The Structure of Compact Radio Sources at 10.7 GHz

Citation

Shaffer, David Bruce (1974) The Structure of Compact Radio Sources at 10.7 GHz. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/FER5-8H88. https://resolver.caltech.edu/CaltechETD:etd-06112008-140732

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Very long baseline interferometry has been used to study the compact structure of seven radio sources at 10709 MHz ([...] = 2.8 cm). The observations, the first of a series, were made on April 28 - May 1, 1972, using the NRAO Mark II recording system. Antennas of the Owens Valley Radio Observatory (California), the Harvard Radio Astronomy Station (Texas), and the National Radio Astronomy Observatory (West Virginia) were used to give three baselines that greatly improved the (u,v)-plane coverage compared to the coverage of previously used single baselines. The three baselines had lengths of 119, 84, and 54x10[...] [...]. The observed sources were 3C 84, NRAO 150, OJ 287, 4C 39.25, 3C 273, PKS 2134+004, and VRO 42.22.01 (BL Lac). They were tracked by all three antennas during the time of mutual visibility, giving 8 to 11.5 hours of continuous coverage. With the maximum baseline of 119x10[...] [...] and a u-v cell size of ~40x10[...] [...], it is unlikely that we have missed any important structure information in the range 0[...]0005 to 0[...]005. Fourier inversion of the observations was impossible because there was no phase calibration, and model fitting procedures were used to interpret the data. For five of the sources (NRAO 150, OJ 287, 4C 39.25, 3C 273, and VRO 42.22.01) models were found that fit the observations quite well. For 3C 84 and PKS 2134+004 no simple model could be found, but a rough idea of the source structure was still possible. For most of the sources, interferometric results at other frequencies and resolutions are consistent with the present findings, and a joint interpretation is given. For all the sources except OJ 287 (which looks like a point source at our resolution and was used to calibrate the correlated flux density scale) and possibly NRAO 150, two or more separate components are required to match the observations. Component separations range from 0[...]0006 to 0[...]005 and their sizes from [...]0[...]0003 to ~0[...]002. Components less than ~0[...]002 contribute 0.85 or more of the total 10.7 GHz flux density for all the sources. Assuming synchrotron self-absorbed components, the magnetic fields in the compact sources are %10-3±1 gauss. This value is less than the equi-partition field, and the individual components are expected to expand from particle pressure. Suggestions are given for additional observations to improve our knowledge of the structure and nature of compact sources.

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