Master Thesis defense by Nicolas K. V. Grunwald

Title: Impact of the Greenland Telescope relocation on future Event Horizon Telescope observations

Abstract:
Very Long Baseline Interferometry (VLBI) radio observations in the mm-regime allow for resolutions capable of resolving the shadow of the supermassive black hole in the center of Messier 87. The progression toward higher frequency observations allows for greater insight into jet-formation mechanics at horizon scales, as well as testing of Einstein's theory of General Relativity in the most extreme of gravitational environments. As the Event Horizon Telescope (EHT) approaches capabilities for 345 GHz observations, the Greenland Telescope (GLT) is proposed to be relocated from Thule to the Summit Camp, central Greenland 3.2 km above sea level, in an attempt to expand VLBI possibilities at the highest frequencies.

The aim of this M.Sc. thesis project is to explore what is gained by including GLT in the EHT network and what further advantages, in particular for image quality, can be achieved by relocating the telescope to the Summit Camp. I simulate 230 GHz and 345 GHz observations of an M87* model, using the simulation software, eht-imaging, and clean the data using the visibility imaging software DIFMAP, probing both the inclusion, as well as the relocation of GLT. I use existing atmospheric opacity data alongside a synthetic atmospheric transmission spectra generation tool to estimate the expected 230 GHz and 345 GHz receiver upgrade for the Greenland Telescope and a variety of technical documents as well as sensitivity estimators to estimate capabilities of the remaining EHT stations.

The proposed new GLT site, the Summit Camp, will ensure better year-round performance for the telescope. Estimated summer-season atmospheric transmissions are better than the old site's winter-season transmissions and significantly widen the limited use of the 345 GHz receiver, which improves sensitivity of simulated 345 GHz EHT campaigns slightly. Simulated EHT observation with GLT at Thule show that thermal noise is not a limiting factor in observing M87* through 345 GHz radiation, but the current GLT site may be limited in performing VLBI observations by atmospheric fluctuations. Recovered image quality is significantly bettered by the inclusion of GLT, but mostly unaltered by the relocation, due to similar uv-coverage.

This MSc thesis defense will take place virtually via zoom and can be joined via the following zoom link: https://ucph-ku.zoom.us/j/61848646914?pwd=L0xjSmF1c1kwNEc2dTRCMW9GbGpnZz09