Constraints on the densities and temperature of the Seyfert 2 narrow line region
Bibliographic record
Abstract
Context. Different studies have reported the so-called temperature problem of the narrow line region (NLR) of active galactic nuclei (AGNs). Its origin is still an open issue. To properly address its cause, a trustworthy temperature indicator is required. Aims. To determine the temperature of an emission line plasma, the [O III ] ( λ 4363Å/ λ 5007Å) line ratio is typically used. However, in the case of the NLR of AGNs, this ratio is not reliable when the electron density extends much above 10 5 cm −3 as collisional deexcitation strongly affects this ratio independently of the temperature. To verify the density regime, we need a density diagnostic that applies to high excitation plasma. Methods. We propose that the weak [Ar IV ] λλ 4711,40Å doublet is the appropriate tool for evaluating the density of the high excitation plasma. We subsequently made use of the recent S7 survey sample to extract reliable measurements of the weak [Ar IV ] doublet in 16 high excitation Seyfert 2s. As a result we could derive the plasma density of the NLR of our Seyfert 2 sample and compared the temperature inferred from the observed [O III ] ( λ 4363Å/ λ 5007Å) ratios. Results. It was found that 13 Seyfert 2s cluster near similar values as the [O III ] ( λ 4363Å/ λ 5007Å) ratio, at a mean value of 0.0146 ± 0.0020. Three objects labeled outliers stand out at markedly higher [O III ] values (> 0.03). Conclusions. If for each object one assumes a single density, the values inferred from the [Ar IV ] doublet for the 13 clustering objects all lie below 60 000 cm −3 , indicating that the [O III ] ( λ 4363Å/ λ 5007Å) ratios in these objects is a valid tracer of plasma temperature. Even when assuming a continuous power-law distribution of the density, the inferred cut-off density required to reproduce the observed [Ar IV ] doublet is in all cases < 10 5.1 cm −3 . The average NLR temperature inferred for the 13 Seyfert 2s is 13 000 ± 703 K, which photoionization models have difficulty reproducing. Subsequently we considered different mechanisms to account for the observed [O III ] ratios. For the three outliers, a double-bump density distribution is likely required, with the densest component having a density > 10 6 cm −3 .
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".