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 ^ { \circ } of the Galactic plane has an inverted ( rising ) spectrum with an average spectral index \alpha = 0.21 \pm 0.05 .
While such a spectrum is inconsistent with steep spectrum synchrotron ( \alpha \sim - 0.7 ) and flat spectrum free-free ( Bremsstrahlung ) ( \alpha \sim - 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 .
Several regions in the plane , e.g. , near the Cygnus arm , have spectra with even larger \alpha .
While low signal to noise of the 19 GHz data precludes a detailed map of spectral index , especially off the Galactic plane , it appears that the bulk of the emission in the plane is correlated with the morphology of dust .
Regions with higher 23 GHz flux tend to have harder spectra .
Off the plane , at Galactic latitudes 7 ^ { \circ } < |b _ { II } | < 20 ^ { \circ } , the spectrum steepens to \alpha = -0.16 \pm 0.15 .