The complex nature of the nuclear star cluster in FCC 277★
Bibliographic record
Abstract
Recent observations have shown that compact nuclear star clusters (NSCs) are present in up to 80 per cent of galaxies. However, detailed studies of their dynamical and chemical properties are confined mainly to spiral galaxy hosts, where they are more easily observed. In this paper, we present our study of the NSC in FCC 277, a nucleated elliptical galaxy in the Fornax cluster. We use a combination of adaptive optics assisted near-infrared integral field spectroscopy, Hubble Space Telescope imaging and literature long-slit data. We show that while the NSC does not appear to rotate within our detection limit of ∼6 kms−1, rotation is detected at larger radii, where the isophotes appear to be discy, suggesting the presence of a nuclear disc. We also observe a distinct central velocity dispersion drop that is indicative of a dynamically cold rotating sub-system. Following the results of orbit-based dynamical modelling, corotating as well as counter-rotating stellar orbits are simultaneously needed to reproduce the observed kinematics. We find evidence for varying stellar populations, with the NSC and nuclear disc hosting younger and more metal rich stars than the main body of the galaxy. We argue that gas dissipation and some level of merging have likely played an important role in the formation of the nucleus of this intermediate-mass galaxy. This is in contrast to NSCs in low-mass early-type galaxies, which may have been formed primarily through the infall of star 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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".