Interferometer Observations of Subparsec-Scale Infrared Emission in the Nucleus of NGC 4151

Swain, Mark R.; Vasisht, Gautam; Akeson, Rachel; Monnier, John D.; Millan-Gabet, R.; Serabyn, Eugene; Creech‐Eakman, M. J.; Belle, Gerald van; Beletic, James W.; Beichman, Charles; Boden, A. F.; Booth, A. J.; Colavita, M. M.; Gathright, J.; Hrynevych, M.; Koresko, C.; Mignant, D. Le; Ligon, R.; Mennesson, Bertrand; Neyman, C.; Sargent, Anneila I.; Shao, Michael; Thompson, R. R.; Unwin, S. C.; Wizinowich, Peter

doi:10.1086/379235

Cited by 96 publications

(114 citation statements)

References 30 publications

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“…2. Figure 3 shows the final calibrated visibilities for NGC 4151 as a function of the projected baseline length, enlarged in the left panel of the insets. We confirm the visibility level observed by Swain et al (2003). The covered range of projected baselines is very limited (note also that the shortest possible for NGC 4151 is ∼70 m due to the KI's delay line restriction).…”

Section: Observations and Data Reductionsupporting

confidence: 87%

“…While the brightest type 1 AGN NGC 4151 and type 2 AGN NGC 1068 have been observed by Swain et al (2003) and Wittkowski et al (2004), respectively, further exploration has been hampered mainly by technical difficulties. Here we report successful observations of four type 1 AGNs with the Keck interferometer (KI) in the near-IR (K-band 2.2 μm).…”

Section: Introductionmentioning

confidence: 99%

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Exploring the inner region of type 1 AGNs with the Keck interferometer

Kishimoto

Hönig

Antonucci

et al. 2009

A&A

116

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The exploration of extragalactic objects with long-baseline interferometers in the near-infrared has been very limited. Here we report successful observations with the Keck interferometer at K-band (2.2 μm) for four type 1 AGNs, namely NGC 4151, Mrk231, NGC 4051, and the QSO IRAS 13349+2438 at z = 0.108. For the latter three objects, these are the first long-baseline interferometric measurements in the infrared. We detect high visibilities (V 2 ∼ 0.8−0.9) for all the four objects including NGC 4151, for which we confirm the high V 2 level measured by Swain et al. (2003, ApJ, 596, L163). We marginally detect a decrease of V 2 with increasing baseline lengths for NGC 4151, although over a very limited range, where the decrease and absolute V 2 are well fitted with a ring model having a radius of 0.45 ± 0.04 mas (0.039 ± 0.003 pc). Strikingly, this matches independent radius measurements from opticalinfrared reverberations that are thought to be probing the dust sublimation radius. We also show that the effective radius of the other objects, obtained from the same ring model, is either roughly equal to or slightly larger than the reverberation radius as a function of AGN luminosity. This suggests that we are indeed partially resolving the dust sublimation region. The ratio of the effective ring radius to the reverberation radius might also give us an approximate probe for the radial structure of the inner accreting material in each object. This should be scrutinized with further observations.

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Section: Observations and Data Reductionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Exploring the inner region of type 1 AGNs with the Keck interferometer

Kishimoto

Hönig

Antonucci

et al. 2009

A&A

116

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“…The Keck Interferometer observations of the Seyfert 1 nucleus of NGC 4151 (Swain et al 2003) showed that the majority of the central (∼3 pc) K-band light arises from very small scales of ≤0.1 pc, probably from the central accretion disk. Our K-band observations of the Seyfert 2 galaxy NGC 1068 show that only part of the central light arises from compact < ∼ 0.4 pc scales while another part arises from larger scales.…”

Section: Discussionmentioning

confidence: 99%

“…The potential of optical/infrared interferometry to investigate AGN was recently discussed by Wittkowski et al (2003). Swain et al (2003) reported the first K-band interferometric observations of the Seyfert 1 galaxy NGC 4151 obtained with the 85 m baseline of the Keck Interferometer. Jaffe et al (2004) reported on the first mid-infrared interferometric observation of the dusty torus of NGC 1068 using VLTI/MIDI.…”

Section: Introductionmentioning

confidence: 99%

VLTI/VINCI observations of the nucleus of NGC 1068 using the adaptive optics system MACAO

Wittkowski

Kervella

Arsenault

et al. 2004

A&A

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Abstract. We present the first near-infrared K-band long-baseline interferometric measurement of the nucleus of the prototype Seyfert 2 Galaxy NGC 1068 with resolution λ/B ∼ 10 mas obtained with the Very Large Telescope Interferometer (VLTI) and the two 8.2 m diameter Unit Telescopes UT 2 and UT 3. The adaptive optics system MACAO (Multi Application Curvature Adaptive Optics) was employed to deliver wavefront-corrected beams to the K-band commissioning instrument VINCI. A squared visibility amplitude of 16.3 ± 4.3% was measured for NGC 1068 at a sky-projected baseline length of 45.8 m and azimuth angle 44.9 deg. This value corresponds to a FWHM of the K-band intensity distribution of 5.0 ± 0.5 mas (0.4 ± 0.04 pc at the distance of NGC 1068) if it consists of a single Gaussian component. Taking into account K-band speckle interferometry observations (Wittkowski et al. 1998;Weinberger et al. 1999;Weigelt et al. 2004), we favor a multi-component model for the intensity distribution where a part of the flux originates from scales clearly smaller than ∼5 mas ( < ∼ 0.4 pc), and another part of the flux from larger scales. The K-band emission from the small ( < ∼ 5 mas) scales might arise from substructure of the dusty nuclear torus, or directly from the central accretion flow viewed through only moderate extinction.

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“…Recently, the IR emission source in a small number of nearby type 1 and type 2 AGN have been resolved in the mid-IR with the interferometric instrument MIDI at the VLTI (Jaffe et al 2004;Tristram et al 2007;Beckert et al 2008;Raban et al 2009;Tristram et al 2009;Burtscher et al 2009) and in the near-IR with the Keck interferometer (Swain et al 2003;Kishimoto et al 2009a). While interferometry provides the most direct access to the torus structure and brightness distribution (Kishimoto et al 2009a), observations are limited to the brightest AGN that are in reach of current facilities.…”

Section: Introductionmentioning

confidence: 99%

The dusty heart of nearby active galaxies

Hoenig

Kishimoto

Gandhi

et al. 2010

A&A

154

135

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In a series of papers, we aim at stepping towards characterizing physical properties of the AGN dust torus by combining IR highspatial resolution observations with 3D clumpy torus models. In this first paper, we present mid-IR imaging and 8−13 μm lowresolution spectroscopy of nine type 1 and ten type 2 AGN. The observations were carried out with the VLT/VISIR mid-IR imager and spectrograph and can be considered the largest currently available mid-infrared spectro-photometric data set of AGN at spatial resolution < ∼ 100 pc. These data resolve scales at which the emission from the dust torus dominates the overall flux, and emission from the host galaxy (e.g. star-formation) is resolved out in most cases. The silicate absorption features are moderately deep and emission features, if seen at all, are shallow. The strongest silicate emission feature in our sample shows some notable shift of the central wavelength from the expected 9.7 μm (based on ISM extinction curves) to ∼10.5 μm. We compare the observed mid-IR luminosities of our objects to AGN luminosity tracers (X-ray, optical and [O iii] luminosities) and find that the mid-IR radiation is emitted quite isotropically. In two cases, IC 5063 and MCG-3-34-64, we find evidence for extended dust emission in the narrow-line region. We confirm the correlation between observed silicate feature strength and Hydrogen column density, which was recently found in Spitzer data at lower spatial resolution. In a further step, our 3D clumpy torus model has been used to interpret the data. We show that the strength of the silicate feature and the mid-IR spectral index α can be used to get reasonable constraints on the radial dust distribution of the torus and the average number of clouds N 0 along an equatorial line-of-sight in clumpy torus models. The mid-IR spectral index α is almost exclusively determined by the radial dust distribution power-law index a, while the silicate feature depth mostly depends on N 0 and the torus inclination. A comparison of model predictions to our type 1 and type 2 AGN reveals that average parameters of a = −1.0 ± 0.5 and N 0 = 5 − 8 are typically seen in the presented sample, which means that the radial dust distribution is rather shallow. As a proof-of-concept of this method, we compared the model parameters derived from α and the silicate feature strength to more detailed studies of full IR SEDs and interferometry and found that the constraints on a and N 0 are consistent. Finally, we may have found evidence that the radial structure of the torus changes from low to high AGN luminosities towards steeper dust distributions, and we discuss implications for the IR size-luminosity relation.

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Interferometer Observations of Subparsec-Scale Infrared Emission in the Nucleus of NGC 4151

Cited by 96 publications

References 30 publications

Exploring the inner region of type 1 AGNs with the Keck interferometer

Exploring the inner region of type 1 AGNs with the Keck interferometer

VLTI/VINCI observations of the nucleus of NGC 1068 using the adaptive optics system MACAO

The dusty heart of nearby active galaxies

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