Radio Recombination Lines

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Radio Recombination Lines

Author : M.A. Gordon
ISBN : 9789401002615
Genre : Science
File Size : 75.80 MB
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Recombination lines at radio wavelengths have been - and still are - a pow erful tool for modern astronomy. For more than thirty years they have allowed astronomers to probe the gases from which stars form. They have even been detected in the Sun. In addition, observations of these spectral lines facilitate basic research into the atom, in forms and environments that can only exist in the huge dimensions and extreme conditions of cosmic laboratories. We intend this book to serve as a tourist's guide to the world of Radio Recombination Lines. It contains three divisions: a history of their discovery, the physics of how they form and how their voyage to us influences their spectral profiles, and a description of their many astronomical contributions to date. The appendix includes supplementary calculations that may be useful to some astronomers. This material also includes tables of line frequencies from 12 MHz to 30THz (AlOJLm) as well as FORTRAN computer code to calculate the fine structure components of the lines, to evaluate radial matrix integrals, and to calculate the departure coefficients of hydrogen in a cosmic environment. It also describes how to convert observational to astrophysical units. The text includes extensive references to the literature to assist readers who want more details.
Category: Science

Radio Recombination Lines 25 Years Of Investigation

Author : Mark Gordon
ISBN : 0792308042
Genre : Science
File Size : 47.4 MB
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Text no 1 Radio Recombination Lines (RRLs), discovered in the USSR in 1964, have become a powerful research tool for astronomers. Available throughout the radio spectrum, these lines carry information regarding the density, temperature, turbulence and velocity of thermal plasmas. Their very existance shows the presence of thermal gas. They also can carry information regarding magnetic fields if Zeeman splitting were to be detected. Containing the proceedings of an IAU Colloquium celebrating the 25th anniversary of their detection, this volume tells us what has happened since. It contains the story of the detection of RRLs and reviews of many areas of physics of the interstellargas from which stars form, HII regions excited by newly formed stars, planetary nebulae involving dying stars, and the structure of our Milky Way and other galaxies reflecting the large-scale morphology of the star formation process. In addition there is an article describing modern laboratory studies of Rydberg atoms to probe the basic physics of atomic structure, and articles describing the theory of collisions and radiation upon Rydberg atoms leading to observate effects to be used as diagnostic tools in astromony. This book focuses on the 25 years of astronomical research with radio recombination lines (RRLs) since their discovery in 1965. It covers a wide range of topics: papers dealing with research into Rydberg atoms both in the laboratory and in the interstellar medium of our galaxy and others; papers on the interaction of radiation and atomic systems, as well as with the effects of inadiabatic collisions between these atoms and both ions and electrons. It deals with astronomical observations of atoms with `diameters' ranging from 0.08 to 50 mum a size factor of 625. It deals with RRLs in absorption, in emission and as true masers. And it deals with plasmas with temperatures ranging from 10 to greater than 104 kelvins, and with an even greater range of volume densities. Much new work is reported, including low frequency RRLs discovered in 1980 and the maser RRLs from the star MWC349, discovered in 1989. The advent of aperture synthesis telescopes and large single-element telescopes have made possible RRL studies with high angular resolution. The sum total of the work reported here will make the volume a platform from which to search new horizons in RRL research.
Category: Science

Radio Recombination Lines

Author : P.A. Shaver
ISBN : 9789027711038
Genre : Science
File Size : 89.51 MB
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Since their first detection 15 years ago, radio recombination lines from several elements have been observed in a wide variety of objects including HII regions, planetary nebulae, molecular clouds, the diffuse interstellar medium, and recently, other galaxies. The observations span almost the entire range from 0.1 to 100 GHz, and employ both single djsh and aperture synthesis techniques. The theory of radio recombination lines has also advanced strongly, to the point where it is perhaps one of the best-understood in astro physics. In a parallel development, it has become possible over the last decade to study these same highly-excited atoms in the laboratory; this work provides further confirmation of the theoretical framework. However there has been continuing controversy over the astrophysical interpre tation of radio recombination line observations, especially regarding the role of stimulated emission. A workshop was held in Ottawa on 24-25 August, 1979, bringing together many of the active scientists to review the field and discuss these questions of interpretation. A broad concensus has emerged: the subtleties of the line-formation process are understood, and the conditions under which reliable in formation can easily be extracted from the line measurements are known. It thus appears likely that the emphasis will shift increasingly from the study of the line phenomenon itself to further application in other areas of astrophysics, ranging from physical processes in plasmas (temperatures, densities, ionization structure), to the large-scale properties of our galaxy (abundances, kinematics, structure), and studies of extragalactic systems.
Category: Science

Theory Observation Of High Order Radio Recombination Lines

Author : Jordan Alexander
ISBN : OCLC:1052730801
Genre : Astronomical spectroscopy
File Size : 62.46 MB
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Author supplied keywords: interstellar medium; H II regions; Rydberg atoms; spectroscopy; radio recombination lines.
Category: Astronomical spectroscopy

Tools Of Radio Astronomy

Author : Thomas Wilson
ISBN : 9783540851219
Genre : Science
File Size : 32.31 MB
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Four signi?cant factors have led us to update this text. The ?rst is the breathtaking progress in technology, especially in receiver and digital techniques. The second is the advance of radio astronomy to shorter wavelengths, and the increased availab- ity of astronomical satellites. The third is a need to reorganize some of the chapters in order to separate the basic theory, that seldom changes, from practical aspects that change often. Finally, it is our desire to enhance the text by including problem sets for each chapter. In view of this ambitious plan, we have expanded the number of authors. In the reorganization of this edition, we have divided Chap. 4 of the 4th edition into two Chaps. 4 and 5. The ?rst remains Chap. 4, with a slightly different - tle, Signal Processing and Receivers: Theory. This was expanded to include digital processing and components including samplers and digitizers. In Chap. 5, Prac- cal Receiver Systems. we have relegated the presentations of maser and parametric ampli?er front ends, which are no longer commonly used as microwave receivers in radio astronomy, to a short section on “historical developments” and We have retained and improved the presentations of current state-of-the-art devices, cooled transistor and superconducting front ends. We have also included descriptions of local oscillators and phase lock loops. Chapters 5 and 6 in the 4th edition has now become Chap. 6, Fundamentals of Antenna Theory and Chap.
Category: Science

Astronomical Masers

Author : M Elitzur
ISBN : 0792312163
Genre : Science
File Size : 84.90 MB
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One of the most spectacular discoveries of molecular astronomy has been the detection of maser emission. The same radiation that is generated in the laboratory only with elaborate, special equipment occurs naturally in interstellar space. This intense radiation probes the smallest structures that can be studied with radio telescopes. By a fortunate coincidence maser radiation is generated in both star forming regions and the envelopes of late-type stars. The early and late stages in the life of a star are considered to be the most interesting phases of stellar evolution. Maser emission has also been detected in external galaxies. This book provides an extensive coverage of the interstellar maser phenomenon. A precondition for maser action is departure from thermal equilibrium. The book therefore starts with a detailed coverage of the basic background concepts required for an understanding of line formation and radiative transfer. It goes on to describe the theoretical and phenomenological aspects of interstellar masers, their formation sites and the inversion mechanisms. The book will interest active researchers in astronomy and astrophysics as well as in other areas of physics. It is suitable as a textbook in a graduate course and will enable a graduate student to embark on research projects in this exciting area in particular, and molecular radio astronomy in general.
Category: Science

Spectroscopy Of Astrophysical Plasmas

Author : A. Dalgarno
ISBN : 052126927X
Genre : Science
File Size : 68.35 MB
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A group of acknowledged experts describe the use of spectroscopy as a diagnostic probe of astronomical environments. The broad sweep of the book enables good coverage to be given to all the situations in which plasmas are encounteres in astronomical investigations. Specifically, the articles include quasars, Seyfert galaxies, active galactic nuclei, the solar chromosphere and corona, galactic HII regions, circumstellar shells, interstellar gas, supernova remnants and interstellar clouds. The book includes an account of the basic aspects of spectroscopy in a chapter on laboratory astrophysics. The book was stimulated by the extraordinary contributions to astronomical spectroscopy of Leo Goldberg, and is dedicated to him. Throughout, this book is written with the needs of students in astronomy and astrophysics in mind. Each chapter includes a summary or conclusions about the future direction of research. Furthermore there are extensive bibliographies. This textbook is therefore an excellent introduction to research in astrophysics and it will act as a pathfinder to the primary literature.
Category: Science

Galactic Radio Astronomy

Author : F.J. Kerr
ISBN : 9789401022637
Genre : Science
File Size : 45.81 MB
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'Galactic Radio Astronomy' was chosen as the subject of this Symposium, which was held in conjunction with the IAU General Assembly that took place in Sydney in August 1973, largely because it is a very suitable Southern Hemisphere topic. This results in part from the advantages of a southern location in studying the Galaxy and in part from the long association of Australia with radio astronomy. Following the General Assembly, the Symposium was held at the Surf air Inter national Hotel in Maroochydore, Queensland, from 3 to 7 September, 1973. The conference participants were effectively isolated from the rest of the world during the Symposium, and the excellent spring weather and geographical situation led to the development of an unusually good rapport. The Symposium was sponsored by Commissions 40, 33, and 34. The Organizing Committee was composed of A. H. Barrett (chairman), J. E. Baldwin, D. S. Heeschen, F. J. Kerr, J. Lequeux, S. W. McCuskey, P. G. Mezger, B. Y. Mills, Yu. N. Parijskij, B. J. Robinson, H. van der Laan, and H. F. Weaver. The Local Committee, consisting ofB. J. Robinson, N. G. Seddon, and P. J. Kelly, looked after the arrangements in very fine style. The Symposium was supported financially by the IAU, the Australian Academy o~ Science, the CSIRO Division of Radiophysics, Union Carbide Australia Limited, and the Science Foundation for Physics within the University of Sydney.
Category: Science

Electron Positron Interactions

Author : B.H. Wiik
ISBN : 9783540347927
Genre : Science
File Size : 83.97 MB
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Radio Recombination Lines is a comprehensive guide to the physics and observations of Radio Recombination Lines from astronomical sources. It includes the history of RRL detections, the astrophysics underlying their intensities and line shapes including topics like departures from LTE and Stark broadening, the maximum possible size of an atom, as well as detailed descriptions of the astronomical topics for which RRLs have proved to be effective tools. In addition, the appendix includes detailed physics underlying the Bohr atomic model, tables of RRL frequencies including fine structure components, techniques for calculating hydrogenic oscillator strengths, and formulas for converting telescope intensity units to astrophysical ones. Radio Recombination Lines is written for astronomers and physicists. It is also suitable as a graduate-level textbook. This softcover contains updates and corrections from the previous hardcover published in 2002. "We now have a splendid book written by two of the pioneers, M.A. Gordon of the National Radio Astronomy Observatory in Tucson and R.L. Sorochenko of the Lebedev Institute. In their Preface the authors say that the book was written by exchanging email. They give a fascinating account of the history of the subject, a detailed discussion of the atomic physics required for the interpretation of the observations, and describe astronomical results obtained using RRL observations for a wide range of astronomical objects." -Mike Seaton, Former President, Royal Astronomical Society, 1979-1981.
Category: Science

An Introduction To Radio Astronomy

Author : Bernard F. Burke
ISBN : 9780521878081
Genre : Science
File Size : 22.10 MB
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This well-established, graduate-level textbook is a thorough introduction to radio telescopes and techniques for students and researchers new to the subject.
Category: Science

Galactic And Extragalactic Radio Astronomy

Author : Gerrit L. Verschuur
ISBN : 9781461239369
Genre : Science
File Size : 69.36 MB
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Galactic and Extragalactic Radio Astronomy is a fundamental text for graduate students and professional astronomers and covers all aspects of radio astronomy beyond the solar system. Each chapter is written by a renowned expert in the field and contains a review of a particular area of radio astronomy and presents the latest observations and interpretations as well as an extensive view of the literature (as of 1988). Topics covered include: galactic continuum emission, HII regions, the diffuse interstellar medium, interstellar molecules, astronomical masers, neutral hydrogen, the galactic center, radio stars, supernova remnants, pulsars, extragalactic hydrogen, radio galaxies and quasars, the microwave background, and cosmological radio sources.
Category: Science

The Universe

Author : Josip Kleczek
ISBN : 9789401014854
Genre : Science
File Size : 29.50 MB
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The universe is the largest system of all. It consists of elementary particles bound together by gravitational, electromagnetic and nuclear forces. Its structural hierar chy in space (from atomic nuclei to supergalaxies) and its evolutionary sequence (from the fireball to the diversity of present forms) is governed by the properties of elementary particles and their interactions. This book is an attempt to interpret the structure and evolution of the universe in terms of elementary particles and of their interactions. This book is intended to present a background for students in astronomy and related sciences, such as geophysics, meteorology, plasma physics, chemistry, nuc lear physics, space sciences and some others. The universe forms a general framework fo: all the phenomena studied by these sciences. It was possible to squeeze an extensive range of topics from various disciplines into one book of acceptable size only under some severe limitations: (a) no references are given; (b) arguments are shortcut; (c) quantities are often expressed in the order of magnitude; and (d) formulae have been limited to a minimum. Often more hypo theses or theories exist for a phenomenon. We have chosen only one. The preference for a theory or hypothesis may be personal and the theory itself may later prove incorrect. But, many theories about a particular phenomenon would cover many pages and might lead to confusing effects.
Category: Science