CAPOS: The bulge Cluster APOgee Survey
Bibliographic record
Abstract
We present results from a study of 15 red giant members of the intermediate-metallicity globular cluster (GC) FSR 1758 using high-resolution, near-infrared spectra collected with the Apache Point Observatory Galactic Evolution Experiment II survey (APOGEE-2) that were obtained as part of CAPOS (the bulge Cluster APOgee Survey). Since its very recent discovery as a massive GC in the bulge region, evoking the name Sequoia, this has been an intriguing object with a highly debated origin, and initially led to the suggestion of a purported progenitor dwarf galaxy of the same name. In this work, we use new spectroscopic and astrometric data to provide additional clues as to the nature of FSR 1758. Our study confirms the GC nature of FSR 1758, and as such we report the existence of the characteristic N-C anticorrelation and Al-N correlation for the first time. We thereby reveal the existence of the multiple-population phenomenon, similar to that observed in virtually all GCs. Furthermore, the presence of a population with strongly enriched aluminum makes it unlikely that FSR 1758 is the remnant nucleus of a dwarf galaxy because Al-enhanced stars are uncommon in dwarf galaxies. We find that FSR 1758 is slightly more metal rich than previously reported in the literature; this source has a mean metallicity [Fe/H] between −1.43 to −1.36, depending on the adopted atmospheric parameters and a scatter within observational error, again pointing to its GC nature. Overall, the α-enrichment (≳ + 0.3 dex), Fe-peak (Fe, Ni), light (C, N), and odd-Z (Al) elements follow the trend of intermediate-metallicity GCs. Isochrone fitting in the Gaia bands yields an estimated age of ∼11.6 Gyr. We used the exquisite kinematic data, including our CAPOS radial velocities and Gaia eDR3 proper motions, to constrain the N-body density profile of FSR 1758, and found that it is as massive (∼2.9 ± 0.6 × 105 M⊙) as NGC 6752. We confirm a retrograde and eccentric orbit for FSR 1758. A new examination of its dynamical properties with the GravPot16 model favors an association with the Gaia-Enceladus-Sausage accretion event. Thus, paradoxically, the cluster that gave rise to the name of the Sequoia dwarf galaxy does not appear to belong to this specific merging event.
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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 | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".