Dust tori in radio galaxies

Wolk, G. van der; Barthel, Pieter; Peletier, Reynier F.; Pel, J. W.

doi:10.1051/0004-6361/200912435

Cited by 39 publications

(45 citation statements)

References 110 publications

(120 reference statements)

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“…Therefore, in the light of the current results, we will discuss probable mechanisms responsible for the observed and possibly intrinsic differences. There is strong evidence that the dusty obscuring torus in low luminosity AGN is absent or is thinner than expected in higher luminosities (e.g., Whysong & Antonucci 2004;Elitzur & Shlosman 2006;Perlman et al 2007;van der Wolk et al 2010). Accordingly, all low luminosity AGN should have been Type I sources, which of course is not the case.…”

Section: Discussionmentioning

confidence: 98%

The dichotomy of Seyfert 2 galaxies: intrinsic differences and evolution

Koulouridis

2014

A&A

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We present a study of the local environment (≤200 h −1 kpc) of 31 hidden broad line region (HBLR) and 43 non-HBLR Seyfert 2 (Sy2) galaxies in the nearby universe (z ≤ 0.04). To compare our findings, we constructed two control samples that match the redshift and the morphological type distribution of the HBLR and non-HBLR samples. We used the NASA Extragalactic Database (NED) to find all neighboring galaxies within a projected radius of 200 h −1 kpc around each galaxy, and a radial velocity difference δu ≤ 500 km s −1 . Using the digitized Schmidt survey plates (DSS) and/or the Sloan Digital Sky Survey (SDSS), when available, we confirmed that our sample of Seyfert companions is complete. We find that, within a projected radius of at least 150 h −1 kpc around each Seyfert, the fraction of non-HBLR Sy2 galaxies with a close companion is significantly higher than that of their control sample, at the 96% confidence level. Interestingly, the difference is due to the high frequency of mergers in the non-HBLR sample, seven versus only one in the control sample, while they also present a high number of hosts with signs of peculiar morphology. In sharp contrast, the HBLR sample is consistent with its control sample. Furthermore, the number of the HBLR host galaxies that present peculiar morphology, which probably implies some level of interactions or merging in the past, is the lowest in all four galaxy samples. Given that the HBLR Sy2 galaxies are essentially Seyfert 1 (Sy1) with their broad line region (BLR) hidden because of the obscuring torus, while the non-HBLR Sy2 galaxies probably also include true Sy2s that lack the BLR as well as heavily obscured objects that prevent even the indirect detection of the BLR, our results are discussed within the context of an evolutionary sequence of activity triggered by close galaxy interactions and merging. We argue that the non-HBLR Sy2 galaxies may represent different stages of this sequence, possibly the beginning and the end of the nuclear activity.

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Section: Discussionmentioning

confidence: 98%

The dichotomy of Seyfert 2 galaxies: intrinsic differences and evolution

Koulouridis

2014

A&A

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“…There is a dust torus around this BLRG extending to ∼ 0.5 kpc (van der Wolk et al 2010) and an emission line region extending to ∼ 100 kpc (Prieto & Zhao 1997). It is an FRII lying in a weak environment (Bgq ∼ 80 -Ramos Almeida et al 2013).…”

Section: Appendix A: Notes On Individual Sourcesmentioning

confidence: 91%

The link between accretion mode and environment in radio-loud active galaxies

Ineson

Croston

Hardcastle

et al. 2015

Mon. Not. R. Astron. Soc.

130

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The interactions between radio-loud AGN and their environments play an important rôle in galaxy and cluster evolution. Recent work has demonstrated fundamental differences between High and Low Excitation Radio Galaxies (HERGs and LERGs), and shown that they may have different relationships with their environments. In the Chandra Large Project ERA (Environments of Radio-loud AGN), we made the first systematic X-ray environmental study of the cluster environments of radio galaxies at a single epoch (z ∼ 0.5), and found tentative evidence for a correlation between radio luminosity and cluster X-ray luminosity. We also found that this relationship appeared to be driven by the LERG sub-population (Ineson et al. 2013).We have now repeated the analysis with a low redshift sample (z ∼ 0.1), and found strong correlations between radio luminosity and environment richness and between radio luminosity and central density for the LERGs but not for the HERGs. These results are consistent with models in which the HERGs are fuelled from accretion discs maintained from local reservoirs of gas, while LERGs are fuelled more directly by gas ingested from the intra-cluster medium.Comparing the samples, we found that although the maximum environment richness of the HERG environments is similar in both samples, there are poorer HERG environments in the z ∼ 0.1 sample than in the z ∼ 0.5 sample. We have therefore tentative evidence of evolution of the HERG environments. We found no differences between the LERG subsamples for the two epochs, as would be expected if radio and cluster luminosity are related.

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“…Alternatively, we would have to isolate the torus spatially from more extended emission. This has been attempted for nearby type 2 AGN (van der Wolk et al 2010) where such an extended component has indeed been identified at λ rest = 12 μm. Both types of observation are beyond the reach of current facilities for our samples.…”

Section: Stellar and Extended Warm Dust Emissionmentioning

confidence: 99%

Jet and torus orientations in high redshift radio galaxies

Drouart

Breuck

Vernet

et al. 2012

A&A

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We examine the relative orientation of radio jets and dusty tori surrounding the active galactic nucleus (AGN) in powerful radio galaxies at z > 1. The radio core dominance R = P 20 GHz core /P 500 MHz extended serves as an orientation indicator, measuring the ratio between the anisotropic Doppler-beamed core emission and the isotropic lobe emission. Assuming a fixed cylindrical geometry for the hot, dusty torus, we derive its inclination i by fitting optically-thick radiative transfer models to spectral energy distributions obtained with the Spitzer Space Telescope. We find a highly significant anti-correlation (p < 0.0001) between R and i in our sample of 35 type 2 AGN combined with a sample of 18 z ∼ 1 3CR sources containing both type 1 and 2 AGN. This analysis provides observational evidence both for the Unified scheme of AGN and for the common assumption that radio jets are in general perpendicular to the plane of the torus. The use of inclinations derived from mid-infrared photometry breaks several degeneracies which have been problematic in earlier analyses. We illustrate this by deriving the core Lorentz factor Γ from the R-i anti-correlation, finding Γ > ∼ 1.3.

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Dust tori in radio galaxies

Cited by 39 publications

References 110 publications

The dichotomy of Seyfert 2 galaxies: intrinsic differences and evolution

The dichotomy of Seyfert 2 galaxies: intrinsic differences and evolution

The link between accretion mode and environment in radio-loud active galaxies

Jet and torus orientations in high redshift radio galaxies

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