Hidden accretion in supermassive black holes in the XMM CDFS survey

The XMM-CDFS survey is the most sensitive observation of the X-ray sky (3Ms exposure) taken with ESA's XMM-Newton mission. The main aim of this survey is to find the most heavily obscured AGN. These play an important role in the history of accretion of super-massive black holes in the Universe as they cannot be detected at other wavelengths. Moreover, they represent the first stage of a birth of an AGN and therefore they have cital implications for AGN-galaxy co-evolution models. We compare the findings of the CDFS survey with our recently developed X-ray background synthesis models. Implications for future missions such as eROSITA are also discussed.