Speaker
Description
Understanding how supermassive black holes (SMBHs) rapidly grew in the early Universe is a central question in extragalactic astrophysics. I will present X-ray studies of extreme accretion onto SMBHs across cosmic history, combining results from local super-Eddington accreting AGN and hyper-luminous quasars at z > 6. Local super-Eddington systems show steep X-ray continua, extremely low coronal temperatures, and strong outflows, providing direct evidence for modified disk-corona coupling at high accretion rates. At high redshift, luminous quasars (QSOs) exhibit systematically steep photon indices suggesting that soft coronal emission is a robust and possibly ubiquitous property of luminous QSOs at z>6. These QSOs also show a tight correlation between X-ray spectral slope and C IV blueshift, linking coronal emission to disk wind physics and SMBH growth. Additionally, a comparisons between high-z Little Red Dots, JWST-selected AGN, showing a strong X-ray weakness, and local highly accreting sources reveal a common regime of large X-ray bolometric corrections and suppressed X-ray emission pointing to a scenario in which in this newly discovered AGN population the SMBHs may be highly accreting. Together, these results hints at a scenario in which early QSOs experienced sustained phases of extreme accretion. The convergence of X-ray properties between low-z super-Eddington AGN and the first QSOs highlights the physical continuity of extreme accretion over ∼13 Gyr and establishes local highly accreting systems as key laboratories to understand the formation of the first SMBHs.