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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-8430
DTSTART:20231005T203000Z
DTEND:20231005T213000Z
DTSTAMP:20260414T051815Z
LAST-MODIFIED:20230920T151630Z
LOCATION:4421 Sterling Hall
SUMMARY:On the Comparison of AGN with GRMHD Simulations: Sgr A* and M8
 7\, Astronomy Colloquium\, Richard Anantua\, University of Texas at Sa
 n Antonio
DESCRIPTION:With the advent of the sub-mm imaging of two distinct blac
 k hole shadows in 2019 and 2022 by the Event Horizon Telescope\, we ar
 e now in position to infer the physical properties of such systems usi
 ng phenomenological models. Models of magnetized plasma in the jet (or
  outflow)/accretion flow/black hole (JAB) system Sagittarius A* based 
 on turbulent heating and deviations from the equipartition of particle
  and magnetic energies are input into a High Accuracy Relativistic Mag
 netohydrodynamics (HARM) simulation. Spectra\, movies and light curves
  simulating hourly timescales show that these models aggregate into fo
 ur quasi-stationary types: 1.) thin\, asymmetric photon ring with best
  fit spectrum\; 2.) coronal boundary layer with thin photon ring and s
 teep spectrum\; 3.) thick photon ring with flat spectrum\; and 4.) ext
 ended outflow with low frequency spectral knee. For M87\, a self-simil
 ar\, stationary\, axisymmetric jet model based on a force-free flow in
  a HARM jet simulation is used to generate Stokes maps at Very Long Ba
 seline Array (VLBA\, 43 GHz) and Event Horizon Telescope (EHT\, 230 GH
 z) scales. The 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 be c
 onstant fractions of the local magnetic pressure. The cleanest observa
 tional signature in the Stokes maps is the vanishing of circular polar
 ization for increasing positron content. Positrons are also incorporat
 ed into the general relativistic ray tracer IPOLE to display positron 
 effects on general relativistic magnetohydrodynamic simulations\, show
 ing stark differences in polarization signatures between standard and 
 normal evolution (SANE) and magnetically arrested disk (MAD) accretion
  modes due to Faraday effects. The inclusion of electrons\, positrons 
 and protons in our radiative transfer pipeline thus provides a powerfu
 l probe of the composition of JAB systems
URL:https://www.physics.wisc.edu/events/?id=8430
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