Radio structure of the most distant radio-detected quasar at the 10-mas scale

Abstract

We present a high-resolution radio image of SDSS 0836+0054, identified recently as the most distant radio-detected quasar at a redshift of z= 5.82. The observation was carried out with 10 antennas of the European Very Long Baseline Interferometry (VLBI) Network, spread from Europe to China and South Africa, at 1.6-GHz frequency on 2002 June 8. The source was detected with a total flux density of 1.1 mJy, equal to its flux density measured in the Very Large Array (VLA) Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. We found no indication of multiple images produced by gravitational lensing. The radio structure of the quasar at ∼10-mas angular resolution appears somewhat resolved. It resembles the radio structure typical for lower-redshift radio-loud active galactic nuclei. We obtained so far the best astrometric position of the source with an accuracy better than 8 mas, limited mainly by the structural effects in the phase-reference calibrator source.