Starburst galaxies in the Hydra I cluster
Bibliographic record
Abstract
Studying the impact of environment on star formation and quenching pathways requires statistically relevant samples of galaxies in a wide mass range. We present a new catalog of 196 galaxies of the nearby Hydra I cluster out to ∼1.75r 200 , consisting of broad u,g,r,i,z along with narrowband H α measurements. These deep optical images were obtained with the DECam camera (CTIO) and reach down to a surface brightness limit of μ (3 σ ; 10″ × 10″) = 26.9 mag arcsec 2 in the g band. We also report the HI properties for 89 cluster members detected with MeerKAT. A color magnitude diagram (CMD) shows a bimodal distribution typical of a cluster population, more evolved than those found in isolation. We combined optical H α and WISE infrared data to compare the star formation history at two distinct timescales. Differences in the star-forming activity depicted by both populations manifest as a starburst in 24 found members. Of these, 18 starburst galaxies have neutral gas measurements, and they show disturbed HI disks that suggest an environmentally triggered boost in star formation within the last 10 7 yrs. Processes such as ram pressure stripping or tidal interactions may underlie their enhanced star-forming activity and asymmetric disks. Since Hydra’s dynamical history is unclear, we examine the spatial and velocity distribution of the sample. We reveal a possible link between the large-scale structure feeding the Hydra I cluster and the heightened star-forming activity of the starburst galaxies. This feeding pattern matches the few substructures that have been identified in Hydra in previous works, and this may explain their origin. Our results portray a picture of a cluster with an evolved nature, plus a population of new infalling galaxies that manifest the impact of their first contact with the cluster environment through star formation, color, morphology, and gas content transformations.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".