Gigahertz Peaked Spectrumsources as Cosmological Probes

We discovered that the optical to near-infrared properties of Gigahertz Peaked Spectrum (GPS) galaxies are consistent with them having old stellar populations , with little or no contamination from their active nuclei. They seem to be a homogeneous class of object, in luminosity and scatter comparable to rst ranked cluster galaxies. At z 1 the K band luminosities are about a magnitude fainter than expected for passively evolving ellipticals, just as in the case of radio-quiet giant ellipticals at similar redshifts. This may be caused by the dynamical evolution of the galaxies counteracting the change in mass-to-light ratio of the systems. We have selected a new sample of faint GPS sources from the Westerbork Northern Sky Survey, which yielded a large sample of potentially high redshift GPS galaxies. We believe that this is an ideal sample to study the evolution of giant ellipticals at z > 1.