A census of radio-selected AGN on the COSMOS field and of their FIR
  properties
  We use the new catalogue by Laigle et al. (2016) to provide a full census of
VLA-COSMOS radio sources. We identify 90% of such sources and sub-divide them
into AGN and star-forming galaxies on the basis of their radio luminosity. The
AGN sample is COMPLETE with respect to radio selection at all z<3.5. Out of 704
AGN, 272 have a counterpart in the Herschel maps. By exploiting the better
statistics of the new sample, we confirm the results of Magliocchetti et al.
(2014): the probability for a radio-selected AGN to be detected at FIR
wavelengths is both a function of radio luminosity and redshift, whereby
powerful sources are more likely FIR emitters at earlier epochs. Such an
emission is due to star-forming processes within the host galaxy. FIR emitters
and non-FIR emitters only differentiate in the z<1 universe. At higher
redshifts they are indistinguishable from each other, as there is no difference
between FIR-emitting AGN and star-forming galaxies. Lastly, we focus on radio
AGN which show AGN emission at other wavelengths. We find that MIR emission is
mainly associated with ongoing star-formation and with sources which are
smaller, younger and more radio luminous than the average parent population.
X-ray emitters instead preferentially appear in more massive and older
galaxies. We can therefore envisage an evolutionary track whereby the first
phase of a radio-active AGN and of its host galaxy is associated with MIR
emission, while at later stages the source becomes only active at radio
wavelengths and possibly also in the X-ray.
