RAM-PRESSURE CONFINEMENT OF EXTRAGALACTIC JETS

The confinement problem of extragalactic jets is considered. It is shown that a significant increase of the kinetic luminosity of the central source can lead to much higher pressure in the jets as compared to the thermal pressure of the external gas. The sideways expansion of such overpressured jets is effectively restrained by the high inertia of the external gas, the expansion velocity being determined by a balance between the kinetic pressure of the jet and the ram pressure of the external gas. The discovery of the expanding envelope around the 3C 120 jet provides strong support for the model.