ALMA Observations of Layered Structures due to CO Selective Dissociation in the ρ Ophiuchi A Plane-parallel PDR
Bibliographic record
Abstract
Abstract We analyze 12CO(J = 2−1), 13CO(J = 2−1), C18O (J = 2−1), and 1.3 mm continuum maps of the ρ Ophiuchi A photodissociation region (PDR) obtained with ALMA. Layered structures of the three CO isotopologues with an angular separation of 10″ = 6.6 × 10−3 pc = 1400 au are clearly detected around the Be star, S1 (i.e., each front of emission shifts from the near to far side in order of 12CO, 13CO, and C18O). We estimate the spatial variations of X(13CO)/X(C18O) abundance ratios, and find that the abundance ratio is as high as 40 near the emission front, and decreases to the typical value in the solar system of 5.5 on a small angular scale of 4″ = 2.6 × 10−3 pc = 560 au. We also find that the I(12CO(2−1))/I(13CO(2−1)) intensity ratio is very high (>21) in the flat-spectrum young stellar object, GY-51, located in the PDR. The enhancement of the ratios indicates that the UV radiation significantly affects the CO isotopologues via selective dissociation in the overall ρ Ophiuchi A PDR, and that the ρ Ophiuchi A PDR has a plane-parallel structure.
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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 | 0.000 | 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".