The Brightest Stars in M32: Comparing Predictions from Spectra with the Resolved Stellar Content
Bibliographic record
Abstract
Broadband and narrowband images covering the 1-4 μm wavelength interval are used to investigate the properties of the brightest asymptotic giant branch (AGB) stars in the Local Group galaxy M32. Data obtained with the NIRI imager on the Gemini North telescope indicate that the brightest AGB stars near the center of M32 have peak M brightnesses and K - L ' colors that are similar to those of luminous AGB stars in the Galactic disk. Data obtained with the CFHTIR imager on the Canada-France-Hawaii Telescope indicate that the density of bright AGB stars per unit visible and near-infrared surface brightness is constant out to projected major-axis distances of 1 kpc, suggesting that the AGB stars and their progenitors are smoothly mixed throughout the main body of the galaxy. In addition, the J - K color distribution of bright AGB stars throughout much of the galaxy is consistent with that of a single population of AGB stars, the majority of which are long-period variables that have a common metallicity and age. Thus, these data do not support spectroscopic studies that find an age gradient in M32. The AGB contributes 70% of the integrated light in the region surveyed. This is consistent with previous estimates made from the integrated near-infrared spectrum and is suggestive of an age of ∼2 Gyr. The stellar content of M32 is compared with that of the M31 bulge at a projected minor-axis distance of 1.4 kpc. While the peak K -band brightnesses of AGB stars in the two systems agree to within a few tenths of a magnitude, M32 contains more bright AGB stars per unit integrated brightness than the outer bulge of M31. This suggests a difference in mean age, and it is concluded that the star-forming histories of M32 and the bulge of M31 have differed over a significant fraction of their lifetimes, which is consistent with spectroscopic studies of these systems. The well-mixed AGB content of M32 is consistent with the galaxy having been tidally stirred, presumably by interactions with M31.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".