Dense Gas in Star Forming Galaxies traced by HCN and CN
Bibliographic record
Abstract
We use archival data from the Atacama Large Millimeter Array to assess the relationship between dense gas, star formation, and gas dynamics in 10 nearby (ultra-)luminous infrared galaxies and spiral galaxy centers on sub-kiloparsec scales. The data from this same sample of galaxies shows a nearly constant CN/HCN line intensity ratio. This result conflicts with simple models of photon dominated regions, which predict that HCN emission traces shielded regions with high column densities while CN traces dense gas exposed to high ultraviolet radiation fields. We use gravo-turbulent models of star formation to measure the dense gas traced by emission from HCN. We find that the HCN/CO ratio in galaxies is a good tracer of gas above densities log(n) = 4.5 but that this ratio does not universally track the ratio of gravitationally bound, star-forming gas. We also find that the depletion time of the dense gas increases with the dense gas fraction.
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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".