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A Search for Radio Recombination Lines from Galaxies and Quasars
Radio Recombination Lines
Author: P.A. Shaver
Publisher: Springer Science & Business Media
Published: 2012-12-06
Total Pages: 281
ISBN-13: 9400990243
DOWNLOAD EBOOK →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.
Intrinsic Absorption Lines in Radio-selected Quasars
Radio Recombination Lines: 25 Years of Investigation
Author: Mark Gordon
Publisher: Springer Science & Business Media
Published: 1990-06-30
Total Pages: 318
ISBN-13: 9780792308041
DOWNLOAD EBOOK →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.
Structure and Kinematics of Quasar Broad Line Regions
Author: C. Martin Gaskell
Publisher:
Published: 1999
Total Pages: 480
ISBN-13:
DOWNLOAD EBOOK →Annotation Proceedings of a March 1998 meeting, with papers in sections on general considerations and photoionization modeling, profile variation and reverberation mapping, flows, disks, narrow-line Seyfert 1 galaxies, the intermediate line region and lower-velocity gas, X-ray warm absorber and dust, and unified theories and connections with extended emission. Specific topics include spectral variability of NGC 4151 during 1990 and disk emission line issues. Lacks a subject index. The editor is associated with the University of Nebraska. Annotation c. Book News, Inc., Portland, OR (booknews.com)
Galactic and Extragalactic Radio Astronomy
Author: E. Bouton
Publisher: Springer Science & Business Media
Published: 2012-12-06
Total Pages: 715
ISBN-13: 1461239362
DOWNLOAD EBOOK →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.
Quasars, Their Importance in Astronomy and Physics
Spectrophotometry of Intermediate and High-redshift Quasars
Broad and Narrow Intrinsic Absorption in Quasars as it Relates to Outflows, Orientation, and Radio Properties
Author: Robert Bernard Stone
Publisher:
Published: 2018
Total Pages: 59
ISBN-13:
DOWNLOAD EBOOK →This work provides evidence that a large fraction of narrow absorption lines (NALs) seen along the line of sight to distant quasars are due to accretion disk winds, while also seeking to understand the relationship between NALs and certain quasar-intrinsic properties. We extend the results from past work in the literature with velocity distributions (dN/d[beta]) of ~ 108,000 NALs from a sample of ~ 58,000 Sloan Digital Sky Survey (SDSS) quasars. The primary results of this work are summarized as follows: (1) the velocity distribution of NALs is independent of radio loudness (or even detection) once marginalized by optical/UV luminosity; (2) there are significant differences in the number and distribution of NALs as a function of both radio spectral index and optical/UV luminosity and these two findings are not entirely interdependent; (3) improvements in quasar systemic redshift measurements, analysis of NALs in broad absorption line quasars, and differences in the NAL distribution as a combined function of optical luminosity and radio spectral index---together provide evidence that a significant portion of NALs are due to quasar outflows; (4) the results are consistent with standard models of accretion disk winds governed by the L_UV-[alpha]_ox relationship and line-of-sight orientation indicated by radio spectral index; and (5) possibly supports the magnetically arrested disk model as an explanation for the semi-stochastic nature of strong radio emission in a fraction of quasars.
