Speaker
Description
With the advent of sub-mm imaging of black hole shadows by the Event Horizon Telescope starting in 2019 with M87*, we are now in a position to infer physical mechanisms powering systems such as M87 (including its relativistic jet) down to the horizon-scale using phenomenological models. First, a self-similar, stationary, axisymmetric jet model based on a force-free flow in a High Accuracy Relativistic Magnetohydrodynamics (HARM) jet simulation is used to generate Stokes maps at Very Long Baseline Array (VLBA, 43 GHz) and Event Horizon Telescope (EHT, 230 GHz) scales– varying 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 constant fractions of the local magnetic pressure. The cleanest observational signatures predicted are the vanishing of intrinsic circular polarization in V/I maps and in polarized spectra for positron-rich jets. Positrons are then incorporated into the general relativistic ray tracer IPOLE to display positron effects in HARM simulations within ~10 gravitational radii from the black hole. Models of magnetized plasma in the M87 jet/accretion flow/black hole (JAB) system based on turbulent heating and deviations from the equipartition of particle and magnetic energies reveal a stark dichotomy in polarization signatures between standard and normal evolution (SANE) and magnetically arrested disk (MAD) accretion modes due to positron-modulated Faraday effects. The inclusion of electrons, positrons and protons in our radiative transfer pipeline thus provides a powerful probe of the composition of JAB systems.
