Dense Molecular Gas and H2O Maser Emission in Galaxies

AbstractWe have detected maser emission from the 36.2 GHz (4−1 → 30E) methanol transition towards NGC 4945. This emission has been observed in two separate epochs and is approximately five orders of magnitude more luminous than typical emission from this transition within our Galaxy. NGC 4945 is only the fourth extragalactic source observed hosting class I methanol maser emission. Extragalactic class I methanol masers do not appear to be simply highly-luminous variants of their galactic counterparts and instead appear to trace large-scale regions where low-velocity shocks are present in molecular gas.

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Water Maser Emission from Dusty Clouds in AGNs

International Astronomical Union Colloquium ◽

10.1017/s0252921100043712 ◽

1997 ◽

Vol 163 ◽

pp. 738-739 ◽

Cited By ~ 1

Author(s):

John F. Kartje ◽

Arieh Königl ◽

Moshe Elitzur

Keyword(s):

Radiation Shielding ◽

Molecular Gas ◽

Dusty Gas ◽

Broad Line ◽

Maser Emission ◽

Disk Wind ◽

Broad Line Region ◽

Central Engine ◽

Line Region ◽

Water Maser

AbstractA natural site for water maser emission in AGNs is provided by dusty gas with properties characteristic of broad line region (BLR) clouds. Radiation shielding by dust in the clouds is critical for allowing molecular gas to exist ≤ 1 pc from the central engine. Thus, the innermost radius at which such masers appear should correspond to the grain sublimation radius rsub. We suggest a dynamical model in which the masing clouds are embedded within a magnetized accretion disk wind.

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Very High Resolution Observations of the Luminous Water Masers in NGC 4258

Symposium - International Astronomical Union ◽

10.1017/s0074180900134539 ◽

1988 ◽

Vol 129 ◽

pp. 231-232

Author(s):

M. J. Claussen ◽

M. J. Reid ◽

M. H. Schneps ◽

K.-Y. Lo ◽

J. M. Moran ◽

...

Keyword(s):

High Resolution ◽

Spatial Resolution ◽

Molecular Gas ◽

Nearby Galaxy ◽

Active Nucleus ◽

Maser Emission ◽

Water Masers ◽

Very High

We summarize the results and interpretation of a four station transcontinental VLBI experiment of the luminous water masers in the nearby galaxy NGC 4258. At a distance of 5 Mpc, the longest baseline of the experiment provides spatial resolution of less than 1016 cm. The strongest maser emission was detected on all baselines, and was found to consist of at least two features separated by about 0.1 mas (1016 cm). Weaker features are possibly spread over a region up to 1 mas in size. These results provide evidence that supports the scenario described by Claussen and Lo (1986) which suggests that the very luminous water masers reside in molecular gas that immediately surrounds the central, active nucleus.

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Spatio-kinematical model of the collimated molecular outflow in the water-fountain nebula IRAS 16342–3814

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834632 ◽

2019 ◽

Vol 629 ◽

pp. A8 ◽

Cited By ~ 4

Author(s):

D. Tafoya ◽

G. Orosz ◽

W. H. T. Vlemmings ◽

R. Sahai ◽

A. F. Pérez-Sánchez

Keyword(s):

Velocity Field ◽

High Velocity ◽

Three Dimensional ◽

Opening Angle ◽

Molecular Gas ◽

Lower Velocity ◽

Maser Emission ◽

Molecular Outflow ◽

Kinematical Model ◽

Water Maser

Context. Water-fountain nebulae are asymptotic giant branch (AGB) and post-AGB objects that exhibit high-velocity outflows traced by water-maser emission. Their study is important for understanding the interaction between collimated jets and the circumstellar material that leads to the formation of bipolar and/or multi-polar morphologies in evolved stars. Aims. The aim of this paper is to describe the three-dimensional morphology and kinematics of the molecular gas of the water-fountain nebula IRAS 16342−3814. Methods. Data was retrieved from the ALMA archive for analysis using a simple spatio-kinematical model. The software SHAPE was employed to construct a three-dimensional, spatio-kinematical model of the molecular gas in IRAS 16342−3814, and to then reproduce the intensity distribution and position-velocity diagram of the CO emission from the ALMA observations to derive the morphology and velocity field of the gas. Data from CO(J = 1 → 0) supported the physical interpretation of the model. Results. A spatio-kinematical model that includes a high-velocity collimated outflow embedded within material expanding at relatively lower velocity reproduces the images and position-velocity diagrams from the observations. The derived morphology is in good agreement with previous results from IR and water-maser emission observations. The high-velocity collimated outflow exhibits deceleration across its length, while the velocity of the surrounding component increases with distance. The morphology of the emitting region, the velocity field, and the mass of the gas as function of velocity are in excellent agreement with the properties predicted for a molecular outflow driven by a jet. The timescale of the molecular outflow is estimated to be ~70–100 yr. The scalar momentum carried by the outflow is much larger than it can be provided by the radiation of the central star. An oscillating pattern was found associated with the high-velocity collimated outflow. The oscillation period of the pattern is T ≈ 60–90 yr and its opening angle is θop ≈ 2°. Conclusions. The CO (J = 3 → 2) emission in IRAS 16342−3814 is interpreted in terms of a jet-driven molecular outflow expanding along an elongated region. The position-velocity diagram and the mass spectrum reveal a feature due to entrained material that is associated with the driving jet. This feature is not seen in other more evolved objects that exhibit more developed bipolar morphologies. It is likely that the jet in those objects has already disappeared since it is expected to last only for a couple hundred years. This strengthens the idea that water fountain nebulae are undergoing a very short transition during which they develop the collimated outflows that shape the circumstellar envelopes. The oscillating pattern seen in the CO high-velocity outflow is interpreted as due to precession with a relatively small opening angle. The precession period is compatible with the period of the corkscrew pattern seen at IR wavelengths. We propose that the high-velocity molecular outflow traces the underlying primary jet that produces such a pattern.

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The molecular environment of massive star forming cores associated with Class II methanol maser emission

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307012677 ◽

2007 ◽

Vol 3 (S242) ◽

pp. 125-129

Author(s):

S. N. Longmore ◽

M. G. Burton ◽

P. J. Barnes ◽

T. Wong ◽

C. R. Purcell ◽

...

Keyword(s):

Massive Star ◽

Class Ii ◽

Dynamic State ◽

Continuum Emission ◽

Molecular Gas ◽

Maser Emission ◽

Star Forming ◽

Methanol Maser ◽

Methanol Masers

AbstractMethanol maser emission has proven to be an excellent signpost of regions undergoing massive star formation (MSF). To investigate their role as an evolutionary tracer, we have recently completed a large observing program with the ATCA to derive the dynamical and physical properties of molecular/ionised gas towards a sample of MSF regions traced by 6.7GHz methanol maser emission. We find that the molecular gas in many of these regions breaks up into multiple sub-clumps which we separate into groups based on their association with/without methanol maser and cm continuum emission. The temperature and dynamic state of the molecular gas is markedly different between the groups. Based on these differences, we attempt to assess the evolutionary state of the cores in the groups and thus investigate the role of class II methanol masers as a tracer of MSF.

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ALMA detection of millimetre 183 GHz H2O maser emission in the Superantennae galaxy at z ∼ 0.06

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slab006 ◽

2021 ◽

Vol 502 (1) ◽

pp. L79-L84

Author(s):

Masatoshi Imanishi ◽

Yoshiaki Hagiwara ◽

Shinji Horiuchi ◽

Takuma Izumi ◽

Kouichiro Nakanishi

Keyword(s):

Line Emission ◽

Flux Ratio ◽

Molecular Gas ◽

Local Universe ◽

Central Mass ◽

Maser Emission ◽

Molecular Emission ◽

Spatially Resolved ◽

Ultraluminous Infrared Galaxy ◽

Highly Sensitive

ABSTRACT We present the results of Atacama Large Millimeter/submillimeter Array (ALMA) band-5 (∼170 GHz) observations of the merging ultraluminous infrared galaxy, the ‘Superantennae’ (IRAS 19254−7245), at z = 0.0617, which has been diagnosed as containing a luminous obscured active galactic nucleus (AGN). In addition to dense molecular line emission (HCNJ = 2–1, HCO+J = 2–1, and HNC J = 2–1), we detect a highly luminous (∼6 × 10$^{4}\, \mathrm{L}_{\odot }$) 183 GHz H2O 31,3–22,0 emission line. We interpret the strong H2O emission as largely originating in maser amplification in AGN-illuminated dense and warm molecular gas, based on (1) the spatially compact (≲220 pc) nature of the H2O emission, unlike spatially resolved (≳500 pc) dense molecular emission, and (2) a strikingly different velocity profile from, and (3) significantly elevated flux ratio relative to, dense molecular emission lines. H2O maser emission, other than the widely studied 22 GHz 61,6–52,3 line, has been expected to provide important information on the physical properties of gas in the vicinity of a central mass-accreting supermassive black hole (SMBH), because of different excitation energy. We here demonstrate that with highly sensitive ALMA, millimetre 183 GHz H2O maser detection is feasible out to >270 Mpc, opening a new window to scrutinize molecular gas properties around a mass-accreting SMBH far beyond the immediately local Universe.

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HCO+ emission possibly related with a shielding mechanism that protects water molecules in the young PN K 3-35

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308021509 ◽

2008 ◽

Vol 4 (S251) ◽

pp. 173-174 ◽

Cited By ~ 1

Author(s):

Y. Gómez ◽

D. Tafoya ◽

G. Anglada ◽

L. Loinard ◽

J. M. Torrelles ◽

...

Keyword(s):

Water Vapor ◽

Ionizing Radiation ◽

Large Distance ◽

Organic Molecules ◽

Planetary Nebulae ◽

Molecular Gas ◽

Water Molecules ◽

Unknown Mechanism ◽

Maser Emission ◽

Water Maser

AbstractWater maser emission has been detected only toward three planetary nebulae (PNe). In particular, in K3-35, the first PN where water vapor maser emission was detected, the components are located in a torus-like structure with a radius of 85 AU and also at the surprisingly large distance of 5000 AU from the star, in the tips of the bipolar lobes. The existence of these water molecules in PNe is puzzling, probably related to some unknown mechanism shielding them against the ionizing radiation. We report the detection of HCO+ (J = 1 − 0) emission toward K 3-35, that not only suggests that dense molecular gas (~105 cm−3) is present in this PN, but also that this kind of PN can enrich their surroundings with organic molecules.

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Central kiloparsec of NGC 1326 observed with SINFONI

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936451 ◽

2020 ◽

Vol 638 ◽

pp. A53

Author(s):

Nastaran Fazeli ◽

Gerold Busch ◽

Andreas Eckart ◽

Françoise Combes ◽

Persis Misquitta ◽

...

Keyword(s):

Black Hole ◽

Galaxy Evolution ◽

Near Infrared ◽

Velocity Fields ◽

Molecular Gas ◽

Nearby Galaxy ◽

Stellar Content ◽

Stellar Rotation ◽

Supermassive Black Hole ◽

Integral Field Spectrograph

Gas inflow processes in the vicinity of galactic nuclei play a crucial role in galaxy evolution and supermassive black hole growth. Exploring the central kiloparsec of galaxies is essential to shed more light on this subject. We present near-infrared H- and K-band results of the nuclear region of the nearby galaxy NGC 1326, observed with the integral-field spectrograph SINFONI mounted on the Very Large Telescope. The field of view covers 9″ × 9″ (650 × 650 pc2). Our work is concentrated on excitation conditions, morphology, and stellar content. The nucleus of NGC 1326 was classified as a LINER, however in our data we observed an absence of ionised gas emission in the central r ∼ 3″. We studied the morphology by analysing the distribution of ionised and molecular gas, and thereby detected an elliptically shaped, circum-nuclear star-forming ring at a mean radius of 300 pc. We estimate the starburst regions in the ring to be young with dominating ages of < 10 Myr. The molecular gas distribution also reveals an elongated east to west central structure about 3″ in radius, where gas is excited by slow or mild shock mechanisms. We calculate the ionised gas mass of 8 × 105 M⊙ completely concentrated in the nuclear ring and the warm molecular gas mass of 187 M⊙, from which half is concentrated in the ring and the other half in the elongated central structure. The stellar velocity fields show pure rotation in the plane of the galaxy. The gas velocity fields show similar rotation in the ring, but in the central elongated H2 structure they show much higher amplitudes and indications of further deviation from the stellar rotation in the central 1″ aperture. We suggest that the central 6″ elongated H2 structure might be a fast-rotating central disc. The CO(3–2) emission observations with the Atacama Large Millimeter/submillimeter Array reveal a central 1″ torus. In the central 1″ of the H2 velocity field and residual maps, we find indications for a further decoupled structure closer to a nuclear disc, which could be identified with the torus surrounding the supermassive black hole.

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