VLA observations of compact radio sources near the galactic plane

Abstract

VLA observations of 44 compact radio sources located within 10 degrees of the galactic plane are presented. Forty of the sources are from the ‘scintar’ candidate list of Rickard & Cronyn which consisted of radio sources whose angular sizes, deduced from interplanetary scintillation measurements, were at least a factor of 5 times smaller than their prediction of interstellar scattering deduced from pulsar data. The goals of the observing program were to obtain accurate positions and coarse structural parameters to help determine whether the sources are galactic or extragalactic. We found that 2/3 of the sources are double in structure and we conclude that they are extragalactic. As a consequence we suggest that interstellar scattering at metre wavelengths in many directions along the galactic plane is less than predicted by Rickard & Cronyn. The new source positions were examined on Sky Survey plates. No obvious optical identifications were found, but in about 20 cases there exist star-like images within 10 arcsec of the radio source positions. Optical spectra of the eight brightest of these objects revealed no emission lines or other features common to extragalactic objects. No new optical identifications are proposed.