scholarly journals Discovery of large-scale masers in W3(OH)

2006 ◽  
Vol 2 (S237) ◽  
pp. 422-422
Author(s):  
L. Harvey-Smith ◽  
R. J. Cohen
Keyword(s):  
Velocity Gradient ◽  
Large Scale ◽  
Velocity Structure ◽  
Central Star ◽  
Line Profiles ◽  
Maser Emission ◽  
Methanol Maser ◽  
Large Velocity ◽  
Structure Line ◽  
Large Velocity Gradient

AbstractWe report a vast filament of hydroxyl and methanol maser emission surrounding the ultra-compact HII region W3(OH). The filament stretches 3100 AU and has a linear velocity gradient. By studying the velocity structure, line profiles and extended methanol maser structures we believe we have located the position of the central star and detected around it a circumstellar disc with a large velocity gradient of 47 km s−1 arcsec−1.

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.

scholarly journals Effect of variation in density on the stability of superposed streams of Fluid

1931 ◽  
Vol 132 (820) ◽  
pp. 499-523 ◽  
Keyword(s):  
Density Gradient ◽  
Velocity Gradient ◽  
Horizontal Plane ◽  
Experimental Results ◽  
Large Velocity ◽  
Formed Part ◽  
The Stability ◽  
Large Velocity Gradient

1. The chief part of the work described in this paper was done in 1914 and formed part of the essay for which the Adams Prize was awarded in 1915. During the war years it was laid aside, and since then I have delayed publica­tion, hoping to be able to undertake experiments designed to verify, or otherwise, the results. Lately, however, Mr. Goldstein has told me that he is engaged on similar problems and he has encouraged me to publish the work without waiting for experimental results. It is well known that when the wind near the ground drops at night owing to the cooling of the ground, the wind at a higher level frequently remains unchanged so that the effect of a decrease in density with height is to enable a large velocity gradient to be maintained. This implies that the turbulence is suppressed or at any rate much reduced by the density gradient. To the mathematician this at once presents the problem of the stability of a fluid in which the density and velocity vary with height above the ground, regarded as a horizontal plane.

On the motion of particles in a fluid under the influence of a large velocity gradient

1993 ◽  
Vol 14 (1-2) ◽  
pp. 42-48 ◽  
Author(s):  
P. J. Thomas ◽  
K. -A. Bütefisch ◽  
K. H. Sauerland
Keyword(s):  
Velocity Gradient ◽  
Large Velocity ◽  
Large Velocity Gradient

scholarly journals 3 mm band line survey toward the high-velocity compact cloud CO−0.40−0.22

2013 ◽  
Vol 9 (S303) ◽  
pp. 202-204
Author(s):  
T. Oka ◽  
K. Tanaka ◽  
S. Matsumura ◽  
K. Miura ◽  
S. Takekawa ◽  
...  
Keyword(s):  
High Velocity ◽  
Velocity Structure ◽  
Frequency Resolution ◽  
Shock Acceleration ◽  
Line Profiles ◽  
Recent Past ◽  
Frequency Range ◽  
Large Velocity ◽  
Line Survey ◽  
Prominent Peak

AbstractHigh-velocity compact clouds (HVCCs) are a population of molecular clouds which have compact appearance (d < 10 pc) and large velocity width (Δ V > 50 km s−1), and are found in the central molecular zone of our Galaxy. We performed a 3 mm band line survey toward CO−0.40−0.22, a spatially unresolved HVCC with an extremely large velocity width (Δ V ≃ 90 km s−1), using the Mopra 22 m telescope. We surveyed the frequency range between 76 GHz and 116 GHz with a 0.27 MHz frequency resolution. We detect at least 54 lines from 32 molecules. Many line profiles show a prominent peak at vLSR ∼ 70 km s−1 with very large velocity width, indicating they are emitted by the HVCC. Detections of largish molecules are indicative of non-equilibrium chemistry. We extracted some prominent lines based on velocity structure, intensity ratios, and PCA analyses. Shock diagnostic lines (SiO, SO, CH3OH, HNCO) and dense gas probes (HCN, HCO+) appear to be prominent. Excitation analysis of CH3OH lines show an enhancement in Trot in the negative high-velocity end of the profile. These results suggest that CO−0.40−0.22 has experienced a shock, acceleration, compression, and heating in the recent past.

scholarly journals The candidates for Class I methanol masers

2021 ◽  
Vol 2103 (1) ◽  
pp. 012012
Author(s):  
A V Nesterenok
Keyword(s):  
Energy Level ◽  
Velocity Gradient ◽  
Chemical Processes ◽  
Class I ◽  
Shock Model ◽  
Collisional Excitation ◽  
Large Velocity ◽  
Methanol Masers ◽  
Essential Chemical ◽  
Large Velocity Gradient

Abstract The collisional excitation of methanol molecule in non-dissociative magnetohydro-dynamic shock waves is considered. All essential chemical processes that determine methanol abundance in the gas are taken into account in the shock model. The large velocity gradient approximation is used in the calculations of energy level populations of the molecule. We calculate the optical depth for inverted methanol transitions, and present the list of candidates for Class I methanol masers that have collisional pumping mechanism.

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