type of rare class I methanol maser, detected only in two high-mass star-forming regions, G357.97-0.16 and G343.12-0.06, and showing a behaviour similar to 9.9, 25 and 104 GHz masers. Interferometric positions suggest that shocks responsible for class I masers could arise from a range of phenomena, not merely an outflow scenario. For example, some masers might be caused by interaction of an expanding Hii region with its surrounding molecular cloud. This has implications for evolutionary sequences incorporating class I methanol masers if they appear more than once during the evolution of the star-forming region. We also make predictions for candidate maser transitions in the ALMA frequency range. Copyright © International Astronomical Union 2012. Source


Voronkov M.A.,CSIRO | Voronkov M.A.,Astro Space Center | Walsh A.J.,James Cook University | Caswell J.L.,CSIRO | And 6 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2011

We report the first detection of a methanol maser in the 101-92 A- transition at 23.4 GHz, discovered during the H2O southern Galactic Plane Survey (HOPS) with the 22-m Mopra Radio Telescope. In the region covered by HOPS, the 23.4-GHz maser was found at only one location, G357.97-0.16, which was also a prominent source of maser emission in the J2-J1 E series near 25GHz. The Australia Telescope Compact Array (ATCA) was used to follow up these detections at high angular resolution and prove the maser nature of the observed emission. The analysis shows that the new methanol maser at 23.4GHz is a class I maser, which has properties similar to the 9.9- and 25-GHz masers (i.e. traces strong shocks with higher than average temperature and density). All class I masers were found to originate at the same spatial location (within the measurement uncertainty of 0.5arcsec) in the vicinity of the dominant infrared source, but at a clearly distinct position from nearby OH, H2O and class II methanol masers at 6.7GHz. All maser species are distributed approximately on a line, but it is not clear at present whether this has any physical significance. We also detected a weak (1.3mJy) continuum source at 25GHz near the OH maser (at the most northern site, associated with a class II methanol maser and an H2O maser renowned for its extremely wide spread of velocity components). The continuum source has not been reported at lower frequencies and is therefore a candidate hypercompact Hii region. We also used the ATCA to find the strongest and only the fifth known 9.9-GHz maser towards G357.97-0.16 and another 23.4-GHz maser towards G343.12-0.06 not seen in HOPS. © 2011 CSIRO Monthly Notices of the Royal Astronomical Society © 2011 RAS. Source

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