The Differences in the Torus Geometry Between Hidden and Non-Hidden Broad Line Active Galactic Nuclei

Authors

Kohei Ichikawa, Kyoto University, Japan
Christopher Packham, University of Texas at San Antonio
Cristina Ramos Almeida, Instituto de Astrofísica de Canarias, Spain
Andrés Asensio Ramos, Instituto de Astrofísica de Canarias, Spain
Almudena Alonso-Herrero, California Institute of Technology
Omaira González-Martín, Instituto de Astrofísica de Canarias, Spain
Enrique Lopez-Rodriguez, University of Texas at San Antonio
Yoshihiro Ueda, Kyoto University, Japan
Tanio Díaz-Santos, California Institute of Technology
Moshe Elitzur, University of KentuckyFollow
Sebastian F. Hönig, Univeristy of Southampton, UK
Masatoshi Imanishi, Subaru Telescope
Nancy A. Levenson, Gemini Observatory, Southern Operations Center, Chile
Rachel E. Mason, Gemini Observatory, Northern Operations Center
Eric S. Perlman, Florida Institute of Technology
Crystal D. Alsip, University of Texas at San Antonio

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.

Document Type

Article

Publication Date

4-15-2015

Notes/Citation Information

Published in The Astrophysical Journal, v. 803, no. 2, 57, p. 1-12.

© 2015. The American Astronomical Society. All rights reserved.

The copyright holder has granted the permission for posting the article here.

Digital Object Identifier (DOI)

https://doi.org/10.1088/0004-637X/803/2/57

Funding Information

This work was partly supported by the Grant-in-Aid for JSPS Fellows for young researchers (K.I.). C.P. acknowledges support from UTSA and NSF (grant number 0904421). C.R.A. is supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934). A.A.-H. acknowledges support from the Spanish Plan Nacional de Astronomia y Astrofisica under grant AYA2012-31447.

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Repository Citation

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; Hönig, Sebastian F.; Imanishi, Masatoshi; Levenson, Nancy A.; Mason, Rachel E.; Perlman, Eric S.; and Alsip, Crystal D., "The Differences in the Torus Geometry Between Hidden and Non-Hidden Broad Line Active Galactic Nuclei" (2015). Physics and Astronomy Faculty Publications. 249.
https://uknowledge.uky.edu/physastron_facpub/249