Context :

Aims : We investigate statistical and individual astrophysical properties of active galactic nuclei ( AGNs ) , such as parsec-scale flux density , core dominance , angular and linear sizes , maximum observed brightness temperatures of VLBI core components , spectral index distributions for core and jet components , and evolution of brightness temperature along the jets .
Furthermore , we statistically compare core flux densities and brightness temperature as well as jet spectral indices of \gamma -ray bright and weak sources .

Methods : We used 19 very long baseline interferometry ( VLBI ) observing sessions carried out simultaneously at 2.3 GHz and 8.6 GHz with the participation of 10 Very Long Baseline Array ( VLBA ) stations and up to 10 additional geodetic telescopes .
The observations span the period 1998–2003 .

Results : We present here single-epoch results from high-resolution radio observations of 370 AGNs .
Our VLBI images at 2.3 GHz and 8.6 GHz as well as Gaussian models are presented and analyzed .
At least one-fourth of the cores are completely unresolved on the longest baselines of the global VLBI observations .
The VLBI core components are partially opaque with the median value of spectral index of \alpha _ { \mathrm { core } } \sim 0.3 , while the jet features are usually optically thin \alpha _ { \mathrm { jet } } \sim - 0.7 .
The spectral index typically decreases along the jet ridge line owing to the spectral aging , with a median value of -0.05 mas ^ { -1 } .
Brightness temperatures are found to be affected by Doppler boosting and reach up to \sim 10 ^ { 13 } K with a median of \sim 2.5 \times 10 ^ { 11 } K at both frequencies .
The brightness temperature gradients along the jets typically follow a power law T _ { \mathrm { b } } \propto r ^ { -2.2 } at both frequencies .
We find that 147 sources ( 40 % ) positionally associated with \gamma -ray detections from the Fermi LAT Second Source Catalog have higher core flux densities and brightness temperatures , and are characterized by the less steep radio spectrum of the optically thin jet emission .

Conclusions :