Optical identifications of sources in the NRAO 5-GHz deep survey

Accurate radio positions of extragalactic radio sources forming a sample complete to 0.1 Jy at 5 GHz were measured with the NRAO dual-frequency interferometer. Comparably accurate positions of all optical objects within 30 arcsec of each source were determined. Identifications were made on the basis of position coincidence without regard to color or morphology. The completeness and the reliability of the identification program were evaluated as functions of position uncertainty, sky density of confusing optical objects, search area, and the fraction of sources associated with empty fields. Over half of the sources are identified with objects on the Sky Survey prints. The morphological content and spectral index distributions of the identified sources are found to be nearly independent of radio flux density.