THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 98:1-32, 1995 May

     THE FIRST CALTECH-JODRELL BANK VLBI SURVEY. I. Lambda = 18 CENTIMETER
                          OBSERVATIONS OF 87 SOURCES

                      A. G. POLATIDIS AND P. N. WILKINSON
       University of Manchester, Nuffield Radio Astronomy Laboratories,
               Jodrell Bank, Macclesfield, Cheshire SK11 9DL, UK

                                      AND

  W. XU, A. C. S. READHEAD, T. J. PEARSON, G. B. TAYLOR, AND R. C. VERMEULEN
      Owens Valley Radio Observatory, California Institute of Technology,
                          105-24, Pasadena, CA 91125


                                   ABSTRACT

        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_6cm >= 0.7 Jy,
     declination delta_1950 >= 35 deg, and Galactic latitude |b^II| > 10
     deg.  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 lambda-18 and 6 cm
     of all 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 lambda-18 cm VLBI observations of 56 CJ1
     and 31 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 lambda-18 cm observations, the lambda-6 cm observations, and
     the analysis and interpretation of the results.

     Subject headings: quasars: general -- radio continuum: galaxies --
                       surveys -- techniques: interferometric