Faraday Rotation of Extended Emission as a Probe of the Large-Scale\n Galactic Magnetic Field
Bibliographic record
Abstract
The Galactic magnetic field is an integral constituent of the interstellar\nmedium (ISM), and knowledge of its structure is crucial to understanding\nGalactic dynamics. The Rotation Measures (RM) of extragalactic (EG) sources\nhave been the basis of comprehensive Galactic magnetic field models. Polarised\nextended emission (XE) is also seen along lines of sight through the Galactic\ndisk, and also displays the effects of Faraday rotation. Our aim is to\ninvestigate and understand the relationship between EG and XE RMs near the\nGalactic plane, and to determine how the XE RMs, a hitherto unused resource,\ncan be used as a probe of the large-scale Galactic magnetic field. We used\npolarisation data from the Canadian Galactic Plane Survey (CGPS), observed near\n1420 MHz with the Dominion Radio Astrophysical Observatory (DRAO) Synthesis\nTelescope. We calculated RMs from a linear fit to the polarisation angles as a\nfunction of wavelength squared in four frequency channels, for both the EG\nsources and the XE. Across the CGPS area, $55^{\\circ} < {\\ell} <193^{\\circ},\n-3^{\\circ} < b < 5^{\\circ}$, the RMs of the XE closely track the RMs of the EG\nsources, with XE RMs about half the value of EG-source RMs. The exceptions are\nplaces where large local HII complexes heavily depolarise more distant\nemission. We conclude that there is valuable information in the XE RM dataset.\nThe factor of 2 between the two types of RM values is close to that expected\nfrom a Burn slab model of the ISM. This result indicates that, at least in the\nouter Galaxy, the EG and XE sources are likely probing similar depths, and that\nthe Faraday rotating medium and the synchrotron emitting medium have similar\nvariation with galactocentric distance.\n
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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".