The CFHT Open Star Cluster Survey. I. Cluster Selection and Data Reduction
Bibliographic record
Abstract
We present this paper in conjunction with a companion paper as the first results in the Canada-France-Hawaii Telescope Open Star Cluster Survey. This survey is a large BVR imaging data set of 19 open star clusters in our Galaxy. This data set was taken with the CFH12K mosaic CCD (42' × 28'), and the majority of the clusters were imaged under excellent photometric, subarcsecond seeing, conditions. The combination of multiple exposures extending to deep ( V ∼ 25) magnitudes with short (≤10 s) frames allows for studies ranging from faint white dwarf stars to bright turnoff, variable, and red giant stars. The primary aim of this survey is to catalog the white dwarf stars in these clusters and establish observational constraints on the initial-final mass relationship for these stars and the upper mass limit to white dwarf production. Additionally, we hope to better determine the properties of the clusters, such as age and distance, and also test evolution and dynamical theories by analyzing luminosity and mass functions. In order to more easily incorporate these data in further studies, we have produced a catalog of positions, magnitudes, colors, and stellarity confidence for all stars in each cluster of the survey. This reduction, along with the computed calibration parameters for all three nights of the observing run will encourage others to use these data in different astrophysical studies outside of our goals. Additionally, the data set is reduced using the new TERAPIX photometric reduction package, PSFex, which is found to compare well with other packages. This paper is intended both as a source for the astronomical community to obtain information on the clusters in the survey and as a detailed reference of reduction procedures for further publications of individual clusters. We discuss the methods employed to reduce the data and compute the photometric catalog. We reserve both the scientific results for each individual cluster and global results from the study of the entire survey for future publications. The first of these further publications is devoted to the old rich open star cluster, NGC 6819, and appears as a companion paper in the same issue of the Journal.
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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 | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.012 | 0.012 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.031 | 0.021 |
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".