Polarimetry and modelling of narrow-line active galaxies

Young, S.; Hough, J.; Efstathiou, A.; Wills, Beverley J.; Bailey, Jeremy; Ward, M. J.; Axon, D. J.

doi:10.1093/mnras/281.4.1206

Cited by 139 publications

(170 citation statements)

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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: 90%

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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Section: Agn Tracersmentioning

confidence: 90%

INFRARED DIAGNOSTICS FOR THE EXTENDED 12 μm SAMPLE OF SEYFERTS

Baum

Gallimore

O’Dea

et al. 2010

ApJ

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“…There are a total of six sources in the final sample. The degree of polarization in type 2 AGNs is generally very low (less than several percent), in most cases, only broad Hα lines in the polarized spectra are visible (e.g., Antonucci 1984;Tran et al 1992;Young et al 1996;Moran et al 2000;Ramos Almeida et al 2016). We assume that broad Hβ and Hα lines have the same widths in the polarized spectrum for each individual object, as has been demonstrated in several objects (Ramos Almeida et al 2016).…”

Section: Virial Factors Of Type 2 Agnsmentioning

confidence: 99%

“…The hidden broad-line regions (BLRs) are observed in the polarized spectra of many type 2 AGNs (e.g., Antonucci 1984;Tran et al 1992;Young et al 1996;Moran et al 2000;Ramos Almeida et al 2016), and are thought to have scattering of BELs by the regions above the poles of accretion disks (called "polar scatter regions") (Antonucci & Miller 1985;Antonucci 1993). However, the detailed geometry and kinematics of BLRs hidden in the centers of type 2 AGNs remain elusive and are not yet fully understood.…”

Section: Introductionmentioning

confidence: 99%

Hidden Broad-line Regions in Seyfert 2 Galaxies: From the Spectropolarimetric Perspective

Wang

Zhang

2017

ApJL

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The hidden broad-line regions (BLRs) in Seyfert 2 galaxies, which display broad emission lines (BELs) in their polarized spectra, are a key piece of evidence in support of the unified model for active galactic nuclei (AGNs). However, the detailed kinematics and geometry of hidden BLRs are still not fully understood. The virial factor obtained from reverberation mapping of type 1 AGNs may be a useful diagnostic of the nature of hidden BLRs in type 2 objects. In order to understand the hidden BLRs, we compile six type 2 objects from the literature with polarized BELs and dynamical measurements of black hole masses. All of them contain pseudobulges. We estimate their virial factors, and find the average value is 0.60 and the standard deviation is 0.69, which agree well with the value of type 1 AGNs with pseudobulges. This study demonstrates that (1) the geometry and kinematics of BLR are similar in type 1 and type 2 AGNs of the same bulge type (pseudobulges), and (2) the small values of virial factors in Seyfert 2 galaxies suggest that, similar to type 1 AGNs, BLRs tend to be very thick disks in type 2 objects.

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“…The first discovery of Polarized Broad Lines (PBL hereafter) in NGC 1068 (Antonucci & Miller 1985) and later in several other Seyfert 2 galaxies (Miller & Goodrich 1990;Tran 1995;Young et al 1996;Heisler et al 1997;Awaki et al 2000;Moran et al 2000;Alexander 2001;Gu et al 2001;Lumsden et al 2001) suggests that Seyfert 2 galaxies harbor a bright Seyfert 1 nucleus hidden from our view by an optically and geometrically thick obscuring torus ("Unified models", see the review of Antonucci 1993). In this frame, the difference between type 1 and 2 Seyfert galaxies is only due to the viewing angle.…”

Section: Introductionmentioning

confidence: 99%

Investigating the central engine of Seyfert 2 galaxieswithandwithoutPolarized Broad Lines

Deluit

2004

A&A

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Abstract.We study the hard X-ray emission of two samples of Seyfert 2 galaxies with and without Polarized Broad Lines (PBL). In the hard X-ray domain, absorption effects do not significantly modify the intrinsic emission allowing us a direct access to the central engine. The purpose of this study is to compare the primary emission of the two Seyfert 2 subclasses in order to investigate the nature of their central engine and to test unified models according to which they both have a hidden Seyfert 1 nucleus. We compute the average hard X-ray spectra of Seyfert 2 galaxies with and without PBL observed with BeppoSAX/PDS (15-136 keV). The two spectra have a common general behavior at first sight, but investigating deeper we find differences in the intrinsic properties of the two categories of Seyfert 2 galaxies. Sy 2 with polarized broad lines have physical conditions close to those of Sy 1 galaxies whereas Sy 2 without PBL differ substantially, suggesting that they may have a particular place in the scheme of Seyfert galaxies.

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Polarimetry and modelling of narrow-line active galaxies

Cited by 139 publications

References 0 publications

INFRARED DIAGNOSTICS FOR THE EXTENDED 12 μm SAMPLE OF SEYFERTS

INFRARED DIAGNOSTICS FOR THE EXTENDED 12 μm SAMPLE OF SEYFERTS

Hidden Broad-line Regions in Seyfert 2 Galaxies: From the Spectropolarimetric Perspective

Investigating the central engine of Seyfert 2 galaxieswithandwithoutPolarized Broad Lines

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