Letter | Published:

Acceleration of petaelectronvolt protons in the Galactic Centre

Nature volume 531, pages 476479 (24 March 2016) | Download Citation

Abstract

Galactic cosmic rays reach energies of at least a few petaelectronvolts1 (of the order of 1015 electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators (‘PeVatrons’), but all proposed models of Galactic cosmic-ray accelerators encounter difficulties at exactly these energies2. Dozens of Galactic accelerators capable of accelerating particles to energies of tens of teraelectronvolts (of the order of 1013 electronvolts) were inferred from recent γ-ray observations3. However, none of the currently known accelerators—not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays—has shown the characteristic tracers of petaelectronvolt particles, namely, power-law spectra of γ-rays extending without a cut-off or a spectral break to tens of teraelectronvolts4. Here we report deep γ-ray observations with arcminute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of petaelectronvolt protons within the central 10 parsecs of the Galaxy. We propose that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outbursts5and an outflow from the Galactic Centre6. Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 106–107 years, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt Galactic cosmic rays.

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References

  1. 1.

    , , & in Astrophysics of Cosmic Rays (ed. ) 33–38 (North-Holland, 1990)

  2. 2.

    & Nonlinear theory of diffusive acceleration of particles by shock waves. Rep. Prog. Phys. 64, 429–481 (2001)

  3. 3.

    Evolution of ground-based gamma-ray astronomy from the early days to the Cherenkov Telescope Arrays. Astropart. Phys. 43, 19–43 (2013)

  4. 4.

    Gamma rays from supernova remnants. Astropart. Phys. 43, 71–80 (2013)

  5. 5.

    et al. Echoes of multiple outbursts of Sagittarius A* revealed by Chandra. Astron. Astrophys. 558, A32 (2013)

  6. 6.

    , & Giant gamma-ray bubbles from Fermi-LAT: active galactic nucleus activity or bipolar galactic wind? Astrophys. J. 724, 1044–1082 (2010)

  7. 7.

    et al. Discovery of very-high-energy γ-rays from the Galactic Centre ridge. Nature 439, 695–698 (2006)

  8. 8.

    , & Fermi-LAT observations of the Sagittarius B complex. Astron. Astrophys. 580, A90 (2015)

  9. 9.

    Very High Energy Cosmic Gamma Radiation: A Crucial Window on the Extreme Universe (World Scientific, 2004)

  10. 10.

    , & Cosmic-ray propagation and interactions in the Galaxy. Annu. Rev. Nucl. Part. Sci. 57, 285–327 (2007)

  11. 11.

    et al. Very high-energy gamma rays from the direction of Sagittarius A*. Astron. Astrophys. 425, L13–L17 (2004)

  12. 12.

    et al. TeV gamma-ray observations of the Galactic Center. Astrophys. J. 608, L97–L100 (2004)

  13. 13.

    et al. Detection of sub-TeV gamma rays from the Galactic center direction by CANGAROO-II. Astrophys. J. 606, L115–L118 (2004)

  14. 14.

    et al. Observation of gamma rays from the Galactic center with the MAGIC telescope. Astrophys. J. 638, L101–L104 (2006)

  15. 15.

    & High-energy gamma rays from the massive black hole in the Galactic center. Astrophys. J. 619, 306–313 (2005)

  16. 16.

    , & G359.95–0.04: pulsar candidate near Sgr A*. Mon. Not. R. Astron. Soc. 367, 937–944 (2006)

  17. 17.

    & Inverse Compton scenarios for the TeV gamma-ray emission of the Galactic centre. Astrophys. J. 657, 302–307 (2007)

  18. 18.

    , & Study of the gamma-ray spectrum from the Galactic Center in view of multi-TeV dark matter candidates. Phys. Rev. D 86, 083516 (2012)

  19. 19.

    et al. Spectrum and variability of the Galactic center VHE γ-ray source HESS J1745–290. Astron. Astrophys. 503, 817–825 (2009)

  20. 20.

    et al. Very-high energy observations of the Galactic center region by VERITAS in 2010–2012. Astrophys. J. 790, 149 (2014)

  21. 21.

    HESS Collaboration. Localising the VHE γ-ray source at the Galactic Centre. Mon. Not. R. Astron. Soc. 402, 1877–1882 (2010)

  22. 22.

    et al. γ-rays and the far-infrared-radio continuum correlation reveal a powerful Galactic Centre wind. Mon. Not. R. Astron. Soc. 411, L11–L15 (2011)

  23. 23.

    Nonthermal particles and photons in starburst regions and superbubbles. Astron. Astrophys. Rev. 22, 1–54 (2014)

  24. 24.

    , , & Cosmic ray acceleration and escape from supernova remnants. Mon. Not. R. Astron. Soc. 431, 415–429 (2013)

  25. 25.

    On the origin of galactic cosmic rays. New Astron. 27, 13–18 (2014)

  26. 26.

    & TeV emission from the Galactic center black hole plerion. Astrophys. J. 617, L123–L126 (2004)

  27. 27.

    , & The Galactic Center massive black hole and nuclear star cluster. Rev. Mod. Phys. 82, 3121–3195 (2010)

  28. 28.

    , , , & Acceleration of cosmic rays and gamma-ray emission from supernova remnants in the Galaxy. Mon. Not. R. Astron. Soc. 434, 2748–2760 (2013)

  29. 29.

    Cosmic ray origin: lessons from ultra-high-energy cosmic rays and the Galactic/extragalactic transition. Nucl. Phys. B 256–257 (Suppl.), 197–212 (2014)

  30. 30.

    , & Dense molecular clouds in the Galactic Center region. I. Observations and data. Astrophys. J. 120 (Suppl.), 1–39 (1999)

  31. 31.

    et al. Observations of the Crab Nebula with HESS. Astron. Astrophys. 457, 899–915 (2006)

  32. 32.

    & A high performance likelihood reconstruction of γ-rays for imaging atmospheric Cherenkov telescopes. Astropart. Phys. 32, 231–252 (2009)

  33. 33.

    , & Background modelling in very-high-energy γ-ray astronomy. Astron. Astrophys. 466, 1219–1229 (2007)

  34. 34.

    et al. Temporal and spectral gamma-ray properties of Mkn 421 above 250 GeV from CAT observations between 1996 and 2000. Astron. Astrophys. 374, 895–906 (2001)

  35. 35.

    , & Energy spectra of gamma-rays, electrons and neutrinos produced at proton-proton interactions in the very high energy regime. Phys. Rev. D 74, 034018 (2006); erratum 79, 039901 (2009)

  36. 36.

    et al. A large-scale CO survey of the Galactic center. Astrophys. J. 118 (Suppl.), 455–515 (1998)

  37. 37.

    et al. Spectral imaging of the Central Molecular Zone in multiple 3-mm molecular lines. Mon. Not. R. Astron. Soc. 419, 2961–2986 (2012)

  38. 38.

    , & Spatial distribution of interstellar gas in the innermost 3 kpc of our Galaxy. Astron. Astrophys. 467, 611–627 (2007)

  39. 39.

    , , , & A lower limit of 50 microgauss for the magnetic field near the Galactic Centre. Nature 463, 65–67 (2010)

  40. 40.

    , & On the detectability of high-energy galactic neutrino sources. Astropart. Phys. 34, 778–783 (2011)

  41. 41.

    & XMM-Newton observations of the Galactic Centre region – I. The distribution of low-luminosity X-ray sources. Mon. Not. R. Astron. Soc. 428, 3462–3477 (2013)

  42. 42.

    , & Obtaining cosmic-ray propagation parameters from diffuse very high energy gamma-ray emission from the galactic center ridge. Astrophys. J. 656, 841–846 (2007)

  43. 43.

    et al. Interacting cosmic rays with molecular clouds: a bremsstrahlung origin of diffuse high energy emission from the inner 2° × 1° of the Galactic center. Astrophys. J. 762, 33 (2013)

  44. 44.

    Supernova remnants: the X-ray perspective. Astron. Astrophys. Rev. 20, 49 (2012)

  45. 45.

    Turbulent amplification of magnetic field and diffusive shock acceleration of cosmic rays. Mon. Not. R. Astron. Soc. 353, 550–558 (2004)

  46. 46.

    et al. The origin of diffuse X-ray and γ-ray emission from the Galactic center region: cosmic ray particles. Astrophys. J. 656, 847–869 (2007)

  47. 47.

    & Propagation of cosmic-ray nucleons in the Galaxy. Astrophys. J. 509, 212–228 (1998)

Download references

Acknowledgements

The support of the Namibian authorities and of the University of Namibia in facilitating the construction and operation of HESS is gratefully acknowledged, as is the support by the German Ministry for Education and Research (BMBF), the Max Planck Society, the German Research Foundation (DFG), the French Ministry for Research, the CNRS-IN2P3 and the Astroparticle Interdisciplinary Programme of the CNRS, the UK Science and Technology Facilities Council (STFC), the IPNP of the Charles University, the Czech Science Foundation, the Polish Ministry of Science and Higher Education, the South African Department of Science and Technology and National Research Foundation, and the University of Namibia. We thank the technical support staff in Berlin, Durham, Hamburg, Heidelberg, Palaiseau, Paris, Saclay and Namibia for the construction and operation of the equipment. R.C.G.C. is funded by an EU FP7 Marie Curie grant (PIEF-GA-2012-332350), J. Conrad is a Wallenberg Academy Fellow, and F.R. is a Heisenberg Fellow (DFG).

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  1. Universität Hamburg, Institut für, Luruper Chaussee 149 D 22761, Hamburg, Germany

    • A. Abramowski
    • , M. V. Fernandes
    • , G. Heinzelmann
    • , D. Horns
    • , M. A. Kastendieck
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    • , F. Spies
    •  & M. Tluczykont
  2. Max-Planck-Institut für Kernphysik, PO Box 103980, D 69029, Heidelberg, Germany

    • F. Aharonian
    • , F. Ait Benkhali
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    •  & A. M. Taylor
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    • , A. G. Akhperjanian
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  6. Institut für Physik, Humboldt-Universität zu Berlin, Newtonstrasse 15 D 12489, Berlin, Germany

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    F.A., S.G., E.M. and A.V. analysed and interpreted the data, and prepared the manuscript. The whole HESS collaboration contributed to the publication, with involvement at various stages ranging from the design, construction and operation of the instrument, to the development and maintenance of all software for data handling, data reduction and data analysis. All authors reviewed, discussed and commented on the present results and on the manuscript.

    Competing interests

    The author declare no competing financial interests.

    Corresponding author

    Correspondence to HESS Collaboration.

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