Statistical analysis of radio jets in quasars

We have performed a statistical analysis of published data for a VLBI surve y of a sample of compact extragalactic radio sources carried out in 1994 an d 1995 at 2.32 and 8.55 GHz. The aim of this survey was to investigate the effect of source radio structure on the accuracy of determining astrometric al coordinates. The radio images of 94 quasars with known redshifts are ana lyzed. Using the dependence of the angular size of the core components on r edshift, the deceleration parameter is estimated for a uniform, isotropic U niverse with zero cosmological constant (q(0) = 0.5 +/- 0.15). The observed brightness temperatures for the core components are confined to the interv al 10(12)-10(13) K; the upper boundary to the distribution is very sharp. T he distribution of spectral indices for various components in the radio ima ges and the distribution of relative component sizes at 2.32 and 8.55 GHz a re also analyzed. The magnetic-field strength near the core region is estim ated in the framework of a Blandford-Konigl relativistic-jet model (B great er than or equal to 0.1 G). The brightness temperatures of the jet componen ts vary with distance from the core according to a power law with index -2. 43. The relation between the total radio fluxes in the VLBI images and inte grated fluxes observed using the RATAN-600 radio telescope is discussed.