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Fermi and eROSITA bubbles as relics of the past activity of the Galaxy’s central black hole

Abstract

The newly launched X-ray satellite, eROSITA, has recently revealed two gigantic bubbles extending to ~80° above and below the Galactic Centre. The morphology of these ‘eROSITA bubbles’ bears a remarkable resemblance to the Fermi bubbles previously discovered by the Fermi Gamma-ray Space Telescope and its counterpart, the microwave haze. The physical origin of these striking structures has been intensely debated; however, because of their symmetry about the Galactic Centre, they probably originate from some energetic outbursts from the Galactic Centre in the past. Here we propose a theoretical model in which the eROSITA bubbles, Fermi bubbles and the microwave haze could be simultaneously explained by a single event of jet activity from the central supermassive black hole a few million years ago. Using numerical simulations, we show that this model could successfully reproduce the morphology and multi-wavelength spectra of the observed bubbles and haze, which allows us to derive critical constraints on the energetics and timescales of the outburst. This study serves as an important step forward in our understanding of the past Galactic Centre activity of our own Galaxy and may bring valuable insights into the broader picture of supermassive-black-hole–galaxy co-evolution in the context of galaxy formation.

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Fig. 1: Simulated gas and CR properties.
Fig. 2: Mock all-sky maps centred at the GC.
Fig. 3: Gamma-ray and microwave profiles.
Fig. 4: X-ray surface brightness profiles.
Fig. 5: Broad-band spectrum for the Fermi bubbles.

Data availability

Source data are provided with this paper. Source data associated with Figs. 1 and 2 are available from the corresponding author upon reasonable request.

Code availability

The simulations were performed using the code FLASH, publicly available at https://flash.rochester.edu/site/flashcode/, with modifications described in refs. 13,15. The CR module is a proprietary software product funded by NASA and NSF and is not publicly available.

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Acknowledgements

H.-Y.K.Y. acknowledges support from the Yushan Scholar Program of the Ministry of Education of Taiwan and Ministry of Science and Technology of Taiwan (MOST 109-2112-M-007-037-MY3). M.R. acknowledges support from National Science Foundation Collaborative Research Grants AST-1715140 and AST-2009227 and National Aeronautics and Space Administration grants 80NSSC20K1541 and 80NSSC20K1583. E.G.Z. acknowledges support from National Science Foundation Collaborative Research Grant AST-2009323. The simulations are performed and analysed using computing facilities operated by the National Center for High-performance Computing and the Center for Informatics and Computation in Astronomy at National Tsing Hua University. FLASH was developed largely by the US Department of Energy-supported ASC/Alliances Center for Astrophysical Thermonuclear Flashes at University of Chicago. Data analysis presented in this paper was conducted with the publicly available yt visualization software48.

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H.-Y.K.Y. carried out the simulations and analyses and prepared the manuscript. M.R. participated in the interpretation of the simulation results and assisted in the preparation of the manuscript. E.G.Z. contributed to the discussions of particle acceleration and assisted in the preparation of the manuscript.

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Correspondence to H.-Y. Karen Yang.

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Nature Astronomy thanks Jun Kataoka and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Yang, HY.K., Ruszkowski, M. & Zweibel, E.G. Fermi and eROSITA bubbles as relics of the past activity of the Galaxy’s central black hole. Nat Astron 6, 584–591 (2022). https://doi.org/10.1038/s41550-022-01618-x

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