* Astronomy

Title: The Phoenix Deep Survey: Extremely Red Galaxies and Cluster Candidates
Authors: Anthony G. Smith (1), Andrew M. Hopkins (1), Richard W. Hunstead (1), Samuel J. Schmidt (2,3), José Afonso (4,5), Antonis E. Georgakakis (6), Lawrence E. Cram (7), Bahram Mobasher (8), Mark Sullivan (9) ((1) University of Sydney, (2) University of Pittsburgh, (3) University of California, (4) Faculdade de Ciências, Universidade de Lisboa, (5) Centro de Astronomia e Astrofísica da Universidade de Lisboa, (6) Imperial College of Science Technology and Medicine, Blackett Laboratory, (7) Australian National University, (8) Space Telescope Science Institute, (9) University of Oxford)

We present the results of a study of a sample of 375 Extremely Red Galaxies (ERGs) in the Phoenix Deep Survey, 273 of which constitute a subsample which is 80% complete to K_s = 18.5 over an area of 1160 arcmin^2. The angular correlation function for ERGs is estimated, and the association of ERGs with faint radio sources explored. We find tentative evidence that ERGs and faint radio sources are associated at z > 0.5. A new overdensity-mapping algorithm has been used to characterise the ERG distribution, and identify a number of cluster candidates, including a likely cluster containing ERGs at 0.5 < z < 1. Our algorithm is also used in an attempt to probe the environments in which faint radio sources and ERGs are associated. We find limited evidence that the I - K_s > 4 criterion is more efficient than R - K_s > 5 at selecting dusty star-forming galaxies, rather than passively evolving ERGs.

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