Carbon Isotope Ratio in<sup>12</sup>CO/<sup>13</sup>CO toward Local Molecular Clouds with Near‐Infrared High‐Resolution Spectroscopy of Vibrational Transition Bands
Bibliographic record
Abstract
We report the carbon monoxide isotope ratio in local molecular clouds toward LkHα 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of 12 CO ν = 2 ← 0 and 13 CO ν = 1 ← 0 were observed with high-resolution near-infrared spectroscopy ( R = 23,000) to measure the 12 CO/ 13 CO ratio. The isotopic ratios are 12 CO/ 13 CO = 137 ± 9 (LkHα 101), 86 ± 49 (AFGL 490), and 158 (Mon R2 IRS 3), which are 1.5-2.8 times higher than the local interstellar medium value of 12 CO/ 13 CO = 57 ± 5 from millimeter C 18 O emission observations. This is not easily explained by saturation of the 13 CO absorption. It is also questionable whether the selective photodestruction of 13 CO can account for the difference between the Galactic trend and the present observation, because the molecular clouds are with high visible extinction ( A V = 10-70 mag), well shielded from destructive FUV radiation. The molecular gas associated with AFGL 490 and Mon R2 IRS 3 consists of multiple temperature components lying in the lines of sight. In the cool component ( T ex < 100 K), the excitation temperature of 12 CO is twice that of 13 CO. We attribute the temperature discrepancy to the photon-trapping effect, which makes the radiative cooling of the main isotopomer less effective.
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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 | 0.000 | 0.000 |
| 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".