Constraints on Warm Dark Matter from Cosmological Reionization
Bibliographic record
Abstract
We study the constraints that high-redshift structure formation in the universe places on warm dark matter (WDM) dominated cosmological models. We modify the extended Press-Schechter formalism to derive the halo mass function in WDM models. We show that our predictions agree with recent numerical simulations at low redshift over the halo masses of interest. Applying our model to galaxy formation at high redshift, we find that the loss of power on small scales, together with the delayed collapse of low-mass objects, results in strong limits on the root-mean-square velocity dispersion v rms,0 of the WDM particles at redshift zero. For fermions decoupling while relativistic, these limits are equivalent to constraints on the mass m X of the particles. The presence of a ≈4 × 10 9 M ☉ supermassive black hole at redshift 5.8, believed to power the quasar SDSS 1044-1215, implies m X ≳ 0.5 keV (or v rms,0 ≲ 0.10 km s -1 ), assuming that the quasar is unlensed and radiating at or below the Eddington limit. Reionization by redshift 5.8 also implies a limit on m X . If high-redshift galaxies produce ionizing photons with an efficiency similar to their redshift-three counterparts, we find m X ≳ 1.2 keV (or v rms,0 ≲ 0.03 s -1 ). However, given the uncertainties in current measurements from the proximity effect of the ionizing background at redshift three, values of m X as low as 0.75 keV (or v rms,0 = 0.06 s -1 ) are not ruled out. The limit weakens further to m X ≳ 0.4 keV (or v rms,0 ≲ 0.14 s -1 ), if, instead, the ionizing-photon production efficiency is 10 times greater at high redshift, but this limit will tighten considerably if reionization is shown in the future to have occurred at higher redshifts. WDM models with m X ≲ 1 keV (or v rms,0 ≳ 0.04 s -1 ) produce a low-luminosity cutoff in the high-redshift galaxy luminosity function that is directly detectable with the Next Generation Space Telescope , and which serves as a direct constraint on m X .
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| 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 | 0.000 | 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".