A faint extended cluster in the outskirts of NGC 5128: evidence of a low mass accretion
Bibliographic record
Abstract
We report the discovery of an extended globular cluster in a halo field in Centaurus A (NGC 5128), situated from the centre of that galaxy, imaged with the Advanced Camera for Surveys on board the Hubble Space Telescope. At the distance of the galaxy, the half-light radius of the cluster is rh∼ 17 pc, placing it among the largest globular clusters known. The faint absolute magnitude of the star cluster, MV,○=−5.2, and its large size render this object somewhat different from the population of extended globular clusters previously reported, making it the first firm detection in the outskirts of a giant galaxy of an analogue of the faint, diffuse globular clusters present in the outer halo of the Milky Way. The colour–magnitude diagram of the cluster, covering approximately the brightest four magnitudes of the red giant branch, is consistent with an ancient, i.e. ≳8 Gyr, intermediate metallicity, i.e. [M/H]∼−1.0 dex, stellar population. We also report the detection of a second, even fainter cluster candidate which would have rh∼ 9 pc and MV,○=−3.4 if it is at the distance of NGC 5128. The properties of the extended globular cluster and the diffuse stellar populations in its close vicinity suggest that they are part of a low mass accretion in the outer regions of NGC 5128.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".