Constraining the Anomalous Microwave Emission beyond the Milky Way

The microwave emission from astrophysical sources is mostly dominated by well-understood emission mechanisms (free-free, synchrothron and thermal dust). However, observations of our own galaxy have revealed an unexpected excess of emission in the microwave between 10GHz and 50GHz which cannot be explained by standard emission mechanisms. The importance of a full understanding of this excess emission (Anomalous Microwave Emission, AME) depends not only on our comprehension of the astrophysical mechanisms at its origin, but also on the need for CMB experiments in order to understand and remove foreground signals.

We have observed the Andromeda galaxy, Messier 31 (M31), at 6.7GHz and 22GHz with the Sardinia Radio Telescope. Observations at 6.7GHz, combined with previous lower and higher frequencies observations, have already revealed a ∼ 8σ evidence of AME in the galactic diffuse emission. The map extracted from these low frequency observations has also shown other interesting properties of the galaxy and of the 93 compact sources we identified in the covered sky area. A joint analysis of the 6.7GHz and 22GH maps, in intensity and in polarization, will put constraints on the intensity and polarization of the AME from another galaxy, for the first time.