The First Caltech--Jodrell Bank VLBI Survey. I. lambda = 18 Centimeter Observations of 87 Sources

We present the first results from the first Caltech-Jodrell Bank VLBI survey (the CJ1 survey). The CJ1 sample includes 135 radio sources with total flux density 1.3 Jy > S_(6 cm) ≥ 0.7 Jy, declination δ_(1950) ≥ 35°, and Galactic latitude |b^II| > 10°. It extends the flux density limit of the complete "PR" sample studied by Pearson & Readhead from 1.3 to 0.7 Jy and increases the total number of sources from 65 to 200. The complete survey includes VLBI images at both λ- 18 and 6 cm of all the objects in the extended sample that have cores strong enough to be mapped with the Mark II VLBI system. These images provide a large enough sample to study, for example, the variety of morphologies exhibited by compact radio sources, cosmological evolution, superluminal motion, and misalignment between parsec-scale and kiloparsec-scale radio structures. In this paper we present λ-18 cm VLBI observations of 56 CJ1 and 3l PR sources made in 1990-1991, including images of 82 sources. The observations were made with a "snapshot" technique in which each source was observed in three 20-30-minute scans using an array of 12-16 antennas. The images have resolution 3-10 mas and dynamic range greater than 100:1. Later papers in the series will present the remaining λ-18 cm observations, the λ-6 cm observations, and the analysis and interpretation of the results.