§7 Thesis outline

The work presented in this dissertation deals mainly with the interaction of extragalactic jets from powerful double radio sources and their environment. In Chapter II the hydrodynamics needed for all the calculations used later are described. This is achieved by converting the basic equations of relativistic hydrodynamics into useful forms for the study of jet interactions, without considerations of magnetic fields. Chapter III deals with the problem of bending of jets due to jet-cloud interactions. Chapter IV analyses the stability of curved jets against the formation of internal shocks. Chapter V deals with the problem of the collision between a shock wave and a high density region, or cloud. Finally, in Chapter VI the astrophysical implications of all the calculations presented in this dissertation are discussed.

Figure I.9: Emission line diagnostic plot for a particular sample of 3CR radio galaxies, compared with theoretical predictions (Best et al., 2000). Some of these galaxies present the alignment effect shown in figs.(I.8)-(I.9). The upper shadowed regions are simple photoionisation models. The continuous curve that increases towards the right of the diagram is the model for photoionisation models including matter bounded clouds, that is, photoionisation of a composite population containing both optically thin (matter bounded) and optically thick (ionisation bounded) clouds. The lower shadowed region is predicted by shock ionisation models. The upper unshadowed region above this last one is the one for shock models including a precursor region, that is an upstream ionised region produced by photons diffusing into this preshocked gas. The five galaxies plotted at the right of the diagram have no data available for one of their emission lines.