Radio Polarization from the Galactic Plane in Cygnus
Bibliographic record
Abstract
We present 1420 MHz (λ = 21 cm) observations of polarized emission from an area of 117 deg 2 in the Galactic plane in Cygnus, covering 82° < l < 95°, -3 5 < b < +5 5, a complex region where the line of sight is directed nearly along the Local spiral arm. The angular resolution is ~1', and structures as large as 45' are fully represented in the images. Polarization features bear little resemblance to features detected in total power: while the polarized signal arises in diffuse Galactic synchrotron emission regions, the appearance of the polarized sky is dominated by Faraday rotation occurring in small-scale structure in the intervening warm ionized medium. There is no concentration of polarization structure toward the Galactic plane, indicating that both the emission and Faraday rotation occur nearby. We develop a conceptual framework for interpretation of the observations. We can detect only that polarized emission which has its origin closer than the "polarization horizon," at a distance d ph ; more distant polarized emission is undetectable because of depth depolarization (differential Faraday rotation) and/or beam depolarization (due to internal and external Faraday dispersion). The value of d ph depends on the instrument used (frequency and beamwidth) as well as the direction being studied. In our data we find that d ph ≈ 2 kpc, consistent with the polarization features originating in the Local arm. The filling factor of the warm ionized medium is constrained by our data to be considerably less than unity: polarized signals that pass through multiple regions of Faraday rotation experience severe depolarization, but polarized fractions up to ~10% are seen, implying that there are lines of sight that intersect only one Faraday rotation region within the polarization horizon. The rotation measure (RM) of the extended polarized emission has a distribution that peaks at -30 rad m -2 and has a width to half-maximum of 300 rad m -2 . The peak and half-width of the distribution of RMs of extragalactic sources in the region are -125 and 600 rad m -2 , respectively. This suggests that RM increases monotonically with length of propagation path through the interstellar medium in this direction. Among localized polarization features that we discuss, G83.2+1.8 and G91.8-2.5 stand out for their circular or quasi-circular form and extent of more than 1°; both are probably related to the impact of stellar activity on the surrounding medium, although the stars responsible cannot be identified. Another polarization feature, G91.5+4.5, extends 2 5 × 1° and coincides with a molecular cloud; it plausibly arises in an ionized skin on the outside of the cloud. Polarized emission seen across the face of the large, dense H II region, W80, must be generated in the 500 pc between the Sun and W80, since W80 must depolarize all extended nonthermal emission generated behind it. Of the supernova remnants G84.2-0.8, G89.0+4.7 (HB 21), G93.7-0.2 (CTB 104A), and G94.0+1.0 (3C 434.1), only HB 21 and CTB 104A show polarized emission; the other two lie beyond the polarization horizon and their emission suffers beam depolarization. Emission from the surrounding medium is depolarized on passage through HB 21.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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) | 0.001 | 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".