Collisional Pumping of H${}_2$O and CH${}_3$OH Masers in C-Type Shock Waves

Abstract

The collisional pumping of H${}_2$O and CH${}_3$OH masers in magnetohydrodynamic nondissociative C-type shocks is considered. A grid of C-type shock models with speeds in the range $5-70$ km s${}^{-1}$ and preshock gas densities $n_{{\mathrm{H}}_2,0}=10^4-10^7$ cm${}^{-3}$ is constructed. The large velocity gradient approximation is used to solve the radiative transfer equation in molecular lines. The para-H${}_2$O 183.3 GHz and ortho-H${}_2$O 380.1 and 448.0 GHz transitions are shown to be inverted and to have an optical depth along the shock velocity $|\tau |\sim 1$ at relatively low gas densities in the maser zone, $n_{{\mathrm{H}}_2}\gtrsim 10^5-10^6$ cm${}^{-3}$. Higher gas densities, $n_{{\mathrm{H}}_2}\gtrsim 10^7$ cm${}^{-3}$, are needed for efficient pumping of the remaining H${}_2$O masers. Simultaneous generation of H${}_2$O and class I CH${}_3$OH maser emission in a shock is possible at preshock gas densities $n_{{\mathrm{H}}_2,0}\approx 10^5$ cm${}^{-3}$ and shock speeds in the range $u_{\mathrm{s}}\approx 17.5-22.5$ km s${}^{-1}$. The possibility of detecting class I CH${}_3$OH and para-H${}_2$O 183.3 GHz masers in star-forming regions and near supernova remnants is investigated.

arXiv comment19 pages, 6 figures, published in Astronomy Letters, 2022, Vol. 48, No. 6, pp. 345-359

References in corpus (31)

• Observations of the Icy Universe
• Interstellar water chemistry: from laboratory to observations
• Quasi-classical rate coefficient calculations for the rotational (de)excitation of H2O by H2
• The Gould's Belt Distances Survey (GOBELINS) III. The distance to the Serpens/Aquila Molecular Complex
• Southern class I methanol masers at 36 and 44 GHz
• Interstellar H${}_2$O Masers from J Shocks
• Physical characteristics of bright Class I methanol masers
• The Physics of Water Masers observable with ALMA and SOFIA: Model Predictions for Evolved Stars
• The Abundance, Ortho/Para Ratio, and Deuteration of Water in the High-Mass Star Forming Region NGC 6334 I
• Detection of Class I Methanol (CH3OH) Maser Candidates in Supernova Remnants
• The OH (1720 MHz) Supernova Remnant Masers in W44: MERLIN and VLBA Polarization Observations
• Physical conditions in shocked regions of Orion from ground-based observations of H_2O
• First results from a VLBA proper motion survey of H2O masers in low-mass YSOs: the Serpens core and RNO15-FIR
• Class I Methanol (CH${}_3$OH) Maser Conditions near Supernova Remnants
• First detection of the 448 GHz ortho-H2O line at high redshift: probing the structure of a starburst nucleus at z = 3.63
• On the Inference of the Cosmic Ray Ionization Rate $\zeta$ from the HCO${}^{+}$-to-DCO${}^{+}$ Abundance Ratio: The Effect of Nuclear Spin
• Sub-arcsecond imaging of the water emission in Arp 220
• Collisional excitation of water by hydrogen atoms
• Modelling CH${}_3$OH masers: Sobolev approximation and accelerated lambda iteration method
• Chemical evolution of the gas in C-type shocks in dark clouds
• First detection of the 448 GHz H2O transition in space
• SOFIA/GREAT Discovery of Terahertz Water Masers
• NH${}_3$(3,3) and CH${}_3$OH near Supernova Remnants: GBT and VLA Observations
• 183 GHz H${}_2$O maser emission around the low-mass protostar Serpens SMM1
• Non--local radiative transfer in strongly inverted masers
• C-type shock modelling -- the effect of new H${}_2$-H collisional rate coefficients
• H_2^{16}O and H_2^{18}O Maser Emission from Gas-Dust Clouds
• Modelling cosmic masers in C-type shock waves -- the coexistence of Class I CH3OH and 1720 MHz OH masers
• H2O Maser Emission in Circumstellar Envelopes around AGB Stars: Physical Conditions in Gas-Dust Clouds
• Searching For the 380 GHz H2O emission from the High-z lensed QSO MG J0414+0534
• Collisional Pumping of OH Masers near Supernova Remnants

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