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Astronomy Colloquium - "Imaging and Beyond - Understanding Near-Horizon Physics Using Movies and Polarization Maps"

Speaker Richard Anantua, Harvard University
Date: 12/8/2020
Time: 3:45 p.m.
Event Contact: Rebecca Bare
217-265-8226
rsbare@illinois.edu
Sponsor: Department of Astronomy
Event Type: Seminar/Symposium
 

Recent observations of radiating magnetized plasma infalling and outflowing in the vicinity of supermassive black holes are linked to physical models via general relativistic magnetohydrodynamic simulations using a methodology called "Observing" Jet (or outflow)/Accretion flow/Black hole (JAB) Systems. For Sagittarius A* in our Galactic Center, movies simulating hourly timescales show that these models, deriving their energy from turbulent heating and magnetic fields, can be classified into at least four types: 1.) thin, asymmetric photon rings with best fit spectrum; 2.) outflow boundary layer with thin photon rings and steep spectrum; 3.) lensed thick disk emission with flat spectrum; and 4.) extended outflow with flat spectrum. For the giant elliptical galaxy M87, a force-free outflow in a HARM jet simulation and related self-similar, stationary, axisymmetric model are used to generate polarization maps at Very Long Baseline Array (43 GHz), Global mm-VLBI Array (86 GHz) and Event Horizon Telescope (230 GHz) scales. The M87 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. Polarized image maps and spectra are found to be sensitive to the positron effects of decreasing intrinsic circular polarization and increased Faraday conversion.

Topic: UIUC Astronomy Colloquium

Time: This is a recurring meeting Meet anytime

 

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