Observations of the Six Most Intense Radio Sources with a 1.0' Fan Beam.

Observations of the radio sources Cassiopeia A, Taurus A, the Orion Nebula, the Omega Nebula, Sagittarius A, and Cygnus A have been made with a beam width of 1 0' in the east-west direction using the Stanford compound interferometer. The adjustment of the phase lengths of the lines and amplifiers was carried out with the aid of modulated reflections from gas-discharge tubes and diodes. The right ascensions and widths of the sources are in good agreement with values from three other fan-beam surveys. The radio emission in Cassiopeia A is generated in a region resembling a hollow spherical shell. The radius of the shell measured at maximum emissivity is 2.0', and the thickness of the shell at the halfemissivity level is 0.45 of the radius. In Taurus A the emissivity is a maximum near the center of the source and decreases outward. The right ascension of the maximum radio brightness in the Orion Nebula coincides with that of the hottest exciting star, oi(C) Orionis, and a second smaller peak coincides in right ascension with the second hottest star, 02 (A) Orionis. There is good agreement between the radio and optical emission measures near the center of the nebula. The Omega Nebula and Sagittarius A both show complex profiles which suggest that their structure is not fully resolved. The maximum radio brightness in the Omega Nebula is displaced from the optical center of the nebula by 23 sec of right ascension to the west. In Sagittarius A the maximum brightness is 4 sec of right ascension to the east of the origin of the revised galactic coordinates. The centroids of the two main components of Cygnus A are separated by 99" in the east-west direction and the flux density of the eastern component is 15 per cent greater than that of the western component.