Abstract:
I present new 1.6 GHz VLBI observations of sample of 43 radio sources in the Southern
celestial Hemisphere. My goals were firstly to establish the suitability of the 43 sources
as calibrators for 1.6 GHz VLBI observations, and secondly to determine, based on some
selected sources from the sample, how the properties of the sources seen at 8.4 GHz are
related to those seen at 1.6 GHz. I used seven telescopes; ASKAP, ATCA, Ceduna,
Hobart, Mopra and Parkes from Australia, and HartRAO from South Africa.
By evaluating the sources radial extents, flux density of the central components of the
sources and their brightness, I classified the sources into very good, good, intermediate
and bad calibrators. Among the 43 sources, I found that 38 sources fell into the good
or very good calibrator classes. Among 35 of our sources, which are known to be good
calibrators at 8.4 GHz, I found that 32 sources fell into the good or very good calibrator
classes. Of the basis of my sample therefore, I can say that 91 percent of the good
calibrators at 8.4 GHz are also safe to use at 1.6 GHz.
