Bibliographic record
Abstract
We have re-analyzed the NRAO VLA Sky Survey (NVSS) data to derive rotation measures (RMs) toward 37,543 polarized radio sources. The resulting catalog of RM values covers the sky area north of declination −40° with an average density of more than one RM per square degree. We present an image of the median RM over 82% of the sky with a resolution of 8° and a typical error of ±1–2 rad m −2 . The image shows large-scale structures in RM that extend to very high Galactic latitudes. A simple analysis of the RM structure at high Galactic latitudes is used to derive properties of the Galactic halo magnetic field in the solar neighborhood. We find the component of the local field perpendicular to the plane (the z -component) equal to +0.30 μG for z < 0 and −0.14 μG for z >0. The reversal of sign across the Galactic plane is consistent with a quadrupole field geometry for the poloidal component of the halo field. The halo magnetic field component parallel to the disk is also found to be antisymmetric and generally consistent with a toroidal field, with strength +0.83 μG for z < 0 and −0.39 μG for z >0. We have identified five regions of the sky where the foreground median RM is consistently less than 1 rad m −2 over several degrees. These holes in the foreground RM will be useful for future studies of possible small-scale fluctuations in cosmic magnetic field structures. In addition to allowing measurement of RMs toward polarized sources, the new analysis of the NVSS data removes the effects of bandwidth depolarization for |RM| ≳ 100 rad m −2 inherent in the original NVSS source catalog. This new catalog of RMs and polarized flux densities is available online, and will be a valuable resource for further studies of the Galactic magnetic field and magnetoionic medium, and extragalactic magnetic fields.
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.016 | 0.005 |
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".