First Very Long Baseline Interferometry Detections at 870{\mu}m

TL;DR

This paper reports the first successful very long baseline interferometry detections at 870μm, achieving unprecedented angular resolution and demonstrating the feasibility of high-frequency VLBI for black hole imaging.

Contribution

It presents the first VLBI detections at 870μm, showing the potential for ultra-high-resolution observations of black holes with the EHT.

Findings

Achieved angular resolution of 19μas on intercontinental baselines.

Confirmed station sensitivity and stability at 870μm.

Demonstrated feasibility of high-frequency VLBI for event horizon imaging.

Abstract

The first very long baseline interferometry (VLBI) detections at 870$\mu$m wavelength (345$\,$GHz 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 11$\,$G$\lambda$ corresponding to an angular resolution, or fringe spacing, of 19$\mu$as. The Allan deviation of the visibility phase at 870$\mu$m is comparable to that at 1.3$\,$mm on the relevant integration time scales between 2 and 100$\,$s. 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$\mu$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.