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 favoured 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 μm, 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2017
- DOI:
- 10.1093/mnras/stx364
- arXiv:
- arXiv:1611.09365
- Bibcode:
- 2017MNRAS.467.3604R
- Keywords:
-
- accretion;
- accretion discs;
- black hole physics;
- MHD;
- relativistic processes;
- Galaxy: centre;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 16 pages, 12 figures, submitted to MNRAS