Dominik Schleicher : Origin of supermassive black holes from dense star clusters

Speaker : Dr. Dominik Schleicher (Sapienza University of Rome) Date : 11th November 2025 Title : Origin of supermassive black holes from dense star clusters: Implications for the Local Universe and for JWST Abstract : Recent discoveries by JWST have provided significant insight into the building-blocks of the high-redshift Universe. A cornerstone is the detection of Young Massive Star Clusters at high redshift, with masses between 10^5 and 10^7 solar. The masses of these clusters exceed the masses of young star clusters in nearby galaxies and even those of the most massive globular clusters. Some of them were found to be very compact with half-mass radii of less than a parsec. In this talk, we show that such clusters provide ideal initial conditions to form massive black holes of ~10^5 solar masses via collision-based channels. For this purpose, we present direct N-body simulations with stellar evolution demonstrating the formation of intermediate-mass black holes from such initial conditions. The models are verified through the comparison with data in the Local Universe, particularly with Nuclear Star Clusters. We subsequently discuss the relevance and implications of these models for Little Red Dots (LRDs), a new population of very compact red galaxies discovered by JWST. We show that such LRDs potentially have ideal conditions to efficiently form supermassive black holes through collision-based channels, and compare the predictions of this channel with upper limits from X-ray stacking based on the Chandra Deep Field South.