The Metallicity of the Red Giant Branch in the Disk of NGC 6822
Bibliographic record
Abstract
Deep J , H , and K ' images obtained with the Canada‐France‐Hawaii Telescope adaptive optics system are used to investigate the metallicity of red giant branch (RGB) stars in three fields in the disk of the Local Group dwarf irregular galaxy NGC 6822. The slope of the RGB on the ( K , J−K ) color‐magnitude diagrams indicates that [Fe/H] = -1.0 ± 0.3. The locus of the RGB is bluer than that of globular clusters with the same RGB slope by an amount that is consistent with the majority of RGB stars in these fields having an age near 3 Gyr. It is demonstrated that if RGB stars in NGC 6822 are this young, then the metallicity computed from the RGB slope may be ∼0.05 dex too low. Finally, the metallicity computed from the RGB slope is lower than spectroscopic‐based metallicities for young stars in NGC 6822, and it is concluded that Δ[Fe/H]/Δ t = −0.2 ± 0.1 dex Gyr −1 in NGC 6822 during the past few gigayears.
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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 | 0.001 | 0.001 |
| 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".