STAR STREAM FOLDING BY DARK GALACTIC SUBHALOS
Bibliographic record
Abstract
Star streams in galactic halos are long, thin, unbound structures that will be disturbed by the thousands of dark matter subhalos that are predicted to be orbiting within the main halo. A subhalo generally induces a localized wave in the stream which often evolves into a "z-fold" as an initially trailing innermost part rotates faster than an initially leading outermost part. The folding, which becomes increasingly complex with time, leads to an apparent velocity dispersion increase and thickening of the stream. We measure the equivalent velocity dispersion around the local mean in the simulations, finding that it rises to about 10 km s −1 after 5 Gyr and 20 km s −1 after 13 Gyr. The currently available measurements of the velocity dispersion of halo star streams range from as small as 2 km s −1 to slightly over 20 km s −1 . The streams with velocity dispersions of 15–20 km s −1 are compatible with what subhalo heating would produce. A dynamical understanding of the low velocity dispersion streams depends on the time since the progenitor's tidal disruption into a thin stream. If the streams are nearly as old as their stars then subhalos cannot be present with the predicted numbers and masses. However, the dynamical age of the streams can be significantly less than the stars. If the three lowest velocity streams are assigned ages of 3 Gyr, they are in conflict with the subhalo heating. The main conclusion is that star stream heating is a powerful and simple test for subhalo structure.
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| 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".