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An 84-μG Magnetic Field in a Galaxy at Z=0.692?

Published online by Cambridge University Press:  01 June 2008

Arthur M. Wolfe ,
Regina A. Jorgenson ,
Timothy Robishaw ,
Carl Heiles  and
Jason X. Prochaska
Arthur M. Wolfe
Affiliation:
Dept. of Physics and Center for Astrophysics and Space SciencesUniversity of California, San DiegoLa Jolla, CA 92093-0424, USA email: [email protected], [email protected]
Regina A. Jorgenson
Affiliation:
Dept. of Physics and Center for Astrophysics and Space SciencesUniversity of California, San DiegoLa Jolla, CA 92093-0424, USA email: [email protected], [email protected]
Timothy Robishaw
Affiliation:
Astronomy Department, University of CaliforniaBerkeley, CA 94720-3411, USA email: [email protected], [email protected]
Carl Heiles
Affiliation:
Astronomy Department, University of CaliforniaBerkeley, CA 94720-3411, USA email: [email protected], [email protected]
Jason X. Prochaska
Affiliation:
UCO-Lick Observatory, University of California, Santa CruzSanta Cruz, CA 95464, USA email: [email protected]
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Abstract

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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 stars (Beck 2005). 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, i.e., Faraday rotation, yield an average value B ≈ 3 μG (Han et al. 2006). The possible detection of Faraday rotation of linearly polarized photons emitted by high-redshift quasars (Kronberg et al. 2008) 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 Galaxy (Heiles et al. 2004). 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 stronger (Parker 1970).

The full text of this paper was published in Nature (Wolfe et al. 2008).

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Issue S254: The Galaxy Disk in Cosmological Context , June 2008 , pp. 95 - 96
Copyright
Copyright © International Astronomical Union 2009

References

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