Heavy versus light super-Eddington seeds: the 10⁵–10⁷ M☉ black-hole mass function of JWST AGN at z = 7–10
Mass estimators for little red dots are contested by an order of magnitude and theory offers several viable channels, so difficulty is above the old early-SMBH entry (42), as the z = 8–10 mass function is a sharper target. Leverage 40, slightly above the old 37, because the seed channel feeds LISA rates, the PTA amplitude and galaxy-formation models. Application value 3.
The problem
How did huge black holes already exist when the universe was under a billion years old?
- 1Webb finds big black holes very early
- 2Speed limit on how fast they can grow
- 3Need a heavy seed or faster feeding
- 4Compare light, medium and heavy seeds
- 5Correct for hidden and missed objects
The observations. JWST has discovered broad-line active galactic nuclei (AGN) and X-ray AGN at redshifts z of 7 and above, such as UHZ1 (z about 10.1), GHZ9 and GN-z11 (z = 10.6). Several lie above the local relation between black-hole mass and host-galaxy stellar mass (more than 3σ in some samples). Spectroscopy of JWST fields such as UNCOVER finds AGN to be common in red galaxies at z above 5.
Built from
earlier problems → this oneThe problems this one is built from: progress or tools it needs (builds on), special cases that come first (generalizes), and weaker results on the way (implies). On the right, what builds on it.
- Start with
- Heavy versus light super-Eddington seeds: the 10⁵–10⁷ M☉ black-hole mass function of JWST AGN at z = 7–10This problem
- Then
Path to understanding
foundations → problemThe research entries this problem rests on, in the order to read them. Each links to its explainer.
- Start with
- Step 2
- Step 3
- ΛCDM, the standard model of cosmologyTheory · host
- Then
- Heavy versus light super-Eddington seeds: the 10⁵–10⁷ M☉ black-hole mass function of JWST AGN at z = 7–10The problem
State of the art
Bogdan et al. interpreted UHZ1 (z ≈ 10.1) as an X-ray quasar consistent with a heavy seed (arXiv:2305.15458), with the spectroscopic confirmation in Goulding et al. (arXiv:2308.02750). Maiolino et al. reported a small, vigorously accreting black hole in GN-z11 at z = 10.6 (arXiv:2305.12492). JWST CEERS and JADES AGN at z = 4–7 lie above the local M_BH–M⋆ relation at more than 3σ (Pacucci et al., arXiv:2308.12331), and UNCOVER spectroscopy found AGN to be common in red galaxies at z > 5 (Greene et al., arXiv:2309.05714). Since 2025 the mass scale of the broad-line 'little red dots' (LRDs) has become the central question. Rusakov et al. (arXiv:2503.16595) argue that electron scattering in dense ionised cocoons broadens the Balmer lines, giving masses of 10⁵–10⁷ M☉, about two orders of magnitude below virial estimates; Brazzini et al. (arXiv:2507.08929) rule out dominant electron scattering in one well-studied LRD using multiple hydrogen lines. Naidu et al. (arXiv:2503.16596) and de Graaff et al. (arXiv:2511.21820, 146 LRDs) interpret the spectra as accreting black holes inside dense gas envelopes ('black hole stars'), so the continuum is not starlight. Against the low-mass view, Juodžbalis et al. (arXiv:2508.21748) measured Keplerian gas rotation in Abell2744-QSO1 at z = 7.04 implying about 5×10⁷ M☉, consistent with the virial estimate and with M_BH/M⋆ > 2. Inayoshi's critical review (arXiv:2512.03130, December 2025) and a September 2026 preprint arguing for 10⁴–10⁵ M☉ seeds accreting at 5–50 times Eddington (Sun et al., arXiv:2609.09274) show that the community has not converged. The envelope picture is now the leading interpretation of LRD spectra, but the black-hole mass function at z = 8–10, and therefore the seeding channel, is not established as of October 2026; the status is IN_PROGRESS.
Realistic applications
The seed channel fixes the black-hole mass function used in galaxy-formation simulations, predictions for LISA mergers at z > 5, and the high-redshift contribution to the nanohertz background. There is no practical application beyond these.
What counts as solved
Resolved when JWST (and Euclid, Chandra and ground-based) samples with validated mass estimators constrain the z = 8–10 black-hole mass function to within a factor of 2–3 at 10⁵–10⁶ M☉ and one seeding channel (or a mix) is shown to reproduce it, with predictions for LISA event rates or 21-cm heating accepted by independent groups.
How it gets verified
ObservationSettled by new measurements or observations.
Settled by JWST, Euclid, Chandra and ground-based samples with validated mass estimators that constrain the z = 8 to 10 black-hole mass function to within a factor of 2 to 3 at 1e5 to 1e6 solar masses, plus a seeding channel that reproduces it and has predictions for LISA event rates or 21-cm heating.
Claims under verification
+ add a claimWhere the work is
Theory and simulation of seeds and super-Eddington growth, plus new spectroscopy and mass calibrations.
Bottlenecks
ranked by votes- #1EmpiricalBlack-hole mass estimators at high accretion rate
Virial masses from broad lines are uncalibrated for super-Eddington accretion and for gas-enshrouded 'little red dots': electron-scattering and dense-envelope models lower them by up to two orders of magnitude, while the one dynamical mass (Abell2744-QSO1) agrees with the virial value. Few dynamical masses exist to settle it.
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Connected problems
Progress
- Aug 29, 2025Dynamical mass in Abell2744-QSO1source
Gas rotation at z = 7.04 gives about 5×10⁷ M☉, consistent with the virial mass.
- Mar 20, 2025Electron-scattering and black-hole-star interpretationssource
Rusakov et al. argue LRD masses are 10⁵–10⁷ M☉; Naidu et al. propose gas-enshrouded "black hole stars".
- Aug 23, 2023Overmassive black holessource
JWST AGN at z = 4–7 lie above the local M_BH–M⋆ relation.
- May 24, 2023UHZ1 heavy-seed interpretationsource
Chandra plus JWST at z ≈ 10.1 interpreted as a heavy-seed black hole.