SUBMILLIMETER H<sub>2</sub>O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

Pesce, Dominic W.; Braatz, J. A.; Impellizzeri, C. M. V.

doi:10.3847/0004-637x/827/1/68

Cited by 24 publications

(27 citation statements)

References 35 publications

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“…The velocity scale is radio LSR. the 183 GHz transition found here is much higher than that found for 321 GHz emission towards NCC 4945 at ∼10 L (Pesce et al 2016;Hagiwara et al 2016). We speculate that this is due to the very different energy requirements of the two lines.…”

Section: Nature Of the Detected Emissioncontrasting

confidence: 73%

“…In the literature, L13, page 3 of 4 A&A 592, L13 (2016) 22 GHz maser spectra do not display velocities much above 1000 km s −1 (e.g. G97; Pesce et al 2016;Hagiwara et al 2016). …”

Section: Does the Emission Originate From The Agn Central Engine?mentioning

confidence: 99%

“…To date extragalactic mm/submm water maser emission has been detected for the 183 GHz transition towards NGC 3079 using the SMA (Humphreys et al 2005), Arp 220 using the IRAM 30 m and APEX (Cernicharo et al 2006;Galametz et al 2016), and for the 321 GHz transition towards Circinus and NGC 4945 using ALMA (Hagiwara et al 2013(Hagiwara et al , 2016Pesce et al 2016). There has also been a tentative, 5σ detection of 439 GHz H 2 O water maser emission towards NGC 3079 using the James Clark Maxwell Telescope (Humphreys et al 2005).…”

Section: Introductionmentioning

confidence: 99%

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Detection of 183 GHz H₂O megamaser emission towards NGC 4945

Humphreys

Vlemmings

Impellizzeri

et al. 2016

A&A

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Aims. The aim of this work is to search Seyfert 2 galaxy NGC 4945, a well-known 22 GHz water megamaser galaxy, for H 2 O (mega)maser emission at 183 GHz. Methods. We used APEX SEPIA Band 5 (an ALMA Band 5 receiver on the APEX telescope) to perform the observations. Results. We detected 183 GHz H 2 O maser emission towards NGC 4945 with a peak flux density of ∼3 Jy near the galactic systemic velocity. The emission spans a velocity range of several hundred km s −1 . We estimate an isotropic luminosity of >1000 L , classifying the emission as a megamaser. A comparison of the 183 GHz spectrum with that observed at 22 GHz suggests that 183 GHz emission also arises from the active galactic nucleus (AGN) central engine. If the 183 GHz emission originates from the circumnuclear disk, then we estimate that a redshifted feature at 1084 km s −1 in the spectrum should arise from a distance of 0.022 pc from the supermassive black hole (1.6 × 10 5 Schwarzschild radii), i.e. closer than the water maser emission previously detected at 22 GHz. This is only the second time 183 GHz maser emission has been detected towards an AGN central engine (the other galaxy being NGC 3079). It is also the strongest extragalactic millimetre/submillimetre water maser detected to date. Conclusions. Strong millimetre 183 GHz H 2 O maser emission has now been shown to occur in an external galaxy. For NGC 4945, we believe that the maser emission arises, or is dominated by, emission from the AGN central engine. Emission at higher velocity, i.e. for a Keplerian disk closer to the black hole, has been detected at 183 GHz compared with that for the 22 GHz megamaser. This indicates that millimetre/submillimetre H 2 O masers can indeed be useful for tracing out more of AGN central engine structures and dynamics than previously probed. Future observations using ALMA Band 5 should unequivocally determine the origin of the emission in this and other galaxies.

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Section: Nature Of the Detected Emissioncontrasting

confidence: 73%

“…In the literature, L13, page 3 of 4 A&A 592, L13 (2016) 22 GHz maser spectra do not display velocities much above 1000 km s −1 (e.g. G97; Pesce et al 2016;Hagiwara et al 2016). …”

Section: Does the Emission Originate From The Agn Central Engine?mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Detection of 183 GHz H₂O megamaser emission towards NGC 4945

Humphreys

Vlemmings

Impellizzeri

et al. 2016

A&A

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“…In our observations, a highly redshifted velocity feature at V LSR =1138.6 kms 1 is marginally detected. In their analysis of this data set, Pesce et al (2016) note that this velocity range is impacted by higher atmospheric absorption resulting in a somewhat higher noise level, and so further observations are required to confirm this feature.…”

Section: High-velocity Dense Gas In Ngc 4945mentioning

confidence: 99%

A SEARCH FOR SUBMILLIMETER H₂O MASERS IN ACTIVE GALAXIES: THE DETECTION OF 321 GHz H₂O MASER EMISSION IN NGC 4945

Hagiwara

Horiuchi

Doi

et al. 2016

ApJ

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We present further results of a search for extragalactic submillimeter H 2 O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H 2 O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H 2 O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H 2 O masers;however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H 2 O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ∼0 54 (∼30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km -s 1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ∼0.020 pc (∼1.5×10 5 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H 2 O masers. This detection confirms that submillimeter H 2 O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

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“…Ellingsen et al (2014) observe offsets of 180 and 300 pc for the northeast and southwest components, respectively. Although the H 2 O maser emission observed in NGC 4945 is not physically associated with the 36.2 GHz maser emission, the redshifted components share an overlapping velocity range (Greenhill et al 1997;Hagiwara et al 2016;Humphreys et al 2016;Pesce et al 2016).…”

Section: Properties Of Methanol Maser Environmentmentioning

confidence: 99%

Detection of 36 GHz Class I Methanol Maser Emission toward NGC 4945

McCarthy

Ellingsen

Chen

et al. 2017

ApJ

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We have searched for emission from the 36.2 GHz (  -4 3 E 1 0 ) methanol transition toward NGC 4945, using the Australia Telescope Compact Array. 36.2 GHz methanol emission was detected offset southeast from the Galactic nucleus. The methanol emission is narrow, with a line width <10 km s −1 and a luminosity five orders of magnitude higher than Galactic class I masers from the same transition. These characteristics combined the with physical separation from the strong central thermal emission suggests that the methanol emission is a maser. This emission is a factor of ∼90 more luminous than the widespread emission detected from the Milky Way central molecular zone. This is the fourth detection of extragalactic class I emission and the third detection of extragalactic 36.2 GHz maser emission. These extragalactic class I methanol masers do not appear to be simply highly luminous variants of Galactic class I emission and instead appear to trace large-scale regions of low-velocity shocks in molecular gas, which may precede, or be associated with, the early stages of large-scale star formation.

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SUBMILLIMETER H₂O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

Cited by 24 publications

References 35 publications

Detection of 183 GHz H₂O megamaser emission towards NGC 4945

Detection of 183 GHz H₂O megamaser emission towards NGC 4945

A SEARCH FOR SUBMILLIMETER H₂O MASERS IN ACTIVE GALAXIES: THE DETECTION OF 321 GHz H₂O MASER EMISSION IN NGC 4945

Detection of 36 GHz Class I Methanol Maser Emission toward NGC 4945

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SUBMILLIMETER H2O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

Cited by 24 publications

References 35 publications

Detection of 183 GHz H2O megamaser emission towards NGC 4945

Detection of 183 GHz H2O megamaser emission towards NGC 4945

A SEARCH FOR SUBMILLIMETER H2O MASERS IN ACTIVE GALAXIES: THE DETECTION OF 321 GHz H2O MASER EMISSION IN NGC 4945

Detection of 36 GHz Class I Methanol Maser Emission toward NGC 4945

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SUBMILLIMETER H₂O MEGAMASERS IN NGC 4945 AND THE CIRCINUS GALAXY

Detection of 183 GHz H₂O megamaser emission towards NGC 4945

Detection of 183 GHz H₂O megamaser emission towards NGC 4945

A SEARCH FOR SUBMILLIMETER H₂O MASERS IN ACTIVE GALAXIES: THE DETECTION OF 321 GHz H₂O MASER EMISSION IN NGC 4945