Electromagnetic Observables of Weakly Collisional Black Hole Accretion
Authors
Vedant Dhruv
Ben Prather
Mani Chandra
Abhishek V. Joshi
Charles F. Gammie
Abstract
The black holes in the Event Horizon Telescope sources Messier 87* and Sagittarius A* (SgrA*) are embedded in a hot, collisionless plasma that is fully described in kinetic theory yet is usually modeled as an ideal, magnetized fluid. In this Letter, we present results from a new set of weakly collisional fluid simulations in which leading order kinetic effects are modeled as viscosity and heat conduction. Consistent with earlier, lower-resolution studies, we find that overall flow dynamics remain very similar between ideal and non-ideal models. For the first time, we synthesize images and spectra of SgrA* from weakly collisional models -- assuming an isotropic, thermal population of electrons -- and find that these remain largely indistinguishable from ideal fluid predictions. However, most weakly collisional models exhibit lower light curve variability, with all magnetically dominated models showing a small but systematic decrease in variability.
