Images of magnetospheric reconnection-powered radiation around supermassive black holes

TL;DR

This paper presents the first 3D global general-relativistic particle-in-cell simulation of a supermassive black hole's magnetosphere, revealing dynamic features in the emitted radiation that could inform future high-resolution observations.

Contribution

It introduces a novel kinetic simulation approach to model black hole magnetospheres, moving beyond fluid-based hypotheses to include nonthermal particle acceleration.

Findings

Identification of a persistent equatorial current sheet.

Detection of variable ring radius and hot spots in simulated images.

Most flux lies inside the critical curve in the model.

Abstract

Accreting supermassive black holes can now be observed at the event-horizon scale at mm wavelengths. Current predictions for the image rely on hypotheses (fluid modeling, thermal electrons) which might not always hold in the vicinity of the black hole, so that a full kinetic treatment is in order. In this letter, we describe the first 3D global general-relativistic particle-in-cell simulation of a black-hole magnetosphere. The system displays a persistent equatorial current sheet. Synthetic images are computed by ray-tracing synchrotron emission from nonthermal particles accelerated in this current sheet by magnetic reconnection. We identify several time-dependent features of the image at moderate viewing angles: a variable radius of the ring, and hot spots moving along it. In this regime, our model predicts that most of the flux of the image lies inside the critical curve. These results could help understand future observations of black-hole magnetospheres at improved temporal and spatial resolution.