GA-NIFS: ISM properties and metal enrichment in a merger-driven starburst during the epoch of reionization probed with <i>JWST</i> and ALMA
Bibliographic record
Abstract
ABSTRACT We present deep JWST/NIRSpec integral-field spectroscopy (IFS) and ALMA [C ii]$\lambda $158$\mu$m observations of COS-3018, a star-forming galaxy at z $\sim$ 6.85, as part of the GA-NIFS programme. Both G395H (R $\sim$ 2700) and PRISM (R $\sim$ 100) NIRSpec observations revealed that COS-3018 is comprised of three separate components detected in [O iii]$\lambda $5007, which we dub as Main, North, and East, with stellar masses of 10$^{9.4 \pm 0.1}$, 10$^{9.2 \pm 0.07}$, 10$^{7.7 \pm 0.15}$ $\mathrm{M}_\odot$. We detect [O iii]$\lambda $$\lambda $5007,4959, [O ii]$\lambda $$\lambda $3727,3729, and multiple Balmer lines in all three components together with [O iii]$\lambda $4363 in the Main and North components. This allows us to measure an interstellar medium temperature of $T_\text{e}$ = 1.27$\pm 0.07\times 10^4$ and $T_\text{e}$ = 1.6$\pm 0.14\times 10^4$ K with densities of $n_{e}$ = 1250$\pm$250 and $n_{e}$ = 700$\pm$200 cm$^{-3}$, respectively. These deep observations allow us to measure an average metallicity of 12 + log(O/H) = 7.9–8.2 for the three components with the T$_{e}$-method. We do not find any significant evidence of metallicity gradients between the components. Furthermore, we also detect [N ii]$\lambda $6585, one of the highest redshift detections of this emission line. We find that in a small, metal-poor clump 0.2 arcsec west of the North component, N/O is elevated compared to other regions, indicating that nitrogen enrichment originates from smaller substructures, possibly proto-globular clusters. [O iii]$\lambda $5007 kinematics show that this system is merging, which is probably driving the ongoing, luminous starburst.
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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 | 0.000 | 0.000 |
| 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) | 0.001 | 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".