The Search for Primordial<sup>3</sup>He Using the 8.665 GHz Hyperfine Spin‐Flip Transition of<sup>3</sup>He<sup>+</sup>
Bibliographic record
Abstract
Frequency-switched observations of the 8.665 GHz hyperfine spin-flip transition of 3 He + have been made in eight Galactic H II regions in both the inner and outer Galaxy. For sources in the outer Galaxy, the observations reported here show no evidence for 3 He + to levels well below the level of detections claimed by Bania et al. using the position-switching technique. There is strong evidence that weak terrestrial interference is the explanation for the variability and relatively high level of 3 He + previously reported in several outer Galaxy sources. In the inner Galaxy, 3 He + is detected in W43, M17S, and W51 at abundance levels similar to those reported by Balser et al. with 3 He + /H + ~ (1-2) × 10 -5 . Contrary to what has been reported previously, the 3 He + /H + abundances are found to decrease rapidly with increasing distance from the Galactic center and fall below detectable levels by the Galactic radius of W49 (~8 kpc). This fall-off in "second-generation" 3 He abundance with distance from the Galactic center is similar to what is predicted by the P d = 0 model of Galli et al. but is at least a factor of 5 underabundant. The upper limit to the antenna temperatures obtained here for the 3 He + lines in Orion A, W49, and S209 gives an upper limit for the abundance of primordial 3 He that is an order of magnitude below the upper limit suggested by Bania et al. This leads to a lower limit for the nucleon-to-photon ratio η that is at least an order of magnitude above the narrow limits set by 7 Li and deuterium. Possible explanations for this are that there is a larger than expected uncertainty in determining 3 He abundances or that some mechanism is destroying primordial 3 He in the Galaxy over a Hubble time.
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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 | 0.000 |
| 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".