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Published June 2007 | Published
Journal Article Open

Metal-Enriched Gaseous Halos around Distant Radio Galaxies: Clues to Feedback in Galaxy Formation


We present the results of an optical and near-IR spectroscopic study of giant nebular emission-line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07, and B2 0902+34. Previous deep narrowband Lyα imaging revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s^(-1) and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions >1000 km s^(-1). The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of ≈60 kpc along the radio axis. The dynamical structures traced in the Lyα line are, in most cases, closely echoed in the carbon and oxygen lines. This shows that the Lyα line is produced in a highly clumped medium of small filling factor and can therefore be used as a tracer of the dynamics of high-redshift radio galaxies (HzRGs). We conclude that these HzRGs are undergoing a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming "red and dead" elliptical galaxies.

Additional Information

© 2007 The American Astronomical Society. Received 2006 July 24; accepted 2007 February 20. We thank all the staff at the W.M. Keck Observatory for their excellent support. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most grateful to have the opportunity to conduct observations from this mountain. M. R. thanks Mario Livio and the Space Telescope Science Institute for generous hospitality. This work was performed under the auspices of the US Department of Energy, National Nuclear Security Administration, by the University of California, Lawrence Livermore National Laboratory, under contract W-7405-Eng-48. W. v. B. acknowledges support for radio galaxy studies at the Institute for Geophysics and Planetary Physics at Lawrence Livermore National Laboratory and at UC Merced, including the work reported here, with the Hubble, Spitzer, and Chandra space telescopes via NASA grants HST GO-9779, GO-10127, SST GO-3482, SST GO- 3329, and Chandra/CXO GO-06701011. M. D. acknowledges the support of the ANU and the Australian Research Council (ARC) for his ARC Australian Federation Fellowship, as well as the ARC Discovery projects DP0208445 and DP0664434. This work was supported by the European Community Research and Training Network program, The Physics of the Intergalactic Medium. A. D.'s research is supported by NOAO, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the National Science Foundation.

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