The Dynamical Interaction of Agn with Their Galaxian Environments

Jet-driven shocks are responsible for an important fraction of the emission of the narrow-line regions (NLRs) in many classes of AGN. However, this cannot explain all observations. It is clear that the remaining sources are photoionised by the active nucleus. The 2-d hydrodynamic models from the RSAA group support an evolutionary scenario whereby the shock-excited NLRs are initially jet-driven but later, ionizing photons from the central engine replace shocks as the main excitation mechanism and shock induced star formation may also become important. In their photoionized phase, dusty and radiation-pressure dominated evolution produces a self-regulated NLR spectrum. This model aso explains the coronal emission lines and fast (3000 km s) outflows seen in some Seyferts. 1. Shock-Driven Radio Galaxies There is increasing evidence that the narrow-line regions (NLRs) associated with many classes of active galactic nuclei (AGN) have a complex dynamical and excitation evolution. Evidence for a cocoon of strong, auto-ionising and radiative shocks (see the theory by Dopita & Sutherland 1995, Dopita & Sutherland 1996 and Bicknell Dopita & O’Dea 1997) is particularly compelling for many luminous classes of radio galaxies. These include the steep-spectrum radio sources (CSS), Fanti et al. 1990, unbeamed Gigahertz-peaked sources (GPS) (see the recent review by O’Dea et al. 1998), compact symmetric objects (CSO) (Wilkinson et al. 1994, and references therein) or compact double sources (CD) Phillips & Mutel 1982. Together, these represent an appreciable fraction (10-30%) of luminous radio sources. Not only are such sources very luminous at