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The differences in the torus geometry between hidden and non-hidden broad line active galactic nuclei

The differences in the torus geometry between hidden and non-hidden broad line active galactic nuclei
The differences in the torus geometry between hidden and non-hidden broad line active galactic nuclei
We present results from the fitting of infrared (IR) spectral energy distributions of 21 active galactic nuclei (AGNs) with clumpy torus models. We compiled high spatial resolution (~0.3–0.7 arcsec) mid-IR (MIR) N-band spectroscopy, Q-band imaging, and nuclear near- and MIR photometry from the literature. Combining these nuclear near- and MIR observations, far-IR photometry, and clumpy torus models enables us to put constraints on the torus properties and geometry. We divide the sample into three types according to the broad line region (BLR) properties: type-1s, type-2s with scattered or hidden broad line region (HBLR) previously observed, and type-2s without any published HBLR signature (NHBLR). Comparing the torus model parameters gives us the first quantitative torus geometrical view for each subgroup. We find that NHBLR AGNs have smaller torus opening angles and larger covering factors than HBLR AGNs. This suggests that the chance to observe scattered (polarized) flux from the BLR in NHBLR could be reduced by the dual effects of (a) less scattering medium due to the reduced scattering volume given the small torus opening angle and (b) the increased torus obscuration between the observer and the scattering region. These effects give a reasonable explanation for the lack of observed HBLR in some type-2 AGNs.
1538-4357
1-12
Ichikawa, Kohei
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Packham, Christopher
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Almeida, Cristina Ramos
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Ramos, Andrés Asensio
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Alonso-Herrero, Almudena
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González-Martín, Omaira
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Lopez-Rodriguez, Enrique
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Ueda, Yoshihiro
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Díaz-Santos, Tanio
af5a170e-5c64-4744-a2c6-e17abc353217
Elitzur, Moshe
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Hoenig, Sebastian
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Imanishi, Masatoshi
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Levenson, Nancy A.
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Mason, Rachel E.
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Perlman, Eric S.
eefe460d-fae0-4165-baec-8bb383ac1b57
Alsip, Crystal D.
b6c55aa0-0cf6-42ed-a3dd-2cae6fa15022
Ichikawa, Kohei
2736f39b-6b71-4477-8f0b-e05ffeb7cb24
Packham, Christopher
044d64e6-ee20-43c9-8e79-42fc9898527c
Almeida, Cristina Ramos
407b9f57-0072-415e-826d-7f711fc5fe65
Ramos, Andrés Asensio
3eccf7ba-ffb2-4171-b63e-e6d2da9f6722
Alonso-Herrero, Almudena
8672ba48-8f27-45f2-a89f-2c62f8e34261
González-Martín, Omaira
9d84142f-c1c3-4d3d-aaf6-ce241e356335
Lopez-Rodriguez, Enrique
ab531f9f-6bfa-4472-9d6c-cfa9dc81943d
Ueda, Yoshihiro
ddeff1dd-582e-40cc-973c-1f30d47cdbef
Díaz-Santos, Tanio
af5a170e-5c64-4744-a2c6-e17abc353217
Elitzur, Moshe
b870c170-3a32-47ee-9442-e03c2f3ee35a
Hoenig, Sebastian
be0bb8bc-bdac-4442-8edc-f735834f3917
Imanishi, Masatoshi
f74c529e-98a7-4367-875f-053e58922144
Levenson, Nancy A.
57c66b17-cc66-4e9e-8251-19132426cf57
Mason, Rachel E.
a5dbb51d-da30-45ba-a299-910d0f02c423
Perlman, Eric S.
eefe460d-fae0-4165-baec-8bb383ac1b57
Alsip, Crystal D.
b6c55aa0-0cf6-42ed-a3dd-2cae6fa15022

Ichikawa, Kohei, Packham, Christopher, Almeida, Cristina Ramos, Ramos, Andrés Asensio, Alonso-Herrero, Almudena, González-Martín, Omaira, Lopez-Rodriguez, Enrique, Ueda, Yoshihiro, Díaz-Santos, Tanio, Elitzur, Moshe, Hoenig, Sebastian, Imanishi, Masatoshi, Levenson, Nancy A., Mason, Rachel E., Perlman, Eric S. and Alsip, Crystal D. (2015) The differences in the torus geometry between hidden and non-hidden broad line active galactic nuclei. The Astrophysical Journal, 803 (57), 1-12. (doi:10.1088/0004-637X/803/2/57).

Record type: Article

Abstract

We present results from the fitting of infrared (IR) spectral energy distributions of 21 active galactic nuclei (AGNs) with clumpy torus models. We compiled high spatial resolution (~0.3–0.7 arcsec) mid-IR (MIR) N-band spectroscopy, Q-band imaging, and nuclear near- and MIR photometry from the literature. Combining these nuclear near- and MIR observations, far-IR photometry, and clumpy torus models enables us to put constraints on the torus properties and geometry. We divide the sample into three types according to the broad line region (BLR) properties: type-1s, type-2s with scattered or hidden broad line region (HBLR) previously observed, and type-2s without any published HBLR signature (NHBLR). Comparing the torus model parameters gives us the first quantitative torus geometrical view for each subgroup. We find that NHBLR AGNs have smaller torus opening angles and larger covering factors than HBLR AGNs. This suggests that the chance to observe scattered (polarized) flux from the BLR in NHBLR could be reduced by the dual effects of (a) less scattering medium due to the reduced scattering volume given the small torus opening angle and (b) the increased torus obscuration between the observer and the scattering region. These effects give a reasonable explanation for the lack of observed HBLR in some type-2 AGNs.

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Accepted/In Press date: 26 January 2015
e-pub ahead of print date: 15 April 2015
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 402386
URI: http://eprints.soton.ac.uk/id/eprint/402386
ISSN: 1538-4357
PURE UUID: 09ffb7be-e2d4-4885-b2f7-2d014155dab1

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Date deposited: 08 Nov 2016 11:23
Last modified: 25 Nov 2021 17:14

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Contributors

Author: Kohei Ichikawa
Author: Christopher Packham
Author: Cristina Ramos Almeida
Author: Andrés Asensio Ramos
Author: Almudena Alonso-Herrero
Author: Omaira González-Martín
Author: Enrique Lopez-Rodriguez
Author: Yoshihiro Ueda
Author: Tanio Díaz-Santos
Author: Moshe Elitzur
Author: Masatoshi Imanishi
Author: Nancy A. Levenson
Author: Rachel E. Mason
Author: Eric S. Perlman
Author: Crystal D. Alsip

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