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Energetics of the molecular gas in the H_2 luminous radio galaxy 3C 326: Evidence for negative AGN feedback

Nesvadba, N. P. H. and Boulanger, F. and Salomé, P. and Guillard, P. and Lehnert, M. D. and Ogle, P. and Appleton, P. and Falgarone, E. and Pineau des Forets, G. (2010) Energetics of the molecular gas in the H_2 luminous radio galaxy 3C 326: Evidence for negative AGN feedback. Astronomy and Astrophysics, 521 . Art. No. A65. ISSN 0004-6361.

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We present a detailed analysis of the gas conditions in the H_2 luminous radio galaxy 3C 326 N at z ~ 0.1, which has a low star-formation rate (SFR ~ 0.07 M_⊙ yr^(−1)) in spite of a gas surface density similar to those in starburst galaxies. Its star-formation efficiency is likely a factor ~ 10−50 lower than those of ordinary star-forming galaxies. Combining new IRAM CO emission-line interferometry with existing Spitzer mid-infrared spectroscopy, we find that the luminosity ratio of CO and pure rotational H_2 line emission is factors 10−100 lower than what is usually found. This suggests that most of the molecular gas is warm. The Na D absorption-line profile of 3C 326 N in the optical suggests an outflow with a terminal velocity of ~−1800 km s^(−1) and a mass outflow rate of 30−40 M_⊙ yr^(−1), which cannot be explained by star formation. The mechanical power implied by the wind, of order 10^(43) erg s^(−1), is comparable to the bolometric luminosity of the emission lines of ionized and molecular gas. To explain these observations, we propose a scenario where a small fraction of the mechanical energy of the radio jet is deposited in the interstellar medium of 3C 326 N, which powers the outflow, and the line emission through a mass, momentum and energy exchange between the different gas phases of the ISM. Dissipation times are of order 10^(7−8) yrs, similar or greater than the typical jet lifetime. Small ratios of CO and PAH surface brightnesses in another 7 H_2 luminous radio galaxies suggest that a similar form of AGN feedback could be lowering star-formation efficiencies in these galaxies in a similar way. The local demographics of radio-loud AGN suggests that secular gas cooling in massive early-type galaxies of ≥ 10^(11) M_⊙ could generally be regulated through a fundamentally similar form of “maintenance-phase” AGN feedback.

Item Type:Article
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Ogle, P.0000-0002-3471-981X
Appleton, P.0000-0002-7607-8766
Additional Information:© 2010 ESO. Received 21 September 2009, Accepted 17 March 2010, Published online 21 October 2010. Based on observations carried out with the IRAM Plateau de Bure Interferometer. We would like to thank the staff at IRAM for carrying out the observations. We are particularly grateful to the referee, C. De Breuck, whose comments helped significantly improve the paper, and to Luc Binette and Geoff Bicknell for helpful discussions. This work was supported by the Centre National d’Etudes Spatiales (CNES). N.P.H.N. also acknowledges financial support through a fellowship of the Centre National d’Etudes Spatiales (CNES). IRAM is funded by the Centre National de Recherche Scientifique, the Max- Planck Gesellschaft and the Instituto Geografico Nacional. This work is partly based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, Caltech, under NASA contract 1407.
Funding AgencyGrant Number
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Max-Planck Gesellschaft UNSPECIFIED
Instituto Geográfico Nacional (IGN)UNSPECIFIED
Subject Keywords:galaxies: evolution – galaxies: ISM – galaxies: jets – radio continuum: galaxies – radio lines: galaxies
Record Number:CaltechAUTHORS:20110103-142824965
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Official Citation:Energetics of the molecular gas in the H2 luminous radio galaxy 3C 326: Evidence for negative AGN feedback N. P. H. Nesvadba, F. Boulanger, P. Salomé, P. Guillard, M. D. Lehnert, P. Ogle, P. Appleton, E. Falgarone and G. Pineau des Forets A&A 521 A65 (2010) DOI: 10.1051/0004-6361/200913333
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21551
Deposited By: Benjamin Perez
Deposited On:03 Jan 2011 23:06
Last Modified:18 Aug 2017 01:07

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