The Sobolev approximation for radiation transport with line overlap and continuous opacity

Nesterenok, A. V.

doi:10.1088/1742-6596/1697/1/012001

Cited by 4 publications

(2 citation statements)

References 10 publications

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“…where A ik and B ik , B ki are the Einstein coefficients; J ik is the radiation intensity in spectral line averaged over the line profile and the direction. The large velocity gradient or Sobolev approximation is used in calculations of spectral line intensities [19]. The system of equations ( 1) is non-linear and the solution is obtained iteratively.…”

Section: The Maser Modellingmentioning

confidence: 99%

The candidates for Class I methanol masers

Nesterenok

2021

Preprint

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The collisional excitation of methanol molecule in non-dissociative magnetohydrodynamic 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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Section: The Maser Modellingmentioning

confidence: 99%

The candidates for Class I methanol masers

Nesterenok

2021

Preprint

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“…where parameters with the subscripts 1 and 2 refer to the first and second line, respectively, Δ𝑥 = (𝜈 1 − 𝜈 2 )/Δ𝜈 D is the difference in the line frequencies normalized on the line profile width. The functions P 11 and P 12 were calculated by Nesterenok (2020b). The simultaneous overlap of three and more lines is not considered.…”

Section: Calculation Of Molecular Energy Level Populationsmentioning

confidence: 99%

Modelling cosmic masers in C-type shock waves -- the coexistence of Class I CH3OH and 1720 MHz OH masers

Nesterenok

2021

Preprint

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The collisional pumping of CH 3 OH and OH masers in non-dissociative C-type shock waves is studied. The chemical processes responsible for the evolution of molecule abundances in the shock wave are considered in detail. The large velocity gradient approximation is used to model radiative transfer in molecular lines. We present calculations of the optical depth in maser transitions of CH 3 OH and OH for a grid of C-type shock models that vary in cosmic ray ionization rate, gas density and shock speed. We show that pre-shock gas densities 𝑛 H,tot = 2 × 10 4 -2 × 10 5 cm −3 are optimal for pumping of methanol maser transitions. A complete collisional dissociation of methanol at the shock front takes place for shock speeds 𝑢 s 25 km s −1 . At high pre-shock gas density 𝑛 H,tot = 2×10 6 cm −3 , the collisional dissociation of methanol takes place at shock speeds just above the threshold speed 𝑢 s ≈ 15-17.5 km s −1 corresponding to sputtering of icy mantles of dust grains. We show that the methanol maser transition E 4 −1 → 3 0 at 36.2 GHz has the optical depth |𝜏| higher than that of the transition A + 7 0 → 6 1 at 44.1 GHz at high cosmic ray ionization rate 𝜁 H 2 10 −15 s −1 and pre-shock gas density 𝑛 H,tot = 2 × 10 4 cm −3 . These results can be applied to the interpretation of observational data on methanol masers near supernova remnants and in molecular clouds of the Central Molecular Zone. At the same time, a necessary condition for the operation of 1720 MHz OH masers is a high ionization rate of molecular gas, 𝜁 H 2 10 −15 s −1 . We find that physical conditions conducive to the operation of both hydroxyl and methanol masers are cosmic ray ionization rate 𝜁 H 2 ≈ 10 −15 -3 × 10 −15 s −1 , and a narrow range of shock speeds 15 𝑢 s 20 km s −1 . The simultaneous observations of OH and CH 3 OH masers may provide restrictions on the physical parameters of the interstellar medium in the vicinity of supernova remnants.

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The candidates for Class I methanol masers

Nesterenok

2021

J. Phys.: Conf. Ser.

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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.

show abstract

The Sobolev approximation for radiation transport with line overlap and continuous opacity

Cited by 4 publications

References 10 publications

The candidates for Class I methanol masers

The candidates for Class I methanol masers

Modelling cosmic masers in C-type shock waves -- the coexistence of Class I CH3OH and 1720 MHz OH masers

The candidates for Class I methanol masers

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