Emission Modeling in the EHT-ngEHT Age

TL;DR

This paper develops a new methodology for testing emission models in GRMHD simulations to interpret EHT images of black holes, incorporating novel plasma physics parametrizations and polarization signatures.

Contribution

It introduces a region-specific parametric modeling approach and explores signatures of plasma physics effects in EHT-like images, advancing emission modeling techniques.

Findings

Different viewing angles produce diverse image morphologies.

Signatures of plasma physics effects are identifiable in polarization maps.

A library of simulated images spans a wide range of observable features.

Abstract

This work proposes a methodology to test phenomenologically-motivated emission processes that account for the flux and polarization distribution and global structure of the 230 GHz sources imaged by the Event Horizon Telescope (EHT): Messier (M)87* and Sagittarius (Sgr) A*. We introduce to general relativistic magnetohydrodynamic (GRMHD) simulations some novel models to bridge the largely uncertain mechanisms by which high-energy particles in jet/accretion flow/black hole (JAB) system plasmas attain billion degree temperatures and emit synchrotron radiation. The "Observing" JAB Systems methodology then partitions the simulation to apply different parametric models to regions governed by different plasma physics -- an advance over methods where one parametrization is used over simulation regions spanning thousands of gravitational radii from the central supermassive black hole. We present several classes of viewing-angle dependent morphologies, and highlight signatures of piecewise modeling and positron effects -- including a MAD/SANE dichotomy in which polarized maps appear dominated by intrinsic polarization in the MAD case and by Faraday effects in the SANE case. The library of images thus produced spans a wide range of morphologies awaiting discovery by the groundbreaking EHT instrument and its yet more sensitive, higher resolution next-generation counterpart ngEHT.