The Nearby Evolved Stars Survey – IV. Mapping cold gas in the circumstellar envelopes of evolved stars with 12CO and 13CO ( <i>J</i> = 1 → 0) emission
Bibliographic record
Abstract
ABSTRACT We have performed mapping observations of 42 AGB stars, of which 23 and 14 stars were detected in $^{12}$CO and $^{13}$CO ($J = 1 \rightarrow 0$) emission, respectively, using 45 m telescope of Nobeyama Radio Observatory. Our aim is to reveal distributions of extended cold gas in circumstellar envelopes and test a possibility of detecting shell structures with high $^{12}$CO/$^{13}$CO ratios caused by thermal pulses and third dredge-ups. By comparing our maps with those of $^{12}$CO ($J = 3 \rightarrow 2$) emission obtained with James Clerk Maxwell Telescope at the same angular resolution, we found that envelopes of $^{12}$CO ($J = 1 \rightarrow 0$) emission has at least twice the sizes of $^{12}$CO ($J = 3 \rightarrow 2$) emission. Among 14 stars detected in both $^{12}$CO and $^{13}$CO emission, nine stars show radial variations of $^{12}$CO/$^{13}$CO ratio along radial direction in their envelopes, which is likely caused by selective photodissociation by interstellar ultraviolet radiation, not thermal pulses or third dredge ups. Based on radiative transfer simulations, we conclude that optical depths are small (typically $\tau \lesssim 0.5$), ruling out the possibility that the absence of detected shells in our data is due to optical depth. This implies no signatures of thermal pulses or third dredge ups in the last $\sim$1500–13 000 yr. We further confirmed aspherical envelope morphologies of o Cet, WX Psc, and RAFGL 618, which were likely formed by bipolar outflows and photodissociation. The elongated morphology of SV Peg that we newly found is subject to study.
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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".