scholarly journals 3D motions of 6.7 GHz methanol masers and effects of the Galactic bar

2012 ◽  
Vol 8 (S289) ◽  
pp. 410-413
Author(s):  
Naoko Matsumoto ◽  
Mareki Honma ◽  
Keyword(s):  
Inclination Angle ◽  
Dynamical Model ◽  
Proper Motions ◽  
Methanol Maser ◽  
Circular Rotation ◽  
Methanol Masers ◽  
Maser Sources ◽  
Better Than ◽  
Simple Models ◽  
Rotation Model

AbstractTo search for kinematic evidence of the existence of the Galactic bar, we observed 10 methanol maser sources at the near end of the bar with VERA (VLBI Exploration of Radio Astrometry). From these observations, we obtained absolute proper motions of eight sources based on the phase-referencing technique. We compared the motions with the predictions of three simple models in a 3D plane. This comparison showed that a non-flat circular rotation model and a dynamical model including a bar potential reproduce the observed data better than a flat rotation model. In addition, the bar model suggests that the inclination angle of the Galactic bar is around 35°, which is consistent with previous studies.

scholarly journals The bar effect in the galactic gas motions traced by 6.7 GHz methanol maser sources with VERA

2012 ◽  
Vol 8 (S287) ◽  
pp. 419-420
Author(s):  
Naoko Matsumoto ◽  
Mareki Honma ◽  
Keyword(s):  
Inclination Angle ◽  
Dynamical Model ◽  
Proper Motions ◽  
Spiral Arms ◽  
Methanol Maser ◽  
Circular Rotation ◽  
Vlbi Data ◽  
Maser Sources ◽  
Better Than ◽  
Rotation Model

AbstractTo establish the existence of the galactic bar, ten methanol maser sources around the starting points of the spiral arms were observed with VERA (VLBI Exploration of radio astrometry) using the phase-referencing technique at 6.7 GHz band. For six out of ten sources, absolute proper motions were obtained with better than 3σ accuracy. Using VLBI 3-D data of eight sources, including our five sources, we compared the observed data with three galactic models and found that the model including the bar effect is better to explain the 3-D data, than a flat circular rotation model. A non-flat circular rotation model is also consistent with the VLBI data. Based on a dynamical model with a bar, we estimate an inclination angle of the bar around 35°, which is consistent with previous studies.

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.

Long term 6.7 GHz methanol maser monitoring program

2017 ◽  
Vol 13 (S336) ◽  
pp. 277-278
Author(s):  
Artis Aberfelds ◽  
Ivar Shmeld ◽  
Karlis Berzins
Keyword(s):  
Radio Astronomy ◽  
Monitoring Program ◽  
Radio Telescopes ◽  
Methanol Maser ◽  
Data Registration ◽  
Methanol Masers ◽  
Maser Sources

AbstractThe first long-term maser (mainly methanol) monitoring program is under way with the radio telescopes of Ventspils International Radio Astronomy Center. The first activity of this program was to develop an observations methodology and data registration and reduction software for the Ventspils telescopes. The developed routines are to be used for maser variability monitoring, investigating short bursts of intensity and a search for new, previously unknown, maser sources. Currently the program consists of 41 methanol masers observed at 6.7 GHz, while new ones are periodically added. The maser sources are observed at 3 – 5 day intervals. It was found that most the sources display a significant level of variability with time, ranging from a few days, up to several months and, perhaps, years. In addition to non-varying masers, several types of maser variability behavior were observed, including: monotonic increases or decreases, un-periodical, quasi-periodic and periodic variations.

Sub-mm observations of periodic methanol masers

2017 ◽  
Vol 13 (S336) ◽  
pp. 301-302
Author(s):  
D. J. van der Walt ◽  
J.-M. Morgan ◽  
J. O. Chibueze ◽  
Q. Zhang
Keyword(s):  
Methanol Maser ◽  
Methanol Masers ◽  
Maser Sources

AbstractWe present the results of sub-millimetre observations on three periodic methanol maser sources. Our results indicate that there are geometric differences between some periodic methanol masers which have different variability profiles.

Systematic velocity drifts of methanol masers associated with G9.62+0.20E

2020 ◽  
Vol 500 (3) ◽  
pp. 3425-3437
Author(s):  
G C MacLeod ◽  
J O Chibueze ◽  
A Sanna ◽  
J D Paulsen ◽  
M Houde ◽  
...  
Keyword(s):  
Inclination Angle ◽  
Time Lags ◽  
Central Mass ◽  
Methanol Maser ◽  
Best Fitting ◽  
Methanol Masers

ABSTRACT The source G9.62+0.20E surprises again! Several of the associated 6.7- and 12.2-GHz methanol masers are experiencing contemporaneous and systematic velocity drifts. Both 6.7- and 12.2-GHz methanol features blueward of v = +1.2 km s−1 are blue shifting while those redward are red shifting. A best-fitting rotating Keplerian disc with a central mass of ∼12 M⊙, radii Rinner = 5 au and Router = 5000 au, and at an inclination angle of 22○ either precessing and/or experiencing infall explains these systematic velocity drifts. Also three more distinct 6.7-GHz methanol maser features are found to vary periodically; two very weak and one obviously periodic only after 2003. Evidence of periodicity is seen as early as 1992. Time lags are confirmed but the cause is unclear. It is possible this source will surprise again.

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 The radial velocity acceleration of the 6.7 GHz methanol maser in Mon R2 IRS3

2012 ◽  
Vol 8 (S287) ◽  
pp. 190-191
Author(s):  
K. Sugiyama ◽  
K. Fujisawa ◽  
N. Shino ◽  
A. Doi
Keyword(s):  
Radial Velocity ◽  
High Mass ◽  
Mass Star ◽  
Spectral Features ◽  
Proper Motions ◽  
Infrared Source ◽  
Young Stellar Object ◽  
Star Forming ◽  
Methanol Maser ◽  
Methanol Masers

AbstractWe present the radial velocity acceleration of the 6.7 GHz methanol maser in a high-mass star-forming region Monoceros R2 (Mon R2). The methanol maser is associated with an infrared source IRS3. The methanol maser of Mon R2 shows at least three spectral features having radial velocities (Vlsr) of 10.8, 12.7, and 13.2 km s−1. The radial velocity of a feature at Vlsr = 12.7 km s−1 has changed during ten years from Aug. 1999 to Oct. 2009, corresponding to an acceleration of 0.08 km s−1 yr−1. We observed the 6.7 GHz methanol masers of Mon R2 in Oct. 2008 using the Japanese VLBI Network (JVN). Compared with the previous VLBI image obtained in Nov. 1998 using the European VLBI Network (EVN), the maser feature at Vlsr = 12.7 km s−1 showed relative proper motions of ~2.5 mas yr−1 (about 10 km s−1 at 0.83 kpc) toward the intensity peak of IRS3. The radial velocity acceleration could be caused by an inflow from a disk or envelope around a high-mass young stellar object (YSO) at IRS3.

scholarly journals Methanol masers: Evolutionary and kinematic tracers of massive star formation

2002 ◽  
Vol 206 ◽  
pp. 147-150
Author(s):  
Vincent Minier ◽  
Roy Booth ◽  
John Conway ◽  
Michele Pestalozzi
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Methanol Masers ◽  
Maser Sources

We summarise our recent VLBI observations of a large sample of methanol maser sources associated with high-mass star-forming regions.

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.

scholarly journals The VLBI mapping survey of the 6.7 GHz methanol masers with the JVN/EAVN

2012 ◽  
Vol 8 (S287) ◽  
pp. 288-289 ◽  
Author(s):  
K. Fujisawa ◽  
K. Hachisuka ◽  
K. Sugiyama ◽  
A. Doi ◽  
M. Honma ◽  
...  
Keyword(s):  
East Asian ◽  
Proper Motions ◽  
Maser Emission ◽  
Methanol Maser ◽  
Methanol Masers

AbstractWe present VLBI maps of the 6.7 GHz methanol maser emission in 32 sources obtained using the Japanese VLBI Network (JVN) and the East-Asian VLBI Network (EAVN). All of the observed sources provide new VLBI maps, and the spatial morphologies have been classified into five categories similar to the results obtained from European VLBI Network observations (Bartkiewicz et al. 2009). The 32 methanol sources are being monitored to measure the relative proper motions of the methanol maser spots.

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