anomalous microwave emission

Anomalous microwave emission (AME) refers to a component of the microwave background which comes from regions of Milky-Way dust. It was discovered in COBE data in 1995. Its frequency is on the order of 30 GHz, but varies by region. Its spectrum is relatively flat (a spectral index close to zero), a hint that it is some type of free-free radiation. It was labeled anomalous because no mechanism was known by which such dust would produce it. It has been a subject of study since, both for understanding dust and for understanding its precise effect on the microwave background: the exact observed pattern of the cosmic microwave background (CMB) is of high interest in cosmology, which requires careful accounting of any other microwave sources. A number of theories for AME production have been developed, one being spinning dust grains.