D. B. Shaffer

The small-scale structure of radio galaxies and quasi-stellar sources at 3.8 centimeters.

Observation of fringes from 31 compact radio sources, including eight known or suspected galaxies and 20 known or suspected QSSs, by using the Goldstack interferometer at lambda = 3.8 cm (d/lambda = 10 to the 8th power). Fringe visibility curves were obtained for nine sources showing structure on a scale of .001 sec of arc, and simple models are fitted to the data. Results for 3C 273 and 3C 279 are compared with data taken by Knight et al. (1971) at an earlier epoch. The apparent changes in brightness distribution of 3C 273 and 3C 279 are difficult to explain.

The small radio source at the galactic center

Very-long-baseline interferometer observations show that the compact radio source at the Galactic Center has dimensions of approximately 200 AU and that about 25% of the emission comes from a region only 10 AU across. There is no evidence for any expansion or contraction of this compact source, with a velocity of at least a few tens of kilometers per second.

A compact radio source in the nucleus of M82

Abstract : The compact radio source in M 87 has been observed with a long baseline interferometer composed of the 210-foot telescope at Goldstone, California, U.S.A., and the 85-foot telescope at Tidbinbilla, near Canberra, A.C.T., Australia. The observations suggest that the radio source is remarkably concentrated to the galactic nucleus and has a linear diameter of about 2.5 light months.

Observations of compact radio nuclei in Cygnus A, Centaurus A, and other extended radio sources

Observations of Cygnus A show a compact radio core 2 milliarcsec in extent oriented in the same direction as the extended components. Other large double- or multiple-component sources, including Centaurus A, have also been found to contain compact radio nuclei with angular sizes in the range 1-10 milliarcsec.

Variations in the Radio Structure of BL Lacerate

We have observed the structure of the rapid variable radio source BL Lac (VRO 42.22.01) using long baseline interferometer systems with baselines up to 266 million wavelengths. Despite large variations in the total flux and in the overall size of this source, it has maintained an elongated brightness distribution, and the direction of elongation has not changed during the 1.3 years of observation. No simple model of stationary variable components or of separating, evolving components appears to fit all the data For this source. In particular, it apparently cannot be explained in terms of a stationary brightness distribution with a single variable component of very small angular size. The peak brightness temperature of VRO 42.22.01 is in excess of 5x 10/sup 12/. K at 11 cm wavelength, a value close to the limit set by inverse Compton scattering.

Observations of further outbursts in the radio galaxy 3C 120.

interferometer observations made during two years with the Goldstack interferometer show considerable increases and decreases in the apparent angular size of the radio galaxy 3C 120. The data suggest that the outbursts occur in regions separated by several light years but are also consistent with the individual components expanding or moving with an apparent velocity close to the speed of light.