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Astron. Astrophys. 325, 511-515

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High resolution radio imaging of the extremely distant quasars 1251-407, 1351-018, 1354-174 and 1508+572

S. Frey1,2, L.I. Gurvits2,3, K.I. Kellermann4, R.T. Schilizzi2,5, and I.I.K. Pauliny-Toth6

1FÖMI Satellite Geodetic Observatory, P.O. Box 546, H-1373 Budapest, Hungary
2Joint Institute for VLBI in Europe, P.O. Box 2, 7990 AA Dwingeloo, The Netherlands
3Astro Space Center of P.N. Lebedev Physical Institute, Leninsky pr. 53, Moscow 117924, Russia
4National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22903-2475, USA
5Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands
6Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany

Received 28 May 1996 / Accepted 28 March 1997


We present results of first epoch high resolution imaging observations of four extremely distant quasars. The sample includes the only two radio-loud quasars at redshift z > 4 known to the date of observations, 1251-407 (z = 4.46) and 1508+572 (z = 4.30). The 5 GHz observations of 1251-407, 1351-018 (z = 3.71) and 1354-174 (z = 3.15) were made with the VLBA in January 1995. The source 1508+572 was observed with the EVN in May 1995. The milliarcsecond scale structures of these quasars are dominated by compact cores. The two z > 4 quasars are unresolved on the baselines observed. We show that the apparently less prominent milliarcsecond scale extended radio structures in high redshift quasars than in their low redshift counterparts may be explained by the difference in spectral indices of the cores and jets.

Key words: galaxies: active - radio continuum: galaxies - galaxies: quasars: general

Send offprint requests to: S. Frey, 1st address

© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 28, 1998