The Redshifted 21 cm Signal in the EDGES Low-band Spectrum
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Bibliographic record
Abstract
The EDGES collaboration reported the finding of an unexpectedly deep absorption in the radio background at 78 MHz and interpreted the dip as a first detection of redshifted 21-cm from Cosmic Dawn. We have attempted an alternate analysis, adopting a maximally smooth function approach to model the foreground. A joint fit to the spectrum using such a function together with a flattened absorption profile yields a best fit absorption amplitude of $921 \pm 35$ mK. The depth of the 21-cm absorption inferred by the EDGES analysis required invoking non-standard cosmology or new physics or new sources at Cosmic Dawn and this tension with accepted models is compounded by our analysis that suggests absorption of greater depth. Alternatively, the measured spectrum may be equally-well fit assuming that there exists a residual unmodeled systematic sinusoidal feature and we explore this possibility further by examining for any additional 21-cm signal. The data then favors an absorption with Gaussian model parameters of amplitude $133 \pm 60$ mK, best width at half-power $9 \pm 3$ MHz and center frequency $72.5 \pm 0.8$ MHz. We also examine the consistency of the measured spectrum with plausible redshifted 21-cm models: a set of 3 of the 265 profiles in the global 21-cm atlas of Cohen et al. 2017 are favored by the spectrum. We conclude that the EDGES data may be consistent with standard cosmology and astrophysics, without invoking excess radio backgrounds or baryon-dark matter interactions.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it