Calendar
Stanza Google Meet: https://meet.google.com/sxz-cctp-tsc
Speaker: Ciro Pinto (INAF / IASF-Palermo)
Titolo: “Fast growth and feedback of black holes accreting beyond the Eddington limit”
Abstract:
The detection of fully-grown supermassive black holes in active galactic nuclei at high redshift, when the Universe was young, 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. In the nearby Universe there are compact objects with a similar accretion regime that can be used as proxy for primordial black holes. Ultraluminous X-ray sources (ULXs) are mainly nearby stellar-mass black holes and neutron stars accreting above their Eddington limit. This was understood after the discovery of coherent pulsations and cyclotron lines in some ULXs, indicating that at least a fraction of them hosts neutron stars as compact objects and, finally, our discovery of powerful winds as predicted by theoretical models of super-Eddington accretion. ULX winds carry a huge amount of power owing to their mildly relativistic speeds (~0.2c) and are able to significantly affect the surrounding medium, producing the observed 100s pc super bubbles, and limit the amount of matter that can reach the central accretor. The study of ULX winds is therefore quintessential to understand 1) how much and how fast can matter be accreted by black holes and 2) how strong is their feedback onto the surrounding medium in the regime of high accretion rate such as for quasars and supermassive black holes at their peak of growth. I will provide an overview on this phenomenology and discuss how we can use similar techniques onto highly-accreting supermassive black holes to understand their fast growth and feedback onto the host galaxy.