Constraints on possible age spreads within young massive clusters in the Large Magellanic Cloud
Bibliographic record
Abstract
Abstract Recent studies have shown that the observed main-sequence turnoff (MSTO) in colour–magnitude diagrams of intermediate-age (1–2 Gyr) clusters in the Large Magellanic Cloud (LMC) is broader than would be nominally expected for a simple stellar population. This has led to the suggestion that such clusters may host multiple stellar populations, with age spreads of 100–500 Myr. However, at intermediate ages, spreads of this magnitude are difficult to discern and alternative explanations have been put forward (e.g. stellar rotation, interacting binaries). A prediction of the age-spread scenario is that younger clusters in the LMC, with similar masses and radii, should also show significant age spreads. In younger clusters (i.e. 40–300 Myr), such large age spreads should be readily apparent. We present an analysis of the colour–magnitude diagrams of two massive young clusters in the LMC (NGC 1856 and NGC 1866) and show that neither have such large age spreads; in fact, both are consistent with a single burst of star formation [σ(age) < 35 Myr]. This leads us to conclude that either the intermediate-age clusters in the LMC are somehow special or the broadened MSTOs are not due to an age spread within the clusters.
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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 | 0.002 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".