The Event Horizon Telescope is an experiment that is being performed on a large and ever-increasing array of radio telescopes that span the Earth from Hawaii to Chile and from the South Pole to Arizona. When data will be taken with the full array, it will image the event horizon of the supermassive black hole at the center of our Galaxy, Sagittarius A*, and the black hole at the center of M87, with an unprecedented 10-microarcssecond resolution! This will allow us to take the first ever picture of a black hole at 1.3 and 0.85 mm wavelengths and look for the shadow that is a direct evidence for a black hole predicted by the theory of General Relativity. In addition to allowing us to test this theory of gravity in regimes that it has never been tested before, EHT will also enable us to study the process by which black holes accrete matter and grow in mass. Arizona is a member of the EHT collaboration with several members that work on large scale black hole simulations in GR, develop detectors for the new telescopes in the array, and run the Arizona Radio Observatory.
When the South Pole Telescope and ALMA join the Event Horizon Telescope array, it will have a interferometric coverage that can image the black hole environment from several thousand Schwarzschild radii down to the horizon scale.
In preparation for these observations, we are running extensive time-dependent simulations of the low-density, radiatively inefficient accretion flow for many possible configurations of the black hole spin, viewing geometries, magnetic field configurations, and thermodynamics of the electrons in the flow. Using El Gato’s capabilities, we are able to track, for the first time, the variability in the flux and the image of the black hole at 1.3 mm, which is crucial for interpreting the observations correctly. The lightcurves below show two examples of predicted variability over 60 hours of densely sampled observations.
By comparing different simulations that have clear signatures of the bright photon ring or the footprints of possible jets, we assess the feasibility of the General Relativity tests that we will perform with these observations.