The Detection of Molecular Gas in the Outskirts of NGC 6946
Bibliographic record
Abstract
We present the results of a search for molecular gas emission via the CO line in the far outer disk of the nearby spiral NGC 6946. The positions targeted were chosen to lie on or near previously identified outer-disk H II regions. Molecular gas was clearly detected out to 1.3 R 25 , with a further tentative detection at 1.4 R 25 . The CO detections show excellent agreement with the H I velocities and imply beam-averaged column densities of (0.3-9) × 10 20 cm -2 and molecular gas masses of (2-70) × 10 5 M ☉ per 21'' beam (560 pc). We find evidence for an abrupt decrease in the molecular fraction at the edge of the optical disk, similar to that seen previously in the azimuthally averaged areal star formation rate. Our observations provide new constraints on the factors that determine the presence and detectability of molecular gas in the outskirts of galaxies, and suggest that neither the H I column, the metallicity, nor the local heating rate alone plays a dominant role.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".