Emission-line abundances of absorption-selected galaxies at z < 0.5
Bibliographic record
Abstract
We have obtained optical spectra of four galaxies associated with Mg ii quasi-stellar object (QSO) absorbers at redshifts 0.10 < z < 0.45. We calculate the gas-phase oxygen abundance of these galaxies using the empirical R23 strong-line method. The absolute B-band magnitudes of the galaxies span −20.6 < MB < −18.3. If the metallicities lie on the R23 upper branch (8.4 < log (O/H) + 12 < 8.9), then the metallicities of these absorption-selected galaxies span the range between 0.5 and 1.4 Z⊙ and would be consistent with the well-known luminosity-metallicity relation for 0.10 < z < 0.45 emission-line galaxies. However, such metallicities would be 0.5–1.0 dex higher than those observed in damped Lyman a systems (DLAs) via absorption-line measurements at similar redshifts. Conversely, the lower R23 branch calibration yields metallicities Z ∼ 1/7 Z⊙, consistent with the DLA absorption metallicities at low redshifts. In this case, the absorption-selected galaxies would lie significantly lower than the luminosity-metallicity relation for emission-line galaxies at z < 0.5. We discuss the implications and possible solutions for each scenario.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.001 | 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".