Simulation of Astrophysical Jets


Principal Investigator

Geoff Bicknell

Mount Stromlo and Siding Spring Observatories




Interest in the evolution of galactic astrophysical jets over the first hundred parsecs of their journey from the nucleus has increased. Recent X-Ray observations have indicated that the jet in the galaxy M87 cannot be confined by the pressure of the surrounding Inter-Stellar Medium within the first hundred parsecs from the nucleus of the galaxy. Indeed this result may prove true for all jets in general.
A number of confinement mechanisms for jets have been forwarded over the last 20 years. Usually is it assumed that the jet is confined by the cocoon formed by the back flow of shocked jet plasma. Other mechanisms include magnetic field confinement, however there is no evidence that magnetic fields confine astrophysical jets. Indeed simulations of magnetically confined jets indicated bizarre morphologies that are not observed.

We have proposed another idea that jets may be confined by the inertia of the denser surrounding medium and we are beginning to simulate this using a Piecewise Parabolic Method (PPM) code. Previous hydrodynamic models have overlooked this region of parameter space and we have dealt with pressure confined jets or jets which are only mildly over-pressured with respect to the ambient medium.


Tavis Hamer

Mount Stromlo and Siding Spring Observatories



w57 - VPP



What are the results to date and the future of the work?

We have successfully reproduced the results of previous numerical simulations of astrophysical jets, using our 2D PPM code and the usual range of parameters as dictated in the literature (i.e. for under-dense pressure equilibrated jets).

We intend to extend our 2D PPM code to incorporate fully three dimensional simulations and magnetic fields in the near future.

What computational techniques are used?

A piecewise Parabolic Method (PPM) code is used.

- Appendix A