The Physics of Non-Thermal Radio Sources NATO ADVANCED STUDY INSTITUTES SERIES Proceedings of the Advanced Study Institute Programme, which aims at the dissemination of advanced knowledge and the formation of contacts among scientists from different countries The series is published by an international board of publishers in conjunction with NATO Scientific Affairs Division A Life Sciences Plenum Publishing Corporation B Physics London and New York C Mathematical and D. Reidel Publishing Company Physical Sciences Dordrecht and Boston D Behavioral and Sijthoff International Publishing Company Social Sciences Leiden E Applied Sciences Noordhoff International Publishing Leiden Series C - Mathematical and Physical Sciences Volume 28 - The Physics of Non-Thermal Radio Sources The Physics of Non-Thermal Radio Sources Proceedings of the NATO Advanced Study Institute held in Urbino, Italy, June 29-July 13, 1975 edited by GIANCARLO SETTI University of Bologna, Laboratorio di Radioastronomia CNR, Via Irnerio 46, 40126 Bologna, Italy D. Reidel Publishing Company Dordrecht-Holland / Boston-U.S.A. Published in cooperation with NATO Scientific Affairs Division ISBN-13: 978-94-010-1519-6 e-ISBN-13: 978-94-010-1517-2 001: 10.1007/978-94-010-1517-2 Published by D. Reidel Publishing Company P.O. Box 17, Dordrecht, Holland Sold and distributed in the U.S.A., Canada, and Mexico by D. Reidel Publishing Company, Inc. Lincoln Building, 160 Old Derby Street, Hingham, Mass. 02043, U.S.A. All Rights Reserved Copyright © 1976 by D. Reidel Publishing Company, Dordrecht, Holland Softcover reprint of the hardcover 18t edition 1976 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any informational storage and retrieval system, without written permission from the copyright owner CONTENTS FOREWORD VII G. Miley 1 MORPHOLOGY OF EXTRAGALACTIC RADIO SOURCES K.I. Kellermann 27 COMPACT RADIO SOURCES IN QUASARS AND GALACTIC NUCLEI E.M. Burbidge 41 THE OPTICAL PROPERTIES OF RADIO GALAXIES P.A. Strittmatter 55 OPTICAL STUDIES OF QUASARS AND BL LAC OBJECTS W.L.W. Sargent 67 RADIO SOURCES AND CLUSTERS OF GALAXIES R.D. Ekers 83 THE RADIO LUMINOSITY FUNCTION OF GALAXIES P.A.G. Scheuer 93 MODELS OF EXTRAGALACTIC RADIO SOURCES M.J. Rees 107 BEAM MODELS FOR DOUBLE SOURCES AND THE NATURE OF THE PRIMARY ENERGY SOURCE G.R. Burbidge 121 SOME PROBLEMS ASSOCIATED WITH NON-THERMAL RADIO SOURCES L. Wo1tjer 131 ENERGETICS OF QUASARS AND RADIO GALAXIES E.N. Parker 137 THE ACCELERATION OF PARTICLES TO HIGH ENERGY VI CONTENTS E.N. Parker 169 THE BASIC PHYSICAL PROPERTIES OF A GALACTIC MAGNETIC FIELD F. Pacini 179 PULSARS L. Wo1tjer 197 SUPERNOVA REMNANTS R.M. Hje11ming 203 RADIO STARS R. Giacconi 229 X-RAY OBSERVATIONS SUBJECT INDEX 271 POREHORD This volume contains a series of lectures presented at the 3rd Course of the International School of Astrophysics held in Urbino, Italy from June 29 - July 13, 1975 under the auspices of the "E. Majorana" Centre for Scientific Culture. The course was jointly planned by L. Woltjer and myself and was fully supported by a grant from the NATO Advanced Study Institute Programme. It was organized with the aim of providing students and young researchers with an up-to-date account on the subject of the structure, origin, and evolution of non-thermal radio sources and was attended by 88 participants from 15 countries. It is well known that radio astronomical research has played a fundamental role in the development of modern astrophysics and cosmology, leading in particular to the exciting discoveries of new and unsuspected classes of objects such as radio galaxies, qua sars and pulsars. However, it is probably fair to say that we are still far from a complete understanding of the physics of non thermal radio sources except for the fact that, in general, the radio emission is adequately explained in terms of the "synchro tron" mechanism. In the case of extragalactic sources, we know that the very large amounts of energy observed are supplied as a consequence of violent activity taking place in galactic nuclei. Yet we are still faced with a number of unsolved problems, for example: what is the nature of the ultimate source of this energy, how and where is the energy so efficiently converted into relativistic particles, and how is the energy collimated to millions of light years away with such a high degree of symmetry, as found in the double radio sources. Phenomena observed in extragalactic sources reoccur with striking similarities in galactic non-thermal radio sources, though, of course, on different space and time scales. For instance, the radio properties of some X-ray stars like Sco X-I and Cyg X-3 are typical of the phenomenology found in quasars. Moreover, the dis covery of the association between supernova remnants and pulsars has triggered the notion that very efficient particle acceleration can be obtained by rotating magnetic objects. On the observational side, a big step forward has been obtained VIII FOREWORD by the completion of large aperture synthesis radio telescopes, which have permitted a detailed mapping of radio sources, and by the development of very long base-line interferometry (VLBI), with resolutions down to 10-3 - 10-4 arc sec, which for the first time has rendered possible radio investigations of the structures of the very compact radio sources found in galactic nuclei and quasars. The observations obtained with this new instrumentation, combined with the work in the optical, infrared and X-ray domain, have made great strides in recent years toward improved testing of radio source models. We feel that the material presented at the Institute represents a rather complete and comprehensive coverage of the present status of studies of non-thermal radio sources, though one is aware of rapid developments in this field of research. The various aspects of this exciting subject were covered in a series of lectures, pre sented in this volume, totaling 44 hours and in 14 topical seminars given by the participants. I wish to express my gratitude to the Scientific Affairs Divi sion of the North Atlantic Treaty Organization for the generous support given to the course. Sincere thanks are also due to Mr. L. Baldeschi for helping with the organization of the meeting and for drawing a number of figures contained in this volume; to Mrs. B. Mandel for the patient typing and help in the editing; and to Mr. R. Primavera for the photographic reproduction of part of the figures. A special thanks is, of course, due to all the lectures and participants who contributed so much to the success of the course and provided. the articles for this volume. Finally, I wish to express my sincere gratitude to L. Woltjer for his fine collaboration as co-director of the course. Prof. Giancarlo Setti University of Bologna Laboratorio di Radio- astronomia CNR Via Irnerio 46 40126 Bologna, Italy MORPHOLOGY OF EXTRAGALACTIC RADIO SOURCES George Miley Sterrewacht, Huygens Laboratorium Leiden, The Netherlands 1. TECHNIQUES FOR MEASURING MORPHOLOGY "The astronomical instruments have been in use from very ancient days, handed down from one dynasty to another, and closely guard ed by the official astronomers. Scholars have therefore had little opportunity to examine them, and this is the reason why unorthodox cosmological theories were able to spread and flourish." - Fang, Hsuan-Ling, History of the Chin Dtnasty, 635 AD. This section is intended to be a bluffers guide' for readers of morphology papers. 1.1 Some peripheral techniques a. Single dish Resolution AS ~ Air (for r = 100m (Bonn dish) at A - 3 em, AS ~ 1'). Only useful for largest sources at short wavelength. Obser vations seriously limited by receiver sta bility. b. Luna~ occultations Variation of source flux density as it is occulted by moon gives one-dimensional brightness distribution convolved with diffraction pattern of moon. For restoration procedure see Scheuer (1962), von Hoerner (1964). AS depends on signal to noise of source. AS ~ 1" readily achievable. G. Setti (ed.). The PhyllicB ofN on-Thermtll RJldio SourceB, 1-26. AU RightB ReBe11led. Copyright e 1976 by D. Reidel PubliBhing Company, Dordrecht-Holiand. 2 GEORGE MILEY Advantages : Resolution not highly dependent on frequency. Disadvantages: Two-dimensional structure difficult to reconstruct. Can only be applied to sources that happen to lie on moon's path (i.e. - 29° < 0 < + 29°). First suggested by Getmansev and Ginzbury (1950). Most notable success in pinpointing 3C 273 (Hazard et al. 1963) led directly to discovery of quasars. Recently several hundred weak sources have been studied with a new telescope in India specially designed for occultation work, e.g. Kapahi et al. (1974). c. Interplanetary scintillations Irregularities in electron density of solar corona (scale ~ 100 km) cause small sources to flicker or "scintillate". Large sources are unaffected - frosted glass effect. Degree of scintillation and its variation with distance from Sun can give useful informa tion on amount of small scale « I") structure in a source. First reported by Hewish et al. (1964). See Cohen et al. (1967), Little and Hewish (1968). Advantages : Easy. High resolution at low frequency. Disadvantages: All but crudest inferences about structure depend on assumed model for solar corona. Can only be applied to limited source list (~ 50° from Sun). 1.2 Interferometry and aperture synthesis This is much the most important tool used by morphologians. It was first developed by Ryle (1952) and independently by Christiansen (1953) and Mills and Little (1953). An excellent account is given by Fomalont and Wright (1974). Here we shall summarize some of the most important points stressing the jargon which is often used by morphologians in their articles //~ Analogue of Young's //8"\ Bp~ double slit experiment. / / Gives roughly same ,~// // resolution as single dish / V2=V02 cos[wt+(BcosBIl / v,' BX stretching between two telescopes.