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

Kishimoto, M.; Hönig, S. F.; Antonucci, Robert; Kotani, Takayuki; Barvainis, Richard; Tristram, K.; Weigelt, G.

doi:10.1051/0004-6361/200913512

Cited by 97 publications

(139 citation statements)

References 13 publications

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“…Here the radial dust distribution is particularly accessible in type 1 AGN. This has been demonstrated recently by Kishimoto et al (2009b) on a set of interferometric data of type 1 AGN and in our Paper I for NGC 3783 (Hönig et al 2010). The main reason for this constraining power is that IR interferometry can measure wavelength-dependent sizes of the continuum emission region that corresponds to the temperature distribution inside the torus and is, in turn, determined by the dust distribution and the source function of the clouds (see Eq.…”

Section: The Constraining Power Of Ir Interferometry On Torus Propertiessupporting

confidence: 57%

“…The most promising tool for this task is IR interferometry, which was already successfully used for a number of nearby objects (Swain et al 2003;Wittkowski et al 2004;Weigelt et al 2004;Jaffe et al 2004;Poncelet et al 2006;Meisenheimer et al 2007;Tristram et al 2007Tristram et al , 2009Beckert et al 2008;Raban et al 2009;Burtscher et al 2009;Kishimoto et al 2009b). However, except for reconstructed images of NGC 1068 obtained from Speckle interferometry (Weigelt et al 2004), long-baseline interferometry usually provides spatial information coded as Fourier space observables, i.e.…”

Section: Interferometry Of Dust Torimentioning

confidence: 99%

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The dusty heart of nearby active galaxies

Hönig

Kishimoto

2010

A&A

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205

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With the possibilities of high spatial resolution imaging and spectroscopy as well as infrared (IR) interferometry, the dusty environments (= "dusty torus") of active galactic nuclei (AGN) are now in reach of observations. Following our Paper I on ground-based mid-IR spectro-photometry, we present an upgrade to our radiative transfer model of three-dimensional clumpy dust tori. The upgrade with respect to earlier work concerns an improved handling of the diffuse radiation field in the torus, which is approximated by a statistical approach. The models are presented as tools to translate classical and interferometric observations into characteristic properties of the dust distribution. We compare model spectral energy distributions (SEDs) for different chemical and grain-size compositions of the dust and find that clouds with standard interstellar matter (ISM) dust and optical depth τ V ∼ 50 appear in overall agreement with observed IR SEDs. By studying parameter dependencies, it is shown that type 1 AGN SEDs, in particular the mid-IR spectral index, can be used to constrain the radial dust cloud distribution power law index a, while other parameters are more difficult to assess using SEDs only. Interferometry adds important additional information for modeling when it is interpreted concurrently with the SED. Although type 2 AGN can in principle be used to constrain model parameters as well, obscuration effects make the analysis more ambiguous. We propose a simple, interferometry-based method to distinguish between "compact" and "extended" radial dust distributions without detailed modeling of the data and introduce a way to easily determine individual or sample average model parameters using the observed optical depth in the silicate feature and the mid-IR spectral index.

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Section: The Constraining Power Of Ir Interferometry On Torus Propertiessupporting

confidence: 57%

Section: Interferometry Of Dust Torimentioning

confidence: 99%

The dusty heart of nearby active galaxies

Hönig

Kishimoto

2010

A&A

Self Cite

205

221

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“…Recently, Hatziminaoglou et al (2015) have performed a comprehensive study of 9.7 μm and 18 μm silicate emission features in a sample of AGNs. In contrast, observational evidence of local Seyfert galaxies dust tori suggests that large graphite grains dominate the sublimation zone of the inner torus (Kishimoto et al 2007(Kishimoto et al , 2009(Kishimoto et al , 2011Mor et al 2009;Mor & Netzer 2012). These studies indicate an altered distribution of grain sizes and their composition.…”

Section: Dust Compositionmentioning

confidence: 72%

Extinction curve template for intrinsically reddened quasars

Zafar

Møller

Watson

et al. 2015

A&A

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We analyzed the near-infrared to UV data of 16 quasars with redshifts ranging from 0.71 < z < 2.13 to investigate dust extinction properties. The sample presented in this work was obtained from the High A V Quasar (HAQ) survey. The quasar candidates were selected from the Sloan Digital Sky Survey (SDSS) and the UKIRT Infrared Deep Sky Survey (UKIDSS), and follow-up spectroscopy was carried out at the Nordic Optical Telescope (NOT) and the New Technology Telescope (NTT). To study dust extinction curves intrinsic to the quasars, we selected 16 cases from the HAQ survey for which the Small Magellanic Cloud (SMC) law could not provide a good solution to the spectral energy distributions (SEDs). We derived the extinction curves using the Fitzpatrick & Massa (1986, ApJ, 307, 286, FM) law by comparing the observed SEDs to a combined previously published quasar template. The derived extinction, A V , ranges from 0.2-1.0 mag. All the individual extinction curves of our quasars are steeper (R V = 2.2-2.7) than that of the SMC, with a weighted mean value of R V = 2.4. We derived an average quasar extinction curve for our sample by simultaneously fitting SEDs by using the weighted mean values of the FM law parameters and a varying R V . The entire sample is well fit with a single best-fit value of R V = 2.2 ± 0.2. The average quasar extinction curve deviates from the steepest Milky Way and SMC extinction curves at a confidence level 95%. Such steep extinction curves suggest that a significant population of silicates is involved in producing small dust grains. Another possibility might be that the large dust grains may have been destroyed by the activity of the nearby active galactic nuclei (AGN), resulting in steep extinction curves.

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“…Similarly, near-IR interferometric sizes would be systematically larger than IR reverberation-mapping radii at lower luminosities, and would better match each other at higher luminosities (cf. Kishimoto et al 2009b, for Keck interferometry results of four objects).…”

Section: A Luminosity Dependence Of the Torus Properties?mentioning

confidence: 99%

The dusty heart of nearby active galaxies

Hoenig

Kishimoto

Gandhi

et al. 2010

A&A

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

Cited by 97 publications

References 13 publications

The dusty heart of nearby active galaxies

The dusty heart of nearby active galaxies

Extinction curve template for intrinsically reddened quasars

The dusty heart of nearby active galaxies

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