Bibliographic record
Abstract
We present the results of a search for strong Hα emission line galaxies (rest frame equivalent widths greater than 50 Å) in the z ≈ 0.23 cluster Abell 2390. The survey contains 1189 galaxies over 270 arcmin2, and is 50 per cent complete at Mr ≈ −17.5+5 log h. The fraction of galaxies in which Hα is detected at the 2σ level rises from 0.0 in the central regions (excluding the cD galaxy) to 12.5±8 per cent at R200. For 165 of the galaxies in our catalogue, we compare the Hα equivalent widths with their [O ii] λ3727 equivalent widths, from the Canadian Network for Observational Cosmology (CNOC1) spectra. The fraction of strong Hα emission line galaxies is consistent with the fraction of strong [O ii] emission galaxies in the CNOC1 sample: only 2±1 per cent have no detectable [O ii] emission and yet significant (> 2σ) Hα equivalent widths. Dust obscuration, non-thermal ionization, and aperture effects are all likely to contribute to this non-correspondence of emission lines. We identify six spectroscopically ‘secure’ k+a galaxies [W0(O ii) < 5 Å and W0(Hδ) ≳ 5 Å]; at least two of these show strong signs in Hα of star formation in regions that are covered by the slit from which the spectra were obtained. Thus, some fraction of galaxies classified as k+a based on spectra shortward of 6000 Å are likely to be undergoing significant star formation. These results are consistent with a ‘strangulation’ model for cluster galaxy evolution, in which star formation in cluster galaxies is gradually decreased, and is neither enhanced nor abruptly terminated by the cluster environment.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.002 |
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".