Compactness of Weak Radio Sources at High Frequencies

Abstract

We have obtained 8.4 GHz VLBA observations of a 31-GHz complete sample of ~100 sources between 10 and 100 mJy. The main goals of these observations are: to determine the angular size, radio spectra and identification for a weak sample of high frequency sources; to find the fraction of sources which have sufficiently compact emission for use as calibrators for VLBI observations; and for design considerations of the proposed DSN Array. We find that a large fraction of observed sources have VLBI detections. A majority of these sources have most of their emission in a compact <1 mas radio core, with remaining sources having steep radio spectra. The source list was provided from GBT observations to remove discrete sources in the CBI fields.