Interferometric Measurement of Brightness Distributions in Discrete Radio Sources

Citation

Moffet, Alan Theodore (1961) Interferometric Measurement of Brightness Distributions in Discrete Radio Sources. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/QCM3-7524. https://resolver.caltech.edu/CaltechETD:etd-04212006-170658

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Information about the brightness distributions in 110 extragalactic and 17 galactic radio sources has been obtained from observations with the Caltech variable spacing interferometer at a wavelength of 31.3 cm. In these observations, the amplitude and phase of the complex visibility function were measured at transit with antenna spacings of 195[...], 389[...], 779[...], and 1557[...] along an east-west baseline. Using these same basic spacings, and by observing at large hour angles, the visibility amplitude was measured at ten other effective spacings between 126[...] and 1363[...]. Not all sources were observed at all spacings. Of the 110 extragalactic sources, 47 are found to have angular diameters greater than [...]. Only 4 of these 47 appear to have smooth, simple structure, while the remaining 43 show some form of complexity, many having two fairly well separated components. It is suggested that the majority of all extragalactic sources have complex structure. For three extragalactic sources (M 87, NGC 5128, and Cygnus A) comparable measurements at other wavelengths have been published, and in each case, significant changes in structure with wavelength are noted. The theory of interferometric investigation of discrete sources is developed in some detail, and previous work in the field is reviewed. Calculations on a number of model sources are described.

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