scholarly journals 0″.4 BIMA Array Mapping of the 107 GHz Methanol Maser in W3(OH)

1998 ◽  
Vol 164 ◽  
pp. 379-380
Author(s):  
V. I. Slysh ◽  
I. E. Val’tts ◽  
S. V. Kalenskii ◽  
G. M. Larionov ◽  
L. G. Mundy
Keyword(s):  
Brightness Temperature ◽  
Lower Limit ◽  
Angular Resolution ◽  
Class Ii ◽  
Methanol Maser ◽  
H Ii Region ◽  
Methanol Masers

AbstractUsing A-configuration of the BIMA-array with 0″.4 angular resolution maps were obtained of the 107 GHz methanol line in W3(OH). The 107 GHz masers have their counterparts in another methanol transition at 6.7 GHz. The strongest maser spots are unresolved with the BIMA-array and are less than , which corresponds to the lower limit of the brightness temperature 5×105 K. A model of Class II methanol masers emitted in the extended atmosphere of icy planets orbiting around the O-star which excites H ɪɪ region is proposed.

scholarly journals The evolutionary status of protostellar clumps hosting class II methanol masers

2020 ◽  
Vol 493 (2) ◽  
pp. 2015-2041 ◽  
Author(s):  
B M Jones ◽  
G A Fuller ◽  
S L Breen ◽  
A Avison ◽  
J A Green ◽  
...  
Keyword(s):  
Galactic Plane ◽  
Dust Emission ◽  
Principal Component ◽  
Far Infrared ◽  
Class Ii ◽  
Young Stellar Objects ◽  
Galactic Centre ◽  
Evolutionary Status ◽  
Methanol Maser ◽  
Methanol Masers

ABSTRACT The Methanol MultiBeam survey (MMB) provides the most complete sample of Galactic massive young stellar objects (MYSOs) hosting 6.7 GHz class II methanol masers. We characterize the properties of these maser sources using dust emission detected by the Herschel Infrared Galactic Plane Survey (Hi-GAL) to assess their evolutionary state. Associating 731 (73 per cent) of MMB sources with compact emission at four Hi-GAL wavelengths, we derive clump properties and define the requirements of an MYSO to host a 6.7 GHz maser. The median far-infrared (FIR) mass and luminosity are 630 M⊙ and 2500 L⊙ for sources on the near side of Galactic centre and 3200 M⊙ and 10000 L⊙ for more distant sources. The median luminosity-to-mass ratio is similar for both at ∼4.2 L⊙  M⊙−1. We identify an apparent minimum 70 μm luminosity required to sustain a methanol maser of a given luminosity (with $L_{70} \propto L_{6.7}\, ^{0.6}$). The maser host clumps have higher mass and higher FIR luminosities than the general Galactic population of protostellar MYSOs. Using principal component analysis, we find 896 protostellar clumps satisfy the requirements to host a methanol maser but lack a detection in the MMB. Finding a 70 μm flux density deficiency in these objects, we favour the scenario in which these objects are evolved beyond the age where a luminous 6.7 GHz maser can be sustained. Finally, segregation by association with secondary maser species identifies evolutionary differences within the population of 6.7GHz sources.

scholarly journals Methanol Masers—Are They in Circumstellar Disks?

1998 ◽  
Vol 164 ◽  
pp. 377-378
Author(s):  
R. P. Norris ◽  
C. J. Phillips ◽  
S. P. Ellingsen
Keyword(s):  
Recent Work ◽  
Circumstellar Disks ◽  
Methanol Maser ◽  
H Ii Region ◽  
Methanol Masers ◽  
Water Masers

AbstractSince the discovery of the 12.2 and 6.7 GHz methanol maser lines, these masers have been studied in great detail. Even in the earliest studies, it appeared that in some fraction of the sources, the maser spots were arranged in lines. This contrasts with the well-studied OH and water masers, in which the masers tended to be clustered almost randomly around a compact H ɪɪ region. Here I describe recent work to investigate the hypothesis that these lines represent edge-on circumstellar disks.

scholarly journals Space-VLBI observations of OH masers

2002 ◽  
Vol 206 ◽  
pp. 105-111 ◽  
Author(s):  
Vyacheslav I. Slysh ◽  
Maxim A. Voronkov ◽  
Irina E. Val'tts ◽  
Victor Migenes ◽  
K.M. Shibata ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Lower Limit ◽  
Radio Telescope ◽  
Angular Resolution ◽  
Main Line ◽  
Radio Telescopes ◽  
Space Radio Telescope ◽  
Vlbi Observations ◽  
Interstellar Scattering

We report on the first space-VLBI observations of the OH masers in two main-line OH transitions at 1665 and 1667 MHz. The observations involved the space radio telescope on board the Japanese satellite HALCA and an array of ground radio telescopes. The maps of the maser region and images of individual maser spots were produced with an angular resolution of 1 mas, which is several times higher than the angular resolution available on the ground. The maser spots were only partly resolved and a lower limit to the brightness temperature 6 × 1012 K was obtained. The masers seem to be located in the direction of low interstellar scattering.

scholarly journals Influence of dust parameters on class II methanol maser pumping

2002 ◽  
Vol 206 ◽  
pp. 183-186
Author(s):  
Andrei B. Ostrovskii ◽  
Andrej M. Sobolev
Keyword(s):  
Chemical Composition ◽  
Dust Emission ◽  
Class Ii ◽  
Dilution Factor ◽  
Model Calculations ◽  
Dust Layer ◽  
Methanol Maser ◽  
Wide Range ◽  
Maser Line ◽  
Methanol Masers

Results of model calculations for class II methanol masers (MMII) are presented. The model of the pumping assumes that an external dust layer provides the source of energy for maser excitation. The dependence of the emergent maser spectrum on the properties of the dust layer is studied. These properties include the chemical composition and sizes of dust grains, the temperature and optical depth of the dust layer. as well as the dilution factor of external dust emission. It is shown that, in order to reproduce the observed patterns of class II methanol maser line ratios, the pumping dust layer should be mostly composed of silicate grains with sizes smaller than 0.01 μ. It is shown that the layer of warm (> 125 K) dust effectively pumps the strongest MMII transitions over a wide range of 30 μ dust opacities (0.01–2) and dilution factors (0.02–0.5).

scholarly journals Imaging of selected sources from the Methanol Multibeam Survey

2007 ◽  
Vol 3 (S242) ◽  
pp. 184-185
Author(s):  
D. Wong-McSweeney ◽  
G. A. Fuller ◽  
S. Etoka
Keyword(s):  
Angular Resolution ◽  
Galactic Plane ◽  
High Angular Resolution ◽  
Maser Emission ◽  
Methanol Maser ◽  
Preliminary Results ◽  
Methanol Masers ◽  
Maser Sources

AbstractHigh angular resolution observations are essential for understanding the nature of maser emission and the sources which excite it. Here we present preliminary results from MERLIN observations of three methanol masers from the Toruń survey. These MERLIN observations are being analysed as part of the interferometric component of the Methanol Multibeam (MMB) Survey which is surveying the Galactic plane at |b|≤2° for 6.67 GHz methanol maser sources.

scholarly journals A Sensitive Search for Predicted Methanol Maser Transitions with the Australia Telescope Compact Array

2016 ◽  
Vol 33 ◽  
Author(s):  
A. Chipman ◽  
S. P. Ellingsen ◽  
A. M. Sobolev ◽  
D. M. Cragg
Keyword(s):  
Star Formation ◽  
Class Ii ◽  
High Mass ◽  
Mass Star ◽  
Radio Telescopes ◽  
Methanol Maser ◽  
Upper Limit ◽  
Methanol Masers ◽  
Star Formation Regions ◽  
Compact Array

AbstractWe have used the Australia Telescope Compact Array to search for a number of centimetre wavelength methanol transitions which are predicted to show weak maser emission towards star formation regions. Sensitive, high spatial, and spectral resolution observations towards four high-mass star formation regions which show emission in a large number of class II methanol maser transitions did not result in any detections. From these observations, we are able to place an upper limit of ≲ 1300 K on the brightness temperature of any emission from the 31A+–31A−, 17−2–18−3 E (vt = 1), 124–133 A−, 124–133 A+, and 41A+–41A− transitions of methanol in these sources on angular scales of 2 arcsec. This upper limit is consistent with current models for class II methanol masers in high-mass star formation regions and better constraints than those provided here will likely require observations with next-generation radio telescopes.

scholarly journals 44 GHz Methanol Maser Surveys

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.

scholarly journals G23.657−0.127, what can we learn from a perfect methanol maser source?

2007 ◽  
Vol 3 (S242) ◽  
pp. 190-191
Author(s):  
Anna Bartkiewicz ◽  
Huib Jan van Langevelde ◽  
Marian Szymczak ◽  
Andreas Brunthaler
Keyword(s):  
Massive Stars ◽  
Ring Structure ◽  
Rotating Disks ◽  
Central Source ◽  
Methanol Maser ◽  
Early Results ◽  
H Ii Region ◽  
Methanol Masers

AbstractIn the course of following up compact methanol masers at 6.7 GHz which were found in the Torun blind survey (Szymczak et al. 2002), we discovered a ring structure in the source G23.657−00.127. This source provides interesting insights into whether methanol masers arise in rotating disks around massive stars, in their outflows, or behind shocks. By monitoring the 12.2 GHz masers, which fortunately follow the same structure, we hope to resolve the kinematics of the ring. Moreover, the symmetry of the source points to the existence of a central source. Early results on the nature of this source indicate the existence of a hyper–compact H II region.

scholarly journals A Protoplanetary Disk in V645 Cyg As Seen with H2O and Methanol Masers

2002 ◽  
Vol 187 ◽  
pp. 279-284
Author(s):  
I.E. Val’tts ◽  
V.I. Slysh ◽  
M.A. Voronkov ◽  
V. Migenes
Keyword(s):  
Radial Velocity ◽  
Brightness Temperature ◽  
Young Star ◽  
Infrared Source ◽  
Maser Emission ◽  
Young Stellar Object ◽  
Methanol Maser ◽  
Maximum Radius ◽  
Methanol Masers ◽  
Lower Limits

AbstractRadio images of maser spots in the infrared source RAFGL 2789, connected with the young stellar object V645 Cyg, have been obtained as a result of radio interferometric observations of the H2O maser at 22 GHz and the methanol maser at 6.7 GHz, with the VLBI arrays VLBA and EVN. It is shown that the position of the masers coincides with the optical object within 02. The maser spots are located along the line North-South, and their position and radial velocity can be described by a model of a Keplerian disk with a maximum radius of 40 AU for the H2O maser and 800 AU for the methanol maser. The H2O and methanol maser spots have not been resolved, and lower limits of the brightness temperature are 2 × 1013 K and 1.4 × 109 k respectively. A model of the maser is suggested in which the maser emission is generated in extended water and methanol envelopes of icy planets orbiting the young star.

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