Description
Super-Eddington accretion may be crucial for explaining the existence of exceptionally massive black holes (BHs), exceeding 10^9 solar masses, observed as Active Galactic Nuclei at high redshifts (z∼6−7). Recent James Webb Space Telescope (JWST) observations strongly support the idea that early BHs grew significantly above the Eddington limit. Concurrently, numerical models are increasingly focusing on understanding the conditions, viability, and limitations of this extreme accretion process.
In this context, I have conducted a detailed investigation into the impact of super-Eddington accretion on various BH seed masses within the typical gas-rich proto-galaxy environments at high redshifts (z∼15). I will present results from a state-of-the-art suite of high-resolution smoothed-particle hydrodynamical simulations. These simulations incorporate key physics, including star formation, photoionization, non-equilibrium cooling of primordial species, and a feedback prescription based on the slim disc model. I specifically tested the effects of both seed mass and feedback intensity on the BH growth process.
I will demonstrate that, for gas-rich galaxies, even when isolated (i.e., without external interactions), neither star formation nor feedback processes can significantly limit the growth of black hole seeds, regardless of their initial mass. Super-Eddington accretion rapidly leads to the formation of very massive BHs (∼10^5 Msun) in just a few thousand years, making them overmassive with respect to their host galaxy, in agreement with JWST observations. Furthermore, I will show that through brief, super-Eddington bursts with small duty cycles, BHs can reach the observed masses by redshifts z∼6−7.