NOAO >   Observing Info >   Approved Programs >   2012B-0138

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Proposal Information for 2012B-0138


PI: Sean McGee, University of Durham, s.l.mcgee@durham.ac.uk
Address: Department of Physics, South Road, Durham DH1 3LE, United Kingdom

CoI: Michael Balogh, University of Waterloo
CoI: Roderik Overzier, University of Texas
CoI: Yi-Kuan Chiang, University of Texas
CoI: Nina Hatch, University of Nottingham
CoI: George Miley, Leiden University
CoI: Bram Venemans, ESO

Title: The high redshift progenitors of massive galaxy clusters

Abstract: We shall trace the development of galaxy clusters from 5 > z > 2 using high-z radio galaxies (HzRGs) as beacons. The most luminous HzRGs are associated with progenitors of brightest cluster galaxies and pinpoint high-density regions in the early Universe - the likely ancestors of typical rich clusters. Because protoclusters contain large numbers of galaxies at the same z, they are prime laboratories for evolution studies. Bright Lyman alpha emitting (LAE) protocluster members provide bright tracers of these environments, and unique kinematical information. As part of an earlier large programme on the VLT, we previously determined LAE redshifts for 151 objects in 6 HzRG fields that were overdense by a factor 3 - 5. Within this small sample there is an intriguing trend for protocluster velocity dispersions to increase from 300 km/s to 1000 km/s between z=5 and z=2, consistent with evolutionary models. We now propose narrow band GMOS imaging, using existing and custom-built filters, to measure LAE overdensities in the field of six northern HzRG over two semesters. Combined with a VLT programme for 14 new southern targets, we aim to increase the current sample of z>2 protoclusters by a factor of four. These systems will be followed up in future semesters with multiobject spectroscopy (including GMOS for the northern targets) of candidate protocluster galaxies to study internal protocluster kinematics, determine the frequency of sub-clustering, confirm the decrease of velocity dispersion with z, investigate evolutionary trends in sizes of LAE halos, relate halo morphologies to the protocluster hosts, and study the evolution of protocluster populations.


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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