The Metal-Poor Inner Spheroid Globular Cluster NGC 6558
Bibliographic record
Abstract
We discuss near-infrared photometric and spectroscopic observations of stars in and around the globular cluster NGC 6558, obtained with the FLAMINGOS-I imaging spectrograph on the Gemini South telescope. Efforts to estimate the metallicity of NGC 6558 from the slope of the red giant branch (RGB) are biased by contamination from bulge stars. The near-infrared spectroscopic properties of the two brightest stars projected against the main body of the cluster are consistent with them belonging to the bulge. After removing probable bulge members, we find that (1) the brightest metal-poor giant near the center of NGC 6558 has M K = -4.6, which is 1–1.5 mag fainter than the expected RGB tip brightness, and (2) [Fe/H] = -1.5 ± 0.5 based on the RGB slope measured from stars that are likely cluster members. This metallicity estimate is consistent with the nondetection of the first-overtone CO bands in the near-infrared spectra of giants midway down the RGB of NGC 6558. The K -band luminosity function (LF) of NGC 6558, corrected for contamination from bulge stars, parallels that of NGC 6121 on the lower RGB and subgiant branch (SGB), indicating that any depletion of giants in NGC 6558 is restricted to the upper portion of the RGB. When scaled according to the number of stars midway up the giant branch, the K LFs of NGC 6121 and NGC 6558 agree to within ±0.1 dex on the SGB, indicating that their ages do not differ by more than ±2 Gyr.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.037 | 0.009 |
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".