Physical conditions in luminous AGN

The phenomenon of active galactic nuclei (AGN) has been one of the most intriguing subjects of astrophysical studies in the past several decades. Radio astronomy and very long baseline interferometry (VLBI) have played a crucial role in these studies, particularly in investigations of reltavistic outflows (jets) commonly observed in luminous AGN. For the past 30 years, radio interferometry has yielded an impressive amount of information about the dynamics and composition of these outflows, as well as about the conditions in the most compact, nuclear environment in the immediate vicinity of central engine of AGN. The jets in particularly well studied sources 3C345, 3C273 and M87 have become the testbeds for numerous numerical and analytical approaches to modelling the relativistic outflows. A review of our recent studies of these three objects will be presented in this talk. Particular attention will be paid to the subject of internal structure observed in these jets and its implications for the dynamical evolution of relativistic outflows.