scholarly journals Unusual properties of the methanol maser emission in W48

2002 ◽  
Vol 206 ◽  
pp. 167-170
Author(s):  
Irina E. Val'tts ◽  
Stella Yu. Lyubchenko
Keyword(s):  
Class Ii ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser

In the star forming region W48 the spectrum of methanol lines is studied. It is found that the intensity of the 20 − 3−1E (12.2 GHz) line anti-correlates with the intensity of the 51-60A+ (6.7 GHz). All other class II methanol lines in the spectrum of W48 (21 − 30A+ (157 GHz), 31 − 40A+ (107 GHz) (possibly) and J0 - J−1E (157 GHz)) demonstrate the same behaviour as 20 − 3−1E (12.2 GHz) line. This fact contradicts to the current models of the class II methanol maser emission. The effect is confirmed in the sample of 67 sources. For the explanation of this fact some possibilities are considered.

scholarly journals The molecular environment of massive star forming cores associated with Class II methanol maser emission

2007 ◽  
Vol 3 (S242) ◽  
pp. 125-129
Author(s):  
S. N. Longmore ◽  
M. G. Burton ◽  
P. J. Barnes ◽  
T. Wong ◽  
C. R. Purcell ◽  
...  
Keyword(s):  
Massive Star ◽  
Class Ii ◽  
Dynamic State ◽  
Continuum Emission ◽  
Molecular Gas ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Methanol Masers

AbstractMethanol maser emission has proven to be an excellent signpost of regions undergoing massive star formation (MSF). To investigate their role as an evolutionary tracer, we have recently completed a large observing program with the ATCA to derive the dynamical and physical properties of molecular/ionised gas towards a sample of MSF regions traced by 6.7GHz methanol maser emission. We find that the molecular gas in many of these regions breaks up into multiple sub-clumps which we separate into groups based on their association with/without methanol maser and cm continuum emission. The temperature and dynamic state of the molecular gas is markedly different between the groups. Based on these differences, we attempt to assess the evolutionary state of the cores in the groups and thus investigate the role of class II methanol masers as a tracer of MSF.

scholarly journals Discovery of polarized 6.7-GHz methanol masers in DR21/W75

2007 ◽  
Vol 3 (S242) ◽  
pp. 154-155
Author(s):  
L. Harvey-Smith ◽  
R. Soria-Ruiz ◽  
A. Duarte-Cabral ◽  
R. J. Cohen
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Class Ii ◽  
Linear Arrangement ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Velocity Gradients ◽  
Methanol Masers

AbstractWe present the first images of 6.7 GHz methanol masers in the DR21 star-forming complex. We have discovered two sites of Class II methanol maser emission; in DR21(OH) and DR21(OH)N. The emission comprises clusters of linearly extended masers which have velocity gradients along their length. There are four maser spots in DR21(OH)N, some of which show a small fraction of linear polarization. The twelve masers in DR21(OH) lie in a linear arrangement stretching approximately 0.7 arcseconds and show no significant linear polarization. We were not able to detect any circular polarization in the masers.

scholarly journals Millimetre wavelength methanol masers survey towards massive star forming regions

2007 ◽  
Vol 3 (S242) ◽  
pp. 234-235
Author(s):  
T. Umemoto ◽  
N. Mochizuki ◽  
K. M. Shibata ◽  
D.-G. Roh ◽  
H.-S. Chung
Keyword(s):  
Detection Rate ◽  
Massive Star ◽  
Molecular Line ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Maser Sources

AbstractWe present the results of a mm wavelength methanol maser survey towards massive star forming regions. We have carried out Class II methanol maser observations at 86.6 GHz, 86.9 GHz and 107.0 GHz, simultaneously, using the Nobeyama 45 m telescope. We selected 108 6.7 GHz methanol maser sources with declinations above −25 degrees and fluxes above 20 Jy. The detection limit of maser observations was ~3 Jy. Of the 93 sources surveyed so far, we detected methanol emission in 25 sources (27%) and “maser” emission in nine sources (10%), of which thre “maser” sources are new detections. The detection rate for maser emission is about half that of a survey of the southern sky (Caswell et al. 2000). There is a correlation between the maser flux of 107 GHz and 6.7 GHz/12 GHz emission, but no correlation with the “thermal” (non maser) emission. From results of other molecular line observations, we found that the sources with methanol emission show higher gas temperatures and twice the detection rate of SiO emission. This may suggest that dust evaporation and destruction by shock are responsible for the high abundance of methanol molecules, one of the required physical conditions for maser emission.

A study of class II methanol maser condensations in the star-forming region W48

2002 ◽  
Vol 46 (4) ◽  
pp. 293-308
Author(s):  
I. V. Val’tts ◽  
S. Yu. Lyubchenko
Keyword(s):  
Class Ii ◽  
Star Forming ◽  
Methanol Maser

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.

Periodic masers in massive star forming regions

2017 ◽  
Vol 13 (S336) ◽  
pp. 225-230
Author(s):  
S. Goedhart ◽  
R. van Rooyen ◽  
D. J. van der Walt ◽  
J. P. Maswanaganye ◽  
G. C. MacCleod ◽  
...  
Keyword(s):  
Linear Response ◽  
Massive Star ◽  
Class Ii ◽  
Light Curves ◽  
Star Forming ◽  
Methanol Maser ◽  
Modes Of Variability ◽  
Star Forming Regions ◽  
Underlying Mechanisms ◽  
Periodic Class

AbstractThe first periodic Class II methanol maser was reported on in 2003. Since that time, a number of different monitoring programmes have found periodic masers, as well as other modes of variability. In a few cases, periodicity has been found in other maser species such as formaldehyde and water. Several distinct characteristics of light curves have been noted, possibly pointing to different underlying mechanisms for periodicity if one assumes a linear response to incoming radiation. I will give a brief overview of the known periodic sources, discuss current theories, and present new results obtained from monitoring mainline hydroxyl masers using the seven-element Karoo Array Telescope (KAT-7) during its science verification phase.

Class II 6.7 GHz Methanol Maser Association with Young Massive Cores Revealed by ALMA

2017 ◽  
Vol 13 (S336) ◽  
pp. 247-250
Author(s):  
James O. Chibueze ◽  
Timea Csengeri ◽  
Ken’ichi Tatematsu ◽  
Tetsuo Hasegawa ◽  
Satoru Iguchi ◽  
...  
Keyword(s):  
Class Ii ◽  
High Mass ◽  
Evolutionary Sequence ◽  
Maser Emission ◽  
Methanol Maser ◽  
Promising Tool ◽  
Dense Cores ◽  
Show Evidence ◽  
Statistical Viewpoint ◽  
Compact Array

AbstractThe association of 6.7 GHz class II methanol (CH3OH) masers with ATLASGAL/ ALMA 0.9 mm massive dense cores is presented in this work from a statistical viewpoint. 42 of the 112 cores (37.5%) detected with the Atacama Compact Array (ACA) excite 6.7 GHz CH3OH masers. ACA cores have offsets 0\rlap.″17 to 4\rlap.″79 from the methanol multibeam survey (MMB), with a median of 2.″19. Approximately 90% of the MMB-associated cores are of masses > 40 M⊙. Because all the cores show evidence of outflow activity, and only a fraction of the cores excited CH3OH masers, we suggest that outflows precede the emergence of maser emission. This first ALMA survey of massive dense cores combined with the MMB survey along with other maser specie surveys is a promising tool to trace the evolutionary sequence of high-mass stars.

scholarly journals The W51 Main/South SFR complex seen through 6-GHz OH and methanol masers

2012 ◽  
Vol 8 (S287) ◽  
pp. 171-175 ◽  
Author(s):  
Sandra Etoka ◽  
Malcolm D. Gray ◽  
Gary A. Fuller
Keyword(s):  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Relationship Of ◽  
The Relationship

AbstractW51 Main/South is one of the brightest and richest high-mass star-forming regions (SFR) in the complex W51. It is known to host many ultra-compact HII (UCHII) regions thought to be the site of massive young stellar objects. Maser emission from various species is also found in the region. We have performed MERLIN astrometric observations of excited-OH maser emission at 6.035 GHz and Class II methanol maser emission at 6.668 GHz towards W51 to investigate the relationship between the maser emission and the compact continuum sources in this SFR complex. Here we present the astrometric distributions of both 6.668-GHz methanol and 6.035-GHz excited-OH maser emission in the W51 Main/South region. The location of maser emission in the two lines is compared with that of previously published OH groundstate emission. The interesting coherent velocity and spatial structure observed in the methanol maser distribution as well as the relationship of the masers to infall or outflow in the region are discussed. It appears that the masers are excited by multiple objects potentially at different stages of evolution.

Exploring the Nature of MMB sources: A Search for Class I Methanol Masers and their Outflows

2017 ◽  
Vol 13 (S336) ◽  
pp. 317-318
Author(s):  
Nichol Cunningham ◽  
Gary Fuller ◽  
Adam Avison ◽  
Shari Breen
Keyword(s):  
Massive Star ◽  
Class Ii ◽  
Class I ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Initial Results ◽  
Maser Sources

AbstractWe present the initial results from a class I 44-GHz methanol maser follow-up survey, observed with the MOPRA telescope, towards 272 sources from the Methanol Multi-beam survey (MMB). Over half (∼60%) of the 6.7 GHz class II MMB maser sources are associated with a class I 44-GHz methanol maser at a greater than 5σ detection level. We find that class II MMB masers sources with an associated class I methanol maser have stronger peak fluxes compared to regions without an associated class I maser. Furthermore, as part of the MOPRA follow-up observations we simultaneously observed SiO emission which is a known tracer of shocks and outflows in massive star forming regions. The presence of SiO emission, and potentially outflows, is found to be strongly associated with the detection of class I maser emission in these regions.

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