Disentangling the AGN and Star-forming Contribution to the Sub-mJy Radio Counts

The true nature of the faint radio population remains elusive despite the many observations of the "sub-mJy" bump over the last two decades. This lack of information is largely due to the faint magnitudes of the optical counterparts to the radio sources. There are strong theoretical reasons (and a few observational ones) to believe that this rise in the counts is due to the emergence of a rapidly evolving star-forming population. Now, for the first time, we are able to separate the AGN and star-forming populations below 1mJy using a combination of multi-wavelength data from Spitzer, GMRT, MERLIN, CFHT, Keck, UKIRT, Subaru, Chandra and XMM-Newton. The many discriminators between these emission mechanisms include MIR colours, MIR/radio flux ratios, X-ray luminosities/spectra, optical spectra, radio morphologies and radio spectra. We can now derive the source counts separately for AGN and star-forming galaxies confirming that the latter population rise sharply at faint flux densities.