Stored in the archives: Uncovering the CN/CO intensity ratio with ALMA in nearby U/LIRGs
Bibliographic record
Abstract
ABSTRACT We present an archival Atacama Large Millimeter/submillimeter Array (ALMA) study of the cyanide radical (CN) N = 1 − 0/carbon monoxide (CO) J = 1 − 0 intensity ratio in nearby (z < 0.05) ultra-luminous and luminous infrared galaxies (U/LIRGs). We identify 16 U/LIRGs that have been observed in both CN and CO lines at ∼500 pc resolution based on 16 different ALMA projects. We measure the (CN bright)/CO and (CN bright)/(CN faint) intensity ratios at an ensemble of molecular clouds scales (CN bright = CN N = 1 − 0, J = 3/2 − 1/2; CN faint = CN N = 1 − 0, J = 1/2 − 1/2 hyperfine groupings). Our global measured (CN bright)/CO ratios range 0.02–0.15 in LIRGs and 0.08–0.17 in ULIRGs. We attribute the larger spread in LIRGs to the variety of galaxy environments included in our sample. Overall, we find that the (CN bright)/CO ratio is higher in nuclear regions, where the physical and excitation conditions favour increased CN emission relative to the disc regions. 10 out of 11 galaxies which contain well-documented active galactic nuclei show higher ratios in the nucleus compared with the disc. Finally, we measure the median resolved (CN bright)/(CN faint) ratio and use it to estimate the total integrated CN line optical depth in ULIRGs (τ ∼ 0.96) and LIRGs (τ ∼ 0.23). The optical depth difference is likely due to the higher molecular gas surface densities found in the more compact ULIRG systems.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".