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Galaxy Evolution: The origin and evoltuion of radio sources  
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Cavendish Astrophysics
Cavendish Laboratory

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Regulating the ISM and star formation
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The origin and evolution of radio sources
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Paul Alexander
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Cavendish Astrophysics

Galaxy Evolution

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.

University of Cambridge    Last modified: 20/1/2002