AAS 203rd Meeting, January 2004
Session 78 Quasars and QSOs
Poster, Wednesday, January 7, 2004, 9:20am-6:30pm, Grand Hall

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[78.13] VLBA observations of z > 4 radio-loud quasars

E. Momjian (NAIC), A. O. Petric (Columbia University), C. L. Carilli (NRAO)

We present high resolution (\leq 20~mas) VLBI observations of the 1.4 GHz radio continuum emission from three high-redshift quasars: J1053-0016 (z=4.29), 1235-0003 (z=4.69), and J0913+5919 (z=5.11), thereby doubling the number of z>4 radio-loud quasars that have been imaged at mas resolution. The observations were carried out with the Very Long Baseline Array (VLBA) of the NRAO. All three sources are unresolved in these observations, with source size limits of a few mas. In all cases the flux densities measured by the VLBA are within 10% of those measured with the VLA, implying that the sources are not highly variable on yearly timescales. We find no indication for multiple images that might be produced by strong gravitational lensing on scales from 20 mas (VLBA) to a few arcseconds (VLA), to dynamic range limits of ~100.

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.