The C-Band All-Sky Survey (C-BASS): template fitting of diffuse galactic microwave emission in the northern sky

Harper, S. E.; Dickinson, C.; Barr, A.; Cepeda-Arroita, R.; Grumitt, R. D. P.; Heilgendorff, H. M.; Jew, L.; Jonas, J. L.; Jones, M. E.; Leahy, J. P.; Leech, J.; Pearson, T. J.; Peel, M. W.; Readhead, A. C. S.; Taylor, A. C.
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Monthly Notices of the Royal Astronomical Society

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The C-Band All-Sky Survey (C-BASS) has observed the Galaxy at 4.76 GHz with an angular resolution of 0${_{.}^{\circ}}$73 full-width half-maximum, and detected Galactic synchrotron emission with high signal-to-noise ratio over the entire northern sky (δ > -15○). We present the results of a spatial correlation analysis of Galactic foregrounds at mid-to-high (b > 10○) Galactic latitudes using a preliminary version of the C-BASS intensity map. We jointly fit for synchrotron, dust, and free-free components between 20 and 1000 GHz and look for differences in the Galactic synchrotron spectrum, and the emissivity of anomalous microwave emission (AME) when using either the C-BASS map or the 408-MHz all-sky map to trace synchrotron emission. We find marginal evidence for a steepening (<Δβ> = -0.06 ± 0.02) of the Galactic synchrotron spectrum at high frequencies resulting in a mean spectral index of <β> = -3.10 ± 0.02 over 4.76-22.8 GHz. Further, we find that the synchrotron emission can be well modelled by a single power law up to a few tens of GHz. Due to this, we find that the AME emissivity is not sensitive to changing the synchrotron tracer from the 408-MHz map to the 4.76-GHz map. We interpret this as strong evidence for the origin of AME being spinning dust emission.
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