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Arxiv: Exploring a primordial solution for early black holes detected with the JWST Published: 7/9/2024 9:01:30 PM Updated: 7/9/2024 9:01:30 PM

Paper abstract: The James Webb Space Telescope (JWST) has unearthed black holes as massive as10^{6.2-8.1}M_\odot at redshifts of z ~ 8.5-10.6 with many systemsshowing unexpectedly high black hole to stellar mass ratios >=30%, posing acrucial challenge for theoretical models. Using analytic calculations, weexplore the combination of {\it astrophysical} seeding mechanisms and Eddingtonaccretion rates that can explain the observed objects. We then appeal to {\itcosmological} primordial black hole (PBH) seeds and show how these present analternative path for "seeding" early structures and their baryonic contents.Assuming seeding (via astrophysical means) at a redshift of z_{\rm seed}=25and continuous accretion, all of the black holes studied here can either beexplained through super-Eddington accretion (at an Eddington fraction off_{\rm Edd}<= 2.1 ) onto low-mass (100M_\odot) seeds or Eddington-limitedaccretion onto high-mass (10^5 M_\odot) seeds. The upper limit, where weassume a primordial origin for all of these black holes, yields a continuousprimordial black hole mass function (between 10^{-5.25} and 10^{3.75}M_\odot) and a fractional PBH value <= 10^{-12}, in good agreement withobservational constraints. Starting at the redshift of matter-radiationequality (z ~ 3400), we show how PBH-driven structure formation canreproduce the observed stellar and black hole masses for two of the highestredshift black holes (UHZ1 and GHZ9 at z ~ 10.3) with the same parametersgoverning star formation, black hole accretion and their feedbacks. Exploring awide swathe of model parameter space for GHZ9, we find black hole-to-stellarmass ratios ranging between 0.1-1.86 i.e. in some cases (of high supernovafeedback), the black hole grows to be more massive than its host halo,presenting an attractive alternative to seeding these puzzling early systems.