A byproduct of experiments designed to map the cosmic microwave background is the recent detection of a new component of foreground Galactic emission .
The anomalous foreground at \sim 10–30Â GHz , unexplained by traditional emission mechanisms , correlates with 100 \mu m dust emission .
We use planetary nebulae ( PNe ) as astrophysical laboratories to test known radio emission processes , and report that in the Helix the emission at 31Â GHz and 100Â \mu m are well correlated , and exhibit similar features on sky images , which are absent in H \beta .
Upper limits on the 250Â GHz continuum emission in the Helix rule out cold grains as candidates for the 31Â GHz emission , and provide spectroscopic evidence for an excess at 31Â GHz over bremsstrahlung .
We estimate that the 100Â \mu m-correlated radio emission , presumably due to dust , accounts for at least 20 % of the 31Â GHz emission in the Helix .
This result strengthens previous tentative interpretations of diffuse interstellar medium spectra involving a new dust emission mechanism at radio frequencies .
Very small grains , thought not to survive in evolved PNe , have not been detected in the Helix , which hampers interpreting the new component in terms of electric dipole emission from spinning grains .
The observed iron depletion in the Helix favors considering the identity of this new component to be magnetic dipole emission from hot ferromagnetic grains .
The reduced level of free-free continuum we report also implies an electronic temperature of T _ { e } = 4600 \pm 1200 ~ { } K for the free-free emitting material , which is significantly lower than the temperature of 9500 \pm 500 Â K inferred from collisionally-excited lines .