Speaker
Description
"Supermassive Black Holes (SMBHs) are believed to be at the center of all massive galaxies, as inferred from observations of Quasars over the years, which places a strong constraint of ∼ 10^9M⊙ at z ∼ 6 on these objects. However, how smaller progenitor seeds for these SMBHs are formed at high redshifts remains an open question. In this work, we investigate the formation of these seeds through the runaway collapse of a dense stellar system. We start with the formation of the dense
stellar system itself through a spherical collapse model, which provides a rotationally supported structure that fragments and allows star formation. The evolution of this system is then followed as it contracts and undergoes core collapse, wherein a small region within the core of the system becomes so dense that the general relativistic instability kicks in and the whole region collapses dynamically to give a massive black hole. The system’s evolution is studied by doing a Fokker-
Planck analysis in a general relativistic framework, along with solving the Einstein field equations for a non-static spherically symmetric metric describing the system. We provide an estimate for the mass of the seed black hole obtained and the total time for the collapse (and hence a formation redshift) for a set of different initial conditions that helps compare with observations. For a cluster core mass of M_c=10^3M⊙, we obtain a seed M_seed=800M⊙, while for a M_c=10^4M⊙, a seed of M_seed = 5000M⊙ was formed, both within z ≥14. Furthermore, we demonstrate how this seed black hole grows through stellar capture and gas accretion using a mass-spin co-evolution model for the black hole. Our results compare well with the observations, including the latest high-redshift JWST objects. Through this, a distribution of seed black holes is also provided, which evolves to a SMBH distribution that again compares well with the observed SMBH population."