The physics of water masers observable with ALMA and SOFIA: model predictions for evolved stars

Gray, M. D.; Baudry, A.; Richards, A. M. S.; Humphreys, E. M. L.; Соболев, А. М.; Yates, J. A.

doi:10.1093/mnras/stv2437

Cited by 82 publications

(60 citation statements)

References 104 publications

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“…About 130 of the detections are associated with AGNs, where they are called megamasers because of their large apparent luminosities. The physical conditions that give rise to maser activity at 22 GHz are also compatible with masing in other transitions of the H 2 O molecule, many of which fall in the submillimeter wavelength band (Neufeld & Melnick 1991;Gray et al 2016). Humphreys et al (2005) presented the first observations of H 2 O megamaser emission in a transition other than 22 GHz, detecting maser emission at 183 GHz and (tentatively) 439 GHz toward the galaxy NGC 3079.…”

Section: Introductionmentioning

confidence: 68%

“…This is to be expected from consideration of the physical conditions required for strong maser activity in these transitions. Gray et al (2016) performed a thorough exploration of the relevant parameter space (i.e., gas density, kinetic temperature, and dust temperature) and found that the 321 GHz transition shares an optimal gas density ( » n 10 H 9 2 cm −3 ) and collisional pumping scheme (i.e., low dust temperature) with the 22 GHz transition, although it prefers a somewhat larger kinetic temperature of » T 1500…”

Section: Ghz H 2 O Masers In Circinusmentioning

confidence: 99%

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SUBMILLIMETER H₂O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

Pesce

Braatz

Impellizzeri

2016

ApJ

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We present 321 GHz observations of five active galactic nuclei (AGNs) from ALMA Cycle 0 archival data: NGC 5793, NGC 1068, NGC 1386, NGC 4945, and the Circinus galaxy. Submillimeter maser emission is detected for the first time toward NGC 4945, and we present a new analysis of the submillimeter maser system in Circinus. None of the other three galaxies show maser emission, although we have detected and imaged the continuum from every galaxy. Both NGC 4945 and Circinus are known to host strong (10 Jy) 22 GHz megamaser emission, and VLBI observations have shown that the masers reside in the innermost ∼1 pc of the galaxies. The peak flux densities of the 321 GHz masers in both systems are substantially weaker (by a factor of ∼100) than what is observed at 22 GHz, although the corresponding isotropic luminosities are more closely matched (within a factor of ∼10) between the two transitions. We compare the submillimeter spectra presented here to the known 22 GHz spectra in both galaxies, and we argue that while both transitions originate from the gaseous environment near the AGNs, not all sites are in common. In Circinus, the spectral structure of the 321 GHz masers indicates that they may trace the accretion disk at radii interior to the 22 GHz masers. The continuum emission in NGC 4945 and NGC 5793 shows a spatial distribution indicative of an origin in the galactic disks (likely thermal dust emission), while for the other three galaxies the emission is centrally concentrated and likely originates from the nucleus.

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Section: Introductionmentioning

confidence: 68%

Section: Ghz H 2 O Masers In Circinusmentioning

confidence: 99%

SUBMILLIMETER H₂O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

Pesce

Braatz

Impellizzeri

2016

ApJ

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“…The pumping of the H 2 O maser transitions that trace highvelocity molecular outflows is thought to be dominated by shocks with neutral molecular gas (Hollenbach et al 2013;Gray et al 2016). The pumping mechanism of the H 2 O transitions is very sensitive to changes of the collisional rates, and requires particular conditions of the density and kinetic temperature of the gas (e.g.…”

Section: Introductionmentioning

confidence: 99%

Deep into the Water Fountains

Pérez-Sánchez

Tafoya

López

et al. 2017

A&A

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Context. The formation of large-scale (hundreds to few thousands of AU) bipolar structures in the circumstellar envelopes (CSEs) of post-Asymptotic Giant Branch (post-AGB) stars is poorly understood. The shape of these structures, traced by emission from fast molecular outflows, suggests that the dynamics at the innermost regions of these CSEs does not depend only on the energy of the radiation field of the central star. Aims. Multi-frequency observations towards a group of post-AGB sources known as Water Fountain nebulae can help to constrain the nature of the mechanism responsible for the launching and collimation of the fast molecular outlflows traced by high-velocity features of H 2 O maser emission. Methods. Deep into the Water Fountains is an observational project based on the results of programs carried out with three telescope facilities: The Karl G. Jansky Very Large Array (JVLA), The Australia Telescope Compact Array (ATCA), and the Very Large Telescope (SINFONI-VLT). Results. Here we report the results of the observations towards the WF nebula IRAS 18043−2116: Detection of radio continuum emission in the frequency range 1.5 GHz -8.0 GHz; H 2 O maser spectral features and radio continuum emission detected at 22 GHz, and H 2 ro-vibrational emission lines detected at the near infrared. Conclusions. The high-velocity H 2 O maser spectral features, and the shock-excited H 2 emission detected could be produced in molecular layers which are swept up as a consequence of the propagation of a jet-driven wind. Using the derived H 2 column density, we estimated a molecular mass-loss rate of the order of 10 −9 M yr −1 . On the other hand, if the radio continuum flux detected is generated as a consequence of the propagation of a thermal radio jet, the mass-loss rate associated to the outflowing ionized material is of the order of 10 −5 M yr −1 . The presence of a rotating disk could be a plausible explanation for the mass-loss rates estimated.

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“…These temperatures and densities are at the bottom of the range of conditions water masers can be found in. They can be found under a wide range of conditions, but they most favour temperatures of ∼800 K and number densities of 10 15 m −3 (Gray et al 2016).…”

Section: Introductionmentioning

confidence: 99%

A search for water masers associated with class II methanol masers – II. Longitude range 341° to 6°

Titmarsh

Ellingsen

Breen

et al. 2016

Mon. Not. R. Astron. Soc.

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This is the second paper in a series of catalogues of 22-GHz water maser observations towards the 6.7-GHz methanol masers from the Methanol Multibeam (MMB) Survey. In this paper we present our water maser observations made with the Australia Telescope Compact Array towards the masers from the MMB survey between l = 341 • through the Galactic centre to l = 6 • . Of the 204 6.7-GHz methanol masers in this longitude range we found 101 to have associated water maser emission (∼ 50 per cent). We found no difference in the 6.7-GHz methanol maser luminosities of those with and without water masers. In sources where both maser species are observed, the luminosities of the methanol and water masers are weakly correlated. Studying the mid-infrared colours from GLIMPSE we found no differences between the colours of those sources associated with both methanol and water masers and those associated with just methanol. Comparing the column density and dust mass calculated from the 870-µm thermal dust emission observed by ATLASGAL, we found no differences between those sources associated with both water and methanol masers and those with methanol only. Since water masers are collisionally pumped and often show emission further away from their accompanying YSO than the radiatively pumped 6.7-GHz methanol masers, it is likely water masers are not as tightly correlated to the evolution of the parent YSO and so do not trace such a well defined evolutionary state as 6.7-GHz methanol masers.

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The physics of water masers observable with ALMA and SOFIA: model predictions for evolved stars

Cited by 82 publications

References 104 publications

SUBMILLIMETER H₂O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

SUBMILLIMETER H₂O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

Deep into the Water Fountains

A search for water masers associated with class II methanol masers – II. Longitude range 341° to 6°

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The physics of water masers observable with ALMA and SOFIA: model predictions for evolved stars

Cited by 82 publications

References 104 publications

SUBMILLIMETER H2O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

SUBMILLIMETER H2O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

Deep into the Water Fountains

A search for water masers associated with class II methanol masers – II. Longitude range 341° to 6°

Contact Info

Product

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About

SUBMILLIMETER H₂O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

SUBMILLIMETER H₂O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY