VLBI observations of 6.7 and 12.2 GHz methanol masers toward high 
mass star-forming regions

AbstractWe have conducted phase-reference VLBI observations of H2O and CH3OH masers toward two high-mass star forming regions, Sh 2-255 IR and AFGL 5142. In Sh 2-255 infrared water masers are aligned along a direction close to the orientation of a large scale H2 jet, tracing possibly shocked material in a precessing jet, or, alternatively, the disk-wind emerging from the disk atmosphere. In AFGL 5142 water masers trace expansion at the base of a protostellar jet, whilst methanol masers are more probably tracing infalling than outflowing gas. Our results suggest that water and methanol masers trace different kinematic structures in the circumstellar gas.

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VLBI observations of 6.7 and 12.2 GHz methanol masers toward high mass star-forming regions

Astronomy and Astrophysics ◽

10.1051/0004-6361:20010124 ◽

2001 ◽

Vol 369 (1) ◽

pp. 278-290 ◽

Cited By ~ 80

Author(s):

V. Minier ◽

J. E. Conway ◽

R. S. Booth

Keyword(s):

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Vlbi Observations ◽

Methanol Masers

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Class I and Class II methanol masers in high-mass star-forming regions

Astronomy and Astrophysics ◽

10.1051/0004-6361/200913679 ◽

2010 ◽

Vol 517 ◽

pp. A56 ◽

Cited By ~ 64

Author(s):

F. Fontani ◽

R. Cesaroni ◽

R. S. Furuya

Keyword(s):

Class Ii ◽

Class I ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Methanol Masers

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44 GHz Methanol Maser Surveys

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312006795 ◽

2012 ◽

Vol 8 (S287) ◽

pp. 133-140

Author(s):

S. E. Kurtz

Keyword(s):

Star Formation ◽

Formation Process ◽

Class Ii ◽

Class I ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Methanol Maser ◽

Star Forming Regions ◽

Methanol Masers

AbstractClass I 44 GHz methanol masers are not as well-known, as common, or as bright as their more famous Class II cousins at 6.7 and 12.2 GHz. Nevertheless, the 44 GHz masers are commonly found in high-mass star forming regions. At times they appear to trace dynamically important phenomena; at other times they show no obvious link to the star formation process. Here, we summarize the major observational efforts to date, including both dedicated surveys and collateral observations. The principal results are presented, some that were expected, and others that were unexpected.

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Periodicity in Class II methanol masers in high-mass star-forming regions

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stt2009 ◽

2013 ◽

Vol 437 (2) ◽

pp. 1808-1820 ◽

Cited By ~ 22

Author(s):

S. Goedhart ◽

J. P. Maswanganye ◽

M. J. Gaylard ◽

D. J. van der Walt

Keyword(s):

Class Ii ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Methanol Masers

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New class I methanol masers

Proceedings of the International Astronomical Union ◽

10.1017/s174392131200748x ◽

2012 ◽

Vol 8 (S287) ◽

pp. 433-440 ◽

Cited By ~ 3

Author(s):

M. A. Voronkov ◽

J. L. Caswell ◽

S. P. Ellingsen ◽

S. L. Breen ◽

T. R. Britton ◽

...

Keyword(s):

Class I ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Methanol Maser ◽

New Class ◽

Star Forming Regions ◽

Rare Class ◽

New Type ◽

Methanol Masers

AbstractWe 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.

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Understanding high-mass star formation through KaVA observations of water and methanol masers

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317011681 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 259-262

Author(s):

Kee-Tae Kim ◽

Tomoya Hirota ◽

Koichiro Sugiyama ◽

Jungha Kim ◽

Do-Young Byun ◽

...

Keyword(s):

Dynamical Evolution ◽

Young Stellar Objects ◽

High Mass ◽

Mass Star ◽

Stellar Objects ◽

Star Forming ◽

3 Dimensional ◽

Star Forming Regions ◽

Large Program ◽

Methanol Masers

AbstractDespite their importance in the formation and evolution of stellar clusters and galaxies, the formation of high-mass stars remains poorly understood. We recently started a systematic observational study of the 22 GHz water and 44 GHz class I methanol masers in high-mass star-forming regions as a four-year KaVA large program. Our sample consists of 87 high-mass young stellar objects (HM-YSOs) in various evolutionary phases, many of which are associated with two or more different maser species. The primary scientific goals are to measure the spatial distributions and 3-dimensional velocity fields of multiple maser species, and understand the dynamical evolution of HM-YSOs and their circumstellar structures, in conjunction with follow-up observations with JVN/EAVN (6.7 GHz class II methanol masers), VERA, and ALMA. In this paper we present details of our KaVA large program, including the first-year results and observing/data analysis plans for the second year and beyond.

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Probing Early Phases of High Mass Stars with 6.7 GHz Methanol Masers

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318000376 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 323-324

Author(s):

Sonu Tabitha Paulson ◽

Jagadheep D. Pandian

Keyword(s):

Star Formation ◽

Massive Star ◽

Dust Emission ◽

Black Body ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Methanol Masers ◽

Early Phases

AbstractMethanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards massive star forming regions. These masers can thus be used as a unique tool to probe the early phases of massive star formation. We present here the SED studies of 284 methanol masers chosen from the MMB catalogue, which falls in the Hi-GAL range (|l| ≤ 60°, |b| ≤ 1°). The masers are studied using the ATLASGAL, MIPSGAL and Hi-GAL data at wavelengths ranging from 24−870 micrometers. A single grey body component fit was used to model the cold dust emission whereas the emission from the warm dust is modelled by a black body. The clump properties such as isothermal mass, FIR luminosity and MIR luminosity were obtained using the best fit parameters of the SED fits. We discuss the physical properties of the sources and explore the evolutionary stages of the sources having 6.7 GHz maser emission in the timeline of high mass star formation.

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