Astronomy Colloquium

According to the recent models for the joint growth of Super Massive Black Holes and their Host Galaxies, heavy, possibly Compton thick, obscuration represents a key phase in their evolution and is expected to play a fundamental role in the feedback mechanisms linking SMBH activity with host galaxy properties. The smoking gun signature of heavily obscured accreting SMBH is the presence of a strong iron line on top of a flat/reflected hard  X-ray spectrum. X-ray spectroscopy thus represents the most efficient method to obtain an almost unbiased view of the accretion history evolution from the early stages (i.e. z > 3)  to the present days. I will review the key results obtained by extragalactic  X-ray surveys with Chandra and XMM in the last 10+ years and the current hard X-ray (3-80 keV) observations with NuSTAR complemented by multi-wavelength follow up. I will also discuss the perspectives for future observations in the X-ray band and the expected breakthroughs in the study of  SMBH evolution, with particular emphasis on the recent ESA recommendation for  the next Large mission in 2028: The hot and energetic Universe.