Molecular Line Emissions from the Photodissociation Region of NGC 7027
Bibliographic record
Abstract
We have observed or searched for 11 molecular species in 17 transitions in the 200 and 300 GHz bands in the young planetary nebula NGC 7027. The results include a first detection of C 2 H in this source. The observed spectra of HCO + , H 13 CO + , HCN, CN, C 2 H, and CO + show line widths wider than that of bulk CO emission but coincident with the full width at detection limit of weak wings in CO spectra. The HCO + , HCN, and CN emitting regions have a size of about 13'', significantly smaller than that of the CO emitting region. Thus, the emission of all the observed molecules other than CO and 13 CO must originate from a very small volume compared with the entire CO envelope. Excitation analyses of six molecules with electron and neutral collisions at a gas temperature of 800 K yield similar density estimates ranging from 1.3 to 5 × 10 5 cm -3 . Estimated column densities for HCO + , HCN, CN, CO + , and C 2 H are in good agreement with predictions by a chemical model for the photodissociation region of NGC 7027. These analyses suggest that photochemistry is active in NGC 7027 and the observed molecular emissions (except CO) originate from the H 2 photodissociation zone of the object.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.000 | 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".