Pozzi, F. and Vignali, C. and Gruppioni, C. and Feltre, A. and Fritz, J. and Fadda, D. and Andreani, P. and Berta, S. and Cimatti, A. and Delvecchio, I. and Lutz, D. and Magnelli, B. and Maiolino, R. and Nordon, R. and Popesso, P. and Rodighiero, G. and Rosario, D. and Santini, P. and Vaccari, M. (2012) The AGN content in luminous infrared galaxies at z ∼ 2 from a global SED analysis including Herschel data. Monthly Notices of the Royal Astronomical Society, 423 (2). pp. 1909-1920. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20120711-093355005
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We use Herschel-PACS far-infrared (IR) data, combined with previous multiband information and mid-IR spectra, to properly account for the presence of an active nucleus and constrain its energetic contribution in luminous IR sources at z∼ 2. The sample is composed of 24 sources in the GOODS-South field, with typical IR luminosity of 10^(12) L_⊙. Data from the 4 Ms Chandra X-ray imaging in this field are also used to identify and characterize active galactic nucleus (AGN) emission. We reproduce the observed spectral energy distribution (SED), decomposed into a host-galaxy and an AGN component. A smooth-torus model for circumnuclear dust is used to account for the direct and reprocessed contribution from the AGN. We confirm that galaxies with typical L_(8-1000µm) ~ 10^(12) L_☉ at z∼ 2 are powered predominantly by star formation. An AGN component is present in nine objects (∼35 per cent of the sample) at the 3σ confidence level, but its contribution to the 8–1000 µm emission accounts for only ∼5 per cent of the energy budget. The AGN contribution rises to ∼23 per cent over the 5–30 µm range (in agreement with Spitzer IRS results) and to ∼60 per cent over the narrow 2–6 µm range. The presence of an AGN is confirmed by X-ray data for three (out of nine) sources, with X-ray spectral analysis indicating the presence of significant absorption, i.e. N_H ∼ 10^(23)–10^(24) cm^(−2). An additional source shows indications of obscured AGN emission from X-ray data. The comparison between the mid-IR-derived X-ray luminosities and those obtained from X-ray data suggests that obscuration is likely present also in the remaining six sources that harbour an AGN according to the SED-fitting analysis.
|Additional Information:||© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 March 29. Received 2012 March 26; in original form 2011 November 29. Article first published online: 17 May 2012. The authors thank the referee for his/her useful comments. FP and CV thank the Sterrenkundig Observatorium (Universiteit Gent), in particular Prof. M. Baes and Dr J. Fritz, for their kind hospitality. The authors are grateful to F. E. Bauer and F. Vito for their help with Chandra spectra. CV acknowledges partial support from the Italian Space Agency (contract ASI/INAF/I/009/10/0). PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAFIFSI/ OAA/OAP/OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX, CEA/CNES (France), DLR (Germany), ASI/INAF (Italy) and CICYT/MCYT (Spain).|
|Subject Keywords:||galaxies: active; galaxies: nuclei; infrared: galaxies|
|Official Citation:||Pozzi, F., Vignali, C., Gruppioni, C., Feltre, A., Fritz, J., Fadda, D., Andreani, P., Berta, S., Cimatti, A., Delvecchio, I., Lutz, D., Magnelli, B., Maiolino, R., Nordon, R., Popesso, P., Rodighiero, G., Rosario, D., Santini, P. and Vaccari, M. (2012), The AGN content in luminous infrared galaxies at z∼ 2 from a global SED analysis including Herschel data. Monthly Notices of the Royal Astronomical Society, 423: 1909–1920. doi: 10.1111/j.1365-2966.2012.21015.x|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||11 Jul 2012 20:20|
|Last Modified:||11 Jul 2012 20:20|
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