ENHANCED DETECTABILITY OF PRE-REIONIZATION 21 cm STRUCTURE
Bibliographic record
Abstract
Before the universe was reionized, it was likely that the spin temperature of intergalactic hydrogen was decoupled from the cosmic microwave background (CMB) by UV radiation from the first stars through the Wouthuysen–Field effect. If the intergalactic medium (IGM) had not yet been heated above the CMB temperature by that time, then the gas would appear in absorption relative to the CMB. Large, rare sources of X-rays could inject sufficient heat into the neutral IGM, so that δ T b >0 at comoving distances of tens to hundreds of Mpc, resulting in large 21 cm fluctuations with δ T b ≃ 250 mK on arcminute to degree angular scales, an order of magnitude larger in amplitude than that caused by ionized bubbles during reionization, δ T b ≃ 25 mK. This signal could therefore be easier to detect and probe higher redshifts than that due to patchy reionization. For the case in which the first objects to heat the IGM are QSOs hosting 10 7 M ☉ black holes with an abundance exceeding ∼1 Gpc −3 at z ∼ 15, observations with either the Arecibo Observatory or the Five Hundred Meter Aperture Spherical Telescope could detect and image their fluctuations at greater than 5σ significance in about a month of dedicated survey time. Additionally, existing facilities such as MWA and LOFAR could detect the statistical fluctuations arising from a population of 10 5 M ☉ black holes with an abundance of ∼10 4 Gpc −3 at z ≃ 10–12.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".