Observations of interstellar H2O emission at 183 gigahertz

Waters, J. W.; Kakar, Ramesh K.; Kuiper, T. B. H.; Roscoe, H. K.; Swanson, Paul N.; Kuiper, E. N. Rodriguez; Kerr, A. R.; Thaddeus, P.; Gustincic, J. J.

doi:10.1086/157609

Cited by 62 publications

(35 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Most of them appear also in models based on the de Jong (1973) mechanism (see also Cooke & Elitzur 1985;Neufeld & Melnick 1991). The 4 14 → 3 21 and 3 13 → 2 20 transitions have been detected in the Orion cloud by Phillips et al (1980) and Waters et al (1980). The masing emission in 10 29 → 9 36 line was observed in a wide variety of sources where the 1.35 cm maser was detected (Menten et al 1990).…”

Section: Other Maser Transitionsmentioning

confidence: 92%

Water masers in dusty environments

Babkovskaia

Poutanen

2004

A&A

View full text Add to dashboard Cite

Abstract. We study in detail a pumping mechanism for the λ = 1.35 cm maser transition 6 16 → 5 23 in ortho-H 2 O based on the difference between gas and dust temperatures. The upper maser level is populated radiatively through 4 14 → 5 05 and 5 05 → 6 16 transitions. The heat sink is realized by absorbing the 45 µm photons, corresponding to the 5 23 → 4 14 transition, by cold dust. We compute the inversion of maser level populations in the optically thick medium as a function of the hydrogen concentration, the water-to-dust mass ratio, and the difference between the gas and the dust temperatures. The main results of the numerical simulations are interpreted in terms of a simplified four-level model. We show that the maser strength depends mostly on the product of hydrogen concentration and the dust-to-water mass ratio but not on the size distribution of the dust particles or their type. We also suggest approximate formulae that describe accurately the inversion and can be used for fast calculations of the maser luminosity. Depending on the gas temperature, the maximum maser luminosity is reached when the water concentration N H 2 O ≈ 10 6 −10 7 cm −3 times the dust-to-hydrogen mass ratio, and the inversion completely disappears at densities just an order of magnitude larger. For a dust temperature of 130 K, the 6 16 → 5 23 transition becomes inverted already at a temperature difference of ∆T ∼ 1 K, while other possible masing transitions require a larger ∆T > ∼ 30 K. We identify the region of the parameter space where other ortho-and para-water masing transitions can appear.

show abstract

Section: Other Maser Transitionsmentioning

confidence: 92%

Water masers in dusty environments

Babkovskaia

Poutanen

2004

A&A

View full text Add to dashboard Cite

show abstract

“…Waters et al 1980;Menten et al 1990a;Maercker et al 2008). At submillimetre wavelengths a number of molecular transitions of H 2 O have been detected displaying high flux density values and narrow line shapes characteristic of maser emission lines (Waters et al 1980;Menten et al 1990b;Yates & Cohen 1996). The most studied water maser emission is the low-frequency 6 16 -5 23 transition at 22.2 GHz.…”

Section: H 2 Omentioning

confidence: 99%

Linear polarization of submillimetre masers

Pérez-Sánchez

Vlemmings

2013

A&A

View full text Add to dashboard Cite

Context. Once ALMA full polarization capabilities are offered, it will become possible to perform detailed studies of polarized maser emission towards star-forming regions and late-type stars, such as (post-) asymptotic giant branch stars and young planetary nebulae. To derive the magnetic field orientation from maser linear polarization, a number of conditions involving the rate of stimulated emission R, the decay rate of the molecular state Γ, and the Zeeman frequency gΩ need to be satisfied. Aims. The goal of this work is to investigate if SiO, H 2 O and HCN maser emission within the ALMA frequency range can be detected with observable levels of fractional linear polarization in the regime where the Zeeman frequency is greater than the stimulated emission rate. Methods. We used a radiative transfer code to calculate the fractional linear polarization as a function of the emerging brightness temperature for a number of rotational transition of SiO, H 2 O and HCN that have been observed to display maser emission at submillimetre wavelengths. We assumed typical magnetic field strengths measured towards galactic star-forming regions and circumstellar envelopes of late-type stars from previous VLBI observations. Since the Landé g-factors have not been reported for the different rotational transitions we modelled, we performed our calculations assuming conservative values of the Zeeman frequency for the different molecular species. Results. Setting a lower limit for the Zeeman frequency that still satisfies the criteria gΩ > R and gΩ > Γ, we find fractional polarization levels of up to 13%, 14% and 19% for the higher J transitions analysed for SiO, H 2 O and HCN, respectively, without considering anisotropic pumping or any other non-Zeeman effect. These upper limits were calculated assuming a magnetic field oriented perpendicular to the direction of propagation of the maser radiation. Conclusions. According to our results, SiO, H 2 O, and HCN maser emission within the ALMA frequency range can be detected with suitable linear polarization to trace the magnetic field structure towards star-forming regions and late-type stars even if the detected polarization has been enhanced by non-Zeeman effects.

show abstract

“…Over the 40 yr since the first detection of interstellar water maser emission in the 22 GHz transition, several additional interstellar maser transitions have been detected at higher frequencies, some in response to a specific prediction of a population inversion (Menten et al 1990a). In the case of pure rotational emissions, these comprise the 183 GHz (Waters et al 1980), 321 GHz (Menten et al 1990b), 325 GHz (Menten et al 1990a), 380 GHz (Phillips et al 1980), 439 GHz (Melnick et al 1993) and 471 GHz (Melnick et al 1993) lines, associated respectively with the 3 13 -2 20 , 10 29 -9 36 , 5 15 -4 22 , 4 14 -3 21 , 6 43 -5 50 , and 6 42 -5 51 transitions. These transitions are shown in the energy level diagram in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

HERSCHEL/HIFI OBSERVATIONS OF A NEW INTERSTELLAR WATER MASER: THE 5₃₂-4₄₁TRANSITION AT 620.701 GHz

Neufeld

Kraus

et al. 2013

ApJ

View full text Add to dashboard Cite

Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have performed mapping observations of the 620.701 GHz 5 32 -4 41 transition of ortho-H 2 O within a ∼1. 5 × 1. 5 region encompassing the Kleinmann-Low nebula in Orion (Orion-KL), and pointed observations of that transition toward the Orion South condensation and the W49N region of high-mass star formation. Using the Effelsberg 100 m radio telescope, we obtained ancillary observations of the 22.23508 GHz 6 16 -5 23 water maser transition; in the case of Orion-KL, the 621 GHz and 22 GHz observations were carried out within 10 days of each other. The 621 GHz water line emission shows clear evidence for strong maser amplification in all three sources, exhibiting narrow (∼1 km s −1 FWHM) emission features that are coincident (kinematically and/or spatially) with observed 22 GHz features. Moreover, in the case of W49N-for which observations were available at three epochs spanning a 2 yr period-the spectra exhibited variability. The observed 621 GHz/22 GHz line ratios are consistent with a maser pumping model in which the population inversions arise from the combined effects of collisional excitation and spontaneous radiative decay, and the inferred physical conditions can plausibly arise in gas heated by either dissociative or non-dissociative shocks. The collisional excitation model also predicts that the 22 GHz population inversion will be quenched at higher densities than that of the 621 GHz transition, providing a natural explanation for the observational fact that 22 GHz maser emission appears to be a necessary but insufficient condition for 621 GHz maser emission.

show abstract

Observations of interstellar H2O emission at 183 gigahertz

Cited by 62 publications

References 0 publications

Water masers in dusty environments

Water masers in dusty environments

Linear polarization of submillimetre masers

HERSCHEL/HIFI OBSERVATIONS OF A NEW INTERSTELLAR WATER MASER: THE 5₃₂-4₄₁TRANSITION AT 620.701 GHz

Contact Info

Product

Resources

About

Observations of interstellar H2O emission at 183 gigahertz

Cited by 62 publications

References 0 publications

Water masers in dusty environments

Water masers in dusty environments

Linear polarization of submillimetre masers

HERSCHEL/HIFI OBSERVATIONS OF A NEW INTERSTELLAR WATER MASER: THE 532-441TRANSITION AT 620.701 GHz

Contact Info

Product

Resources

About

HERSCHEL/HIFI OBSERVATIONS OF A NEW INTERSTELLAR WATER MASER: THE 5₃₂-4₄₁TRANSITION AT 620.701 GHz