MASS-LOADED RELATIVISTIC JETS

The stars of the parent galaxies inject matter into extragalactic jets in the form of stellar winds. From the present-day estimated mean mass-loss rate by stars in ellipticals, M = 10(-12) M. yr-1, we can infer that the mass injected is high enough to slow the jets of weak FR-1 radio sources down to subrelativistic velocities, but not FR-II jets. This deceleration overcomes the apparent contradiction between the unification scheme for FR-Is and BL Lacs and the low velocities of FR-I jets at kiloparsec scales. In this paper the interaction between a relativistic e--e+ jet and stellar winds is considered, and the conditions under which total mixing is achieved are found. A quasi-one-dimensional approximation of the fluid model with a smoothly distributed source of mass is used to study the dynamics of these mass-loaded jets in a galaxy with a King distribution of stars and a Hubble distribution of intergalactic gas. The solutions found can qualitatively explain the behaviour of the FR-1 jets near their 'gaps', but underestimate the observed lengths of the gaps. It is proposed that the development of a turbulent boundary may be crucially important in the dynamics of the FR-I jets.