Quasar jets and their fields

Abstract

Observations of jets from quasars and other types of accreting black holes are briefly summarized. The importance of beaming and gamma–ray observations for understanding the origin of these jets is emphasized. It is argued that both the power source and the collimation are likely to be magnetic in origin, although the details remain controversial. Ultrarelativistic jets may be formed by the spinning hole and collimated by a hydromagnetic disc wind. Progress in understanding jets has been handicapped by our inadequate knowledge of how the magnetic field really behaves under cosmic conditions. Fortunately, significant insights are coming from solar observations, numerical simulations and laboratory plasma experiments. Some possible evolutionary ramifications are briefly discussed and it is suggested that it is the mass of the black hole relative to that of the galaxy which determines the eventual galaxy morphology.