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An 84-μG magnetic field in a galaxy at redshift z = 0.692


The magnetic field pervading our Galaxy is a crucial constituent of the interstellar medium: it mediates the dynamics of interstellar clouds, the energy density of cosmic rays, and the formation of stars1. The field associated with ionized interstellar gas has been determined through observations of pulsars in our Galaxy. Radio-frequency measurements of pulse dispersion and the rotation of the plane of linear polarization, that is, Faraday rotation, yield an average value for the magnetic field of B ≈ 3 μG (ref. 2). The possible detection of Faraday rotation of linearly polarized photons emitted by high-redshift quasars3 suggests similar magnetic fields are present in foreground galaxies with redshifts z > 1. As Faraday rotation alone, however, determines neither the magnitude nor the redshift of the magnetic field, the strength of galactic magnetic fields at redshifts z > 0 remains uncertain. Here we report a measurement of a magnetic field of B ≈ 84 μG in a galaxy at z = 0.692, using the same Zeeman-splitting technique that revealed an average value of B = 6 μG in the neutral interstellar gas of our Galaxy4. This is unexpected, as the leading theory of magnetic field generation, the mean-field dynamo model, predicts large-scale magnetic fields to be weaker in the past rather than stronger5.

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Figure 1: Line-depth spectra of Stokes parameters.
Figure 2: HIRES velocity profiles for dominant low-ionization states of abundant elements in the 21-cm absorber in the direction of quasar 3C 286.


  1. Beck, R. in Cosmic Magnetic Fields 41–68 (Lect. Notes Phys. 664, Springer, 2005)

    Book  Google Scholar 

  2. Han, J. L., Manchester, R. N., Lyne, A. G., Qiao, G. J. & van Straten, W. Pulsar rotation measures and the large-scale structure of galactic magnetic fields. Astrophys. J. 642, 868–881 (2006)

    ADS  CAS  Article  Google Scholar 

  3. Kronberg, P. P. et al. A global probe of cosmic magnetic fields to high redshifts. Astrophys. J. 676, 70–79 (2008)

    ADS  CAS  Article  Google Scholar 

  4. Heiles, C. & Troland, T. H. The millennium Arecibo 21 centimeter absorption-line survey. III. Techniques for spectral polarization and results for Stokes V . Astrophys. J. Suppl. Ser. 151, 271–297 (2004)

    ADS  CAS  Article  Google Scholar 

  5. Parker, E. The origin of magnetic fields. Astrophys. J. 160, 383–404 (1970)

    ADS  Article  Google Scholar 

  6. Brown, R. L. & Roberts, M. S. 21-centimeter absorption at z = 0.692 in the quasar 3C 286. Astrophys. J. 184, L7–L10 (1973)

    ADS  CAS  Article  Google Scholar 

  7. Davis, M. M. & May, L. S. New observations of the radio absorption line in 3C 286, with potential application to the direct measurement of cosmological deceleration. Astrophys. J. 219, 1–4 (1978)

    ADS  Article  Google Scholar 

  8. Wolfe, A. M., Gawiser, E. & Prochaska, J. X. Damped Lyα systems. Annu. Rev. Astron. Astrophys. 43, 861–918 (2005)

    ADS  CAS  Article  Google Scholar 

  9. Wolfe, A. M., Broderick, J. J., Condon, J. J. & Johnston, K. J. 3C 286: A cosmological QSO? Astrophys. J. 208, L47–L50 (1976)

    ADS  CAS  Article  Google Scholar 

  10. Meiring, J. D. et al. Elemental abundance measurements in low-redshift damped Lyα absorbers. Mon. Not. R. Astron. Soc. 370, 43–62 (2006)

    ADS  Article  Google Scholar 

  11. Wolfe, A. M., Prochaska, J. X. & Gawiser, E. CII* absorption in damped Lyα systems. I. Star formation rates in a two-phase medium. Astrophys. J. 593, 215–234 (2003)

    ADS  CAS  Article  Google Scholar 

  12. Boisse, P., Le Brun, V., Bergeron, J. & Deharveng, J.-M. A HST spectroscopic study of QSOs with intermediate redshift damped Lyα systems. Astron. Astrophys. 333, 841–863 (1998)

    ADS  CAS  Google Scholar 

  13. Kennicutt, R. C. Star formation in galaxies along the Hubble sequence. Annu. Rev. Astron. Astrophys. 36, 189–231 (1998)

    ADS  CAS  Article  Google Scholar 

  14. Morganti, R. et al. Neutral hydrogen in nearby elliptical and lenticular galaxies: the continuing formation of early-type galaxies. Mon. Not. R. Astron. Soc. 371, 157–169 (2006)

    ADS  CAS  Article  Google Scholar 

  15. Le Brun, V., Bergeron, J. & Deharveng, J. M. The nature of intermediate-redshift damped Lyα absorbers. Astron. Astrophys. 321, 733–748 (1997)

    ADS  Google Scholar 

  16. Steidel, C. C., Pettini, M., Dickinson, M. & Persson, S. E. Imaging of two damped Lyman-alpha absorbers at intermediate redshifts. Astron. J. 108, 2046–2053 (1994)

    ADS  Article  Google Scholar 

  17. McKee, C. F. & Ostriker, J. P. A theory of the interstellar medium: three components regulated by supernova explosions in an inhomogeneous substrate. Astrophys. J. 218, 148–169 (1977)

    ADS  CAS  Article  Google Scholar 

  18. Morganti, R., Greenhill, L. J., Peck, A. B., Jones, D. L. & Henkel, C. Disks, tori, and cocoons: emission and absorption diagnostics of AGN environments. N. Astron. Rev. 48, 1195–1209 (2004)

    ADS  Article  Google Scholar 

  19. Lotz, J. M. et al. The evolution of galaxy mergers and morphology at z 1.2 in the extended Groth strip. Astrophys. J. 672, 177–197 (2008)

    ADS  CAS  Article  Google Scholar 

  20. Bernet, M. L., Miniati, F., Lilly, S. J., Kronberg, P. P. & Dessauges–Zavadsky, M. Strong magnetic fields in normal galaxies at high redshift. Nature 454, 302–304 (2008)

    ADS  CAS  Article  Google Scholar 

  21. Rees, M. J. Origin of cosmic magnetic fields. Astron. Nachr. 327, 395–398 (2006)

    ADS  Article  Google Scholar 

  22. Wolfe, A. M. & Chen, H.-W. Searching for low surface brightness galaxies in the Hubble ultra deep field: implications for the star formation efficiency in neutral gas at z 3. Astrophys. J. 652, 981–993 (2006)

    ADS  CAS  Article  Google Scholar 

  23. Heiles, C. Cross-correlation spectropolarimetry in single-dish radio astronomy. Publ. Astron. Soc. Pacif. 113, 1243–1246 (2001)

    ADS  Article  Google Scholar 

  24. Baym, G. Lectures on Quantum Mechanics Ch. 1 (Benjamin, 1981)

    MATH  Google Scholar 

  25. Savage, B. D. & Sembach, K. R. Interstellar abundances from absorption- line observations with the Hubble-Space Telescope. Annu. Rev. Astron. Astrophys. 34, 279–329 (1996)

    ADS  CAS  Article  Google Scholar 

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We wish to thank F. H. Shu for suggesting the merger model and H.-W. Chen for providing us with her reanalysed images of 3C 286. We also thank F. H. Shu, E. Gawiser and A. Lazarian for comments and the US National Science Foundation for financial support. The GBT is one of the facilities of the National Radio Astronomy Observatory, which is a center of the National Science Foundation operated under cooperative agreement by Associated Observatories, Inc. A.M.W., R.A.J. and J.X.P. are Visiting Astronomers at the W. M. Keck Telescope. The Keck Observatory is a joint facility of the University of California, the California Institute of Technology and the National Aeronautics and Space Administration.

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Correspondence to Arthur M. Wolfe.

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Wolfe, A., Jorgenson, R., Robishaw, T. et al. An 84-μG magnetic field in a galaxy at redshift z = 0.692. Nature 455, 638–640 (2008).

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