Applications of the source-frequency phase-referencing technique for ngEHT observations

TL;DR

The paper discusses the implementation of the source-frequency phase-referencing technique with the ngEHT to improve calibration, coherence, and astrometry in mm-VLBI observations, enabling better weak source detection and high-precision measurements.

Contribution

It introduces the application of SFPR with simultaneous multi-frequency systems on ngEHT antennas, enhancing calibration and astrometry capabilities for future observations.

Findings

Enhanced phase coherence in ngEHT data

Feasibility of high-precision astrometry at sub-mm wavelengths

Potential for improved weak source detection

Abstract

The source-frequency phase-referencing (SFPR) technique has been demonstrated to have great advantages for mm-VLBI observations. By implementing simultaneous multi-frequency receiving systems on the next generation Event Horizon Telescope (ngEHT) antennas, it is feasible to carry out a frequency phase transfer (FPT) which could calibrate the non-dispersive propagation errors and significantly increase the phase coherence in the visibility data. Such increase offers an efficient approach for weak source or structure detection. SFPR also makes it possible for high precision astrometry, including the core-shift measurements up to sub-mm wavelengths for Sgr A* and M87* etc. We also briefly discuss the technical and scheduling considerations for future SFPR observations with the ngEHT.