A Glimpse into Horizon-Scale Physics by Observing Movies and Polarization Maps

Recent observations of radio emission from inflowing and outflowing plasma in the vicinity of supermassive black holes are linked to simple phenomenological models via general relativistic magnetohydrodynamic simulations in a methodology called “Observing” Jet/Accretion flow/Black hole (JAB) Systems. For Sagittarius A* in our Galactic Center, intensity map movies simulating hourly timescales show that these models can be classified into at least four types: 1.) thin, asymmetric photon ring with best fit spectrum; 2.) coronal boundary layer with thin photon ring and steep spectrum; 3.) thick photon torus with flat spectrum; and 4.) extended outflow with flat spectrum. For M87, a HARM jet simulation is used to replicate the observed collimation and magnetic substructure, while serving as the basis for a self-similar, stationary, axisymmetric force-free outflow model used to generate polarization maps at Global mm-VLBI Array (86 GHz) and Event Horizon Telescope (230 GHz) scales. This model varies plasma content from ionic (e-p) to pair (e-e+). Emission at the observed frequency is assumed to be synchrotron radiation from electrons and positrons, whose pressure is set to relate to the local magnetic pressure through parametric prescriptions. Polarization maps and spectra are found to be observationally distinguishable through positron effects such as decreasing intrinsic circular polarization and increased Faraday conversion.

Host: Guido Mueller