“Be Nice to One Another!”

Wittkowski, Wolfgang

doi:10.1007/978-94-009-1604-3_25

Cited by 3 publications

(3 citation statements)

References 1 publication

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“…Yet, on parsec scales the emission is dominated by the circumnuclear dust and extends about perpendicular to the large-scale outflow cavity (Jaffe et al 2004;Raban et al 2009). It is noteworthy, though, that the elongation in outflow direction has also been observed by Speckle imaging in the near-IR (H and K bands) with a K-band size of 1.3 pc × 2.8 pc (error ±0.3 pc; Wittkowski et al 1998;Weigelt et al 2004). While one may argue about peculiarities of NGC 1068, NGC 424 and Circinus indicate that a polar-extended mid-IR emission is not untypical in AGN.…”

Section: Polar Elongation In Other Agnmentioning

confidence: 76%

Parsec-Scale Dust Emission From the Polar Region in the Type 2 Nucleus of NGC 424

Hönig

Kishimoto

Antonucci

et al. 2012

ApJ

155

179

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Advancements in infrared (IR) interferometry open up the possibility to spatially resolve active galactic nuclei (AGN) on the parsec-scale level and study the circumnuclear dust distribution, commonly referred to as the "dust torus", that is held responsible for the type 1/type 2 dichotomy of AGN. We used the mid-IR beam combiner MIDI together with the 8 m telescopes at the Very Large Telescope Interferometer (VLTI) to observe the nucleus of the Seyfert 2 galaxy NGC 424, achieving an almost complete coverage of the uv-plane accessible by the available telescope configurations. We detect extended mid-IR emission with a relatively baseline-and model-independent mid-IR half-light radius of (2.0 ± 0.2) pc × (1.5 ± 0.3) pc (averaged over the 8 − 13 µm wavelength range). The extended mid-IR source shows an increasing size with wavelength. These properties are in agreement with the idea of dust heated in thermal equilibrium with the AGN. The orientation of the major axis in position angle ∼ −27 • is closely aligned with the system axis as set by optical polarization observations. Torus models typically favor extension along the mid-plane at mid-IR wavelengths instead. Therefore, we conclude that the majority of the pc-scale mid-IR emission ( 60%) in this type 2 AGN originates from optically-thin dust in the polar region of the AGN, a scenario consistent with the near-to far-IR SED. We suggest that a radiatively-driven dusty wind, possibly launched in a puffed-up region of the inner hot part of the torus, is responsible for the polar dust. In this picture, the torus dominates the near-IR emission up to about 5 µm, while the polar dust is the main contributor to the mid-IR flux. Our results of NGC 424 are consistent with recent observations of the AGN in the Circinus galaxy and resemble large-scale characteristics of other objects. If our results reflect a general property of the AGN population, the current paradigm for interpreting and modeling the IR emission of AGN have to be revised.

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Section: Polar Elongation In Other Agnmentioning

confidence: 76%

Parsec-Scale Dust Emission From the Polar Region in the Type 2 Nucleus of NGC 424

Hönig

Kishimoto

Antonucci

et al. 2012

ApJ

155

179

View full text Add to dashboard Cite

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“…Until now long-based interferometry has been carried out for a couple of dozen Type I and II AGN (Wittkowski et al, 1998;Weinberger et al, 1999;Swain et al, 2003;Weigelt et al, 2004;Jaffe et al 2004;Wittkowski et al, 2004;Meisenheimer et al, 2007;Tristram et al, 2007;Beckert et al, 2008;Kishimoto et al, 2009ab;, with the largest sample found in Tristram et al (2009). Four objects in this last work are in common with our sample: NGC1068, F05189-2524, NGC5506 and NGC7582, however the observations for NGC5506 and NGC7582 did not provide useful data, while for F05189-2524 only a very faint fringe detection was possible.…”

Section: Comparison With Interferometric Observationsmentioning

confidence: 99%

Modeling the Nuclear Infrared Spectral Energy Distribution of Type Ii Active Galactic Nuclei

Lira

Videla

et al. 2013

ApJ

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We present results from model fitting to the Spectral Energy Distribution (SED) of a homogeneous sample of Seyfert II galaxies drawn from the 12µm Galaxy Sample. Imaging and nuclear flux measurements are presented in an accompanying paper (Videla et al., 2013). Here we add IRS Spitzer observations to further constrain the SEDs after careful subtraction of a starburst component. We use the library of CLUMPY torus models from Nenkova et al. (2008ab) and also test the two-phase models recently produced by Stalevski et al. (2012). We find that photometric and spectroscopic observations in the mid-IR (λ 5µm) are crucial to properly constrain the best-fit torus models. About half of our sources show clear near-IR excess of their SEDs above the best fit models. This problem can be less severe when using the Stalevski et al. (2012) models. It is not clear what is the nature of this emission since best fitted black body temperatures are very high (∼ 1700 − 2500 K) and the Type II classification of our sources would correspond to a small probability to peer directly into the hottest regions of the torus. Crucially, the derived torus parameters when using CLUMPY models are quite robust,, independently of whether the sources require an additional black body component or not. Our findings suggest that tori are characterized by N 0 5, σ 40, τ 25, ∠i 40 degrees, Y 50 and A los v ∼ 100 − 300, where N 0 is the number of clouds in the equatorial plane of the torus, σ is the characteristic opening angle of the cloud distribution, τ is the opacity of a single cloud, ∠i is the line-of-sight orientation of the torus, Y is the ratio of the inner to the outer radii, and A los v is the total opacity along the line-of-sight. From these we can determine that typical torus sizes and masses of 0.1 − 5.0 pc and 10 4−6 M ⊙ . We find tentative evidence that those nuclei with a detected Hidden Broad Line Regions are characterized by lower levels of extinction than those without one. Finally, we find no correlation between the torus properties and the presence of circumnuclear or more global star-formation.

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“…More direct support for unification comes from the HST, which has imaged an extended nuclear structure of ∼ 90 pc in NGC 4261 (Jaffe et al 1993), while interferometry observations are starting to shed light on the inner obscuring torus (Wittkowski et al 1998Weinberger et al 1999;Swain et al 2003;Jaffe et al 2004;Weigelt et al 2004;Meisenheimer et al 2007;Tristram et al 2007Beckert et al 2008;Kishimoto et al 2009Kishimoto et al , 2011Raban et al 2009).…”

Section: Unified Modelmentioning

confidence: 99%

Nuclear Infrared Spectral Energy Distribution of Type Ii Active Galactic Nuclei

Videla

Lira

Andrews

et al. 2013

ApJS

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We present near and mid-IR observations of a sample of Seyfert II galaxies drawn from the 12µm Galaxy Sample. The sample was observed in the J, H, K, L, M and N bands. Galaxy Surface Brightness Profiles are modeled using nuclear, bulge, bar (when necessary) and disk components.To check the reliability of our findings the procedure was tested using Spitzer observations of M 31. Nuclear Spectral Energy Distributions (SEDs) are determined for 34 objects, and optical spectra are presented for 38, including analysis of their stellar populations using the STARLIGHT spectral synthesis code. Emission line diagnostic-diagrams are used to discriminate between genuine AGN and HII nuclei. Combining our observations with those found in the literature, we have a total of 40 SEDs. It is found that about 40% of the SEDs are characterized by an upturn in the near-IR, which we have quantified as a NIR slope α < 1 for an SED characterized as λf λ ∝ λ α . Three objects with an HII nucleus and two Seyfert nuclei with strong contamination from a circumnuclear starburst, also show an upturn. For genuine AGN this component could be explained as emission from the accretion disk, a jet, or from a very hot dust component leaking from the central region through a clumpy obscuring structure. The presence of a very compact nuclear starburst as the origin for this NIR excess emission is not favored by our spectroscopic data for these objects. Subject headings:

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“Be Nice to One Another!”

Cited by 3 publications

References 1 publication

Parsec-Scale Dust Emission From the Polar Region in the Type 2 Nucleus of NGC 424

Parsec-Scale Dust Emission From the Polar Region in the Type 2 Nucleus of NGC 424

Modeling the Nuclear Infrared Spectral Energy Distribution of Type Ii Active Galactic Nuclei

Nuclear Infrared Spectral Energy Distribution of Type Ii Active Galactic Nuclei

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