Tidal debris of dwarf spheroidals as a probe of structure formation models
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Bibliographic record
Abstract
Recent observations suggest that Carina and other nearby dwarf spheroidal galaxies (dSphs) are surrounded by unbound stars tidally stripped by the Milky Way. We have run high-resolution N-body simulations of dwarf galaxies orbiting within the Milky Way halo to determine if such observations can be explained with dark matter potentials like those implied by current structure formation models. We show that tidal forces acting on dwarfs with constant density cores or with cuspy profiles having a low concentration parameter c≲ 7) lead to flat outer stellar density profiles like that of Carina for a variety of orbital configurations. On the contrary, it is more difficult to remove stars from cuspy dark matter haloes with concentrations as high as predicted by cold dark matter (CDM) models at the mass scale of dwarf galaxies (c > 10), and the data can only be reproduced assuming nearly radial orbits. Our simulations show that Carina is losing mass at a fractional rate <0.1 Gyr−1 and its mass-to-light ratio could be inflated by at most a factor of 2 due to unbound stars projected along the line of sight. We follow the evolution of the tidal debris within a triaxial clumpy cold dark matter Milky Way halo which causes differential precession and small-scale heating of the stellar streams. This renders them useless as a dynamical tracer of the Galactic potential in CDM cosmogonies. Models with warm dark matter (WDM) or collisional fluid dark matter (FDM) produce dwarf haloes with lower central densities than CDM and would be consistent with the observed tidal tails even for orbits with eccentricities as low as indicated by current data on nearby dwarf spheroidals. Galactic haloes in models with FDM are expected to be smooth and spherical and would be favoured by the detection of cold coherent streams such as that associated with the Sagittarius dwarf spheroidal. In this respect the distribution of stellar streams on the plane of the sky can provide a novel test of the nature of the dark matter. On the other end, the streams could be similarly dispersed in lumpy CDM haloes and in smoother, triaxial WDM haloes
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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 it