The Brightness Distribution of Core-Halo Radio Sources

Citation

Sramek, Richard Anthony (1970) The Brightness Distribution of Core-Halo Radio Sources. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/3HJ1-PE18. https://resolver.caltech.edu/CaltechETD:etd-05092008-133654

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The east-west visibility of 28 extragalactic radio sources with both large and very small components was obtained at 605 MHz using the radio interferometer at the Owens Valley Radio Observatory. A 2' HPBW fan beam was synthesized from observations made at twelve spacings between 62 and 977 wavelengths. The availability of such low spatial frequencies permitted the calculation of the brightness distribution of components as large as 56'. The brightness distributions of the following galaxies are plotted: (spiral galaxies) P0045-25, P1302-49 P1334-29, (elliptical galaxies) 3C40, 3C105, P0843-33, 3C236, 3C247, 3C264, P1216-10, 3C274, 3C287.1, 3C293, and P2247+11. Fourteen of the observed sources had a core-halo or asymmetric double structure and had their large components well resolved at the 977[...] spacing. The spectral indices of the large and small components of these sources were obtained by comparing the flux densities given here with those at other frequencies. The spectra of the large components are generally steeper than those of the small components with an average difference of spectral indices of [...] = +0.3. Assuming equipartition of magnetic and particle energies the total energies of the large halos are ~ [...] ergs. This is sufficient energy to maintain the current radio luminosities for ~ [...] years. Three of these fourteen sources have a core-halo structure and are associated with spiral galaxies; the remaining eleven are associated with elliptical galaxies. Two of the remaining sources are asymmetric doubles, and nine have a core-halo structure. Four of the core-halo sources have simple halos, two have double halos, and three have an undetermined halo structure. The ratio of observed double to simple halos can be explained by the projection of double halos randomly oriented in three dimensions provided the ratio of component separation to diameter, R, is less than two. Since doubles without a core have R between two and four, the mechanism of radio galaxy formation is likely to produce a core for low values of R. From the present investigation it is impossible to conclude whether there exists a class of core-halo radio galaxies with simple halos (R [...] 1) or whether the observed core-halo objects represent the low-R end of the ensemble of double radio sources.

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