NOAO >   Observing Info >   Approved Programs >   2003A-0330

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Proposal Information for 2003A-0330


PI: Gary Hill, University of Texas, hill@astro.as.utexas.edu
Address: Astronomy Department, RLM 15.308, Austin, Texas TX 78712, USA

CoI: Steve Rawlings, Oxford University
CoI: Ewan Mitchell, Oxford University
CoI: Chris Willott, University of Victoria
CoI: Ross McClure, Edinburgh University

Title: The Dynamic Cluster Environments of Radio Galaxies

Abstract: The host galaxies of radio sources are known to be massive ellipticals. However, whether these galaxies reside preferentially in rich clusters or poor groups is still a matter of controversy. In particular, it has not been well-established how the clustering environments of radio galaxies (RG) depend upon radio luminosity. There have recently been exciting hints that the triggering, on small scales, of powerful radio jets may be linked to the evolution of large-scale structure. Whether or not radio activity is triggered in virialized clusters, in merging groups or in dark-matter filaments is an open question. We are in a unique position to determine this with three- colour wide-field imaging of a new, statistically complete, sample of 46 radio galaxies spanning ~ 3 decades in radio luminosity at a single cosmic epoch (0.4 < z < 0.6). We propose to use MARS to confirm cluster or group membership, and to determine velocity dispersions which will reveal the dynamic state of any substructure as well as dynamical cluster masses. Data we have already obtained (including 44 orbits of HST imaging and 60 hours of VLA time) show sites of weak radio activity (AGN and possibly starburst galaxies), clustered around the powerful radio galaxies, which will also be targeted as part of our MOS program. These data are important to and will complete our definitive study of powerful radio galaxies and their dynamic cluster environments at z ~ 0.5.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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