Low-Ionization Emission-Line Regions around the Nucleus of the Seyfert Galaxy NGC 1068

We present the results of tridimensional spectrophotometric observations of the central region of the Seyfert galaxy NGC 1068 obtained by using Kyoto tridimensional spectrograph I. A brief description of the instrument is presented. We have found the existence of low-ionized gas extending out of the ionization cone. It is characterized by higher ([S II]λ6716 + λ6731)/Hα than within the cone. The ratio peaks at 5 �� –6 �� east and west of the nucleus and reaches to 0.5–0.6. The ionization of the gas outside the cone by the scattered nuclear continuum is examined. We argue that a substantial fraction of the gases outside the cone could be ionized by the scattered nuclear continuum, including the diffuse arc structure seen in an HST image. In addition, we also attempt discussions according to the kinematic and spectroscopic properties of two possible gaseous components derived by the line decomposition: a narrow component that seems to follow the galactic rotation, and a broad one that may be deviated from it.