Bayesian Accretion Modeling: Axisymmetric Equatorial Emission in the Kerr Spacetime

Abstract The Event Horizon Telescope (EHT) has produced images of two supermassive black holes, Messier 87* (M 87*) and Sagittarius A* (Sgr A*). EHT collaboration used these to indirectly constrain hole parameters by calibrating measurements the sky-plane emission morphology general relativistic magnetohydrodynamic (GRMHD) simulations. Here, we develop a model for directly constraining mass, spin, inclination through signatures lensing, redshift, frame dragging, while simultaneously marginalizing over unknown accretion properties. By assuming optically thin, axisymmetric, equatorial near hole, our gains orders magnitude in speed similar approaches that require radiative transfer. Using 2017 M baseline coverage, use fits itself show data are insufficient demonstrate existence photon ring. We then survey time-averaged GRMHD simulations fitting EHT-like data, find is best-suited magnetically arrested disks, which favored class both Sgr A*. For simulations, best-fit within ?10% true mass ?10° inclination. With coverage 1% fractional uncertainty on amplitudes, spin unconstrained. Accurate inference axis position angle depends strongly electron temperature. Our results promise spacetimes with interferometric but they also nearly identical permit large differences properties, highlighting degeneracies between plasma spacetime, and, most crucially, geometry when studying lensed flow at single frequency.