The Narrow-Line Regions of Seyfert and Radio Galaxies

摘要: This paper reviews the morphology, excitation, and ionization of gas in narrow extended line regions (NLRs ENLRs) AGNs. Many high-resolution images NLRs Seyfert galaxies are now available from HST. In some galaxies, these reveal straight, sharp-edged V-shaped structures (believed to be projections 3-dimensional cones), while others there is a close association between ionized radio components. The latter effect arises through radiative shocks driven into surrounding interstellar by outwardly moving components or jets. Photoionization models ionization-bounded clouds quite successful reproducing intensity ratios, but number problems remain. These may resolved if matter-bounded also present. Differences excitation levels different ENLRs reflect variations fraction as well parameter. I discuss issue whether radiation responsible for photoionizing 2 originates hidden, compact type 1 nucleus within NLR. two scenarios hard distinguish between. photoionizing-shock model requires surprisingly high pre-shock densities, raising question sufficiently energetic power observed emission.