Probing the Central Regions of Nearby Compact Elliptical Galaxies
Bibliographic record
Abstract
K -band spectroscopic observations recorded with NIFS+ALTAIR on Gemini North are used to probe the central arcsecond of the compact elliptical galaxies NGC 4486B, NGC 5846A, and M32. The angular resolution of these data is ~0.1 '' FWHM; this corresponds to a spatial scale of 12 pc in NGC 5846A, which is the most distant galaxy in the sample. Indices that probe the strengths of various atomic and molecular features are measured. The central stellar contents of NGC 4486B and NGC 5846A are similar in the sense that they occupy the same regions of the (Ca I, 12 CO), (Na I, 12 CO), and ( 13 CO, 12 CO) diagrams. The NGC 4486B and NGC 5846A observations depart from the sequence defined by solar neighborhood giants in the (Na I, 12 CO) diagram in a sense that is consistent with both galaxies having nonsolar chemical mixtures. For comparison, the M32 data are consistent with a chemical enrichment history like that in the Galactic disk; M32 could not have formed from the stripping of a larger elliptical galaxy. The behavior of the near-infrared line indices as a function of radius is also investigated. The stellar content in the central arcsecond of M32 appears to be well mixed. However, the radial behavior of the indices in NGC 4486B and NGC 5846A show complicated behavior, with the gradients that are present at large radii breaking down or reversing within a few tenths of an arcsec of the nucleus. Based on the age gradients predicted from visible wavelength spectra, coupled with the radial behavior of the ⟨Fe I⟩ and 12 CO(2, 0) indices, it is suggested that the nuclear regions of NGC 4486B and NGC 5846A harbor intermediate-age populations.
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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 | 0.000 | 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".