AAS 204th Meeting, June 2004
Session 60 Quasars
Poster, Wednesday, June 2, 2004, 10:00am-7:00pm, Ballroom

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[60.14] Sensitive VLBI observations of the z=4.7 QSO BRI 1202-0725

E. Momjian (NAIC, Arecibo Observatory), C. L. Carilli (NRAO), A. O. Petric (U. Columbia)

We present sensitive phase-referenced VLBI results on the radio continuum emission from the z=4.7 double source BRI~1202--0725. The observations were carried out at 1425 MHz using the Very Long Baseline Array (VLBA), the phased Very Large Array (VLA), and the Green Bank Telescope (GBT).

BRI~1202--0725 was identified in the Automatic Plate Measuring survey (Irwin et al.~1991). Continuum at mm wavelengths, CO emission, and 1.4~GHz VLA continuum observations, reveal a double source, northern and southern, with an angular separation of 4~arcsec. Optical observations (Hu et al.~1996) show a point-like QSO coincident with the southern component of BRI~1202--0725.

Our sensitive VLBI images of BRI~1202--0725 at 0.25 \times 0.14~arcsec resolution, obtained by applying a gaussian taper on the UV data, show a continuum structure in each of its two components. The total flux densities of the northern and the southern components are 331.5 ±24.5 and 204.3 ±10~\muJy, respectively. Both components are over-resolved at the full resolution of the array. The highest angular resolution with at least 4\sigma detection is about ~100 mas. The continuum structures of the two components have intrinsic brightness temperatures on the order of 105~K.

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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