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Dust in active galactic nuclei. Mid-infrared T-ReCS/Gemini spectra using the new RedCan pipeline

González-Martín, O. and Rodríguez-Espinosa, J. M. and Díaz-Santos, T. and Packham, C. and Alonso-Herrero, A. and Esquej, P. and Ramos Almeida, C. and Mason, R. and Telesco, C. (2013) Dust in active galactic nuclei. Mid-infrared T-ReCS/Gemini spectra using the new RedCan pipeline. Astronomy and Astrophysics, 553 . Art. No. A35. ISSN 0004-6361. doi:10.1051/0004-6361/201220382.

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Context. The unified model of active galactic nuclei (AGN) claims that the properties of AGN depend on the viewing angle of the observer with respect to a toroidal distribution of dust surrounding the nucleus. Both the mid-infrared (MIR) attenuation and continuum luminosity are expected to be related to dust associated with the torus. Therefore, isolating the nuclear component is essential for studying the MIR emission of AGN. Aims. This work is aimed at studying the MIR emission of AGN with the highest spatial resolution available to date, isolating its contribution from extended emission. We would like to address three fundamental questions: (1) how important is the AGN contribution to the MIR spectrum; (2) where dust attenuation arises; and (3) how does spatial resolution affect these issues. Methods. We compiled all the T-ReCS spectra (Gemini Observatory) available in the N-band for 22 AGN: 5 Type-1 and 17 Type-2 AGN. The high angular resolution of the T-ReCS spectra allowed us to probe physical regions of 57 pc (median). We used a novel pipeline called RedCan capable of producing flux- and wavelength-calibrated spectra for the CanariCam (GTC) and T-ReCS (Gemini) instruments. We measured the fine-structure [S IV] at 10.5 μm and the PAH at 11.3 μm line strengths, together with the silicate absorption/emission features. We also compiled Spitzer/IRS spectra to understand how spatial resolution influences the results. We complemented our sample with the results of 19 VISIR/VLT spectra (Paranal Observatory) and 20 nearby, highly obscured AGN (N_H > 1.5 × 10^(24) cm^(-2)) Spitzer spectra. Results. The 11.3 μm PAH feature is only clearly detected in the nuclear spectra of two AGN, while it is more common in the Spitzer data. For those two objects, the AGN emission in NGC 7130 accounts for more than 80% of the MIR continuum at 12 μm, while in the case of NGC 1808 the AGN does not dominate the MIR emission. This is confirmed by the correlation between the MIR and X-ray continuum luminosities. The [S IV] emission line at 10.5 μm, which is believed to originate in the narrow line region, is detected in most AGN. We have found an enhancement of the optical depth at 9.7 μm (τ_(9.7)) in the high-angular resolution data for higher values of N_H. Clumpy torus models reproduce the observed values only if the host-galaxy properties are taken into account.

Item Type:Article
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URLURL TypeDescription DOIArticle Material
Díaz-Santos, T.0000-0003-0699-6083
Packham, C.0000-0001-7827-5758
Alonso-Herrero, A.0000-0001-6794-2519
Additional Information:© 2013 ESO. Article published by EDP Sciences. Received 13 September 2012; Accepted 21 December 2012. Published online 26 April 2013. The authors acknowledge the Spanish MINECO through project Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC ( This work was also partially funded by the Spanish MINECO through a Juan de la Cierva Fellowship. 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: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministerio da Ciencia, Tecnología e Inovacao (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). The Cornell Atlas of Spitzer/IRS Sources (CASSIS) is a product of the Infrared Science Center at Cornell University, supported by NASA and JPL. C. M. Telesco acknowledges support from NSF grant AST-0903672. A.A.-H. and P.E. acknowledge support from the Spanish Plan Nacional de Astronomía y Astrofísica under grant AYA2009-05705-E. A.A.-H. is also supported by the Universidad de Cantabria through the Augusto González Linares Program and by AYA2010-21161-C02- 01. C.R.A. acknowledges the Estallidos group through project PN AYA2010-21887-C04.04.
Funding AgencyGrant Number
Ministerio de Economía, Industria y Competitividad (MINECO)CSD2006-00070
Juan de la Cierva FellowshipUNSPECIFIED
Plan Nacional de Astronomía y AstrofísicaAYA2009-05705-E
Universidad de Cantabria Augusto González Linares ProgramUNSPECIFIED
Ministerio de Ciencia e Innovación (MCINN)AYA2010-21161-C02-01
Estallidos GroupPN AYA2010-21887-C04.04
Subject Keywords:accretion, accretion disks – galaxies: active – galaxies: Seyfert – infrared: galaxies – techniques: imaging spectroscopy
Record Number:CaltechAUTHORS:20130723-093832008
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39518
Deposited By: Tony Diaz
Deposited On:12 Aug 2013 22:40
Last Modified:09 Nov 2021 23:45

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