The most extreme phase of black holes growth and feedback

Deep surveys have revealed fully-grown supermassive black holes powering active galactic nuclei at very high redshifts, when the Universe was a few hundred Myr old, less than 10% of its current age. This challenges the theories of black holes growth, requiring long periods of high accretion, most likely above the Eddington limit. These objects will be difficult to study in detail, even with future advanced observatories. However, in the nearby Universe, there are several objects that shine beyond Eddington, can be studied in great detail and used as proxy for primordial black holes. In the supermassive regime we have some narrow line Seyfert 1 galaxies and tidal disruption events, whilst hundreds of stellar-mass black holes and neutron stars are known to power ultraluminous X-ray sources (ULXs). A common denominator to these stellar-mass and supermassive objects is the presence of extreme winds which confirm the predictions by theoretical models of super-Eddington accretion. These winds carry a huge amount of power owing to their mildly-relativistic speeds (~0.2c) and are able to significantly affect the surrounding medium and limit the amount of matter that can reach the central accretor. In this seminar I will discuss the state-of-art of super-Eddington accretion in different mass regimes and highlight future missions that will decisively boost this research field.