First Very Long Baseline Interferometry Detections at 870μm

Abstract

The first very long baseline interferometry (VLBI) detections at 870$\hat{I}¼$m wavelength (345GHz frequency) are reported, achieving the highest diffraction-limited angular resolution yet obtained from the surface of the Earth, and the highest-frequency example of the VLBI technique to date. These include strong detections for multiple sources observed on inter-continental baselines between telescopes in Chile, Hawaii, and Spain, obtained during observations in October 2018. The longest-baseline detections approach 11G$\hat{I}»$ corresponding to an angular resolution, or fringe spacing, of 19$\hat{I}¼$as. The Allan deviation of the visibility phase at 870$\hat{I}¼$m is comparable to that at 1.3mm on the relevant integration time scales between 2 and 100s. The detections confirm that the sensitivity and signal chain stability of stations in the Event Horizon Telescope (EHT) array are suitable for VLBI observations at 870$\hat{I}¼$m. Operation at this short wavelength, combined with anticipated enhancements of the EHT, will lead to a unique high angular resolution instrument for black hole studies, capable of resolving the event horizons of supermassive black holes in both space and time.

Corresponding author: S. Doeleman