The sub-mJy radio sky
We have used deep 1.4GHz VLA observations of the ECDFS (rms~6 microJy) to study the sub-mJy radio source population. The sub-mJy radio sky is a complex mix of star-forming galaxies and radio quiet AGN, with a declining radio-loud AGN component. We find convincing evidence that the radio emission in radio-quiet AGN is related to star-formation rather than to emission from the central SMBH. These results have important implication for future radio surveys, including those with the SKA. 
Find here the full list of publications by our group on this topic.
X-ray surveys
X-ray imaging has been the primary tool I have used to study AGNs. During my PhD thesis I have used deep XMM-Newton observations in the Lockman Hole and later 1Ms-2Ms-4Ms-(7Ms) Chandra observation in the CDF-S. In COSMOS I have used both XMM and Chandra imaging of the 2 square degree area. 
Spectroscopic surveys
Mainly to obtain redshifts for large samples of AGN, I have embarked in a series of spectroscopic surveys:
CDFS 1Ms follow-up
GOODS spectroscopy
AGN feedback
AGN feedback (either radiative or mechanical) is largely used in numerical and semi-analytical simulations of galaxies evolution. Although There is mounting evidence that AGN outflows are ubiquitous, observational proofs of the impact that such AGN-driven outflows have on their host galaxies are still largely missing. This is one of my main research interests at the moment, and I am using FIR photometry (Herschel), IFU observations (SINFONI/VLT), sub-mm interferometry (PdBI and ALMA).