Abstract
The halo of the Milky Way provides a laboratory to study the properties of the shocked hot gas that is predicted by models of galaxy formation. There is observational evidence of energy injection into the halo from past activity in the nucleus of the Milky Way1,2,3,4; however, the origin of this energy (star formation or supermassive-black-hole activity) is uncertain, and the causal connection between nuclear structures and large-scale features has not been established unequivocally. Here we report soft-X-ray-emitting bubbles that extend approximately 14 kiloparsecs above and below the Galactic centre and include a structure in the southern sky analogous to the North Polar Spur. The sharp boundaries of these bubbles trace collisionless and non-radiative shocks, and corroborate the idea that the bubbles are not a remnant of a local supernova5 but part of a vast Galaxy-scale structure closely related to features seen in γ-rays6. Large energy injections from the Galactic centre7 are the most likely cause of both the γ-ray and X-ray bubbles. The latter have an estimated energy of around 1056 erg, which is sufficient to perturb the structure, energy content and chemical enrichment of the circumgalactic medium of the Milky Way.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on SpringerLink
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
The datasets analysed during this study are not yet publicly available. Their proprietary scientific exploitation rights were granted by the project funding agencies (Roscosmos and DLR) to two consortia led by MPE (Germany) and IKI (Russia), respectively. The SRG–eROSITA all-sky survey data will be released publicly after a minimum period of 2 years.
References
Su, M., Slatyer, T. R. & Finkbeiner, D. P. Giant gamma-ray bubbles from Fermi-LAT: active galactic nucleus activity or bipolar Galactic wind? Astrophys. J. 724, 1044–1082 (2010).
Ackermann, M. et al. The spectrum and morphology of the Fermi bubbles. Astrophys. J. 793, 64 (2014).
Heywood, I. et al. Inflation of 430-parsec bipolar radio bubbles in the Galactic centre by an energetic event. Nature 573, 235–237 (2019).
Ponti, G. et al. An X-ray chimney extending hundreds of parsecs above and below the Galactic centre. Nature 567, 347–350 (2019).
Egger, R. & Aschenbach, B. Interaction of the Loop I supershell with the local hot bubble. Astron. Astrophys. 294, L25–L28 (1995).
Sofue, Y. Bipolar hypershell Galactic center starburst model: further evidence from ROSAT data and new radio and X-ray simulations. Astrophys. J. 540, 224–235 (2000).
Kataoka, J. et al. X-ray and gamma-ray observations of the Fermi bubbles and NPS/Loop I structures. Galaxies 6, 27 (2018).
Merloni, A. et al. eROSITA science book: mapping the structure of the energetic Universe. Preprint at https://arxiv.org/abs/1209.3114 (2012).
Gaia Collaboration. Gaia data release 2. Summary of the contents and survey properties. Astron. Astrophys. 616, A1 (2018).
Eisenhardt, P. R. M. et al. The CatWISE preliminary catalog: motions from WISE and NEOWISE data. Astrophys. J. Suppl. Ser. 247, 69 (2020).
Berkhuijsen, E. M. A survey of the continuum radiation at 820 MHz between declinations -7° and +85°. A study of the Galactic radiation and the degree of polarization with special reference to the loops and spurs. Astron. Astrophys. 14, 359–386 (1971).
Zubovas, K., King, A. R. & Nayakshin, S. The Milky Way’s Fermi bubbles: echoes of the last quasar outburst? Mon. Not. R. Astron. Soc. 415, L21–L25 (2011).
Guo, F. & Mathews, W. G. The Fermi bubbles. I. Possible evidence for recent AGN jet activity in the galaxy. Astrophys. J. 756, 181 (2012).
Mou, G. et al. Fermi bubbles inflated by winds launched from the hot accretion flow in Sgr A*. Astrophys. J. 790, 109 (2014).
Zhang, R. & Guo, F. Simulating the Fermi bubbles as forward shocks driven by AGN jets. Astrophys. J. 894, 117 (2020).
Crocker, R. M. & Aharonian, F. Fermi bubbles: giant, multibillion-year-old reservoirs of Galactic center cosmic rays. Phys. Rev. Lett. 106, 101102 (2011).
Lacki, B. C. The Fermi bubbles as starburst wind termination shocks. Mon. Not. R. Astron. Soc. 444, L39–L43 (2014).
Crocker, R. M., Bicknell, G. V., Taylor, A. M. & Carretti, E. A unified model of the Fermi bubbles, microwave haze, and polarized radio lobes: reverse shocks in the Galactic center’s giant outflows. Astrophys. J. 808, 107 (2015).
Miller, M. J. & Bregman, J. N. The Interaction of the Fermi Bubbles with the Milky Way’s Hot Gas Halo. Astrophys. J. 829, 9 (2016).
Sofue, Y. Propagation of magnetohydrodynamic waves from the Galactic center. Origin of the 3-kpc arm and the North Polar Spur. Astron. Astrophys. 60, 327–336 (1977).
Lallement, R. et al. On the distance to the North Polar Spur and the local CO-H2 factor. Astron. Astrophys. 595, A131 (2016).
Bland-Hawthorn, J. & Cohen, M. The large-scale bipolar wind in the Galactic center. Astrophys. J. 582, 246–256 (2003).
Nakahira, S. et al. MAXI/SSC all-sky maps from 0.7 keV to 4 keV. Publ. Astron. Soc. Japan 72, 17 (2020).
Bland-Hawthorn, J. & Gerhard, O. The galaxy in context: structural, kinematic, and integrated properties. Annu. Rev. Astron. Astrophys. 54, 529–596 (2016).
Casandjian, J.-M. The Fermi-LAT model of interstellar emission for standard point source analysis. Preprint at https://arxiv.org/abs/1502.07210 (2015).
Carretti, E. et al. Giant magnetized outflows from the centre of the Milky Way. Nature 493, 66–69 (2013).
Böhringer, H. et al. A ROSAT HRI study of the interaction of the X-ray emitting gas and radio lobes of NGC 1275. Mon. Not. R. Astron. Soc. 264, L25–L28 (1993).
Kraft, R. et al. X-ray emission from the hot interstellar medium and southwest radio lobe of the nearby radio galaxy Centaurus A. Astrophys. J. 592, 129–146 (2003).
Churazov, E. et al. Asymmetric, arc minute scale structures around NGC 1275. Astron. Astrophys. 356, 788–794 (2000).
Fabian, A. C. et al. Chandra imaging of the complex X-ray core of the Perseus cluster. Mon. Not. R. Astron. Soc. 318, L65–L68 (2000).
Strickland, D. K. & Stevens, I. R. Starburst-driven galactic winds – I. Energetics and intrinsic X-ray emission. Mon. Not. R. Astron. Soc. 314, 511–545 (2000).
Rieke, G. H. et al. The nature of the nuclear sources in M82 and NGC 253. Astrophys. J. 238, 24–40 (1980).
Tumlinson, J., Peeples, M. S. & Werk, J. K. The circumgalactic medium. Annu. Rev. Astron. Astrophys. 55, 389–432 (2017).
Sanders, J. et al. Annotated version of the eROSITA first all-sky image. http://www.mpe.mpg.de/7461950/erass1-presskit (2020).
Selig, M., Vacca, V., Oppermann, N. & Enßlin, T. A. The denoised, deconvolved, and decomposed Fermi γ-ray sky. An application of the D3PO algorithm. Astron. Astrophys. 581, 126 (2015).
Predehl, M. et al. The eROSITA X-ray telescope on SRG. Astron. Astrophys. https://doi.org/10.1051/0004-6361/202039313 (2020).
Kataoka, J. et al. Suzaku observations of the diffuse X-ray emission across the Fermi bubbles’ edges. Astrophys. J. 779, 57 (2013).
Ursino, E., Galeazzi, M. & Liu, W. Studying the Interstellar medium and the inner region of NPS/LOOP 1 with shadow observations toward MBM36. Astrophys. J. 816, 33 (2016).
Sutherland, M. S. & Dopita, M. A. Cooling functions for low-density astrophysical plasmas. Astrophys. J. Suppl. Ser. 88, 253–327 (1993).
Acknowledgements
This work is based on data from eROSITA, the primary instrument aboard SRG, a joint Russian–German science mission supported by the Russian Space Agency (Roskosmos), in the interests of the Russian Academy of Sciences, represented by its Space Research Institute (IKI), and the Deutsches Zentrum für Luft- und Raumfahrt (DLR). The SRG spacecraft was built by Lavochkin Association (NPOL) and its subcontractors, and is operated by NPOL with support from IKI and the Max Planck Institute for Extraterrestrial Physics (MPE). The development and construction of the eROSITA X-ray instrument was led by MPE, with contributions from the Dr. Karl Remeis Observatory Bamberg and ECAP (FAU Erlangen-Nuernberg), the University of Hamburg Observatory, the Leibniz Institute for Astrophysics Potsdam (AIP), and the Institute for Astronomy and Astrophysics of the University of Tübingen, with the support of DLR and the Max Planck Society. The Argelander Institute for Astronomy of the University of Bonn and the Ludwig Maximilians Universität Munich also participated in the science preparation for eROSITA. The eROSITA data shown here were processed using the eSASS/NRTA software system developed by the German eROSITA consortium. We thank the entire eROSITA collaboration team, in Germany and Russia, who, over many years, have given fundamental contributions to the development of the mission, the instrument and the science exploitation of the eROSITA data. SRG–eROSITA data processing and calibration and data analyses were performed by a large number of collaboration members in both the German and Russian teams, who also discussed and approved the scientific results presented here. This research made use of Montage. It is funded by the National Science Foundation under grant number ACI-1440620, and was previously funded by NASA’s Earth Science Technology Office, Computation Technologies Project, under cooperative agreement number NCC5-626 between NASA and the California Institute of Technology. G.P. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 865637).
Author information
Authors and Affiliations
Contributions
H.B., M.F., C.M. and J.S.S. developed software to process the eROSITA data and processed the German proprietary data that resulted in the all-sky maps. E.C., M.G., I.K., and P.M. processed the Russian proprietary data. H.B., E.C., M.G., C.M. and J.S.S. performed the analysis that resulted in Fig. 1. V.D., I.K. and J.S.S. performed the image processing that resulted in Figs. 2, 3 and Extended Data Figs. 1, 2. The majority of the text was written by P.P., W.B., M.F., M.G., E.C., G.P., A.W.S., M.S., H.B. and V.D. V.D. and E.C. worked on Fig. 2; Fig. 3 was created by I.K. and V.D. Extended Data Fig. 1 was prepared by A.M. with the support of an MPE graphic design expert. K.N., A.M. and R.A.S. contributed to writing and editing the manuscript. The above-named authors all contributed to the discussion and interpretation of the results and their implications. The remaining co-authors made important contributions to SRG mission planning and operations, eROSITA data acquisition and analysis, and software development for SRG–eROSITA.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Peer review information Nature thanks Jun Kataoka and Roland Crocker for their contribution to the peer review of this work. Peer reviewer reports are available.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data figures and tables
Extended Data Fig. 1 Schematic of the eROSITA and Fermi bubbles.
Schematic of the geometry of the eROSITA bubbles (EBs; yellow) and Fermi bubbles (FBs; purple) with respect to the Galaxy and the Solar System. The approximate sizes of these structures, as derived from our analysis, are also marked (green and purple arrows).
Extended Data Fig. 2 Soft-X-ray data compared to a thick-shell model for the eROSITA bubbles.
Comparison between the thick-shell model (cyan line in Fig. 2) and eROSITA data (0.6–1.0-keV band) in a Lambert zenithal equal-area projection. The model is in red; the data are in cyan. The northern bubble is shown on the left (N); the southern bubble is shown on the right (S). The northern bubble is spherical, with an outer radius of 7 kpc and an inner radius of 5 kpc. It is slightly offset from the vertical above the Galactic centre. The southern shell is instead an ellipse, slightly elongated in the north–south direction (semi-major axis is 7 kpc; semi-minor axis 4.9 kpc).
Supplementary information
Rights and permissions
About this article
Cite this article
Predehl, P., Sunyaev, R.A., Becker, W. et al. Detection of large-scale X-ray bubbles in the Milky Way halo. Nature 588, 227–231 (2020). https://doi.org/10.1038/s41586-020-2979-0
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41586-020-2979-0
This article is cited by
-
Non-thermal outflows of the Milky Way traced by radio polarization and gamma-ray emission
Nature Astronomy (2024)
-
A magnetized Galactic halo from inner Galaxy outflows
Nature Astronomy (2024)
-
Simulation of asteroid deflection with a megajoule-class X-ray pulse
Nature Physics (2024)
-
The Fermi/eROSITA bubbles: a look into the nuclear outflow from the Milky Way
The Astronomy and Astrophysics Review (2024)
-
Bipolar outflows out to 10 kpc for massive galaxies at redshift z ≈ 1
Nature (2023)
