Radio galaxy-selected clusters at high redshift and associated extremely red object overdensities

Galaxy clusters at high redshift present a superb opportunity to study gala xy evolution, with large galaxy samples at fixed distances. Several lines o f evidence point toward large formation redshifts and passive evolution for cluster elliptical galaxies. At redshifts higher than z similar to 0.8, th is picture rests on data from only a handful of rich clusters. We have obse rved four potential clusters to sample sparser environments in a critical r edshift range, 0.8 < z < 1.2. We compare the photometric evolution and radi al density profiles in our clusters with more massive clusters studied in a similar manner. We also highlight the overdense extremely red object (I-K > 5) population, significantly redder than the old elliptical population at the cluster redshift. We discuss the implications of our clusters at high redshift and possible differences in environment from richer clusters at si milar redshifts selected through X-ray or optical techniques.