THE UV-RADIATION FROM Z-SIMILAR-TO-2.5 RADIO GALAXIES - KECK SPECTROPOLARIMETRY OF 4C-23.56 AND 4C-00.54

We present the results of deep spectropolarimetry of two powerful radi o galaxies at z similar to 2.5 (4C 00.54 and 4C 23.56) that was obtain ed with the W. M. Keck II 10 m telescope and which was aimed at studyi ng the relative contribution of the stellar and nonstellar components to the ultraviolet continuum, Both galaxies show strong linear polariz ation of the continuum between rest-frame similar to 1300-2000 Angstro m, and the orientation of the electric vector is perpendicular to the main axis of the UV continuum. In this sense, our objects are like mos t 3C radio galaxies at z similar to 1. The total flux spectra of 4C 00 .54 and 4C 23.50 do not show the strong P Cygni absorption features or the photospheric absorption lines expected when the UV continuum is d ominated by young and massive stars, The only features detected can be ascribed to interstellar absorptions by Si II, C II, and O I, Our res ults are similar to those for 3C radio galaxies at lower z, which sugg ests that the UV continuum of powerful radio galaxies at z similar to 2.5 is still dominated by nonstellar radiation and that young massive stars do not contribute more than approximate to 50% to the total cont inuum flux at 1500 Angstrom.