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Abstract

We present a study of the magnetic field of the Small Magellanic Cloud (SMC), carried out using radio Faraday rotation
and optical starlight polarization data. Consistent negative rotation measures (RMs) across the SMC indicate
that the line-of-sight magnetic field is directed uniformly away from us with a strength 0.19 f 0.06 pG. Applying the
Chandrasekhar-Fermi method to starlight polarization data yields an ordered magnetic field in the plane of the sky of
strength 1.6 f 0.4 pG oriented at a position angle 4" f 12", measured counterclockwise from the great circle on the
sky joining the SMC to the Large Magellanic Cloud (LMC). We construct a three-dimensional magnetic field model
of the SMC, under the assumption that the RMs and starlight polarization probe the same underlying large-scale field. The
vector defining the overall orientation of the SMC magnetic field shows a potential alignment with the vector joining the
center of the SMC to the center of the LMC, suggesting the possibility of a "pan-Magellanic" magnetic field. A cosmicray-
driven dynamo is the most viable explanation of the observed field geometry, but has difficulties accounting for
the observed unidirectional field lines. A study of Faraday rotation through the Magellanic Bridge is needed to further
test the pan-Magellanic field hypothesis.

Item Type:	Article
Authors/Creators:	Mao, SA and Gaensler, BM and Stanimirovic, S and Haverkorn, M and McClure-Griffiths, NM and Staveley-Smith, L and Dickey, JM
Keywords:	magnetic fields - polarization - Magellanic Clouds
Journal or Publication Title:	Astrophysical Journal
ISSN:	0004-637X
DOI / ID Number:	10.1086/590546
Additional Information:	© 2008, American Astronomical Society
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