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

Ichikawa, Kohei and Packham, Christopher and Ramos Almeida, Cristina and Asenio Ramos, Andrés and Alonso-Herrero, Almudena and González-Martín, Omaira and Lopez-Rodriguez, Enrique and Ueda, Yoshihiro and Díaz-Santos, Tanio and Elitzur, Moshe and Hönig, Sebastian F. and Imanishi, Masatoshi and Levenson, Nancy A. and Mason, Rachel E. and Perlman, Eric S. and Alsip, Crystal D. (2015) The Differences in the Torus Geometry between Hidden and Non-hidden Broad Line Active Galactic Nuclei. Astrophysical Journal, 803 (2). Art. No. 57 . ISSN 0004-637X.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ichikawa, Kohei0000-0002-4377-903X
Packham, Christopher0000-0001-7827-5758
Alonso-Herrero, Almudena0000-0001-6794-2519
Lopez-Rodriguez, Enrique0000-0001-5357-6538
Ueda, Yoshihiro0000-0001-7821-6715
Díaz-Santos, Tanio0000-0003-0699-6083
Elitzur, Moshe0000-0001-8143-3550
Imanishi, Masatoshi0000-0001-6186-8792
Levenson, Nancy A.0000-0003-4209-639X
Additional Information:© 2015 The American Astronomical Society. Received 9 October 2014, accepted for publication 26 January 2015; Published 15 April 2015. We are grateful for useful comments from the anonymous referee. We also thank C. Ricci, T. Kawamuro, K. Matsuoka, and M. Stalevski for useful comments and discussions. K.I. thanks the Department of Physics and Astronomy at University of Texas at San Antonio, where most of the research was conducted. This paper is based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership. 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.
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
University of Texas-San AntonioUNSPECIFIED
Marie Curie FellowshipPIEF-GA-2012-327934
Nacional de Astronomia y AstrofisicaAYA2012-31447
Subject Keywords:galaxies: active; galaxies: nuclei; infrared: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20150529-110252094
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Official Citation:The Differences in the Torus Geometry between Hidden and Non-hidden Broad Line Active Galactic Nuclei Kohei Ichikawa et al. 2015 ApJ 803 57
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57903
Deposited By: Jason Perez
Deposited On:29 May 2015 23:38
Last Modified:09 Mar 2020 13:19

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