2025/06/09 by Pratika Dayal, R. Maiolino, Dayal, Pratika +1 · 4 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Black Holes and Theoretical Physics
paper · doi:10.48550/arxiv.2506.08116
James Webb Space Telescope (JWST) observations have opened a tantalising new window onto possible black holes as early as redshifts of z ∼ 10.4. These show a number of puzzling properties including unexpectedly massive black holes in place by z ∼ 10 and inexplicably high black hole-to-stellar mass ratios of M\rm BH/M_*≥ 0.1. These pose a serious challenge for "astrophysical" seeding and growth models that we aim to explain with ``cosmological" primordial black holes (PBHs) in this work. We present PHANES, an analytic framework that follows the evolution of dark matter halos, and their baryons in the first billion years, seeded by a population of PBHs with seed masses between 100.5-106 M_\odot. PBH seeded models yield a black hole mass function that extends between 101.25-11.25 ~(100.75-7.25)M_\odot at z ∼ 5 (15) for the different models considered in this work. Interestingly, PBH-seeded models (with spin s=0 or -1) naturally result in extremely high values of M\rm BH/M_*≥ 0.25 at z ∼ 5-15. For a typical stellar mass of M_* =109 M_\odot, we find an average value of M\rm BH/M_* ∼ 0.4~ (1.6) for s=0~(-1) at z=5, providing a smoking gun for PBH-seeded models. Another particularity of PBH-seeded models is their ability of producing systems with high black hole-to-stellar mass ratios that are extremely metal poor (Z ≤ 10-2~Z_\odot). Yielding a PBH-to-dark matter fraction ≤ 10-9 and a stellar mass function that lies four orders of magnitude below observations, our model is in accord with all current cosmological and astrophysical bounds.