<i>Hubble Space Telescope</i>Imagery and Canada‐France‐Hawaii Telescope Fabry‐Perot Two‐dimensional Spectroscopy in Hα of the Ejected Nebula M1‐67: Turbulent Status
Notice bibliographique
Résumé
Bright circumstellar nebulae around massive stars are potentially useful to derive time-dependent mass-loss rates and hence constrain the evolution of the central stars. A key case in this context is the relatively young ejection-type nebula M1-67 around the runaway Population I Wolf-Rayet star WR 124 (=209 BAC), which exhibits a WN 8 spectrum. With HST -WFPC2 we have obtained a deep, Hα image of M1-67. This image shows a wealth of complex detail that was briefly presented previously by Grosdidier et al. With the interferometer of the Université Laval (Québec, Canada), we have obtained complementary Fabry-Perot Hα data using Canada-France-Hawaii Telescope (CFHT) MOS/SIS. From these data M1-67 appears more or less as a spherical (or elliptical, with the major axis along the line of sight), thick, shell seen almost exactly along its direction of rapid spatial motion away from the observer in the ISM. However, a simple thick shell by itself would not explain the observed multiple radial velocities along the line of sight. This velocity dispersion leads one to consider M1-67 as a thick accelerating shell. Given the extreme perturbations of the velocity field in M1-67, it is virtually impossible to measure any systematic impact of the present WR (or previous LBV) wind on the nebular structure. The irregular nature of the velocity field is likely due to either large variations in the density distribution of the ambient ISM or large variations in the central star mass-loss history. In addition, either from the density field or the velocity field, we find no clear evidence for a bipolar outflow, as was claimed in other studies. On the deep Hα image we have performed continuous wavelet transforms to isolate stochastic structures of different characteristic size and look for scaling laws. Small-scale wavelet coefficients show that the density field of M1-67 is remarkably structured in chaotically (or possibly radially) oriented filaments everywhere in the nebula. We draw attention to a short, marginally inertial range at the smallest scales (6.7-15.0 × 10 -3 pc), which can be attributed to turbulence in the nebula, and a strong scale break at larger scales. Examination of the structure functions for different orders shows that the turbulent regime may be intermittent. Using our Fabry-Perot interferograms, we also present an investigation of the statistical properties of fluctuating gas motions using structure functions traced by Hα emission-line centroid velocities. We find that there is a clear correlation at scales 0.02-0.22 pc between the mean quadratic differences of radial velocities and distance over the surface of the nebula. This implies that the velocity field shows an inertial range likely related to turbulence, though not coincident with the small inertial range detected from the density field. The first- and second-order moments of the velocity increments are found to scale as ⟨|Δ v ( r )|⟩ ~ r 0.5 and ⟨|Δ v ( r )| 2 ⟩ ~ r 0.9 . The former scaling law strongly suggests that supersonic, compressible turbulence is at play in the nebula; on the other hand, the latter scaling law agrees very well with Larson-type laws for velocity turbulence. Examination of the structure functions for different orders shows that the turbulent regime is slightly intermittent and highly multifractal with universal multifractal indexes α ≈ 1.90-1.92 and C 1 ≈ 0.04 ± 0.01.
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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 | 0,003 | 0,002 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 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) | 0,027 | 0,006 |
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 ».