MISDIRECTED QUASARS AND EVOLVED STARS IN DISTANT RADIO GALAXIES

We present the results of spectropolarimetry of radio galaxies with re dshift close to 1, complemented by imaging polarimetry. These show: (1 ) a flat (in f(lambda)) polarized UV continuum, (2) broad polarized Mg II emission fine, (3) narrow unpolarized forbidden emission lines, (4 ) a drop in the polarization of the continuum to the red of 4000 angst rom, (5) a strong absorption feature at 2598 angstrom, and (6) perpend icularity between the E vector of polarization, as measured with imagi ng polarimetry, and the optical/radio axis. These data provide evidenc e that distant radio galaxies harbor a quasar which is hidden from dir ect view but seen by scattering from the interstellar medium in the ga laxy. Hot electrons cannot be the dominant scattering agent because of the presence of polarized Mg II lines with a width similar to that ob served in quasars. The drop in the continuum polarization to the red o f the 4000 angstrom break suggests dilution by a red stellar populatio n. The absorption line at 2598 angstrom is probably due to interstella r Fe II. We discuss a two-component model consisting of a dust scatter ed quasar and an evolved stellar population, which reproduces simultan eously the polarization measurements and the UV/optical spectral energ y distribution. Our results provide strong observational support to th e unified model for the most luminous active galactic nuclei and to th e idea that the alignment effect in distant radio galaxies is due to s cattering, and they add an important tool for the study of the early e volution of galaxies.