JCMT POL-2 observations of magnetic fields potentially shaped by outflows in the pre-planetary nebulae CRL 618 and OH231.8+4.2
Bibliographic record
Abstract
ABSTRACT We present the first observations of magnetic fields in pre-planetary nebulae (PPNe) made with the POL-2 polarimeter on the James Clerk Maxwell Telescope. We observed the PPNe CRL 618 and OH231.8+4.2 in 850 $\mu$m polarized light. In both cases, we observe ordered magnetic fields that appear to arise from dusty circumstellar material that has been swept up by the passage of outflows driven by the central post-asymptotic giant branch star. CRL 618 shows a magnetic field aligned with one of the most extreme position angles of the outflowing bullets ejected from the central source. We hypothesize that polarized emission in CRL 618 may preferentially arise from material in the walls of the dust cavity opened by the ejected bullets. Conversely, OH231.8+4.2 shows a magnetic field that is aligned approximately perpendicular to the outflow direction, which may preferentially arise from an infrared-bright dense clump embedded near the base of the outflow. Despite CRL 618 being carbon-rich and OH231.8 being oxygen-rich, there is no significant difference in the polarization fractions of the two sources. This suggests that at linear resolutions $\sim 10^{4}$ au, the complexity of the magnetic field geometry on scales smaller than the beam, rather than grain composition, sets the measured polarization fraction of these sources.
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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) | 0.002 | 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".