Extraction of homogeneous turbulent motions in the ionized interstellar medium: application to the NGC 595 nebula
Bibliographic record
Abstract
Relatively unexplored in recent years, turbulence in the ionized interstellar medium could allow us to explain peculiar gas motions observed in H ii regions. We present an improved method that allows the extraction of quasi-homogeneous turbulent motions from bidimensional radial velocity maps. This paper is an application to the NGC 595 nebula, a giant H ii region in M33. The use of the Zurflueh filter is re-instated in order to separate ordered motions from turbulent fluctuations in astronomical observations. A statistical approach, based on the application of the autocorrelation and second-order structure functions, is used on the filtered centroid measurements in Hα, [O iii] and [S ii]. Following the work of Brunt & Mac Low, an investigation of the density inhomogeneities in NGC 595 suggests that turbulence in the large nebula could be at least partially supersonic. Compressible shock waves related to stellar winds of massive stars are presented as the main source for stirring up optical gases into high-amplitude turbulent velocity fluctuations. Unfortunately, the transition from a 2D to 3D geometry, required in order to compare observations to existing turbulence models, could not be appropriately accomplished. This is attributed to an important scattering characterizing the supersonic regime in the theoretical results. Using particular conclusions reached in our ongoing work on standard H ii regions in M33, the kinematical disorder induced by turbulent velocities and observed on the plane of the sky is translated into a mean broadening effect along the line of sight for each investigated ion. This confirms that the O++ sphere is largely governed by supersonic turbulence while the same argument remains inconclusive in Hα and [S ii]. The amplitude of the turbulent motions (velocities) seems to decrease with distance from the central star cluster. This provides a reasonable explanation for a well-defined signature in non-thermal linewidths already identified in our first paper on NGC 595.
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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 | 0.001 | 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) | 0.000 | 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".