Modelling CH${}_3$OH masers: Sobolev approximation and accelerated lambda iteration method

Abstract

A simple one-dimensional model of CH${}_3$OH maser is considered. Two techniques are used for the calculation of molecule level populations: the accelerated lambda iteration (ALI) method and the large velocity gradient (LVG), or Sobolev, approximation. The LVG approximation gives accurate results provided that the characteristic dimensions of the medium are larger than 5-10 lengths of the resonance region. We presume that this condition can be satisfied only for the largest observed maser spot distributions. Factors controlling the pumping of class I and class II methanol masers are considered.

9 pages, 5 figures; accepted for publication in MNRAS

References in corpus (8)

• A Class I and Class II Methanol Maser Survey of Extended Green Objects (EGOs) from the GLIMPSE Survey
• Southern class I methanol masers at 36 and 44 GHz
• Class I Methanol (CH${}_3$OH) Maser Conditions near Supernova Remnants
• The First Very Long Baseline Interferometry Image of 44 GHz Methanol Maser with the KVN and VERA Array (KaVA)
• Model of the vibrationally excited H${}_2$O maser at 658 GHz in circumstellar envelopes around asymptotic giant branch stars
• H${}_2$O Maser Pumping: The Effect of Quasi-Resonance Energy Transfer in Collisions between H${}_2$ and H${}_2$O Molecules
• H2O Maser Emission in Circumstellar Envelopes around AGB Stars: Physical Conditions in Gas-Dust Clouds
• Simulation of pumping mechanism of H2O-masers in circumstellar envelopes of late-type stars

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• 36 GHz methanol lines from nearby galaxies: maser or quasi-thermal emission?
• Modelling cosmic masers in C-type shock waves -- the coexistence of Class I CH3OH and 1720 MHz OH masers
• Collisional Pumping of OH Masers near Supernova Remnants
• An nl-model with radiative transfer for hydrogen recombination line masers
• The Sobolev approximation for radiation transport with line overlap and continuous opacity
• A 95 GHz Methanol Emission Survey Toward Eight Small Supernova Remnants
• Collisional Pumping of H${}_2$O and CH${}_3$OH Masers in C-Type Shock Waves
• An nl-model with a full radiative transfer treatment for level populations of hydrogen atoms in a spherically symmetric H II region