JWST: Deuterated PAHs, PAH Nitriles, and PAH Overtone and Combination Bands. I. Program Description and First Look
Bibliographic record
Abstract
Abstract A first look is taken at the NIRSpec 1–5 μ m observations from James Webb Space Telescope program 1591 that targets seven objects along the low-mass stellar life cycle with polycyclic aromatic hydrocarbon (PAH) emission. Spectra extracted from a 1.″5 radius circular aperture are explored, showing a wealth of features, including the 3 μ m PAH complex, the PAH continuum, and atomic and molecular emission lines from H i , He, H 2 , and other species. CO 2 - and H 2 O-ice absorption and CO emission is also seen. Focusing on the bright-PDR position in M17, the PAH CH stretch falls at 3.29 μ m (FWHM = 0.04 μ m). Signs of its 1.68 μ m overtone are confused by line emission in all targets. Multicomponent decomposition reveals a possible aliphatic deuterated PAH feature centered at 4.65 μ m (FWHM = 0.02 μ m), giving [D/H] alip. = 31% ± 12.7%. However, there is little sign of its aromatic counterpart between 4.36 and 4.43 μ m. There is also little sign of PAH nitrile emission between 4.34 and 4.39 μ m. A PAH continuum rises from ∼1 to 3.2 μ m, after which it jumps by about a factor of 2.5 at 3.6 μ m, with bumps at 3.8, 4.04, and 4.34 μ m adding structure. The CO 2 absorption band in M17 is matched with 10:1 H 2 O:CO 2 ice at 10 K. The v = 0 pure rotational molecular hydrogen population diagram reveals >2200 K UV-pumped gas. The hydrogen Pfund series runs from levels 10 to >30. Considering Br α /Br β = 0.381 ± 0.01966 and Case B recombination results in A V ≃ 8. CO emission in IRAS 21282+5050 originates from 258 K gas. In-depth spectral–spatial analysis of all features and targets is planned for a series of forthcoming papers.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.023 | 0.007 |
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".