Offsets of Masers with Respect to the Middle of the Perseus Arm and the Corotation Radius in the Milky Way
Bibliographic record
Abstract
Abstract The radial distance to the corotation radius R coro (where the angular speed of the gas and stars, Ω gas , in orbit around the Galactic center (GC) is equal to the angular speed of the spiral arm pattern, Ω sp ) has often been predicted (at various places), but not measured with high precision. Here we test the locations of masers with respect to the Perseus arm (Table 1). Our analysis of the masers and H ii regions near the Perseus arm (mostly located on the inner arm side, by about 0.4 ± 0.1 kpc from the cold CO mid-arm) shows that the corotation R coro must be >10.8 kpc from the GC (Figure 1). This implies that the angular rotation speed of the spiral pattern Ω sp < 21.3 km s−1 kpc−1. Another test in Galactic quadrant II shows that the radial velocity of the masers is generally more negative than that of the CO mid-arm (Figure 2), indicating a deceleration with respect to the CO mid-arm, by about 9 ± 3 km s−1. This implies that Ω sp < 20.7 km s−1 kpc−1, and thus R coro > 11.1 kpc. Finally, comparing our results with other published results (Table 2), we find a statistical mean corotation radius R coro predicted to be near 12 ± 1 kpc from the GC (beyond the Perseus arm; before the Cygnus arm), and a mean angular spiral pattern speed, Ω sp , predicted to be near 19 ± 2 km s−1 kpc−1.
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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 | 0.002 |
| 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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".