MusE GAs FLOw and Wind (MEGAFLOW) X. The cool gas and covering fraction of Mg <scp>ii</scp> in galaxy groups
Bibliographic record
Abstract
ABSTRACT We present a study of the cool gas (≈104 K) traced by Mg ii absorptions around groups of galaxies in the MEGAFLOW (MusE GAs FLOw and Wind) survey. Using a combination of two algorithms, we blindly identify 32 groups of more than 5 galaxies at 0.3 < z < 1.5 with $10.7 \lt \log _{10}(M/\rm {\rm M}_{\odot }) \lt 13.7$. Among them 26 can be used to study potential counterpart Mg ii absorptions. We report that 21 out of the total 120 Mg ii absorption systems present in MEGAFLOW are associated with groups. We observe that the Mg ii rest-frame equivalent width ($W_{\rm r}^{2796}$) drops at an impact parameter of ≈150 projected kpc from the closest galaxy and ≈ one virial radius from the identified group centre indicating that Mg ii haloes scale with the mass of the groups. The impact parameter where the covering fraction exceeds 50 per cent is $\log _{10}(b/\rm kpc) = 2.17 \pm 0.47$ (2σ) and (b/Rvir) = 1.67 ± 0.98, which is ≈3 times larger than for field galaxies ($\log _{10}(b/\rm kpc)=1.67\pm 0.15$). Finally, we estimate the cool gas column density profile in groups (from the $W_{\rm r}^{2796}$) and show that its shape follows closely the typical dark matter column density profile for haloes at similar redshift and masses.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 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) | 0.003 | 0.001 |
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".