A global 86-GHz VLBI survey of compact radio sources

Abstract

We present results from a large 86 GHz global very long baseline interferometry (VLBI) survey of compact radio sources. The main goal of the survey is to increase by factors of 3-5 the total number of objects accessible for future 3 mm VLBI imaging. The survey observations reach a baseline sensitivity of 0.1 Jy and an image sensitivity of better than 10 mJy beam–1. A total of 127 compact radio sources have been observed. The observations have yielded images for 109 sources, extending the database of the sources imaged at 86 GHz with VLBI observation by a factor of 5, and only six sources have not been detected. The remaining 12 objects have been detected but could not be imaged due to insufficient closure phase information. Radio galaxies are less compact than quasars and BL Lac objects on the sub-milliarcsecond scale. The flux densities and sizes of the core and jet components of all imaged sources have been estimated using Gaussian model fitting. From these measurements, brightness temperatures have been calculated, taking into account the resolution limits of the data. The cores of 70% of the imaged sources are resolved. The core brightness temperatures of the sources peak at ~1011 K and only 1% have brightness temperatures higher than 1012 K. The cores of intraday variable (IDV) sources are smaller in angular size than those of non-IDV sources, and so yield higher brightness temperatures.