A SEARCH FOR AN INCREASE IN THE ANGULAR S IZES OF COMPACT EXTRAGALACTIC RADIO-SOURCES CAUSED BY SCATTERING

The angular sizes of the compact cores of 9 extragalactic radio source s are estimated from VLBI images obtained by various authors from 1965 to 1994. The dependence of the angular sizes of the cores on frequenc y is constructed in order to determine the influence of scattering in neutral and ionized media located along the lines of sight to the radi o sources. The measured angular sizes do not follow a v(-2) dependence , and are better described by a v(-1) dependence. This apparently indi cates that the angular sizes for the compact cores are determined more by the internal structure of the source than by the scattering functi on. The dependence obtained is very close to that for the frequency de pendence of the antenna beam, indicating that these cores are unresolv ed to Earth-based VLBI observations.