Synthetic gravitational lens image of the Sagittarius A${}^*$ black hole with a thin disk model

TL;DR

This paper generates and compares synthetic images of Sagittarius A* using a simple accretion disk model with actual Event Horizon Telescope data, suggesting an edge-on disk configuration based on image resemblance.

Contribution

It introduces a new simulation approach for Sgr A* images using ray tracing and geodesic deviation, exploring different disk orientations and comparing with EHT data.

Findings

Best synthetic image resembles April 6 EHT data

Edge-on disk configuration is supported by image comparison

Simulation method accounts for relativistic effects

Abstract

The images of Sagittarius A${}^*$ published by the Event Horizon Telescope (ETH) Collaboration in 2022 present features that were associated with an emission ring consistent with what is expected from an accretion disc surrounding the supermassive black hole at the center of our Galaxy. Here, we generate images of Sgr~A${}^*$ across different configurations of a simple accretion disc model that became successful, in our previous work, in reproducing the main features observed in M87*. Their best image, here reproduced in Fig. 1, suggests a geometric configuration of an inclined disk with three bright regions; which we have considered as our first configuration. Since we were not convinced with the results of this first configuration, we also explore in detail the case of nearly edge-on orientations which are a priori the expected geometry for a relaxed disc, as seen from the plane of the galaxy. We have produced simulated images using an efficient ray tracing and geodesic deviation methodology that allows to account for deformation, relativistic and magnification effects. We compare our synthetic images with the EHT images reconstructed with data from April 6 and 7 of 2017. We found that, although the EHT Collaboration seems to discard the image from April 6, our best suggested image resembles the output from the {\sc Themis} pipeline for April 6; which for us gives support for the edge-on configuration.