First limits on the 21 cm power spectrum during the Epoch of X-ray heating
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Bibliographic record
Abstract
We present first results from radio observations with the Murchison Widefield \nArray seeking to constrain the power spectrum of 21 cm brightness temperature \nfluctuations between the redshifts of 11.6 and 17.9 (113 and 75 MHz). Three \nhours of observations were conducted over two nights with significantly \ndifferent levels of ionospheric activity. We use these data to assess the \nimpact of systematic errors at low frequency, including the ionosphere and \nradio-frequency interference, on a power spectrum measurement. We find that \nafter the 1-3 hours of integration presented here, our measurements at the \nMurchison Radio Observatory are not limited by RFI, even within the FM band, \nand that the ionosphere does not appear to affect the level of power in the \nmodes that we expect to be sensitive to cosmology. Power spectrum detections, \ninconsistent with noise, due to fine spectral structure imprinted on the \nforegrounds by reflections in the signal-chain, occupy the spatial Fourier \nmodes where we would otherwise be most sensitive to the cosmological signal. We \nare able to reduce this contamination using calibration solutions derived from \nautocorrelations so that we achieve an sensitivity of 10 mK⁴ on comoving \nscales k ≲ 0.5 h Mpc⁻¹. This represents the first upper limits on \nthe 21 cm power spectrum fluctuations at redshifts 12 ≲ z ≲ 18 \nbut is still limited by calibration systematics. While calibration improvements \nmay allow us to further remove this contamination, our results emphasize that \nfuture experiments should consider carefully the existence of and their ability \nto calibrate out any spectral structure within the EoR window.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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