  In classifying the ensemble of powerful extragalactic radio sources,
considerable evidence has accumulated that radio galaxies and quasars are
orientation-dependent manifestations of the same parent population: massive
spheroidal galaxies containing correspondingly massive black holes. [...] In
this study, we exploit the opportunity to eliminate the quasar glare by
performing sensitive spectropolarimetry with the Keck II telescope of a sample
of radio galaxies with redshifts around 2.5. [...] We show that dust-reflected
quasar light generally dominates the restframe ultraviolet continuum of these
sources and that a highly clumped scattering medium results in almost grey
scattering of the active galactic nucleus photons. The observations, however,
do not exclude a substantial star formation rate averaged over a Gyr of
evolution. The sub-mm reradiation from the scattering dust is likely to
represent only a small fraction (~10%) of the total far infrared luminosity. An
analysis of the emission lines excited in the interstellar medium of the host
galaxy by the hard quasar radiation field reveals evidence of a dramatic
chemical evolution within the spheroid during this epoch. Secondary nitrogen
production in intermediate mass stars produces a characteristic signature in
the NV/CIV and NV/HeII line ratios which has been seen previously in the broad
line region of quasars at similar redshifts. We find intriguing correlations
between the strengths of the Ly alpha and NV emission lines and the degree of
ultraviolet continuum polarization which may represent the dispersal of dust
associated with the chemical enrichment of the spheroid.
