Positional Coincidence of H<sub>2</sub>O Maser and a Plasma‐Obscuring Torus in Radio Galaxy NGC 1052

Sawada-Satoh, Satoko; Kameno, Seiji; Nakamura, Kayoko; Namikawa, D.; Shibata, Katsunori M.; Inoue, Makoto

doi:10.1086/587886

Cited by 39 publications

(61 citation statements)

References 28 publications

(65 reference statements)

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“…Alternatively, it could also be the result of the amplification of the radio continuum of the jet by foreground molecular clouds along the line of sight (as in NGC 1052; Sawada-Satoh et al 2008). In this framework, the maser and continuum intensities in MG J0414+0534 would then be expected to show a similar behaviour to that in the aforementioned cases.…”

Section: Origin Of the H 2 O Emissionmentioning

confidence: 91%

Water vapour at high redshift: Arecibo monitoring of the megamaser in MG J0414+0534

Castangia

Impellizzeri

McKean

et al. 2011

A&A

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Aims. The study of water masers at cosmological distances would allow us to investigate the parsec-scale environment around powerful radio sources, to probe the physical conditions of the molecular gas in the inner parsecs of quasars, and to estimate their nuclear engine masses in the early universe. To derive this information, the nature of the maser source needs to be assessed through a detailed investigation of the observational characteristics of the line emission. This will determine whether the emission is from a jet-or diskmaser source. Methods. We monitored the maser line in the lensed quasar MG J0414+0534 at z = 2.64 with the 300-m Arecibo telescope for ∼15 months to detect possible additional maser components and to measure a potential velocity drift of the lines. In addition, we followed the maser and continuum emissions to reveal significant variations in their flux density and to determine whether correlation or time-lag exists between them. Results. The main maser line profile is complex and can be resolved into a number of broad features with line widths of 30-160 km s −1 . A new maser component was tentatively detected in October 2008, and is redshifted by 470 km s −1 compared to the systemic velocity of the quasar. The line width of the main maser feature increased by a factor of two between the discovery Effelsberg and EVLA observations and the first epoch of the Arecibo monitoring campaign. After correcting for the lens magnification, we find that the total H 2 O isotropic luminosity of the maser in MG J0414+0534 is now ∼30 000 L , making this source the most luminous ever discovered. Both the main line peak and continuum flux densities are surprisingly stable throughout the period of the observations. The integrated flux density instead shows significant variations on monthly time scales, possibly due to changes in the individual velocity components. We place an upper limit on the velocity drift of the peak of the line emission of 2 km s −1 yr −1 . Conclusions. The large line width of the main maser line and the absence of a clear triple-peak pattern in the maser spectrum of MG J0414+0534 favours the jet-maser scenario. However, the stability of the line and continuum emission, and the presence of the tentative new maser component, which is potentially identified as a high-velocity feature of a rotating disk, seems to partly contradict this interpretation. Sensitive monitoring on a longer time scale and VLBI observations are mandatory for drawing a definite conclusion.

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Section: Origin Of the H 2 O Emissionmentioning

confidence: 91%

Water vapour at high redshift: Arecibo monitoring of the megamaser in MG J0414+0534

Castangia

Impellizzeri

McKean

et al. 2011

A&A

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“…Here we take T ex = 100 K and 230 K, as recent millimeter and submillimeter interferometric observations have detected the vibrationally excited HCN emission lines in the dust-enshrouded AGN of the luminous infrared galaxies (Sakamoto et al 2010;Imanishi & Nakanishi 2013 23 cm −2 from modeling of Xray spectra (Guainazzi & Antonelli 1999;Weaver et al 1999;Guainazzi et al 2000;Brenneman et al 2009), and the electron column density of ∼ 10 23 cm −2 estimated from the FFA opacity of the dense plasma (Sawada-Satoh et al 2009). Kameno et al (2005) and Sawada-Satoh et al (2008) proposed that the circumnuclear torus consists of several phase layers. On the inner surface of the torus, a hot (∼ 8000 K) plasma layer is formed by X-ray emission from the central engine and it causes FFA.…”

Section: Absorbing Molecular Gas Propertiesmentioning

confidence: 99%

“…An H 2 O megamaser emission is detected at velocities by redshifted 50-350 km s −1 with respect to V sys (Braatz et al 1994(Braatz et al , 2003Kameno et al 2005), and the H 2 O maser gas lies on the inner components in the center of NGC 1052, where the plasma torus is obscured (Claussen et al 1998;Sawada-Satoh et al 2008). Neutral atomic hydrogen (H I), OH, HCO + , HCN, CO tran-sitions are found toward the center of NGC 1052 as absorptions (van Gorkom et al 1986;Omar et al 2002;Liszt & Lucas 2004;Impellizzeri et al 2008).…”

Section: Introductionmentioning

confidence: 96%

“…Claussen et al 1998;Vermeulen et al 2003). VLBI images at 43 GHz, however, show an innermost component in the gap (Kadler et al 2004;Sawada-Satoh et al 2008). Kameno et al (2001) proposed the existence of a parsec-scale circumnuclear torus consisting of cold dense plasma from the convex radio continuum spectra due to the free-free absorption (FFA) by the foreground plasma.…”

Section: Introductionmentioning

confidence: 99%

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Spatially Resolved HCN Absorption Features in the Circumnuclear Region of NGC 1052

Sawada-Satoh

Roh

et al. 2016

ApJL

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We present the first VLBI detection of HCN molecular absorption in the nearby active galactic nucleus NGC 1052. Utilizing the 1 mas resolution achieved by the Korean VLBI Network, we have spatially resolved the HCN absorption against a double-sided nuclear jet structure. Two velocity features of HCN absorption are detected significantly at the radial velocity of 1656 and 1719 km s −1 , redshifted by 149 and 212 km s −1 with respect to the systemic velocity of the galaxy. The column density of the HCN molecule is estimated to be 10 15 -10 16 cm −2 , assuming an excitation temperature of 100-230 K. The absorption features show high optical depth localized on the receding jet side, where the free-free absorption occurred due to the circumnuclear torus. The size of the foreground absorbing molecular gas is estimated to be on approximately one-parsec scales, which agrees well with the approximate size of the circumnuclear torus. HCN absorbing gas is likely to be several clumps smaller than 0.1 pc inside the circumnuclear torus. The redshifted velocities of the HCN absorption features imply that HCN absorbing gas traces ongoing infall motion inside the circumnuclear torus onto the central engine.

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“…Secondly, they are associated with radio jets, where they are either the result of an interaction between the jet(s) and a molecular cloud or a coincidental overlap along the line of sight between a warm, dense molecular cloud and the radio continuum of the jet (NGC 1052: e.g. Sawada-Satoh et al 2008; NGC 1068: e.g. Gallimore et al 2001; Mrk 348: e.g.…”

Section: Introductionmentioning

confidence: 99%

Narrow-line Seyfert 1 galaxies: an amasing class of AGN

Tarchi

Castangia

Columbano

et al. 2011

A&A

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Context. Narrow-line Seyfert 1 (NLS1) galaxies are a class of active galactic nuclei (AGN) that have all the properties of type 1 Seyfert galaxies but show peculiar characteristics, including the narrowest Balmer lines, strongest Fe II emission, and extreme properties in the X-rays. Line and continuum radio observations provide an optimal tool to access the (often) optically obscured innermost regions of AGN and reveal the kinematics of the gas around their central engines. Aims. We investigate the interplay between the peculiar NLS1 class of AGN and the maser phenomenon, to help us understand the nature of the maser emission in some NLS1s where water maser emission has been detected. Methods. We observed a sample of NLS1 galaxies with the Green Bank Telescope in a search for water maser emission at 22 GHz. We also reduced and analysed archival Green Bank Telescope and Very Large Array data and produced 22-GHz spectra for the five NLS1 galaxies with detected maser emission. In particular, we imaged the maser and nuclear radio continuum of NGC 5506 at subarcsec scales with the Very Large Array. Results. We discovered maser emission in two NLS1 galaxies: IGR J16385-2057, and IRAS 03450+0055. In addition to the three previously known maser detections in the NLS1s Mrk 766, NGC 4051, and NGC 5506, this yields a water maser detection rate in NLS1 galaxies of ∼7% (5/71). This value rises significantly to ∼21% (5/24) when considering only NLS1 galaxies at recessional velocities less than 10 000 km s −1 . For NGC 4051 and NGC 5506, we find that the water maser emission is located within 5 and 12 pc, respectively, of nuclear radio continuum knots, which are interpreted as core-jet structures. Conclusions. The water maser detection rate in NLS1s is surprisingly high, much higher than the detection rate obtained for type 1 AGN and similar to those in Seyfert 2 and low-ionization nuclear emission-line region galaxies. The masers in NGC 4051 and NGC 5506 are nuclear and associated with the AGN, either with an accretion disk, a radio jet, or a nuclear outflow. The apparent lack of high-velocity maser features and evidence, recently reported, of radiative outflows and radio jets in the host galaxies seems to favour interpretation as a jet or an outflow. A similar association is also seemingly true for the maser in Mrk 766, IGR J16385-2057, and IRAS 03450+0055, although, in these cases, without radio interferometric measurements we cannot rule out an off-nuclear origin of the emission.

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Positional Coincidence of H₂O Maser and a Plasma‐Obscuring Torus in Radio Galaxy NGC 1052

Cited by 39 publications

References 28 publications

Water vapour at high redshift: Arecibo monitoring of the megamaser in MG J0414+0534

Water vapour at high redshift: Arecibo monitoring of the megamaser in MG J0414+0534

Spatially Resolved HCN Absorption Features in the Circumnuclear Region of NGC 1052

Narrow-line Seyfert 1 galaxies: an amasing class of AGN

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Positional Coincidence of H2O Maser and a Plasma‐Obscuring Torus in Radio Galaxy NGC 1052

Cited by 39 publications

References 28 publications

Water vapour at high redshift: Arecibo monitoring of the megamaser in MG J0414+0534

Water vapour at high redshift: Arecibo monitoring of the megamaser in MG J0414+0534

Spatially Resolved HCN Absorption Features in the Circumnuclear Region of NGC 1052

Narrow-line Seyfert 1 galaxies: an amasing class of AGN

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Positional Coincidence of H₂O Maser and a Plasma‐Obscuring Torus in Radio Galaxy NGC 1052