Monday, September 28, 2026 at 3:30 pm

Sasha Tchehkovskoy

Sasha Tchekhovskoy, CIERA @ Northwestern

"From Spherical Cows to Relativistic Jets: 3D GRMHD Simulations of Galactic Centers "

Abstract:

Accreting black hole systems can produce large-scale relativistic collimated outflows, or jets, that emit across the entire electromagnetic spectrum. However, how these jets form, propagate, interact with the ambient medium, and radiate remain open questions. I will present recent results from 3D general relativistic magnetohydrodynamic (GRMHD) simulations utilizing a "spherical cow" model for an accreting black hole at the center of a galaxy: a black hole immersed in a uniform, magnetized, rotating ambient gas. This seemingly simple setup yields rich dynamics, including the launching, propagation, and destruction of relativistic jets. We find that the majority of the gas entering the black hole's sphere of influence is ultimately expelled. In systems with powerful jets, the outflow mass rate scales with radius as a power-law with a universal radial slope (s = 0.66 ± 0.03) that is remarkably independent of the ambient medium's temperature, magnetization, and rotation. In contrast, when jets are weaker, the disk wind launches further out and exhibits a steeper slope (s = 0.87 ± 0.05), yet this still results in approximately the same overall fraction of ejected gas. I will conclude by discussing the broader theoretical and observational consequences of these findings for our understanding of black hole feedback.

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