| Following on from the work of the late Seungyoup Chi (Chi et al. 2013, or see the daily image 28-06-2013), a new, ultra-sensitive wide-field VLBI survey, targeting the Hubble Deep Field North (HDF-N), has recently been conducted. It is one of the biggest VLBI projects ever undertaken by the EVN, involving some 699 different phase centres and acquiring (in the first instance) 72 hours of observing time. From the first epoch of data, eight new radio quiet AGN have been discovered, taking the total in the field to 20.
A new calibration technique was trialed on these data, termed Multi-Source Self-Calibration (MSSC). MSSC uses the combined response of many faint sources in the field, in order to acquire phase corrections. The technique allowed one more source in the field to be detected, permitted the detection of several others with uniform weighting, and greatly improves the dynamic range of all sources in the field.
This wide-field approach to phase calibration could be relevant to many other VLBI observations, in particular those that target faint sources and currently employ phase-referencing. The calibration technique makes the detection of sub-mJy sources routine, and permits us to move towards detecting microJy compact sources.
The full paper describing MSSC is now in press and can be found at: http://arxiv.org/abs/1601.04452
|ASTRON, University of Manchester and University of Groningen