Gravitational Collapse of Filamentary Magnetized Molecular Clouds
Bibliographic record
Abstract
We develop models for the self-similar collapse of magnetized isothermal cylinders. We find solutions for the case of a fluid with a constant toroidal flux-to-mass ratio (Γ ϕ = constant) and the case of a fluid with a constant gas to magnetic pressure ratio (β = constant). In both cases, we find that a low magnetization results in density profiles that behave as ρ ∝ r -4 at large radii, and at high magnetization we find density profiles that behave as ρ ∝ r -2 . This density behavior is the same as for hydrostatic filamentary structures, suggesting that density measurements alone cannot distinguish between hydrostatic and collapsing filaments—velocity measurements are required. Our solutions show that the self-similar radial velocity behaves as v r ∝ r during the collapse phase, and that unlike collapsing self-similar spheres, there is no subsequent accretion (i.e., expansion-wave) phase. We also examine the fragmentation properties of these cylinders and find that in both cases, the presence of a toroidal field acts to strengthen the cylinder against fragmentation. Finally, the collapse timescales in our models are shorter than the fragmentation timescales. Thus, we anticipate that highly collapsed filaments can form before they are broken into pieces by gravitational fragmentation.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".