Evaluation of New Submillimeter VLBI Sites for the Event Horizon Telescope

TL;DR

This study evaluates potential new sites for the Event Horizon Telescope to enhance imaging of supermassive black holes, using meteorological and radiative transfer data to identify locations with optimal atmospheric conditions.

Contribution

It provides a comprehensive analysis of over forty candidate sites for the EHT, identifying locations with suitable atmospheric transparency for high-frequency observations.

Findings

Approximately half of the new sites have 230 GHz opacity comparable to current sites.

At least seventeen new sites could support 345 GHz observations effectively.

New sites with favorable transmittance improve the EHT's imaging capabilities.

Abstract

The Event Horizon Telescope (EHT) is a very long baseline interferometer built to image supermassive black holes on event-horizon scales. In this paper, we investigate candidate sites for an expanded EHT array with improved imaging capabilities. We use historical meteorology and radiative transfer analysis to evaluate site performance. Most of the existing sites in the EHT array have median zenith opacity less than 0.2 at 230 GHz during the March/April observing season. Seven of the existing EHT sites have 345 GHz opacity less than 0.5 during observing months. Out of more than forty candidate new locations analyzed, approximately half have 230 GHz opacity comparable to the existing EHT sites, and at least seventeen of the candidate sites would be comparably good for 345 GHz observing. A group of new sites with favorable transmittance and geographic placement leads to greatly enhanced imaging and science on horizon scales.