Observations of Energy Transport

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Next: A Long-Range Perspective

Observations of Energy Transport

Alan H. Bridle

National Radio Astronomy Observatory,
520 Edgemont Road, Charlottesville, VA 22903-2475, U.S.A.


There is now good evidence for long-expected ingredients of the jet-launcher in nearby galaxies, and for possible miniatures of it in our galaxy. There is also now a strong case for energy transport at bulk relativistic velocities  to kiloparsec scales in FR I sources,  and to the hot spots in FR II sources.  It therefore seems that the dynamical pictures of (outward) energy transport in FR I and FR II sources can be unified, by studying (both theoretically and observationally) how jets decelerate  in elliptical  galaxies. Our view of jets in lobe-dominated FR II sources may be conditioned by Doppler ``hiding", which favors the emission from their slower-moving outer layers. Some old problems in jet confinement  have faded as we learned more about hypersonic jet propagation, but some old solutions may be jeopardized by recent X-ray data. Radio source environs are now understood to be dynamic, and able to bend jets  without large peculiar motions of the ``engine". Some important transition scales, both across and along jets, are being identified: imaging and polarimetry of radio galaxies and quasars on these scales should help to refine models of jet acceleration, deceleration and disruption.


  1. A Long-Range Perspective
  2. Jet Launching
  3. The Nearest Engines?
  4. Transport Velocities
    1. ``Speed bumps''
  5. Velocity Fields
    1. Acceleration and collimation near the nucleus
    2. Deceleration on kiloparsec scales in FR I sources 
    3. Boundary layers and Doppler ``hiding'' in FR II sources?
  6. Jet Confinement
  7. Jet Bending and the Environment
  8. Tranverse Scales
    1. Exoscales-sheaths around FR I and FR II jets
    2. Endoscales-More Signs of the Spines?
  9. Longitudinal Scales-Jets in Transition
  10. Evolution of Radio Sources
  11. Conclusion: Crossing the FR I/FR II Division
  12. Acknowledgments
  13. References
  14. About this document ...

Alan Bridle
Wed Apr 10 10:19:46 EDT 1996