Revisiting the relationship between 6 μm and 2-10 keV continuum luminosities of AGN
Date Issued
2015
Author(s)
Mateos, S.
•
Carrera, F. J.
•
Alonso-Herrero, A.
•
Rovilos, E.
•
Hernán-Caballero, A.
•
Barcons, X.
•
Blain, A.
•
•
•
Description
This work is based on observations obtained with XMM–Newton , an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. Based on data from the WISE , which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society and the Higher Education Funding Council for England. The SDSS website is http://www.sdss.org/ . Based on observations collected at the European Organization for Astronomical Research in the Southern hemisphere, Chile, programme IDs 084.A-0828, 086.A-0612, 087.A-0447 and 088.A-0628. Based on observations made with the William Herschel Telescope and its service programme (programme IDs: SW2009a17, SW2009b15, SW2010b20) – operated by the Isaac Newton Group, the Telescopio Nazionale Galileo (programme IDs: TNG12-09B, TNG15-10A, TNG11-10B, TNG12-11A) – operated by the Centro Galileo Galilei and the Gran Telescopio de Canarias (programme IDs: GTC38-09B, GTC32–10A, GTC18-10B, GTC44-11A, GTC41-12A, GTC25-13A) installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma. SM, FJC, XB, AH-C and AA-H acknowledge funding from the Spanish Ministry of Economy and Competitiveness under grant AYA2012-31447, which is partly funded by the FEDER programme. SM, FJC and AA-H acknowledge financial support from the ARCHES project (7th Framework of the European Union, no. 313146). AA-H acknowledges support from the Universidad de Cantabria through the Augusto G. Linares programme. AC, RDC and PS acknowledge financial support from the Italian Ministry of Education, Universities and Research (PRIN2010-2011, grant no. 2010NHBSBE) and from ASI (grant no. I/088/06/0). The authors wish to thank the anonymous referee for constructive comments.
Abstract
We have determined the relation between the AGN luminosities at rest-frame 6 μm associated with the dusty torus emission and at 2-10 keV energies using a complete, X-ray-flux-limited sample of 232 AGN drawn from the Bright Ultra-hard XMM-Newton Survey. The objects have intrinsic X-ray luminosities between 10^(42) and 10^(46) erg s^(-1) and redshifts from 0.05 to 2.8. The rest-frame 6 μm luminosities were computed using data from the Wide-field Infrared Survey Explorer and are based on a spectral energy distribution decomposition into AGN and galaxy emission. The best-fitting relationship for the full sample is consistent with being linear, L(6 μm) ∝ L_{2-10 keV}^{0.99± 0.03}, with intrinsic scatter, ∆ log L(6 μm) = 0.35 dex. The L(6 μ m)/L(2-10 keV) luminosity ratio is largely independent of the line-of-sight X-ray absorption. Assuming a constant X-ray bolometric correction, the fraction of AGN bolometric luminosity reprocessed in the mid-IR decreases weakly, if at all, with the AGN luminosity, a finding at odds with simple receding torus models. Type 2 AGN have redder mid-IR continua at rest-frame wavelengths <12 μm and are overall ̃1.3-2 times fainter at 6 μm than type 1 AGN at a given X-ray luminosity. Regardless of whether type 1 and type 2 AGN have the same or different nuclear dusty toroidal structures, our results imply that the AGN emission at rest-frame 6 μm is not isotropic due to self-absorption in the dusty torus, as predicted by AGN torus models. Thus, AGN surveys at rest-frame ̃6 μm are subject to modest dust obscuration biases.
Volume
449
Issue
2
Start page
1422
Issn Identifier
0035-8711
Ads BibCode
2015MNRAS.449.1422M
Rights
open.access
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