Serching for AGNs with VST: optical variability in the COSMOS and CDFS regions

Active Galactic Nuclei (AGN) are characterised by strong variability at all wavelengths. We exploited 3 years of VST monitoring observations of the COSMOS and CDFS regions, performed within the SUDARE/VOICE surveys, to assemble a sample of AGN candidates based on variability. Variability selection does not make strong a-priori assumptions about the properties of the sources and can thus integrate and complete samples selected by other techniques. We investigate the effectiveness and reliability of this selection method by comparing it with spectroscopic, X-ray and IR selected samples, showing that variability-selection can yield extremely pure samples, with completeness 〉50% with respect of X-ray and IR selections. We explore the dependence of variability from obscuration, mass and accretion rate, and predict the performance that can be expected by future monitoring surveys such as LSST.