Revisited "cluster-Cluster" VLBI with future multi-beam low frequency radio interferometers

Abstract

We revisit the "Cluster-Cluster" or multi-view VLBI technique from the perspective of its synergy with the multi-beam features inherent in the Australian Square Kilometer Array Pathfinder (ASKAP) and its potential to improve the outcomes of VLBI observations with ASKAP. We include a list of candidate VLBI sites that already support or can be upgraded to support multiview VLBI located in Australia and overseas, and which have common visibility with ASKAP. The results of our previous cluster-cluster observations at 1.6 GHz demonstrated the advantages of this configuration to calibrate the ionospheric distortions responsible for the loss of positional accuracy at low frequencies, using multiple calibrators in a range between 1 to 6 degrees away from the target. Therefore, we conclude that joint observations of ASKAP with other multi-view sites using cluster-cluster techniques would improve the outcomes of the high spatial resolution component of ASKAP applied to astrometric projects, achieving higher precision for many more targets, and with lower detection thresholds. Also very wide-field VLBI mapping becomes a possibility. Looking to the future, this would contribute to the development of new techniques that are relevant for future high resolution observations with the SKA.