Deep learning inference with the Event Horizon Telescope III. Zingularity results from the 2017 observations and predictions for future array expansions

TL;DR

This paper uses advanced neural networks trained on synthetic EHT data to infer black hole parameters from 2017 observations and predicts how future array upgrades will improve these inferences.

Contribution

It introduces the Zingularity framework that achieves narrow parameter posteriors without being affected by data biases, and demonstrates the impact of future array enhancements on inference accuracy.

Findings

M87* has a spin between 0.5 and 0.94 with a retrograde MAD accretion flow.

Sgr A* has a high spin of 0.8-0.9 with a prograde accretion flow and weak jet emission.

Future array upgrades will reduce parameter inference errors by a factor of three.

Abstract

(abridged) In the first two papers of this publication series, we present a comprehensive library of synthetic EHT observations and used this library to train and validate Bayesian neural networks for the parameter inference of accreting supermassive black hole systems. The considered models are ray-traced GRMHD simulations of Sgr A* and M87*. In this work, we infer the best-fitting accretion and black hole parameters from 2017 EHT data and predict improvements that will come with future upgrades of the array. Compared to previous EHT analyses, we considered a substantially larger synthetic data library and the most complete set of information from the observational data. We made use of the Bayesian nature of the trained neural networks and apply bootstrapping of known systematics in the observational data to obtain parameter posteriors. Within a wide GRMHD parameter space, we find M87* to be best described by a spin between 0.5 and 0.94 with a retrograde MAD accretion flow and strong synchrotron emission from the jet. Sgr A* has a high spin of $\sim$ 0.8 $-$ 0.9 and a prograde accretion flow beyond the standard MAD/SANE models with a comparatively weak jet emission, seen at a $\sim$ 20$^\circ$ $-$ 40$^\circ$ inclination and $\sim$ 106$^\circ$ $-$ 137$^\circ$ position angle. While previous EHT analyses could rule out specific regions in the model parameter space considered here, we are able to obtain narrow parameter posteriors with our Zingularity framework without being impacted by the unknown foreground Faraday screens and data calibration biases. We further demonstrate that the AMT extension to the EHT will reduce parameter inference errors by a factor of three for non-Kerr models, enabling more robust tests of general relativity. It will be instructive to produce new GRMHD models with the inferred interpolated parameters to study their accretion rate plus jet power.