SIMBAD references

A revised sample of the 2 cm Very Long Baseline Array (VLBA) survey is studied to test the isotropic distribution of radio sources on the sky and their uniform distribution in space. The sample is complete to flux-density limits of 1.5Jy for positive declinations and 2 Jy for 0°>δ>-20°. At present the sample contains 122 flat-spectrum AGNs (99 confirmed members and 23 candidates). The application of the two-dimensional Kolmogorov-Smirnov (K-S) test shows that there is no significant deviation from a uniform distribution in the sky, while the V/V_max test shows that the space distribution of active nuclei is not uniform at high confidence level (99.9 %). There is a significant positive evolution of flat-spectrum quasars at low-redshifts (z<0.5) and negative evolution at redshifts z>1.7 with space density decline up to z∼2.5. This implies that the powerful jets were more populous at redshifts between 0.5 and 1.7.