The Pearson-Readhead survey of compact extragalactic radio sources from space. I. The images

We present images from a space-VLBI survey using the facilities of the VLBI Space Observatory Programme (VSOP), drawing our sample from the well-studi ed Pearson-Readhead survey of extragalactic radio sources. Our survey has t aken advantage of long space-VLBI baselines and large arrays of ground ante nnas, such as the Very Long Baseline Array and European VLBI Network, to ob tain high-resolution images of 27 active galactic nuclei and to measure the core brightness temperatures of these sources more accurately than is poss ible from the ground. A detailed analysis of the source properties is given in accompanying papers. We have also performed an extensive series of simu lations to investigate the errors in VSOP images caused by the relatively l arge holes in the (u, v)-plane when sources are observed near the orbit nor mal direction. We find that while the nominal dynamic range (defined as the ratio of map peak to off-source error) often exceeds 1000:1, the true dyna mic range (map peak to on-source error) is only about 30:1 for relatively c omplex core-jet sources. For sources dominated by a strong point source, th is value rises to approximately 100:1. We find the true dynamic range to be a relatively weak function of the difference in position angle (P.A.) betw een the jet P.A. and u-v coverage major axis P.A. For regions with low sign al-to-noise ratios, typically located down the jet away from the core, larg e errors can occur, causing spurious features in VSOP images that should be interpreted with caution.