Radio Polarization from the Galactic Plane in Cygnus
Notice bibliographique
Résumé
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.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».