Overmassive black holes in the early Universe can be explained by gas-rich, dark matter-dominated galaxies
Bibliographic record
Abstract
ABSTRACT James Webb Space Telescope (JWST) has revealed the apparent evolution of the black hole (BH)–stellar mass ($M_\mathrm{BH}$–$M_\mathrm{\ast }$) relation in the early Universe, while remaining consistent with the BH–dynamical mass ($M_\mathrm{BH}$–$M_\mathrm{dyn}$) relation. We predict BH masses for $z>3$ galaxies in the high-resolution thesan-zoom simulations by assuming that the $M_\mathrm{BH}$–$M_\mathrm{dyn}$ relation is fundamental. Even without live BH modelling, our approach reproduces the JWST-observed $M_\mathrm{BH}$ distribution, including overmassive BHs relative to the local $M_\mathrm{BH}$–$M_\mathrm{\ast }$ relation. We find that $M_\mathrm{BH}/M_\mathrm{\ast }$ declines with $M_\mathrm{\ast }$, evolving from $\sim$0.1 at $M_\mathrm{\ast }=10^6\ \mathrm{M_\odot }$ to $\sim$0.01 at $M_\mathrm{\ast }=10^{10.5}\ \mathrm{M_\odot }$. This trend reflects the dark matter ($f_\mathrm{DM}$) and gas fractions ($f_\mathrm{gas}$), which decrease with $M_\mathrm{\ast }$ but show little redshift evolution down to $z=3$, resulting in small $M_\mathrm{\ast }/M_\mathrm{dyn}$ ratios and thus overmassive BHs in low-mass galaxies. We use prospector-derived stellar masses and star formation rates to infer $f_\mathrm{gas}$ across 48 022 galaxies in the JWST Advanced Deep Extragalactic Survey at $3< z< 9$, finding excellent agreement with our simulation. Our results demonstrate that overmassive BHs would naturally result from a fundamental $M_\mathrm{BH}$–$M_\mathrm{dyn}$ relation and be typical of the gas-rich, dark matter-dominated nature of low-mass, high-redshift galaxies. Such overmassive BHs may strongly influence early galaxy formation, and we caution that our approach does not include the self-consistent BH–galaxy co-evolution required for a complete understanding.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".