Fifty Years of Quasars

Fifty Years of Quasars For further volumes: http://www.springer.com/series/5664 Astrophysics and Space Science Library EDITORIAL BOARD Chairman W. B. BURTON, National Radio Astronomy Observatory, Charlottesville, Virginia, U.S.A. ([email protected]); University of Leiden, The Netherlands ([email protected]) F. BERTOLA, University of Padua, Italy J. P. CASSINELLI, University of Wisconsin, Madison, U.S.A. C. J. CESARSKY, Commission for Atomic Energy, Saclay, France P. EHRENFREUND, Leiden University, The Netherlands O. ENGVOLD, University of Oslo, Norway A. HECK, Strasbourg Astronomical Observatory, France E. P. J. VAN DEN HEUVEL, University of Amsterdam, The Netherlands V. M. KASPI, McGill University, Montreal, Canada J. M. E. KUIJPERS, University of Nijmegen, The Netherlands H. VAN DER LAAN, University of Utrecht, The Netherlands P. G. MURDIN, Institute of Astronomy, Cambridge, UK F. PACINI, Istituto Astronomia Arcetri, Firenze, Italy V. RADHAKRISHNAN, Raman Research Institute, Bangalore, India B . V. S O M OV, Astronomical Institute, Moscow State University, Russia R. A. SUNYAEV, Space Research Institute, Moscow, Russia Mauro D’Onofrio Paola Marziani Jack W. Sulentic Editors Fifty Years of Quasars From Early Observations and Ideas to Future Research 123 Editors Mauro D’Onofrio Paola Marziani Dipartimento di Astronomia Osservatorio Astronomico di Padova UniversitadiPadova` Istituto Nazionale di Astrofisica (INAF) Padova Padova Italy Italy Jack W. Sulentic (IAA-CSIC) Instituto de Astrofisica de Andalucia Granada Spain ISSN 0067-0057 ISBN 978-3-642-27563-0 ISBN 978-3-642-27564-7 (eBook) DOI 10.1007/978-3-642-27564-7 Springer Heidelberg New York Dordrecht London Library of Congress Control Number: 2012941739 c Springer-Verlag Berlin Heidelberg 2012 This work is subject to copyright. 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Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) To all people who dedicated most of their lives to understanding quasars • Foreword It’s good, on occasion, to reflect on the fact that science is fundamentally a very human endeavor. The essential principles of the scientific method, drummed into us at an early age, are that science is dispassionate, objective, and self-correcting: none of which are virtues that humans necessarily come by naturally. But this view of how science works reflects an ideal to which we aspire and not necessarily the world in which we live. Scientists are in fact passionate about their work, sometimes with the result that it’s difficult to achieve true objectivity. On the other hand, science is indeed self-correcting—but usually at a much slower pace than we’d like, and with consequential forays down wrong paths while the facts get sorted out. Unfortunately, the false steps are just an inevitable part of a long process. When we attempt to examine the present state of a vibrant scientific field, we see a mixture of things that are going to be very important in the final assembly of the puzzle, things that will turn out to be of lesser importance, and some things that will turn out to be misleading, and perhaps even wrong. At any given time, however, distinguishing among these possible outcomes is not easy. But it’s entertaining to try. The editors of this volume recognized that the fiftieth anniversary of the discovery of quasars presented an interesting opportunity to open a discussion on both the current state of an exciting field of research and how it got to where it is now. The latter is actually manageable as quasars have almost no “pre-history,” notwithstanding the birth of radio astronomy, which led to identification of the first quasars, and limited work on the bright nuclei of local spiral galaxies beginning with Seyfert twenty years earlier. Fifty years is long enough for the field to have reached some level of maturity, but short enough that many of the pioneers of quasar studies are still with us, and some of them have contributed their insights and recollections to this book. In some sense, it’s surprising how slow progress has been, given that the correct basic physics was recognized by Zel’dovich and Novikov, Salpeter, and Lynden- Bell within a few years of Schmidt’s interpretation of the redshifted spectrum of 3C 273 in 1963. But over at least the first two decades of quasar research, the question that dominated discussion was whether quasars were indeed at the cosmological distances implied by their redshifts! This problem was resolved definitively (or at vii viii Foreword least to my personal satisfaction), first, with the identification of normal galaxies in close proximity to and at the same redshift as relatively low-redshift quasars by Stockton in 1978, and then with the detection of host galaxy starlight in the spectrum of 3C 48 by Boroson and Oke in 1982 in one of the first uses of an astronomical CCD detector. Another similar diversion was the nearly universal assumption that the UV-optical-IR continuum radiation of quasars was synchrotron radiation: that the continuum shortward of one micron is thermal emission from an accretion disk was suggested by Shields in 1978 and that the near-IR continuum is reradiation by dust was posited by Rieke the same year. But these points were not broadly appreciated until the optical work of Malkan and Sargent in 1982 and the near- IR study of Sanders, Phinney, Neugebauer, Soifer, and Mathews in 1989. It was only around 15 years ago that the supermassive black hole paradigm achieved any kind of consensus, even though Rees had convincingly argued as early as 1984 that supermassive black holes in galactic nuclei are inevitable. As recently as 1992, Blandford noted that “it remains true that, even by the lax standards of astronomy, there is no proof that black holes exist in AGN, or indeed anywhere else.1”But within only a few more years, solid detection of supermassive black holes at the center of the Milky Way, M87, and NGC 4258 shifted the paradigm once again, and the question was no longer “are quasars powered by accretion onto supermassive black holes?” but instead became “why are some supermassive black holes active (i.e., accreting matter) and others are not?” So after 50 years of efforts to understand quasars, where are we currently, how did we get here, and where do we think we are headed next? That, in essence, was what the editors of this volume asked 50 quasar researchers (one for each year, it seems). Except for a short contextual introduction and a summary chapter, the book is formatted as a series of epistolary interviews: questions from the editors are phrased as letters to each of the 50 quasar researchers, with each researcher being asked to address a restricted set of questions covering topics selected by the editors. As an active researcher in the field for 35 years, I find this to be fascinating reading: this is not a formal history, but rather it has elements of collected individual memoirs. It’s not a consensus view of the state of the field either, but rather the specific points of view of individual researchers looking at the overall field of quasar research, each from his or her own vantage point, in answer to particular questions addressed to them. For me, the most interesting aspect was hearing the opinions of fellow quasarphiles on what things they believe are important now and what are the most promising directions for future research. One of the current themes in quasar research is that quasars are not only tracers of the evolution of galaxies, but agents of galactic evolution through energetic feedback processes: will this currently popular view hold up to continued scrutiny or it is another massive diversion? Will we ever understand the dichotomy between radio-loud and radio-quiet quasars? And what 1Blandford, R.D., 1992 in Relationships Between Active Galactic Nuclei and Starburst Galaxies, ed. A.V. Filippenko, ASP Conf. Series Vol.

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