The properties of primordially-seeded black holes and their hosts in the first billion years: implications for JWST
Bibliographic record
Abstract
Aims. James Webb Space Telescope (JWST) observations have opened a tantalising new window onto possible black holes as early as redshifts of z ∼ 10.4. Using local relations for calibration, these systems show a number of puzzling properties including black holes as massive as M BH ≳ 10 8 M ⊙ in place at z ∼ 10, unexpectedly high black hole-to-stellar mass ratios of M BH / M * ≳ 0.1 and, for some of them, extremely low metallicities. 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. Methods. We present PHANES ( P rimordial black h oles a ccelerating the assembly of n ascent e arly s tructures), 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 10 0.5 − 10 6 M ⊙ . In addition to a fiducial model where black holes are considered non-spinning ( s = 0), we also explore two “maximal” scenarios where black holes show maximally prograde ( s = +1) or retrograde ( s = −1) spins. Results. PBH seeded models yield a black hole mass function that extends between 10 1.25−11.25 (10 0.75−7.25 ) M ⊙ at z ∼ 5(15) for the different models considered in this work. Interestingly, PBH-seeded models (with s = 0 or −1) naturally result in extremely high values of M BH / M * ≳ 0.25 at z ∼ 5 − 15. For a typical stellar mass of M ∗ = 10 9 M ⊙ , we find an average value of M BH / M * ∼ 0.4(1.6) for s = 0(−1) at z = 5, providing a smoking gun for PBH-seeded models. Showing Eddington accretion fractions that range over two orders of magnitude ( f Edd ∼ 0.01 − 1), 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 ⊙ ). 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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.007 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".