YOUNG STARS AND SCATTERED-LIGHT IN THE POWERFUL RADIO GALAXY-3C-321

Blue spectropolarimetry observations are presented for the low-redshif t radio galaxy 3C 321 (z = 0.096). The percentage polarization is foun d to show a spectacular decline from the UV to the optical - by a fact or of 5 from the shortest to the longest wavelengths covered by the ob servations - and the polarization angle is within 15 degrees of the pe rpendicular to the radio axis. These results are consistent with the p resence of a scattered AGN component which comprises 20-70 per cent of the UV continuum, but is diluted by the light of the old stellar popu lations at optical wavelengths. Attempts to model the continuum spectr al energy distribution in terms of quasar + E-galaxy or power-law + E- galaxy produce generally good fits over much of the spectrum, but ther e is a significant excess over the models in the rest-wavelength range 3900-4300 Angstrom. This excess, and the detection of the higher orde r Balmer lines in absorption, provides strong evidence for the presenc e of a population of young (A-type) stars. The best-fitting model comp rises a combination of a quasar, a 1-Gyr starburst, a 15-Gyr-old stell ar population and nebular continuum, with these components contributin g 22, 34, 34 and 10 per cent of the total flux at 3639 Angstrom respec tively. Overall, our results serve to emphasize the multicomponent nat ure of the optical/UV continuum of powerful radio galaxies.