Abstract

Contributed Talk - Splinter NonThermalAccel   (MW-1250)

Probing anisotropic particle acceleration and limb brightening in Centaurus A's jet

Felix Glaser, Christian M. Fromm, Luca Ricci, Yosuke Mizuno, Matthias Kadler, Karl Mannheim, Michael Janssen
Institute for Theoretical Physics and Astrophysics, University of Würzburg, Emil-Hilb-Weg 31, 97074 Würzburg, Germany

The EHT observation of Centaurus A (CenA; Janssen et al., 2021) imaged the jet close to its launching site and found a pronounced limb-brightened morphology, i.e., most emission was concentrated along the presumed jet edges (limbs). We explored the physical origins of this phenomenon in Glaser et al. (2026b) employing general-relativistic magnetohydrodynamic (GRMHD) simulations of magnetically arrested accretion disks (MADs) and advanced radiative transfer calculations directly fitting the interferometric data. The most natural explanation is that the nonthermal electron distribution function is not isotropic, as commonly assumed, but must be anisotropic to fit the observed jet morphology. In our models, the emission along the magnetic field is enhanced and diminished perpendicular to it, which recreates the limb brightening in our simulations. We further derive predictions from our model for future space-VLBI observations, the most important being, that the nuclear disk and photon ring of CenA will be observable in the THz-regime in accordance with analytical estimates (Janssen et al., 2021). Based on our modeling, we find that future observations of CenA could prove the existence of magnetic flux tubes escaping the black hole, which is a major prediction of MAD simulations, imprinting distinct radiative signatures, especially, in the source variability.