The most luminous quasars of the universe: probing the AGN/galaxy co-evolution at its extremes

The systematic, multi-frequency investigation of hyper-luminous quasars shining at the golden epoch of AGN activity offers the unique opportunity of studying the power and the effect of AGN feedback at its extreme. The WISE/SDSS- selected hyper-luminous quasar (WISSH) survey is an extensive multi-band observing program to investigate the role of nuclear activity in SMBH-galaxy self-regulated growth via extended outflows. We found that WISSH AGN are typically powered by highly accreting (0.3-3 Ledd), ten billion solar masses SMBHs, demonstrating that WISSH provides a simple and valuable tool to complete the census of the extreme SMBH population in the universe. We found that the 70% of quasars lacks [OIII] emission but shows strong winds traced by 3000-8000 km/s blueshifts of the high-ionization (CIV) with respect to low-ionization (HBeta) broad emission lines, revealing strong radiatively driven winds that dominate the BLR kinematics. We investigated about the possible origins of this intriguing dichotomy which involves fundamental parameters such as bolometric luminosity, SMBH mass, Eddington ratio and shape of the UV-X-ray spectrum.