A spectropolarimetric atlas of Seyfert 1 galaxies

Smith, James E.; Young, S.; Robinson, Andrew; Corbett, E. A.; Giannuzzo, M. E.; Axon, D. J.; Hough, J. H.

doi:10.1046/j.1365-8711.2002.05665.x

Cited by 132 publications

(257 citation statements)

References 40 publications

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“…This type of signature is the same that was found by previous authors when modeling smooth-density or clumpy distributions of matter in complex AGN models (Kartje 1995;Marin et al 2012. This is also the typical amount of polarization found in nearby Seyferts that are dominated by equatorial-scattering (Smith et al 2002). The case of an intermediate inclination is similar: the polarization position angle is almost always parallel to the symmetry axis of the model, with polarization degrees of between 2 and 3%.…”

Section: Polarization From An Agn With a Warped Equatorial Obscurersupporting

confidence: 87%

Polarized radiative transfer modeling of warped and clumpy dusty tori

Marin

Schartmann

2017

A&A

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Context. Active galactic nuclei (AGN) are anisotropic objects surrounded by an optically thick equatorial medium whose true geometry still defies observers. Aims. We aim to explore the optical scattering-induced polarization that emerges from clumpy and warped dusty tori to check whether they can fit the unified model predictions. Methods. We ran polarized radiative transfer simulations in a set of warped and non-warped clumpy tori to explore the differences induced by distorted dust distributions. We then included warped tori in a more complex model representative of an AGN to check, using polarimetry and imaging methods, whether warps can reproduce the expected polarization dichotomy between Seyfert-I and Seyfert-II AGN. Results. The main results from our simulations highlight that isolated warped structures imprint the polarization degree and angle with distinctive signatures at Seyfert-I orientations. Included in an AGN model, the signatures of warps are easily (but not always) washed out by multiple scattering in a clumpy environment. Imaging polarimetry may help to detect warped tori, but we prove that warps can exist in AGN circumnuclear regions without contradicting observations. Conclusions. Two warped tori with a non-significant difference in geometry in terms of photometry or spectroscopy can have entirely different signatures in polarimetry. Testing the geometry of any alternative model to the usual dusty torus using polarized radiative transfer is a necessary approach to verify or reject a hypothesis.

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Section: Polarization From An Agn With a Warped Equatorial Obscurersupporting

confidence: 87%

Polarized radiative transfer modeling of warped and clumpy dusty tori

Marin

Schartmann

2017

A&A

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“…In Figure 13 Deo et al 2007;de Grijp et al 1992;Gu et al 2006;Kewley et al 2001;Kim et al 1995;Kirhakos & Steiner 1990;Meléndez et al 2008;Panessa & Bassani 2002;Smith et al 2002;Tran 2003;Véron-Cetty & Véron 2001;Winkler 1992;Whittle 1992;Young et al 1996). The rank correlations are also present but weaker between the fluxes of the lines.…”

Section: Agn Tracersmentioning

confidence: 89%

INFRARED DIAGNOSTICS FOR THE EXTENDED 12 μm SAMPLE OF SEYFERTS

Baum

Gallimore

O’Dea

et al. 2010

ApJ

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We present an analysis of Spitzer IRS spectroscopy of 83 active galaxies from the extended 12 μm sample. We find rank correlations between several tracers of star formation which suggest that (1) the polycyclic aromatic hydrocarbon feature is a reliable tracer of star formation, (2) there is a significant contribution to the heating of the cool dust by stars, and (3) the H 2 emission is also primarily excited by star formation. The 55-90 versus 20-30 spectral index plot is also a diagnostic of the relative contribution of starburst to active galactic nuclei (AGNs). We see there is a large change in spectral index across the sample: Δα ∼ 3 for both indices. Thus, the contribution to the IR spectrum from the AGN and starburst components can be comparable in magnitude but the relative contribution also varies widely across the sample. We find rank correlations between several AGN tracers. We find correlations of the ratios14 μm with the silicate strength which we adopt as an orientation indicator. This suggests that some of the [O iii]λ5007 emission in these Seyferts is subject to orientation dependent obscuration as found by Haas et al. for radio galaxies and quasars. There is no correlation of [Ne v] equivalent width with the silicate 10 μm strength, indicating that the [Ne v] emission is not strongly orientation dependent. This suggests that the obscuring material (e.g., torus) is not very optically thick at 14 μm consistent with the results of Buchanan et al. We search for correlations between AGN and starburst tracers and we conclude that the AGN and starburst tracers are not correlated. This is consistent with our conclusion that the relative strength of the AGN and starburst components varies widely across the sample. Thus, there is no simple link between AGN fueling and black hole growth and star formation in these galaxies. The density diagnostic [Ne v] 14/24 μm and [S iii] 18/33 μm line ratios are consistent with the gas being near the low density limit, i.e., ∼10 3 cm −3 for [Ne v] and n e ∼ few hundred cm −3 for [S iii]. The distribution of silicate 10 μm and 18 μm strengths is consistent with the clumpy torus models of Sirocky et al. We find a rank correlation between the [Ne v] 14 μm line and the 6.7 μm continuum which may be due to an extended component of hot dust. The Sy 2's with a hidden broad-line region (HBLR) have a higher ratio of AGN-to-starburst contribution to the spectral energy distribution than Sy 2's without an HBLR. This may contribute to the detection of the HBLR in polarized light. The Sy 2's with an HBLR are more similar to the Sy 1's than they are to the Sy 2's without an HBLR.

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“…Based on our clumpy torus models we would not expect that the torus itself produces these kind of deviation. Interestingly the larger size in PA 120 • is pointing in a similar direction as the polarization angle (θ pol ∼ 135 • Smith et al 2002), which implies that the mid-IR nucleus is elongated towards the NLR. This may Fig.…”

Section: Comparison To Ir Interferometrymentioning

confidence: 87%

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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A spectropolarimetric atlas of Seyfert 1 galaxies

Cited by 132 publications

References 40 publications

Polarized radiative transfer modeling of warped and clumpy dusty tori

Polarized radiative transfer modeling of warped and clumpy dusty tori

INFRARED DIAGNOSTICS FOR THE EXTENDED 12 μm SAMPLE OF SEYFERTS

The dusty heart of nearby active galaxies

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