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The galactic and extragalactic background radiation components are of major importance in astrophysical studies of a variety of problems related to galactic structure, interstellar matter, the distribution and evolution of galaxies and intergalactic matter, and cosmology. The back ground radiation is a unique source of information in cases where the source is of a truly diffuse nature, as with scattering and emission by interstellar dust and gas, or where the discrete emission sources are so faint (e. g. , very distant galaxies) that they can be observed only by their integrated emission. The galactic and extragalactic background must be discussed together because they are observationally entangled and their proper separation requires a knowledge of both components. The above points are equally valid for the entire electromag netic spectrum, from gamma rays to long radio waves. Thus, the study of the galactic and extragalactic background radiation is interdisciplinary in its character, and a multi wavelength approach would appear to be dictated by the nature of the topic. The proper separation of the galactic and extragalactic background components requires a knowledge of both. In addition, the foreground components, i. e. , zodiacal light, airglow, and atmospheric scattered light, must be treated carefully.
List of contents
I. A Historical Review.- II. Galactic Background Starlight from UV to IR: Observations and Models.- III. Diffuse Galactic Radiation from Dust and Gas: Observations and Models.- IV. Extragalactic Background Radiation and Cosmology.- V. Future Plans and Approaches.- VI. Conference Summaries.- Author Index.
Summary
Proceedings of the 139th Symposium of the International Astronomical Union on `The Galactic and Extragalactic Background Radiation, held in Heidelberg, FRG, June 12-16, 1989
