Optical Characteristics of the Astrometric Radio Sources
  A new list of physical characteristics of 3914 astrometric radio sources,
including all 717 ICRF-Ext.2 sources, observed during IVS and NRAO VCS sessions
have been compiled. The list includes source type, redshift and visual
magnitude (if available). In case of doubt detailed comment is provided. The
list of sources with their positions was taken from the Goddard VLBI
astrometric catalog with addition of two ICRF-Ext.2 sources. At this stage the
source characteristics were mainly taken from the NASA/IPAC Extragalactic
Database (NED). 667 sources from our list are included into the IERS list.
Comparison has shown a significant difference in characteristics for about half
of these 667 common sources. We compiled a list of frequently observed sources
without known physical characteristics for urgent optical identification and
spectrophotometric observations with large optical telescopes. This presented
list of physical characteristics can be used as a supplement material for the
ICRF-2, as well as a database for kinematic studies of the Universe and other
related works, including scheduling of dedicated IVS programs.
