Searching for signatures of Fe II atomic processes in spectra of active galactic nuclei
Bibliographic record
Abstract
Aims. We use a large sample of Type 1 active galactic nuclei (AGNs) spectra in order to investigate which atomic processes are responsible for some observed properties of the Fe II emission lines and how they are connected with macroscopic physical characteristics of AGN emission regions. We especially focus on the violated relative intensities between different optical Fe II lines, whose relative strengths do not follow the expected values according to atomic parameters. We investigated the connection between this effect and the ratio of optical to UV Fe II lines (Fe II opt /Fe II UV ). Methods. We divided the optical Fe II lines into two large line groups: consistent (Fe II cons ), whose relative intensities are in accordance with their atomic properties, and inconsistent (Fe II incons ), whose relative intensities are significantly stronger than theoretically expected. We fitted the spectra with a flexible and complex optical Fe II model, where both consistent and inconsistent Fe II lines were divided into several line groups according to their atomic characteristics and fitted independently in order to obtain more empirical clues about their properties. We focused particularly on understanding the processes that produce strong inconsistent Fe II lines, and therefore, we investigated their correlations with Fe II cons as well as with UV Fe II lines and some measured spectral parameters. Results. The ratios of Fe II incons /Fe II cons and Fe II opt /Fe II UV increase as the Eddington ratio increases and as the line widths decrease. It is possible that both ratios are affected by the process of self-absorption of stronger lines, which is responsible for the transmission of energy from the UV to the optical Fe II emission lines and, analogously, from the Fe II cons to the Fe II incons lines. In this scenario, the high Eddington ratio causes an increase in the optical depth in Fe II lines, which results in the triggering of the process of self-absorption. Measured average widths for different Fe II line groups indicate the stratification of the optical Fe II emission region. This implies that the observed Fe II spectrum is probably a complex mixture of radiation from emission regions with different physical conditions and distances from the black hole.
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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 | 0.000 | 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".