Orbital polarimetric tomography of a flare near the Sagittarius A* supermassive black hole
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1.
California Institute of Technology
Abstract
The interaction between the supermassive black hole at the centre of the Milky Way, Sagittarius A*, and its accretion disk occasionally produces high-energy flares seen in X-ray, infrared and radio. One proposed mechanism that produces flares is the formation of compact, bright regions that appear within the accretion disk and close to the event horizon. Understanding these flares provides a window into accretion processes. Although sophisticated simulations predict the formation of these flares, their structure has yet to be recovered by observations. Here we show a three-dimensional reconstruction of an emission flare recovered from Atacama Large Millimeter/Submillimeter Array light curves observed on 11 April 2017. Our recovery shows compact, bright regions at a distance of roughly six times the event horizon. Moreover, it suggests a clockwise rotation in a low-inclination orbital plane, consistent with prior studies by GRAVITY and the Event Horizon Telescope. To recover this emission structure, we solve an ill-posed tomography problem by integrating a neural three-dimensional representation with a gravitational model for black holes. Although the recovery is subject to, and sometimes sensitive to, the model assumptions, under physically motivated choices, our results are stable and our approach is successful on simulated data.
Copyright and License
© The Author(s) 2024. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Acknowledgement
We thank V. Ravi and B. Ripperda for fruitful discussions. This work was supported by National Science Foundation awards 1935980 and 2048237 and the Carver Mead New Adventures Fund. A.A.C. is supported by the Princeton Gravity Initiative. M.W.’s research is supported by the ERC advanced grant ‘M2FINDERS—Mapping Magnetic Fields with INterferometry Down to Event hoRizon Scales’ (grant no. 101018682).
Contributions
A.L. and K.L.B. identified and formulated the tomography problem and conceived and designed the experiments. A.L., K.L.B. and P.P.S. developed the neural representation-based tomography approach. A.A.C. and A.L. developed the polarimetric ray tracing. A.A.C formulated and implemented the geodesic computations. M.W. worked on data calibration. A.L. performed the tomographic reconstructions. All authors contributed to the analysis, interpretation, discussion and writing of the paper.
Data Availability
This paper makes use of the ALMA dataset ADS/JAO.ALMA#2016.1.01404.V, available through the ALMA data portal. Fully calibrated data and other materials are available from the corresponding author upon reasonable request.
Supplementary analysis of simulations, Figs. 1–9 and details on general relativistic ray tracing
Code Availability
The software packages used to analyse the data are available at the following sites: kgeo (https://github.com/achael/kgeo) and bhnerf (https://github.com/aviadlevis/bhnerf).
Conflict of Interest
The authors declare no competing interests.
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Additional details
- National Science Foundation
- AST-1935980
- National Science Foundation
- CCF-2048237
- California Institute of Technology
- Carver Mead New Adventure Fund
- Princeton University
- European Research Council
- 101018682
- Caltech groups
- Astronomy Department