THE RADIO STRUCTURE OF EXTENDED QUASARS .1. A VLBI SURVEY OF THE NUCLEAR-EMISSION

Snapshot VLBI observations at 5 GHz have been obtained for a subset of a sample of 30 quasars with extended radio structure. For all but one of the 12 sources involved, the objects were detected at one or more baselines. In 9 quasars, the visibility data revealed the presence of resolved core structure. Model-fitting indicated the nuclear emission of these sources to be quasi-linear and, in most cases, of core-jet type. Spearman rank correlations show that, for the total sample of 30 extended quasars, the projected radio size, the degree of jet curvature and the lobe arm length asymmetry are strongly correlated with the radio core luminosity, in the sense predicted by relativistic beaming models; they are uncorrelated with the relative core strength R, however. Follow-up observations of both pc-scale and overall radio morphologies of those quasars having resolved milliarcsec-scale structure are described in a companion paper

THE RADIO STRUCTURE OF EXTENDED QUASARS .2. THE RADIO-EMISSION ON PC-SCALES AND KPC-SCALES

VLBI and VLA observations of the nuclear and overall radio structures are presented for eight quasars possessing large double-lobed radio emission. On milli-arcsec scales, the nuclei of five sources show an asymmetric (core-jet) morphology, one has a symmetric appearance, one is unresolved and one is too weak to allow a reliable determination of its structure. Total intensity, polarization and spectral index maps of the associated kpc-scale emission were obtained for six of the eight quasars. The inner and outer radio jet emission generally are well aligned and pointing in the same direction; in one source, the pc- and kpc-scale jet are oppositely directed. Jet velocities close to the hot spots were estimated for several quasars from the intensity of their hot spot emission. The velocity estimates were relativistic in all cases (ranging from 0.5 to 0.9 c)

VLBI observations of a sample of 15 EGRET-detected AGNs at 5 GHz

We report VLBI observations of 15 EGRET-detected AGNs with European VLBI Network (EVN) at 5 GHz. All sources in the sample display core-jet structures