A DETAILED STUDY OF THE COMPLEX LINE-EMISSION REGIONS IN THE RADIO GALAXY 3C-34

We present the results of an extensive Fabry-Perot investigation of th e extended line-emission gas surrounding powerful radio galaxies. High spatial (less than or similar to 1.'' 4) and kinematical (400 km s(-1 )) resolution observations of the [O II] lambda 3727 emission line of the powerful, double radio source 3C 34 (z = 0.689) are given. We pres ent evidence that anisotropic radiation emanating from a hidden AGN is responsible for photoionizing a line-emission region extending more t han 120 kpc. This is indicated by the distinctively biconical morpholo gy of 3C 34's [O II] gas. A number of line-emission components may als o show various degrees of ''shadowing'' outward from the central ioniz ing source. A simple photoionization model is used to show that this i nterpretation is energetically viable on these length scales. The lumi nosity of the hidden central AGN, necessary to account for the observe d [O II] luminosity, is compatible with that of a typical 3CR quasar a t a similar redshift. Although this interpretation can account for the excitation and most of the unique shape of the warm gas, it is insuff icient to explain the velocity and line width structures observed with our Fabry-Perot. Therefore, we also propose that the illuminated medi um surrounding 3C 34 is the result of gas swept up by the lateral expa nsion and backflow of the radio source lobes.