Event Calendar

Tuesday, March 30, 2021

Tue, Mar 30, 2021

Richard Anantua, Center for Astrophysics at Harvard and Smithsonian: "A Glimpse into Horizon-Scale Physics by 'Observing' Movies and Polarization"

Recent radio observations of infalling and outflowing plasma radiating in the vicinity of supermassive black holes are linked to simple phenomenological models via general relativistic magnetohydrodynamic simulations using a methodology called "Observing" Jet (or outflow)/Accretion flow/Black hole (JAB) Simulations.

For Sagittarius A* in our Galactic Center, 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 observed collimation and magnetic substructure, while serving as the basis for a self-similar, stationary, axisymmetric force-free flow model used to generate Stokes 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 are found to be sensitive to the positron effects of decreasing intrinsic circular polarization and increased Faraday conversion.