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

Abstract

The C-Band All-Sk y Surv e y (C-BASS) has observed the Galaxy at 4.76 GHz with an angular resolution of 0 . °73 full-width half-maximum, and detected Galactic synchrotron emission with high signal-to-noise ratio o v er 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 ( < = -0.06 ±0.02) of the Galactic synchrotron spectrum at high frequencies resulting in a mean spectral index of < = -3.10 ±0.02 o v er 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.