The Disc-Jet Symbiosis Emerges: Modeling the Emission of Sagittarius A* with Electron Thermodynamics

TL;DR

This paper presents advanced 3D GRMHD models that incorporate electron thermodynamics to accurately simulate Sagittarius A*'s emission, variability, and imaging, aligning with observational data and revealing the disc-jet structure.

Contribution

It introduces the first 3D, physically motivated models evolving electron thermodynamics in GRMHD simulations of Sagittarius A*'s emission.

Findings

Low frequency radio emission dominated by polar outflow

High frequency emission from inner accretion disc region

Clear photon ring visible at 230 GHz and 2 microns

Abstract

We calculate the radiative properties of Sagittarius A* -- spectral energy distribution, variability, and radio-infrared images -- using the first 3D, physically motivated black hole accretion models that directly evolve the electron thermodynamics in general relativistic MHD simulations. These models reproduce the coupled disc-jet structure for the emission favored by previous phenomenological analytic and numerical works. More specifically, we find that the low frequency radio emission is dominated by emission from a polar outflow while the emission above 100 GHz is dominated by the inner region of the accretion disc. The latter produces time variable near infrared (NIR) and X-ray emission, with frequent flaring events (including IR flares without corresponding X-ray flares and IR flares with weak X-ray flares). The photon ring is clearly visible at 230 GHz and 2 microns, which is encouraging for future horizon-scale observations. We also show that anisotropic electron thermal conduction along magnetic field lines has a negligible effect on the radiative properties of our model. We conclude by noting limitations of our current generation of first-principles models, particularly that the outflow is closer to adiabatic than isothermal and thus underpredicts the low frequency radio emission.