scholarly journals A blind survey of the 6.7 GHz methanol maser line

2002 ◽  
Vol 206 ◽  
pp. 143-146
Author(s):  
Marian Szymczak ◽  
Andrzej J. Kus ◽  
Grzegorz Hrynek
Keyword(s):  
Grid Point ◽  
Hii Regions ◽  
Triangular Grid ◽  
Average Sensitivity ◽  
Grid Pattern ◽  
Methanol Maser ◽  
Peak Flux ◽  
Maser Line ◽  
Methanol Masers ◽  
Ultracompact Hii

A blind survey for 6.7GHz methanol maser emission has been made with the 32 m Toruń radio telescope. The survey consists of 4,800 spectra on an equilateral triangular grid pattern with each grid point separated by 4.4 covering a field of ∼21 deg2 at galactic longitudes 20° to 40° and galactic latitudes ±0°52. The average sensitivity was 1.6 Jy and the spectral resolution was 0.04kms−1. A total of 99 sources were detected, 28 of which were not found during previous searches of IRAS-selected ultracompact HII regions. The peak flux density of new detections is usually lower than 30 Jy. About half of the methanol masers have no IRAS counterparts within a radius of 2. The nature of these sources is unclear.

14 years of 6.7 GHz periodic methanol maser observations towards G188.95+0.89

2019 ◽  
Vol 15 (S356) ◽  
pp. 393-394
Author(s):  
Martin M. Mutie ◽  
Paul Baki ◽  
James O. Chibueze ◽  
Khadija El Bouchefry
Keyword(s):  
Radio Telescope ◽  
Exponential Decay ◽  
Hii Regions ◽  
Monitoring Period ◽  
Methanol Maser ◽  
Spectral Components ◽  
Methanol Masers ◽  
Compact Hii Regions

AbstractWe report the results of 14 years of monitoring of G188.95+0.89 periodic 6.7 GHz methanol masers using the Hartebeesthoek 26-m radio telescope. G188.95+0.89 (S252, AFGL5180) is a radio-quiet methanol maser site that is often interpreted as precursors of ultra-compact HII regions or massive protostar sites. At least five bright spectral components were identified. The maser feature at 11.36 km s-1 was found to experience an exponential decay during the monitoring period. The millimetre continuum reveals two cores associated with the source.

Zeeman Effect Observations in Class I Methanol Masers

2018 ◽  
Vol 14 (A30) ◽  
pp. 140-140
Author(s):  
Emmanuel Momjian ◽  
Anuj P. Sarma
Keyword(s):  
Zeeman Effect ◽  
Linear Structure ◽  
Class I ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Splitting Factor ◽  
Maser Line ◽  
Methanol Masers ◽  
Expected Values

AbstractWe report the detection of the Zeeman effect in the 44 GHz Class I methanol maser line toward the star forming region DR21W. The 44 GHz methanol masers in this source occur in a ∼3” linear structure that runs from northwest to southeast, with the two dominant components at each end, and several weaker maser components in between. Toward a 93 Jy maser in the dominant northwestern component, we find a significant Zeeman detection of −23.4 ± 3.2 Hz. If we use the recently published result of Lankhaar et al. (2018) that the F=5-4 hyperfine transition is responsible for the 44 GHz methanol maser line, then their value of z = −0.92 Hz mG−1 yields a line-of-sight magnetic field of Blos =25.4 ± 3.5 mG. If Class I methanol masers are pumped in high density regions with n∼107–8 cm−3, then magnetic fields in these maser regions should be a few to several tens of mG. Therefore, our result in DR21W is certainly consistent with the expected values.Using the above noted splitting factor in past Zeeman effect detections in Class I methanol masers reported by Sarma & Momjian (2011) and Momjian & Sarma (2017) in the star forming regions OMC-2 and DR21(OH) result in Blos values of 20.0 ± 1.2 mG and 58.2 ± 2.9 mG, respectively. These are also consistent with the expected values.

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 Methanol and water maser observations separate disc and outflow sources in IRAS 19410+2336

2020 ◽  
Vol 493 (3) ◽  
pp. 4442-4452 ◽  
Author(s):  
M S Darwish ◽  
K A Edris ◽  
A M S Richards ◽  
S Etoka ◽  
M S Saad ◽  
...  
Keyword(s):  
Flux Density ◽  
High Mass ◽  
High Angular Resolution ◽  
Mass Star ◽  
Star Forming ◽  
Peak Flux ◽  
Maser Line ◽  
Methanol Masers ◽  
Water Masers ◽  
Water Maser

ABSTRACT We investigate the kinematics of high-mass protostellar objects within the high-mass star-forming region IRAS 19410+2336. We performed high angular resolution observations of 6.7-GHz methanol and 22 GHz water masers using the Multi-Element Radio Linked Interferometer Network (MERLIN) and e-MERLIN interferometers. The 6.7-GHz methanol maser emission line was detected within the ∼16–27 km s−1 velocity range with a peak flux density ∼50 Jy. The maser spots are spread over ∼1.3 arcsec on the sky, corresponding to ∼2800 au at a distance of 2.16 kpc. These are the first astrometric measurements at 6.7 GHz in IRAS 19410+2336. The 22-GHz water maser line was imaged in 2005 and 2019 (the latter with good astrometry). Its velocities range from 13 to ∼29 km s−1. The peak flux density was found to be 18.7 and 13.487 Jy in 2005 and 2019, respectively. The distribution of the water maser components is up to 165 mas, ∼350 au at 2.16 kpc. We find that the Eastern methanol masers most probably trace outflows from the region of millimetre source mm1. The water masers to the West lie in a disc (flared or interacting with outflow/infall) around another more evolved millimetre source (13-s). The maser distribution suggests that the disc lies at an angle of 60° or more to the plane of the sky and the observed line-of-sight velocities then suggest an enclosed mass between 44 M⊙ and as little as 11 M⊙ if the disc is edge-on. The Western methanol masers may be infalling.

scholarly journals 44-GHz class I methanol maser survey towards 6.7-GHz class II methanol masers

2012 ◽  
Vol 8 (S287) ◽  
pp. 284-285 ◽  
Author(s):  
Do-Young Byun ◽  
Kee-Tae Kim ◽  
Jae-Han Bae
Keyword(s):  
Class Ii ◽  
Class I ◽  
Young Stellar Objects ◽  
High Mass ◽  
Radio Telescopes ◽  
Stellar Objects ◽  
Methanol Maser ◽  
Peak Flux ◽  
Methanol Masers ◽  
Water Maser

AbstractThe Class II 6.7-GHz methanol maser is a tracer of high mass young stellar objects. We present results of a 44-GHz class I methanol maser and 22-GHz water maser survey using the KVN (Korean VLBI Network) 21-m single dish radio telescopes towards 284 6.7-GHz maser sites. Class I methanol maser and water maser emission is detected towards 116 (41%) and 136 (48%) sources, respectively. About 50 sources have a peak flux density higher than 10 Jy at 44-GHz. They are candidates for VLBI studies using the KVN.

Class I Methanol Maser Emission in NGC 4945

2017 ◽  
Vol 13 (S336) ◽  
pp. 105-108
Author(s):  
Tiege P. McCarthy ◽  
Simon P. Ellingsen ◽  
Xi Chen ◽  
Shari L. Breen ◽  
Maxim A. Voronkov ◽  
...  
Keyword(s):  
Large Scale ◽  
Class I ◽  
Molecular Gas ◽  
Low Velocity ◽  
Extragalactic Source ◽  
Maser Emission ◽  
Methanol Maser ◽  
Methanol Masers

AbstractWe have detected maser emission from the 36.2 GHz (4−1 → 30E) methanol transition towards NGC 4945. This emission has been observed in two separate epochs and is approximately five orders of magnitude more luminous than typical emission from this transition within our Galaxy. NGC 4945 is only the fourth extragalactic source observed hosting class I methanol maser emission. Extragalactic class I methanol masers do not appear to be simply highly-luminous variants of their galactic counterparts and instead appear to trace large-scale regions where low-velocity shocks are present in molecular gas.

Synchronized periodic maser flares of multiple OH and CH3OH lines in G323.459–0.079

2021 ◽  
Vol 502 (4) ◽  
pp. 5658-5667
Author(s):  
G C MacLeod ◽  
Derck P Smits ◽  
J A Green ◽  
S P van den Heever
Keyword(s):  
Magnetic Field ◽  
Excited State ◽  
Central Region ◽  
Time Lags ◽  
Field Reversal ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Upper Limit ◽  
Methanol Masers ◽  
Magnetic Field Reversal

ABSTRACT The first confirmed periodically varying 6.031 and 6.035 GHz hydroxyl masers are reported here. They vary contemporaneously with the 6.7 GHz methanol masers in G323.459–0.079. The 1.665 GHz hydroxyl and 12.2  GHz methanol masers associated with G323.459–0.079 are also periodic. Evidence for periodicity is seen in all features in all transitions save a single 1.665 GHz hydroxyl maser feature. Historical excited-state hydroxyl maser observations set a stricter upper limit on the epoch in which a significant accretion event occurred. The associated burst in 6.7 GHz methanol maser activity has subsided significantly while the hydroxyl transitions are brightening possibly the result of changing physical conditions in the masing cloudlets. Time lags in methanol are confirmed and may be the result of the periodic flaring propagating outward from the central region of maser activity. A possible magnetic field reversal occurred during the accretion event.

Radio Continuum Emission from Sculptor Galaxies

1986 ◽  
Vol 6 (3) ◽  
pp. 325-329 ◽  
Author(s):  
J . I. Harnet
Keyword(s):  
Radio Emission ◽  
Blue Light ◽  
Hii Regions ◽  
Radio Continuum ◽  
Radial Dependence ◽  
Continuum Emission ◽  
Upper Limits ◽  
Peak Flux

AbstractThe five major members of the Sculptor Group of galaxies and NGC 45 have been observed with the Molonglo observatory synthesis telescope. NGC 247 and NGC 300 were not detected and upper limits to their 843 MHz flux densities are given. Radio emission from NGC 7793 is discussed with particular attention to its morphology, radial dependence compared with that of the blue light and possible coincidences between HII regions and 843 MHz peak flux densities.

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.

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.

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