The H [CSC]ii[/CSC] Regions of the Extreme Outer Disk of NGC 628
Bibliographic record
Abstract
Employing deep Hα narrowband imagery, we identified and measured the fluxes of 137 small H II regions in the extreme outer disk ( R ≥ R 25 ) of the nearly face-on, Sc I galaxy NGC 628. A majority of these H II regions are located in two faint, outer spiral arms visible in H I maps. The faintest H II regions that could be measured have fluxes of only a few times 10 -16 ergs cm -2 s -1 , which correspond to luminosities of ∼10 36 ergs s -1 , or a fraction of the Orion Nebula luminosity. The most distant object detected is at R ∼ 27 kpc from the galaxy center. The massive star formation rate, as measured from the azimuthally averaged Hα flux, is consistent with a monotonic decrease as far as R ≈ 1.3 R 25 (20 kpc), where there is a sharp drop. The Schmidt law for the whole disk of NGC 628 corresponds to a relatively steep power law with n = 2.9 ± 0.2, but it "fails" below Σ gas ≤ 4 M ⊙ pc -2 ; the index depends strongly on the CO data used. We derived the luminosity function (LF) of 598 H II regions over the whole disk, and we compared the shapes of the cumulative LFs between R ≥ R 25 and R < R 25 ; the LF of the outer regions is significantly steeper than that of the inner regions.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".