Dissecting the Luminosity Function of the Coma Cluster of Galaxies Using Canada‐France‐Hawaii Telescope1 Wide‐Field Images
Bibliographic record
Abstract
We determined the relative spatial density of the Coma Cluster galaxies, selected by luminosity and by central brightness, i.e., the luminosity function bivariate in central brightness. The Coma Cluster and control fields were imaged using the CFH12K (42' × 28') and UH8K (28' × 28') wide-field cameras at the Canada-France-Hawaii Telescope. Selected Hubble Space Telescope ( HST ) images were used for testing. Quantities were derived from measurements in at least two colors, which have the following features: (1) galaxies as faint as 3 times the luminosity of the brightest globular clusters are in the completeness region of our data. (2) We have a complete census (in the explored region) of low surface brightness galaxies with a central surface brightness almost as low as the faintest ones so far cataloged. (3) The explored area is among the largest ever sampled with CCDs at comparable depth for any cluster of galaxies. (4) The error budget includes all sources of errors known to date. Using HST images, we also discovered that blends of globular clusters, not resolved into individual components due to seeing, look like dwarf galaxies when observed from the ground and are numerous and bright. When mistaken as extended sources, they increase the steepness of the luminosity function at faint magnitudes. The derived Coma luminosity function is relatively steep (α = -1.4) over the 11 magnitudes sampled, but the slope and shape depend on color. A large population of faint low surface brightness galaxies was discovered, representing the largest contributor (in number) to the luminosity function at faint magnitudes. We found a clear progression for a faintening of the luminosity function from high surface brightness galaxies (μ ~ 20 mag arcsec -2 ) to galaxies of very faint central brightness (μ ~ 24.5 mag arcsec -2 ), and some evidence for a steepening. Compact galaxies, usually classified as stars and therefore not included in the luminosity function, are found to be a minor population in Coma.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".