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1. How do Radio Galaxies form?
In the late 1970s, jets were discovered in megaparsec-long
radio galaxies. I developed a 'slender' hydrodynamical theory
for jets. This involved the first quantitative analysis of jet warping,
bending and disruption in galactic halos. I established a
background of theory to which observed behaviour is compared and
contrasted. A
full treatment of laminar jets, including the nozzle, gravity and splitting,
has since been completed.
2. What are Hot Spots?
Hot spots are created where a jet finally crashes into the
surrounding medium. I made the first sophisticated numerical simulations
of supersonic jets with Michael Norman and Larry Smarr
(Illinois)$^7$. Cocoons, oblique shocks and Mach discs were revealed.
Synthetic 'hot spot' maps were generated which contain many of the observed
hot spot features and led to the first classification scheme.
3. How do Jets form?
Stellar and extragalactic outflows may be funnelled through
de Laval nozzles$^4$, regions which are prone to Rayleigh-Taylor and Kelvin-Helmholtz
fluid instabilities. I extended the so-called Twin Exhaust Model,
using
numerical simulations to show that hot gas can be ejected in three forms:
jets, bubbles and clouds. The properties of black holes were then
constrained.
4. How do Galactic Nuclei and Quasars interact with their environments?
I produced the 'Catapult' model for the
extended regions of Active Galactic Nuclei and the
'Candle Flame' model for the focussing of Stellar Winds into
bipolar outflows via accretion disks.
Active Galactic Nuclei were further explored in the
mid 80s. The interaction of a central 'monster' with its environment is through
a number of supply and escape routes.
This was discussed in the 'Duelling Wind'
and 'Floppy Disc'.
Here a wind from a black hole collides into an
X-ray heated wind from a surrounding disc. Predictions for the core of a quasar
were then presented. The model is appropriate for the class of
'Broad Absorption Line' quasars which possess the signature of a
disk-shaped outflow.
5. Are Protostellar Outflows driven by Jets?
I have confirmed that
Molecular Jets do indeed generate the structures observed
around protostars. A
hydrocode to follow the molecular-atomic transitions of hydrogen was developed with Suttner and Yorke (Wuerzburg).
The simulated images and spectroscopy
from infrared and submullimetre lines solve a number of problems and
make clear predictions for the classical
Bipolar Outflows.
6. What do Jets reveal about Protostars?
What Jet Structure arises when a pulsating energy source drives a
supersonic flow. The pulsation model has been examined for identifying
features with Suttner (Wuerzburg) and Zinnecker (Potsdam). Sawtooth velocity structures were found
to develop intermediate teeth. These teeth possess high velocity gradients,
providing a motivation for high-resolution observations. The
hypotheses that the pulses are hammer-like and that the jet is sheared
are being tested in the 'Hammer Jet' model.
Last Revised: 2010 June 30th |