Quasars and active galaxies are the most powerful emitters of radiation in the universe. Modern radio telescope arrays have shown that the ultimate energy source resides in the central few parsecs of the galactic nucleus, and powers the emitting regions by way of two oppositely-directed relativistic jets. This volume presents the latest observations and theories of these remarkable objects. Topics discussed include superluminal motions, the physics of jets and shock fronts in jets, related optical observations and cosmic evolution. Particular attention is given to the 'unified theories' which attempt to show that many of the phenomena in powerful extragalactic objects are different aspects of a single basic mechanism, the main difference in their appearance being due to their different orientations with respect to the observer. The book is based on papers presented at a workshop in October 1989 held at the National Radio Astronomy Observatory's Array Operations Center in Socorro, New Mexico, and attended by about 60 astronomers from around the world. It provides an up-to-date review of the subject and is supplemented with a comprehensive bibliography. It should serve as a useful introduction and reference for professional astronomers and graduate students whose research interests include active galactic nuclei, quasars, and astrophysical fluid dynamics.
Preface; Acknowledgments; Workshop participants; 1. Parsec-scale radio jets; 2. VLBI observations of 3C 273; 3. Linear polarization of 3C 273 on parsec scales; 4. The compact radio jet in the quasar 3C 345; 5. Recent evolution of jet components in 3C 345 at 3.6 cm; 6. The jet in quasar 0836+71; 7. Apparent proper motion in the quasar 1038+538 A; 8. The Caltech survey of strong, highly variable sources; 9. Variations in the structure of the QSS 2134+004 ; 10. Detection of a new component in the peculiar superluminal quasar 4C 39.25; 11. 4C 39.25: a twisted compact jet?; 12. The jet in the nucleus of NGC 1275; 13. Monitoring 3C 84 at 1.3 cm: 1985-1987; 14. Images of parsec-scale jets from 7 mm VLBI; 15. VLBI observations at 100 GHz; 16. The radio structure of BL lac nuclei; 17. Parsec-scale linear-polarization properties of quasars, galaxies, and BL lacertae objects; 18. Very weak cores of extended quasars; 19. 3C 111 and 3C 390.3: beaming in nearby radio galaxies; 20. Velocity structure of the M 87 jet: preliminary results; 21. The milliarcsecond structure of the low-luminosity radio galaxy NGC 315; 22. Active nuclei in nearby elliptical galaxies; 23. The VLBI structure of Cyg X-3 during the 1985 October radio outburst; 24. Kiloparsec-scale jets in CSS radio sources; 25. High-quality images of the CSS quasar 3C 309.1; 26. Compact triple radio sources; 27. The dark side of radio jets in powerful extended sources; 28. 3C 196: the jets that are not; 29. Intraday variability of extragalactic radio sources; 30. Sources showing apparent shock events; 31. Flux variations and superluminal components in extragalactic radio sources; 32. VLBI observations of steep-spectrum low-frequency variable sources; 33. Interpretation of compact jet observations; 34. What do we learn from modeling variability data?; 35. Numerical modeling of 'born-again' radio jets; 36. Fluid dynamical structure and implications for superluminal motions; 37. Numerical jet simulations and parsec-scale jets; 38. Optical observations; 39. Unified schemes and core-dominated radio sources; 40. On the unification of quasar and radio galaxies; 41. Beaming, unification, and H0; 42. Significance of the small angles; 43. Relativistic ejections from nuclei of galaxies: application to cosmology; 44. Light echoes revisited; 45. The effect of relativistic beaming on source counts; Summary: an outsider's view; Summary: an insider's view; Bibliography; Index of authors; Index of objects; Index of subjects.