Evidence for Inverted Spectrum 20 GHz Emission in the Galactic Plane
Abstract
A comparison of a 19 GHz full-sky map with the WMAP satellite K band (23 GHz) map indicates that the bulk of the 20 GHz emission within 7 degrees of the Galactic plane has an inverted (rising) spectrum with spectral index alpha ~ 0.3. While such a spectrum is inconsistent with steep spectrum synchrotron (alpha ~ -0.7) and flat spectrum free-free (Bremsstrahlung) (alpha ~ -0.1) emission, it is consistent with various models of electric dipole emission from thermally excited spinning dust grains as well as models of magnetic dipole emission from ferromagnetic dust grains. A few regions in the plane, e.g., near the Cygnus arm, have spectra with even larger alpha. It appears that the bulk of the emission in the plane is correlated with the morphology of dust. Between 7 and 20 degrees from the Galactic plane the spectrum steepens to alpha ~ -0.3.Keywords
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