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Paul Alexander
P.Alexander@mrao.cam.ac.uk
Cavendish Astrophysics
The Origin and Evolution of Radio Sources
Radio sources are among the most powerful of the family of Active Galactic Nuclei (AGN). Jets of (probably) electron-positron plasma are produced close to the AGN itself and propagate in many cases for hundreds of kpc into the surrounding galaxy and beyond. While interesting in their own right they significantly effect their environment and there is growing evidence that the occurence of AGN is linked closely linked to the overall evolution of galaxies.
The radio
galaxy 3C215 observed with the VLA at 8.0 GHz
In order to understand the role of radio sources in galaxy evolution,
we must first understand the physics of radio sources themselves.
We are therefore making a detailed study of the structures and properties
of the FR II sources in the complete 3CR sample to investigate their dynamical
evolution and the transport of energy within them. High resolution,
high sensitivity maps of all the sources out to a redshift of 1 have been
made with the VLA and MERLIN. By mapping a complete sample we are
able to test orientation and beaming models and to examine the relative
importance of relativistic effects and intrinsic/environmental asymmetries.
We have detected jets in up to 80 percent of the sources, providing constraints
on the jet dynamics and we find that jets on kpc scales must have mildly
relativistic speeds.
A simulation of the early stages of a jet propagating into a uniform atmosphere.
The overall properties of radio sources are well predicted by analytical
models of self-modifying evolution of the radio source which we have developed,
and many of the more unusual structures observed can be reproduced using
computational models.
Last modified: 20/1/2002