THE SHAPE AND PROFILE OF THE MILKY WAY HALO AS SEEN BY THE CANADA-FRANCE-HAWAII TELESCOPE LEGACY SURVEY
Bibliographic record
Abstract
We use Canada-France-Hawaii Telescope Legacy Survey data for 170 deg^2, recalibrated and transformed to the Sloan Digital Sky Survey ugri photometric system, to study the distribution of near-turnoff main-sequence stars in the Galactic halo along four lines of sight to heliocentric distances of ~35 kpc. We find that the halo stellar number density profile becomes steeper at Galactocentric distances greater than R_(gal) ~ 28 kpc, with the power-law index changing from n_(inner) = –2.62 ± 0.04 to n_(outer) = –3.8 ± 0.1. In particular, we test a series of single power-law models and find them to be strongly disfavored by the data. The parameters for the best-fit Einasto profile are n = 2.2 ± 0.2 and R_e = 22.2 ± 0.4 kpc. We measure the oblateness of the halo to be q ≡ c/a = 0.70 ± 0.01 and detect no evidence of it changing across the range of probed distances. The Sagittarius stream is detected in the l = 173° and b = –62° direction as an overdensity of [Fe/H] ~ -1.5 dex stars at R_(gal) ~ 32 kpc, providing a new constraint for the Sagittarius stream and dark matter halo models. We also detect the Monoceros stream as an overdensity of [Fe/H] > -1.5 dex stars in the l = 232° and b = 26° direction at R_(gal) ≲ 25 kpc. In the two sight lines where we do not detect significant substructure, the median metallicity is found to be independent of distance within systematic uncertainties ([Fe/H] ~ -1.5 ± 0.1 dex).
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How this classification was reachedexpand
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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 teacher head, 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".