We estimate the frequency spectrum of the diffuse anomalous microwave emission ( AME ) on the North Celestial Pole ( NCP ) region of the sky with the Correlated Component Analysis ( CCA ) component separation method applied to WMAP 7-yr data .
The NCP is a suitable region for this analysis because the AME is weakly contaminated by synchrotron and free-free emission .
By modeling the AME component as a peaked spectrum we estimate the peak frequency to be 21.7 \pm 0.8 GHz , in agreement with previous analyses which favored \nu _ { p } < 23 GHz .
The ability of our method to correctly recover the position of the peak is verified through simulations .
We compare the estimated AME spectrum with theoretical spinning dust models to constrain the hydrogen density n _ { H } .
The best results are obtained with densities around 0.2–0.3 cm ^ { -3 } , typical of warm ionised medium ( WIM ) to warm neutral medium ( WNM ) conditions .
The degeneracy with the gas temperature prevents an accurate determination of n _ { H } , especially for low hydrogen ionization fractions , where densities of a few cm ^ { -3 } are also allowed .