Stellar population trends in S0 galaxies
Bibliographic record
Abstract
We present stellar population age and metallicity trends for a sample of 59 S0 galaxies based on optical Sloan Digital Sky Survey (SDSS) and near-infrared (NIR) J and H photometry. When combined with optical g and r passband imaging data from the SDSS archive and stellar population models, we obtain radial age and metallicity trends out to at least five effective radii for most of the galaxies in our sample. The sample covers a range in stellar mass and light concentration. We find an average central light-weighted age of ∼4 Gyr and central metallicity [Z/H]∼ 0.2 dex. Almost all galaxies show a negative metallicity gradient from the centre out, with an average value of Δ[Z/H]/Δlog (r/Re) =−0.6. An age increase, decrease and minimal change with radius is observed for 58 per cent, 19 per cent and 23 per cent, respectively, for a mean age gradient of Δage/Δlog (r/Re) = 2.3 Gyr dex−1. For 14 out of 59 galaxies, the light-weighted age of the outer region is greater than 10 Gyr. We find that galaxies with both lower mass and lower concentration have younger light-weighted ages and lower light-weighted metallicities. This mass–metallicity relation extends into the outer regions of our S0 galaxies. Our results are consistent with the formation of S0 galaxies through the transformation of spiral galaxy discs. Determining the structural component that makes up the outer region of galaxies with old outskirts is a necessary step to understand the formation history of S0 galaxies.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| 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 | 0.001 |
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".