Tracing quasar narrow-line regions across redshift: a library of high-S/N optical spectra
Bibliographic record
Abstract
In a single optical spectrum, the quasar narrow-line region (NLR) reveals low-density, photoionized gas in the host galaxy interstellar medium (ISM), while the immediate vicinity of the central engine generates the accretion disc continuum and broad emission lines. To isolate these two components, we construct a library of high-S/N optical composite spectra created from the Sloan Digital Sky Survey Data Release 7. We divide the sample into bins of continuum luminosity and Hβ full width at half-maximum that are used to construct median composites at different redshift steps up to 0.75. We measure the luminosities of the narrow-emission lines [Ne v] λ3427, [Ne iii] λ3870, [O iii] λ5007, and [O ii] λ3728 with ionization potentials (IPs) of 97, 40, 35, and 13.6 eV, respectively. The high IP lines’ luminosities show no evidence of increase with redshift consistent with no evolution in the AGN spectral energy distribution or the host galaxy ISM illuminated by the continuum. In contrast, we find that the [O ii] line becomes stronger at higher redshifts, and we interpret this as a consequence of enhanced star formation contributing to the [O ii] emission in host galaxies at higher redshifts. The SFRs estimated from the [O ii] luminosities show a flatter increase with z than non-AGN galaxies given our assumed AGN contribution to the [O ii] luminosity. Finally, we confirm an inverse correlation between the strength of the Fe ii λ4570 complex and both the [O iii] equivalent width (though not the luminosity) and the width of the Hβ line as known from the eigenvector 1 correlations.
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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 | 0.001 |
| Bibliometrics | 0.005 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".