A comparison of the acceleration mechanisms in YSO and AGN jets


D.J. Price, J.E. Pringle, A.R. King,

Institute of Astronomy, Madingley Rd, Cambridge, CB3 0HA, UK
Department of Physics and Astronomy, University of Leicester, Leicester, LE1
7RH, UK

MNRAS 339, 1223-1236


Abstract

We examine the hypothesis that there exists a simple scaling between the observed velocities of jets found in Young Stellar Objects (YSOs) and jets found in Active Galactic Nuclei (AGN). We employ a very simplified physical model of the jet acceleration process. We use time-dependent, spherically symmetric wind models in Newtonian and relativistic gravitational fields to ask whether the energy input rates required to produce the jet velocities observed in YSOs (of about 2 $\times$ the escape velocity from the central object) can also produce AGN jet velocities (Lorentz factors of $\gamma \sim$ 10). Such a scaling would be expected if there is a common production mechanism for such jets. We demonstrate that such a scaling does exist, provided that the energy input process takes place sufficiently deep in the gravitational potential well, enabling physical use to be made of the speed of light as a limiting velocity, and provided that the energy released in the accretion process is imparted to a small fraction of the available accreting material.

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