What produces the anomalous microwave emission from dust?
In plain words
Our Galaxy emits extra microwaves that follow the distribution of dust but are not explained by its warmth. Tiny spinning dust grains could produce it, but which grains is not known.
Precise statement
Anomalous microwave emission peaks at roughly 20 to 40 GHz and correlates with far-infrared dust emission. Determine the carrier: electric-dipole emission from rapidly rotating nanoparticles (PAHs, nanosilicates, iron nanoparticles) or magnetic-dipole emission, using spectral shape, polarization (observed below about 1 percent) and correlations with tracers of each grain type.
What would settle it
Spatially resolved correlation of the emission with PAH emission versus other grain tracers, together with polarization limits matched to each candidate's predicted alignment.
Status in the literature
An all-sky analysis found no preferential correlation with PAH emission (Hensley, Draine and Meisner 2016), leaving the carrier unsettled.