SQ-A: A Collision-triggered Starburst in the Intragroup Medium of Stephan’s Quintet
Bibliographic record
Abstract
Abstract We present new observational evidence supporting the hypothesis that SQ-A, a starburst in the intragroup medium (IGrM) of Stephan’s Quintet (SQ), is triggered by a high-speed collision between two gas systems, one associated with the IGrM (v ∼ 6900 km s−1) and another with the intruder galaxy NGC 7318b (v ∼ 6000 km s−1). The new CO(2–1) data set from the Atacama Large Millimeter/submillimeter Array has angular resolutions between 0 . ″ 2 and 7 . ″ 0 and the new Very Large Array H i data cube has an angular resolution of 6 . ″ 6 × 7 . ″ 9 . The CO maps show that the two gas systems are bridged by another system with an intermediate velocity of ∼6600 km s−1, whereas the H i data show that the component of v ∼ 6600 km s−1 fits well into a gap in the more extended v ∼ 6000 km s−1 component, albeit with a displacement of ∼5 kpc. Both the bridge and the complementary distributions between different gas systems are common features of starbursts triggered by cloud–cloud collision. An analysis of clumps (sizes of 100–200 pc) reveals very diversified star formation (SF) activity in clumps belonging to different kinematic systems, with the molecular gas depletion time of the v ∼ 6900 km s−1 clumps being more than 10 times longer than that of the v ∼ 6600 km s−1 clumps. The results are consistent with a scenario in which the enhanced SF activity (and the starburst) in the system of v ∼ 6600 km s−1 is due to gas compression generated in cloud–cloud collisions, whereas the suppression of SF in the v ∼ 6900 km s−1 system is due to vortices (i.e. gas rotation) generated in more complex collisions involving dense clouds and diffuse intercloud gas associated with high-speed shocks.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 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) | 0.003 | 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".