Search for clusters at high redshift - I. Candidate Lya emitters near   1138-262 at z=2.2
  Radio, optical and X-ray observations of the powerful radio galaxy PKS 1138-262 at z=2.156 have suggested that this galaxy is a massive galaxy in the center of a forming cluster. We have imaged 1138-262 and the surrounding 38 square arcminute field with the Very Large Telescope in a broad band and a narrow band encompassing the redshifted Lya emission. We detect 50 objects with rest equivalent width larger than 20 A and a luminous, highly extended Lya halo around 1138-262. If the radio galaxy is at the center of a forming cluster, these objects are candidate Lya emitting cluster galaxies. 
J.D. Kurk, H.J.A. Rottgering, L. Pentericci, G.K. Miley, W. van   Breugel, C.L. Carilli, H. Ford, T. Heckman, P. McCarthy, A...