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Description
We present the results of a large program conducted with the Very Large Telescope and augmented by observations with the Keck telescope to search for forming clusters of galaxies near powerful radio galaxies at 2.0<z<5.2. Besides MRC 1138-262 at z=2.16, the radio galaxy observed in our pilot program, we obtained narrow- and broad-band images of eight radio galaxies and their surroundings. The imaging was used to select candidate Ly{alpha} emitting galaxies in ~3x3Mpc^2^ areas near the radio galaxies. A total of 300 candidate emitters were found with a rest-frame Ly{alpha} equivalent width of EW0>15{AA} and significance Sigma{equiv.to}(EW0/DEW0)>3. Follow-up spectroscopy was performed on 152 candidates in seven of the radio galaxy fields. Of these, 139 were confirmed to be Ly{alpha} emitters, four were low redshift interlopers and nine were non-detections. With the adopted criteria the success rate is 139/152=91%. In addition, 14 objects with EW0<15 and/or Sigma<3 were confirmed to be Ly{alpha} emitters. Combined with the 15 Ly{alpha} emitters near MRC 1138-262, we have determined Ly{alpha} redshifts for 168 objects near eight radio galaxies.
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