The disc-jet symbiosis emerges: modelling the emission of Sagittarius A* with electron thermodynamics

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.

Variability in GRMHD Simulations of Sgr : Implications for EHT Closure Phase Observations

“…In the first model, we assume a constant electron-to-ion temperature ratio (which is different than the ratio for the disk region) and, in the second, a constant electron temperature. These models reproduce a disk/funnel structure that is similar to the results discussed in Ressler et al (2017), who use a more detailed treatment developed to model particle heating in the solar wind (Howes 2010(Howes , 2011.…”

Evolving non-thermal electrons in simulations of black hole accretion

“…Recent work (Ressler et al 2015;Sadowski et al 2017;Ressler et al 2017) has extended single-fluid GRMHD simulations by introducing methods for self-consistent evolution of separate ion and electron populations. Ressler et al (2015Ressler et al ( , 2017) evolve a single-temperature non-radiative accretion flow and then evolve viscously heated electrons during a separate post-processing step.…”

Modeling Polarized Emission from Black Hole Jets: Application to M87 Core Jet

“…Inspired by early models for radio cores in quasars [1] and the Solar corona plasma models [19,29,30], we have developed a simple parametric description for electron thermodynamics in the simulation of accretion flows. In combination with radiative transfer model, this finally makes our numerical simulations of accretion flows resemble observations of underluminous accreting black holes [13,14,16,18,31].…”

“…Until recently, the least understood part of these models was a proper treatment of radiating electrons. Finally, however, this issue has been addressed [13][14][15][16][17][18][19]. With new and more detailed observations, we are beginning to directly compare the numerical simulations of accretion flows to real astronomical systems such as Galactic center Sgr A* and the core of M87 galaxy [20].…”