Simulation of Astrophysical Jets
Principal Investigator
Geoff Bicknell
Mount Stromlo and Siding Spring Observatories
Co-Investigators
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
Projects
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.