Identification of Spinning Dust in Halpha-Correlated Microwave Emission

Understand

CMB experiments commonly use maps of Halpha intensity as a spatial template for Galactic free-free emission, assuming a power law I_nu \propto nu^-0.15 for the spectrum.

• Any departure from the assumed free-free spectrum could have a detrimental effect on determination of the primary CMB anisotropy.
• We show that the Halpha-correlated emission spectrum in the diffuse warm ionized medium (WIM) is not the expected free-free spectrum at WMAP frequencies.
• Instead, there is a broad bump in the spectrum at ~50 GHz which is consistent with emission from spinning dust grains.