Compact groups of galaxies in GAMA
Bibliographic record
Abstract
Context. Several compact group catalogues have been constructed over the years using different methods, but most of them are not deep enough to go beyond the very local Universe with a high level of redshift completeness. Aims. We build a statistically reliable sample of compact groups to study the influence of its inner extreme environment at intermediate redshifts. Methods. We adopted the Galaxy And Mass Assembly (GAMA) redshift survey as a parent galaxy catalogue, complemented with a small sample of galaxies from the Sloan Digital Sky Survey, to identify compact groups using Hickson-like criteria. We explored the parameter space to perform several identifications, with which we built samples with different characteristics. Particularly, we reduced the maximum galaxy separation in the line of sight to 500 km s−1, and we implemented different magnitude ranges to define membership: a difference between three, two, or one magnitudes between the brightest galaxy and the other members, and no restriction at all. For comparison, we used control samples extracted from a catalogue of loose groups to compare their properties with those of the compact groups. Results. We built five considerably large compact group samples, ranging from more than 400 up to roughly 2400 systems, and maximum redshifts from 0.2 to 0.4, depending on the selected parameters. The overall properties of each sample agree with previous findings. Moreover, compact groups have a tendency for a larger fraction of quenched galaxies than control loose groups, mainly for galaxies with a low stellar mass in compact groups with short crossing times. In addition, ∼45% of the compact groups are embedded in loose galaxy systems and are highly compact, have the shortest crossing times, and the brightest first-ranked galaxies than compact groups that are considered to be non-embedded or isolated. The compact group properties almost do not evolve at all with redshift. Conclusions. Our results confirm previous findings that postulated that compact groups are one of the suitable places in which the suppression of the star formation rate in galaxies that is primarily due to galaxy interactions can be studied. These new Hickson-like compact group samples will be valuable to deepen the analysis of these peculiar galaxy systems in a redshift regime that was poorly explored so far.
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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 | 0.000 | 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 | 0.000 |
| 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".