A mid-infrared view of the inner parsecs of the Seyfert galaxy Mrk 1066 using CanariCam/GTC

Creators: Ramos Almeida, C.; Alonso-Herrera, A.; Esquej, P.; González-Martín, O.; Riffel, R. A.; García-Bernete, I.; Rodríguez-Espinosa, J. M.; Packham, C.; Levenson, N. A.; Roche, P.; Díaz-Santos, T.; Aretxaga, I.; Álvarez, C.

Abstract

We present mid-infrared (MIR) imaging and spectroscopic data of the Seyfert 2 galaxy Mrk 1066 obtained with CanariCam (CC) on the 10.4-m Gran Telescopio CANARIAS (GTC). The galaxy was observed in imaging mode with an angular resolution of 0.24 arcsec (54 pc) in the Si-2 filter (8.7 μm). The image reveals a series of star-forming knots within the central ∼400 pc, after subtracting the dominant active galactic nucleus (AGN) component. We also subtracted this AGN unresolved component from the 8–13 μm spectra of the knots and the nucleus, and measured equivalent widths (EWs) of the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature which are typical of pure starburst galaxies. This EW is larger in the nucleus than in the knots, confirming that, at least in the case of Mrk 1066, the AGN dilutes, rather than destroys, the molecules responsible for the 11.3 μm PAH emission. By comparing the nuclear GTC/CC spectrum with the Spitzer/Infrared Spectrograph (IRS) spectrum of the galaxy, we find that the AGN component that dominates the continuum emission at λ < 15 μm on scales of ∼60 pc (90–100 per cent) decreases to 35–50 per cent when the emission of the central ∼830 pc is considered. On the other hand, the AGN contribution dominates the 15–25 μm emission (75 per cent) on the scales probed by Spitzer/IRS. We reproduced the nuclear infrared emission of the galaxy with clumpy torus models, and derived a torus gas mass of 2 × 10^5 M_⊙, contained in a clumpy structure of ∼2 pc radius and with a column density compatible with Mrk 1066 being a Compton-thick candidate, in agreement with X-ray observations. We find a good match between the MIR morphology of Mrk 1066 and the extended Paβ, Brγ and [O iii] λ5007 emission. This coincidence implies that the 8.7 μm emission is probing star formation, dust in the narrow-line region and the oval structure previously detected in the near-infrared. On the other hand, the Chandra soft X-ray morphology does not match any of the previous, contrary to what it is generally assumed for Seyfert galaxies. A thermal origin for the soft X-ray emission, rather than AGN photoionization, is suggested by the different data analysed here.

Additional Information

© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 August 27. Received 2014 August 27; in original form 2014 April 28. This research was supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934). CRA and IG-B acknowledge financial support from the Instituto de Astrofísica de Canarias and the Spanish Ministry of Science and Innovation (MICINN) through project PN AYA2010-21887-C04.04 (Estallidos). IG-B is grateful to the PhD contract funded by Fundación La Caixa. AA-H acknowledges support from the Spanish Plan Nacional de Astronomía y Astrofísica under grant AYA2012-31447 and from the Augusto G. Linares Program through the Universidad de Cantabria. RAR thanks the support of Brazilian institutions CNPq and FAPERGS. PE acknowledges support from the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA2012-31277. CP acknowledges support from UTSA to help enable this research. OG-M and JMRE acknowledge financial support from the Spanish Ministry of Science and Innovation (MICINN) through project AYA2012-39168-C03-01. Based on observations made with the Gran Telescopio CANARIAS (GTC), installed on the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The scientific results reported in this paper are based in part on data obtained from the Chandra Data Archive. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. 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 (USA), the Science and Technology Facilities Council (UK), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnologia e Innovación Productiva (Argentina). The authors acknowledge Santiago García Burillo, Andrés Asensio Ramos and Mar Mezcua for useful discussions. Finally, we are extremely grateful to the GTC staff for their constant and enthusiastic support, and to the anonymous referee for useful comments.

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