The Continuing Mystery of the Anomalous Microwave Emission

Bruce T. Draine (Princeton University)

December 07, 2015

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Abstract: “Anomalous Microwave Emission” (AME) refers to dust-correlated emission in the 15-50 GHz frequency range that is far stronger than had been expected from the low-frequency “tail” of the thermal infrared emission from dust grains at ~20K. Discovered in the course of CMB studies, it presents a significant “foreground” that CMB observers would like to remove. In 1998 it was proposed that the AME was rotational emission from ultrasmall dust grains with rotational frequencies of 15-50 GHz. The population of polycyclic aromatic hydrocarbons (PAHs) responsible for strong infrared emission bands between 3.3 and 17um were natural candidates for the emitter. This “spinning dust” hypothesis appeared to be a very natural explanation for the AME, and was supported by upper limits on polarization of the AME. I will describe recent observational efforts to demonstrate a link between the AME and the PAHs. Surprisingly, the results do not support the conjectured AME- PAH linkage. Other possibilities for the source of the AME will be discussed.