Very high-resolution radio observations of HzRGs

We report on first results of an ongoing effort to image a small sample of high-redshift radio galaxies (HzRGs) with milliarcsecond (mas) resolution, using very-long-baseline interferometry (VLBI) techniques. Here, we present 1.7 and 5.0 GHz VLBA observations of B3 J2330+3927, a radio galaxy at z = 3.087. Those observations, combined with 8.4 GHz VLA-A observations, have helped us interpret the source radio morphology, and most of our results have already been published (Perez-Torres & De Breuck 2005). In particular, we pinpointed the core of the radio galaxy, and also detected both radio lobes, which have a very asymmetric flux density ratio, R > 11. Contrary to what is seen in other radio galaxies, it is the radio lobe furthest from the nucleus which is the brighest. Almost all of the Ly-alpha emission is seen between the nucleus and the furthest radio lobe, which is also unlike all other radio galaxies. The values of radio lobe distance ratio, and flux density ratio, as well as the fraction of core emission make of B3 J2330+3927 an extremely asymmetric source, and challenges unification models that explain the differences between quasars and radio galaxies as due to orientation effects. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)