Greenland Telescope (GLT) Project: "A Direct Confirmation of Black Hole with Submillimeter VLBI"

TL;DR

The Greenland Telescope project aims to directly image the shadow of the supermassive black hole in M87 using submillimeter VLBI, achieving unprecedented angular resolution and baseline coverage in the northern hemisphere.

Contribution

This paper reports the deployment and status of the Greenland Telescope, enhancing VLBI network capabilities for black hole imaging with high angular resolution.

Findings

Greenland station provides high-altitude, low-opacity conditions comparable to ALMA.

VLBI network achieves ~20 μas resolution at 350 GHz.

Baseline lengths over 9,000 km enable detailed black hole shadow imaging.

Abstract

The GLT project is deploying a new submillimeter (submm) VLBI station in Greenland. Our primary scientific goal is to image a shadow of the supermassive black hole (SMBH) of six billion solar masses in M87 at the center of the Virgo cluster of galaxies. The expected SMBH shadow size of 40-50 $\mu$as requires superbly high angular resolution, suggesting that the submm VLBI would be the only way to obtain the shadow image. The Summit station in Greenland enables us to establish baselines longer than 9,000 km with ALMA in Chile and SMA in Hawaii as well as providing a unique $u$--$v$ coverage for imaging M87. Our VLBI network will achieve a superior angular resolution of about 20 $\mu$as at 350 GHz, corresponding to $\sim2.5$ times of the Schwarzschild radius of the supermassive black hole in M87. We have been monitoring the atmospheric opacity at 230 GHz since August. 2011; we have confirmed the value on site during the winter season is comparable to the ALMA site thanks to high altitude of 3,200 m and low temperature of $-50\degr$C. We will report current status and future plan of the GLT project towards our expected first light on 2015--2016.