ENVIRONMENTAL EFFECTS IN THE EVOLUTION OF GALACTIC BULGES
Bibliographic record
Abstract
We investigate possible environmental trends in the evolution of galactic bulges over the redshift range 0 < z < 0.6. For this purpose, we construct the fundamental plane (FP) for cluster and field samples at redshifts 〈 z 〉 = 0.4 and 〈 z 〉 = 0.54 using surface photometry based on Hubble Space Telescope imaging and velocity dispersions based on Keck spectroscopy. As a reference point for our study, we include data for pure ellipticals, which we model as single-component Sérsic profiles; whereas for multi-component galaxies we undertake decompositions using Sérsic and exponential models for the bulge and disk, respectively. Although the FP for both distant cluster and field samples is offset from the local relation, consistent with evolutionary trends found in earlier studies, we detect significant differences in the zero point of ≃0.2 dex between the field and cluster samples at a given redshift. For both clusters, the environmentally dependent offset is in the sense expected for an accelerated evolution of bulges in dense environments. By matching the mass range of our samples, we confirm that this difference does not arise as a result of the mass-dependent downsizing effects seen in larger field samples. Our result is also consistent with the hypothesis that—at fixed mass and environment—the star formation histories of galactic bulges and pure spheroids are indistinguishable and difficult to reconcile with the picture whereby the majority of large bulges form primarily via secular processes within spiral 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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".