THE ORIGIN OF N-III LAMBDA-990 AND C-III LAMBDA-977 EMISSION IN AGN NARROW-LINE REGION GAS

We discuss implications of HUT detections of C III lambda 977 and N II I lambda990 emission from the narrow-line region of the Seyfert 2 gala xy NGC 1068. In their discovery paper Kriss et al. showed that the une xpectedly great strength of these lines implies that the emitting gas must be shock-heated if the lines are collisionally excited. Here we i nvestigate other processes which excite these lines in photoionization equilibrium. Recombination, mainly dielectronic, and continuum fluore scence are strong contributors to the line. The resulting intensities are sensitive to the velocity field of the emitting gas and require th at the turbulence be of the same order of magnitude as the observed li ne width. We propose optical observations that will decide whether the gas is collisionally or radiatively heated.