Journal Article

Connecting synchrotron, cosmic rays and magnetic fields in the plane of the Galaxy

T. R. Jaffe, A. J. Banday, J. P. Leahy, S. Leach and A. W. Strong

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 416, issue 2, pages 1152-1162
Published in print September 2011 | ISSN: 0035-8711
Published online September 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19114.x
Connecting synchrotron, cosmic rays and magnetic fields in the plane of the Galaxy

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We extend previous work modelling the Galactic magnetic field in the plane using synchrotron emission in total and polarized intensity. In this work, we include a more realistic treatment of the cosmic ray electrons using the galprop propagation code optimized to match the existing high-energy data. This addition reduces the degeneracies in our previous analysis and when combined with an additional observed synchrotron frequency allows us to study the low-energy end of the cosmic ray electron spectrum in a way that has not previously been done. For a pure diffusion propagation, we find a low-energy injection spectrum slightly harder than generally assumed: for J(E) ∝Eα, we find α=−1.34 ± 0.12, implying a very sharp break with the spectrum above a few GeV. This then predicts a synchrotron brightness temperature spectral index, β, on the Galactic plane, that is −2.8 < β < −2.74 below a few GHz and −2.98 < β < −2.91 up to 23 GHz. We find that models including cosmic ray re-acceleration processes appear to be incompatible with the synchrotron data.

Keywords: polarization; radiation mechanisms: general; cosmic rays; ISM: magnetic fields; Galaxy: structure; radio continuum: ISM

Journal Article.  8938 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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