LoCuSS: THE SLOW QUENCHING OF STAR FORMATION IN CLUSTER GALAXIES AND THE NEED FOR PRE-PROCESSING
Bibliographic record
Abstract
We present a study of the spatial distribution and kinematics of star-forming galaxies in 30 massive clusters at 0.15 < z < 0.30, combining wide-field Spitzer 24 m and GALEX near-ultraviolet imaging with highly complete spectroscopy of cluster members. The fraction (f SF ) of star-forming cluster galaxies rises steadily with clustercentric radius, increasing fivefold by 2r 200 , but remains well below field values even at 3r 200 . This suppression of star formation at large radii cannot be reproduced by models in which star formation is quenched in infalling field galaxies only once they pass within r 200 of the cluster, but is consistent with some of them being first pre-processed within galaxy groups. Despite the increasing f SF -radius trend, the surface density of star-forming galaxies actually declines steadily with radius, falling 15 from the core to 2r 200 . This requires star formation to survive within recently accreted spirals for 2-3 Gyr to build up the apparent over-density of star-forming galaxies within clusters. The velocity dispersion profile of the star-forming galaxy population shows a sharp peak of 1.44 at 0.3r 500 , and is 10%-35% higher than that of the inactive cluster members at all cluster-centric radii, while their velocity distribution shows a flat, top-hat profile within r 500 . All of these results are consistent with star-forming cluster galaxies being an infalling population, but one that must also survive 0.5-2 Gyr beyond passing within r 200 . By comparing the observed distribution of star-forming galaxies in the stacked caustic diagram with predictions from the Millennium simulation, we obtain a best-fit model in which star formation rates decline exponentially on quenching timescales of 1.73 0.25 Gyr upon accretion into the cluster.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".