The major science driver for the AMT is its participation in the EHT network to image black holes. Their defining feature is the event horizon, the surface that even light cannot escape and where time and space exchange their nature. Up to very recently, we had never actually seen a black hole. The Event Horizon Telescope (EHT) provides us with the highest image resolution in astronomy. This allowed us to make the first ever image of the supermassive black hole in M87, clearly revealing the shadow cast by its event horizon. The observations, confirm one of the basic fundamental predictions of GR. Detailed supercomputer simulations of gas and light surrounding a black hole - and alternatives thereof - make it possible to use that image for tests of the theory of gravity in its most extreme limit, and helps to constrain models for jet formation and energy extraction from black holes. More tests of GR will be possible in the coming years, and the EHT consortium will now attempt to imaging the supermassive black hole Sgr A* in our own galaxy. Because of the temporal variability in Sgr A*, this requires regular observations and even more telescopes to join the network.
Here the AMT will provide the missing link in the existing network, and the case for the need for the AMT can be summarized as follows:
Baselines:. The number of connections increases almost quadratically with the number of telescopes: a new telescope placed on the Gamsberg mountain in Namibia will hence increase the number of baselines, and hence improve the image quality by a critical margin. Location: The AMT on the Gamsberg location provides new and essential connections to major nodes across the globe and provides the longest and least disturbed view of the black hole in Sgr A* and hence allowing for detailed studies of the temporal behaviour of the emission. Redundancy: Although the AMT can never replace facilities like ALMA in terms of collecting area, it does show that a single and dedicated mm-radio telescope in Southern Africa can provide the required redundancy.
Observing as part of the EHT will occupy up to 20% of the AMT’s time. Given the location of the other mm-wave telescopes in the network, the EHT makes its observations in March/April, as this is the time of the year when the precipitable water vapour (PWV) is lowest for most of the observing sites. This leaves some 48 weeks of the year when the AMT will be able to do other science, unrelated to its EHT work.
During this time, which includes the June-August months, the driest at Mount Gamsberg, the AMT science team plan to conduct a number of observing projects, which make use of the fact that the AMT is the only mm-wave radio telescope on the African Continent. These following single-dish science goals are identified:
• A survey of the sky visible from Gamsberg at 100 and 300 GHz;
• Continuum emission from the Milky Way at 100 and 300 GHz
• The inner parts of rotation curves of spiral galaxies to map the dark matter
• Monitoring of Active Galactic Nuclei
• Wide-field spectroscopic mapping
• The Sunyaev-Zel’dovich (SZ) in low-redshift galaxy clusters
In the PDR baseline design the AMT will use the decommissioned SEST telescope which will be refurbished in close collaboration with IRAM, a NOEMA front-end populated with a 1.3mm and 3mm recievers, a dedicated back end network which includes a VLBI and single-dish analogue processors, digitisers, recorders, and VLBI and single-dish control computers. The AMT will have a dedicated database which provides the science and engineering data to all the users. The site will be developed as the Gamsberg Observing Facility (GOF) complete with a solar panel farm, equipment- and control rooms, and observer quarters.