Speaker
Description
Deep JWST surveys have revolutionized our knowledge of the formation and early evolution of Active Galactic Nuclei at the cosmic dawn.
Webb uncovered a large population of compact Broad Lined AGN with moderate luminosities, log LBOL ~ 42-45, high redshifts, z > 4, and black holes’ inferred masses 106-8 MSUN. A subclass exhibits red, V-shaped UV-optical continua and is commonly classified as Little Red Dots (LRD). Among the most remarkable properties of the JWST-discovered AGN, their extreme X-ray weakness is the most puzzling. High obscuration by dust-free gas (to account for the broad lines) or intrinsically weak X-rays, as in super-Eddington accretion models, were two possible explanations.
Another open and widely debated issue concerns their large abundance at early epochs, the evolution of the faint end of the luminosity function, and the implications for BH growth and the setup of the BH host galaxy relations.
I will review the most recent results in light of current models, highlighting their weaknesses and the consequences for the early evolution of supermassive black holes.
In the second part of the talk, if time allows, I would like to review the most recent results obtained from the calorimeter onboard the Japanese mission XRISM. High-resolution (5-7 eV) X—ray spectroscopy at the energies of the iron lines complex (6—7 keV) has radically changed our understanding of AGN physics in the innermost regions of the accretion disk close to the central Black Hole.