Dust Emission from Active Galactic Nuclei

By M. Nenkova, Željko Ivezic´, M. Elitzur. 2002

391 citations recorded by the source corpus.

Unified schemes of active galactic nuclei require an obscuring dusty torus around the central source, giving rise to a Seyfert 1 line spectrum for pole-on viewing and Seyfert 2 characteristics in edge-on sources. Although the observed IR is in broad agreement with this scheme, the behavior of the 10 μm silicate feature and the width of the far-IR emission peak remained serious problems in all previous modeling efforts. We show that these problems find a natural explanation if the dust is contained in approximately five to 10 clouds along radial rays through the torus. The spectral energy distributions of both type 1 and type 2 sources are properly reproduced from different viewpoints of the same object if the optical depth of each cloud is ≳60 at visual wavelengths and if the clouds' mean free path increases roughly in proportion to the radial distance.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/896448760d29d317d85df0704915438437f742db

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In Astronomy and Astrophysics

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Citations in the corpus

• REVERBERATION MEASUREMENTS OF THE INNER RADIUS OF THE DUST TORUS IN 17 SEYFERT GALAXIES (2014, background): “…has been conducted to explain the infrared spectral energy distribution (SED) of AGNs and to understand the dust torus structure (e.g., Pier & Krolik 1992; Nenkova et al. 2002, 2008; Dullemond & van Bemmel 2005; Schartmann et al. 2005, 2008; Hönig et al. 2006; Mor et al. 2009; Deo et al. 2011).”
• Dusty Star Forming Galaxies at High Redshift (2014, background): “…generate SEDs (Efstathiou and Rowan-Robinson, 1995; Efstathiou et al., 2000; Efstathiou and Rowan-Robinson, 2003; Efstathiou and Siebenmorgen, 2009; Nenkova et al., 2002; Dullemond and van Bemmel, 2005; Piovan et al., 2006; Nenkova et al., 2008; Takagi et al., 2003; Fritz et al., 2006; Hönig et…”
• The relation between AGN hard X-ray emission and mid-infrared continuum from ISO spectra: Scatter and unification aspects , (2004, background): “Radiative transfer models of the emission from a geometrically and optically thick torus (e.g. Pier et al. 1992; Efstathiou & Rowan-Robinson 1995; Granato et al. 1997; Nenkova et al. 2002) predict a strong anisotropy of the mid-infrared emission.”
• The Star-forming Torus and Stellar Dynamical Black Hole Mass in the Seyfert 1 Nucleus of NGC 3227 (2006, background): “Scales of a few tens of parsecs are exactly those on which theoretical models predict the obscuring torus should lie (Pier & Krolik 1992a, 1993; Granato & Danese 1994; Nenkova et al. 2002; Schartmann et al. 2005).”
• The Detection of Silicate Emission from Quasars at 10 and 18 Microns (2005, methodology): “These results are similar to those by Nenkova et al. (2002) and Dullemond & van Bemmel (2005), but their highest 10mm feature-to-continuum ratios are around 0.7 and 0.4, respectively.”
• Spitzer Quasar and ULIRG Evolution Study (QUEST). II. The Spectral Energy Distributions of Palomar-Green Quasars (2007, background): “There are a number of such models in the literature including those of Pier & Krolik (1992; 1993), Granato & Danese (1994), Efstathiou & Rowan-Robinson (1995), Nenkova et al. (2002) and Kuraszkiewicz et al. (2003).”
• Active galactic nuclei: what’s in a name? (2017, background): “…and van Bemmel 2005; Fritz et al. 2006), whether it is clumpy in the form of optically and geometrically thick clouds (Krolik and Begelman 1988; Nenkova et al. 2002, 2008; Elitzur and Shlosman 2006; Tristram et al. 2007), or a combination of the two (Stalevski et al. 2012; Assef et al. 2013).”
• Towards a physical model of dust tori in Active Galactic Nuclei (2005, methodology): “Another more realistic way to cope with the silicate feature problemwas proposed by Nenkova et al. (2002).”
• Revisiting the infrared spectra of active galactic nuclei with a new torus emission model (2005, background): “Nenkova et al. (2002) © 0000 RAS, MNRAS 000, 000–000 suggested that a clumpy distribution of dust may provide an explanation for the lack of the silicate feature in type-1 sources, while Dullemond & van Bemmel (2005) claim that the same result can be achieved in smooth tori.”
• Smooth and clumpy dust distributions in AGN: a direct comparison of two commonly explored infrared emission models (2012, background): “With this in mind, Nenkova et al. (2002) were the first to present a torus model with dust distributed in clumps, with the silicate emission feature attenuated and the IR bump broad enough to fit the observations.”
• The dusty torus in the Circinus galaxy: a dense disk and the torus funnel (2013, neutral): “For this reason, radiative transfer calculations of clumpy dust distributions have been carried out more recently (e.g. Nenkova et al. 2002; Schartmann et al. 2008; Hönig & Kishimoto 2010).”
• Radiative transfer modeling of three-dimensional clumpy AGN tori and its application to NGC 1068 (2006, background): “〈N〉 is the expectation value for Poisson statistics (Nenkova et al. 2002).”
• X-ray obscuration and obscured AGN in the local universe (2005, background): “Smooth (Granato et al. 1997) or clumpy (Nenkova et al. 2002) density distributions, anisotropic flares and tapered disk geometries (Efstathiou & Rowan-Robinson 1995) are all equally successful in reproducing the data.”
• THE DISCOVERY OF THE FIRST “CHANGING LOOK” QUASAR: NEW INSIGHTS INTO THE PHYSICS AND PHENOMENOLOGY OF ACTIVE GALACTIC NUCLEI (2014, background): “However, assuming a gas density of 105 cm−3, appropriate for the torus (e.g. Nenkova et al. 2002), the dust formation time scale is ∼103 years (see equation (8) of Draine 2009), which is much too long for this scenario to be viable.”
• AGN Dusty Tori. II. Observational Implications of Clumpiness (2008, methodology): “The updated models plotted with the data differ from the original ones in Nenkova et al. (2002) in three significant ways: (1) the optical properties of the silicate component of the dust are taken from the tabulation for ‘‘cool’’ silicates in Ossenkopf et al. (1992) instead of the Draine & Lee…”
• Deep Spitzer 24 μm COSMOS Imaging. I. The Evolution of Luminous Dusty Galaxies—Confronting the Models (2009, background): “…(8µm <∼λ<∼ 1000µm) plays a major role in shaping the panchromatic appearance of star-forming galaxies and active galactic nuclei (e.g., Silva et al. 1998; Gordon et al. 2000; Nenkova et al. 2002; Dopita et al. 2005; Marshall et al. 2007; Siebenmorgen & Krügel 2007; da Cunha et al. 2008).”
• Resolving the obscuring torus in NGC 1068 with the power of infrared interferometry: revealing the inner funnel of dust (2009, background): “Following the pioneering work of Nenkova et al. (2002) on clumpy models, Hönig et al. (2006) and Schartmann et al. (2008) showed that three-dimensional radiative transfer models of clumpy tori were consistent with the low spatial resolution SED data and the J04 interferometricdata of NGC 1068.”