Abstract
Recent models for the large-scale Galactic magnetic fields in the literature
were largely constrained by synchrotron emission and Faraday rotation measures.
We select three different but representative models and compare their predicted
polarized synchrotron and dust emission with that measured by the Planck
satellite. We first update these models to match the Planck synchrotron
products using a common model for the cosmic-ray leptons. We discuss the impact
on this analysis of the ongoing problems of component separation in the Planck
microwave bands and of the uncertain cosmic-ray spectrum. In particular, the
inferred degree of ordering in the magnetic fields is sensitive to these
systematic uncertainties. We then compare the resulting simulated emission to
the observed dust emission and find that the dust predictions do not match the
morphology in the Planck data, particularly the vertical profile in latitude.
We show how the dust data can then be used to further improve these magnetic
field models, particularly in the thin disc of the Galaxy where the dust is
concentrated. We demonstrate this for one of the models and present it as a
proof of concept for how we will advance these studies in future using
complementary information from ongoing and planned observational projects.
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