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In classifying the ensemble of powerful extragalactic radio sources,considerable evidence has accumulated that radio galaxies and quasars areorientation-dependent manifestations of the same parent population: massivespheroidal galaxies containing correspondingly massive black holes. [...] Inthis study, we exploit the opportunity to eliminate the quasar glare byperforming sensitive spectropolarimetry with the Keck II telescope of a sampleof radio galaxies with redshifts around 2.5. [...] We show that dust-reflectedquasar light generally dominates the restframe ultraviolet continuum of thesesources and that a highly clumped scattering medium results in almost greyscattering of the active galactic nucleus photons. The observations, however,do not exclude a substantial star formation rate averaged over a Gyr ofevolution. The sub-mm reradiation from the scattering dust is likely torepresent only a small fraction (~10%) of the total far infrared luminosity. Ananalysis of the emission lines excited in the interstellar medium of the hostgalaxy by the hard quasar radiation field reveals evidence of a dramaticchemical evolution within the spheroid during this epoch. Secondary nitrogenproduction in intermediate mass stars produces a characteristic signature inthe NV/CIV and NV/HeII line ratios which has been seen previously in the broadline region of quasars at similar redshifts. We find intriguing correlationsbetween the strengths of the Ly alpha and NV emission lines and the degree ofultraviolet continuum polarization which may represent the dispersal of dustassociated with the chemical enrichment of the spheroid.

Radio galaxies at $z\sim$ 2.5: Results from Keck spectropolarimetry