2026ApJ..1000...29T

We explore the impact of “slow-light” radiative transfer-i.e., general relativistic radiative transfer calculations in which the simulated fluid evolves while light rays are propagating through it-in general relativistic magnetohydrodynamic models of the M87 jet. Because the plasma in the jet-launching region is accelerated to relativistic velocities, and because the jet in M87 is nearly aligned with the line of sight (offset by ∼17°), a slow-light treatment is important for accurate modeling of the observable structure. While fast-light images exhibit prominent helical or loop-shaped features in the jet-which we associate with narrow bundles of magnetic field lines-these features become stretched and smoothed-out in slow-light images. Our slow-light images instead exhibit a double-edged, cone-like morphology that is more consistent with observations of M87 than conventional fast-light images. We find that the radius at which the plasma transitions from subrelativistic to relativistic velocities is imprinted on slow-light images via a transition from loop-dominated at small distances from the black hole (BH) to edge-dominated at a larger distance, with the loop-edge transition occurring at larger distances for lower BH spins. The jet image dynamics also vary with BH spin, with low-spin models producing jets that exhibit substantial “wobbling,” while high-spin models produce jets that are straighter and more stable in time. The spin-dependent jet morphology and variability are revealed by slow-light imaging both because slow-light effects are enhanced as the plasma velocity becomes more relativistic and because the plasma acceleration is itself a strong function of the spin.