Effect of asymmetry of the radio source distribution on the apparent
  proper motion kinematic analysis
  A new list of physical characteristics of 4261 astrometric radio sources,
including all 717 ICRF-Ext.2 sources has been compiled. Comparison of our data
of optical characteristics with the official International Earth Rotation and
Reference Systems Service (IERS) list showed significant discrepancies for
about half of 667 common sources. We also found that asymmetry in the radio
sources distribution between hemispheres could cause significant correlation
between the vector spherical harmonics, especially if the case of sparse
distribution of the sources with high redshift. We identified radio sources
having many-year observation history and lack redshift. This sources should be
urgently observed at large optical telescopes. The list of optical
characteristics created in this paper is recommended for use as a supplement
material for the next International Celestial Reference Frame (ICRF)
realization. It can be also effectively used for cosmological studies and
planning of observing programs both in radio and optics.
