Radio to infrared spectra of late-type galaxies with Planck and WMAP
  data
  We use the Planck Early Release Compact Source Catalogue combined with WMAP
and other archival measurements to construct continuum spectra of three nearby
dusty star-forming galaxies: Messier 82, NGC 253 and NGC 4945. We carry out a
least-squares fit to the spectra using a combination of simple synchrotron,
free-free and thermal dust models, and look for evidence of anomalous microwave
emission (AME). We find that the radio spectra of all three galaxies are
consistent with steep spectrum synchrotron emission, with a significant amount
of free-free emission required to explain the Planck and WMAP data points in
the frequency range 30-150 GHz. This brings the star-formation rate based on
free-free emission into better agreement with that from the non-thermal
emission. We place limits on the presence of AME in these galaxies, finding
that it is lower than expectations based on the ratio of far infrared to AME
from the Galaxy. Nevertheless, the shape of the spectrum of NGC 4945 hints at
the presence of AME with a peak around 30 GHz. Future Planck data will let us
look more closely at these galaxies, as well as to extend the analysis to many
more galaxies.
