Letter | Published:

An almost head-on collision as the origin of two off-centre rings in the Andromeda galaxy

Nature volume 443, pages 832834 (19 October 2006) | Download Citation

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Abstract

The unusual morphology of the Andromeda galaxy (Messier 31, the closest spiral galaxy to the Milky Way) has long been an enigma. Although regarded for decades as showing little evidence of a violent history, M31 has a well-known1,2,3,4,5,6,7 outer ring of star formation at a radius of ten kiloparsecs whose centre is offset from the galaxy nucleus. In addition, the outer galaxy disk is warped, as seen at both optical8 and radio9 wavelengths. The halo contains numerous loops and ripples. Here we report the presence of a second, inner dust ring with projected dimensions of 1.5 × 1 kiloparsecs and offset by about half a kiloparsec from the centre of the galaxy (based upon an analysis of previously-obtained data10). The two rings appear to be density waves propagating in the disk. Numerical simulations indicate that both rings result from a companion galaxy plunging through the centre of the disk of M31. The most likely interloper is M32. Head-on collisions between galaxies are rare, but it appears nonetheless that one took place 210 million years ago in our Local Group of galaxies.

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References

  1. 1.

    & A high resolution hydrogen line survey of Messier 31. I. Observations and data reduction. Astron. Astrophys. Suppl. 55, 179–251 (1984)

  2. 2.

    , , & A complete CO survey of M31. I. Distribution and kinematics. Astrophys. J. 418, 730–742 (1993)

  3. 3.

    Nieten, Ch. et al. Molecular gas in the Andromeda galaxy. Astron. Astrophys. 453, 459–475 (2006)

  4. 4.

    et al. Cold dust in the Andromeda Galaxy mapped by ISO. Astron. Astrophys. 338, L33–L36 (1998)

  5. 5.

    et al. Spitzer MIPS Infrared Imaging of M31: Further evidence for a spiral-ring composite structure. Astrophys. J. Lett. 638, L87–L92 (2006)

  6. 6.

    , & A deep λ20 cm radio continuum survey of M 31. Astron. Astrophys. 329–336 (1998)

  7. 7.

    et al. A survey of H II regions in M31. Astron. Astrophys. 439–461 (1978)

  8. 8.

    et al. A giant stream of metal-rich stars in the halo of the galaxy M31. Nature 412, 49–51 (2001)

  9. 9.

    The distribution and kinematics of neutral gas in M31. Astrophys. J. 372, 54–66 (1991)

  10. 10.

    et al. Dusty waves on a starry sea: the mid-infrared view of M31. Astrophys. J. Lett. (in the press); preprint at 〈〉 (2006)

  11. 11.

    et al. The Infrared Array Camera (IRAC) for the Spitzer Space Telescope. Astrophys. J. Suppl. 154, 10–17 (2004)

  12. 12.

    & Distance to M31 with the Hubble Space Telescope and HIPPARCOS red clump stars. Astrophys. J. Lett. 503, L131–L134 (1998)

  13. 13.

    Evolution of Stars and Galaxies 56–68 (Harvard Univ. Press, Cambridge, 1963)

  14. 14.

    , & Ionized gas in the center of M31. Astrophys. J. 290, 136–139 (1985)

  15. 15.

    , , & in The Promise of the Herschel Space Observatory (eds Pilbratt, G. L. et al.) 519–521 (ESA-SP-460, European Space Agency, Noordwijk, 2001)

  16. 16.

    et al. The morphology of the ionized gas in M31’s bulge. Astron. J. 95, 438–444 (1988)

  17. 17.

    & Collisional ring galaxies. Fundamentals Cosmic Phys. 16, 111–220 (1996)

  18. 18.

    The catalog of southern ringed galaxies. Astrophys. J. Suppl. 96, 39–116 (1995)

  19. 19.

    et al. The gravitational torque of bars in optically unbarred and barred galaxies. Astron. Astrophys. 375, 761–769 (2001)

  20. 20.

    et al. Unveiling the boxy bulge and bar of the Andromeda Spiral Galaxy. Astrophys. J. Lett. (submitted).

  21. 21.

    & Formation of polar ring galaxies. Astron. Astrophys. 401, 817–833 (2003)

  22. 22.

    & The Interstellar Medium of M32. Astrophys. J. 557, 671–680 (2001)

  23. 23.

    , & A stellar and gas dynamical numerical model of ring galaxies. Mon. Not. R. Astron. Soc. 278, 345–366 (1996)

  24. 24.

    Neutral hydrogen in the Andromeda Nebula—III. The velocity field. Mon. Not. R. Astron. Soc. 205, 773–786 (1983)

  25. 25.

    , & Nonlinear gaseous density waves and galactic shocks. Astrophys. J. 183, 819–842 (1973)

  26. 26.

    & Hydrodynamic models of the Cartwheel ring galaxy. Astrophys. J. 411, 108–124 (1993)

  27. 27.

    & A model for the Cartwheel ring galaxy. Astrophys. Space Sci. 276, 1141–1149 (2001)

  28. 28.

    , , , & Probing the evolution of the galaxy interaction/merger rate using collisional ring galaxies. Astrophys. J. 612, 679–689 (2004)

  29. 29.

    , , & Galaxy morphologies in the Hubble Ultra Deep Field: dominance of linear structures at the detection limit. Astrophys. J. 631, 85–100 (2005)

  30. 30.

    Dwarf galaxies of the Local Group. Annu. Rev. Astron. Astrophys. 36, 435–506 (1998)

Download references

Acknowledgements

This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Funding for this work was provided by the Anglo American Chairman’s Fund as well as by NASA through an award issued by JPL/Caltech. Author Contributions P.B., G.G.F., M.L.N.A., M.A.P. and S.P.W. provided the IRAC data of M31 on which the analyses are based. D.L.B. initiated the collaboration between the USA, France and WITS, South Africa and identified Baade dust spirals in emission in the central region of M31. F.C. discovered the central ring between the inner Baade arms and believed it to be induced by a head-on collision. F.B. performed the numerical simulations which fully corroborated this interpretation and also generated Figs 1 and 2. R.G. cleaned the IRAC images of foreground stars and conducted Fourier spectral analysis of the Baade arms. F.C. and F.B. provided crucial drafts of this Letter. The final revised versions were prepared by D.L.B., S.P.W, R.G. and M.L.N.A.

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Author notes

    • F. Bournaud

    Present address: DSM/DAPNIA/Service d'Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France

Affiliations

  1. Anglo American Cosmic Dust Laboratory, School of Computational and Applied Mathematics, University of the Witwatersrand, Private Bag 3, WITS 2050, South Africa

    • D. L. Block
    •  & R. Groess
  2. Observatoire de Paris, LERMA, 61 Avenue de l'Observatoire, F-75014 Paris, France

    • F. Bournaud
    •  & F. Combes
  3. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA

    • P. Barmby
    • , M. L. N. Ashby
    • , G. G. Fazio
    • , M. A. Pahre
    •  & S. P. Willner

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Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

Corresponding author

Correspondence to D. L. Block.

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    Supplementary Notes

    This file contains the Supplementary Methods and Supplementary Figures 1–3.

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https://doi.org/10.1038/nature05184

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