OLD GLOBULAR CLUSTERS IN MAGELLANIC-TYPE DWARF IRREGULAR GALAXIES
Bibliographic record
Abstract
We have performed a search for old globular clusters (GCs) using archival F606W and F814W Hubble Space Telescope /Advanced Camera for Surveys images of 19 Magellanic-type dwarf Irregular (dIrr) galaxies. Those dIrrs reside in nearby (2–8 Mpc) associations of dwarf galaxies only. All dIrrs have absolute magnitudes fainter than or equal to that of the SMC ( M V = −16.2 mag). We detect in total 50 GC candidates in 13 dIrrs, of which 37 have ( V − I ) colors consistent with "blue" (old, metal-poor) GCs (bGCs). The luminosity function (LF) of the bGC candidates in our sample shows a turnover magnitude of M V = −7.41 ± 0.22 mag, consistent with other galaxy types. The width of the LF is σ = 1.79 ± 0.31, which is typical for dIrrs, but broader than the typical width in massive galaxies. The half-light radii and ellipticities of the GCs in our sample are similar to those of old GCs in the Magellanic Clouds and to those of "old halo" (OH) GCs in our Galaxy, but not as extended and spherical as the Galactic "young halo" (YH) GCs . The distribution shows a turnover rather than a power law as observed for the Galactic GCs. This might suggest that GCs in dIrrs are kinematically young and not yet fully relaxed. The present-day specific frequencies of GCs ( S N ) in the galaxies in our sample span a broad range: 0.3 < S N < 11. Assuming a dissipationless age fading of the galaxy light, the S N values would increase by a factor of ∼2.5–16, comparable with values for early-type dwarfs (dE/dSphs). A bright central GC candidate, similar to nuclear clusters of dEs, is observed in one of our dIrrs: NGC 1959. This nuclear GC has luminosity, color, and structural parameters similar to that of ω Cen and M 54, suggesting that the latter might have their origin in the central regions of similar Galactic building blocks as the dIrrs in this study. A comparison between properties of bGCs and Galactic YH GCs, suspected to have originated from similar dIrrs, is performed.
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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 | 0.001 | 0.007 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.022 | 0.003 |
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".