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Polycyclic aromatic hydrocarbon emission in powerful high-redshift radio galaxies

Rawlings, J. I. and Seymour, N. and Page, M. J. and de Breuck, C. and Stern, D. and Symeonidis, M. and Appleton, P. N. and Dey, A. and Dickinson, M. and Huynh, M. and Le Floc'h, E. and Lehnert, M. and Mullaney, J. R. and Nesvadba, N. and Ogle, P. and Sajina, A. and Vernet, J. and Zirm, A. (2013) Polycyclic aromatic hydrocarbon emission in powerful high-redshift radio galaxies. Monthly Notices of the Royal Astronomical Society, 429 (1). pp. 744-756. ISSN 0035-8711.

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We present the mid-infrared (IR) spectra of seven of the most powerful radio-galaxies known to exist at 1.5 < z < 2.6. The radio emission of these sources is dominated by the AGN with 500 MHz luminosities in the range 10^(27.8)–10^(29.1) W Hz^(−1). The AGN signature is clearly evident in the mid-IR spectra; however, we also detect polycyclic aromatic hydrocarbon emission, indicative of prodigious star formation at a rate of up to ∼1000 M_⊙ yr^(−1). Interestingly, we observe no significant correlation between AGN power and star formation in the host galaxy. We also find most of these radio galaxies to have weak 9.7 μm silicate absorption features (τ_(9.7 μm) < 0.8) which implies that their mid-IR obscuration is predominantly due to the dusty torus that surrounds the central engine, rather than the host galaxy. The tori are likely to have an inhomogeneous distribution with the obscuring structure consisting of individual clouds. We estimate that these radio galaxies have already formed the bulk of their stellar mass and appear to lie at a stage in their evolution where the obscured AGN dominates the energy output of the system but star formation is also prevalent.

Item Type:Article
Related URLs:
URLURL TypeDescription
Seymour, N.0000-0003-3506-5536
Page, M. J.0000-0002-6689-6271
de Breuck, C.0000-0002-6637-3315
Stern, D.0000-0003-2686-9241
Appleton, P. N.0000-0002-7607-8766
Dey, A.0000-0002-4928-4003
Dickinson, M.0000-0001-5414-5131
Lehnert, M.0000-0003-1939-5885
Mullaney, J. R.0000-0002-3126-6712
Ogle, P.0000-0002-3471-981X
Sajina, A.0000-0002-1917-1200
Vernet, J.0000-0002-8639-8560
Additional Information:© 2012 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. First published online: December 5, 2012. Accepted 2012 November 6. Received 2012 November 6; in original form 2012 July 18. We thank the anonymous referee and R.C. Hickox for their useful comments which improved the manuscript. JIR acknowledges the support of a Science and Technologies Facilities Council studentship. NS is the recipient of an Australian Research Council Future Fellowship. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech) under contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. The IRS was a collaborative venture between Cornell University and Ball Aerospace Corporation funded by NASA through JPL and Ames Research Center. This work benefitted from the NASA/IPAC Extragalactic Database (NED), which is operated by the JPL, Caltech, under contract with NASA.
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Australian Research CouncilUNSPECIFIED
NASA Ames Research CenterUNSPECIFIED
Subject Keywords:galaxies: active galaxies: high-redshift galaxies: nuclei quasars: general galaxies: star formation
Issue or Number:1
Record Number:CaltechAUTHORS:20130625-104025806
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Official Citation:J. I. Rawlings, N. Seymour, M. J. Page, C. De Breuck, D. Stern, M. Symeonidis, P. N. Appleton, A. Dey, M. Dickinson, M. Huynh, E. Le Floc'h, M. Lehnert, J. R. Mullaney, N. Nesvadba, P. Ogle, A. Sajina, J. Vernet, and A. Zirm Polycyclic aromatic hydrocarbon emission in powerful high-redshift radio galaxies MNRAS (February 11, 2013) Vol. 429 744-756 first published online December 5, 2012 doi:10.1093/mnras/sts368
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39078
Deposited By: Ruth Sustaita
Deposited On:25 Jun 2013 18:14
Last Modified:04 Nov 2019 01:51

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