A search for neutral carbon towards two<i>z</i>= 4.05 submillimetre galaxies, GN���20 and GN���20.2
Bibliographic record
Abstract
Using the IRAM Plateau de Bure Interferometer (PdBI) we have searched for the upper fine structure line of neutral carbon [] and 12CO(J= 7 → 6) (νrest= 806 GHz) towards the submillimetre galaxies (SMGs) GN 20 (SMM J123711.9+622212, z= 4.055) and GN 20.2 (SMM J123708.8+622202, z= 4.051). The far-infrared continuum is detected at 8σ significance in GN 20, with a flux density of S1.8 mm= 1.9 ± 0.2 mJy, while no continuum is detected in GN 20.2. Both sources are statistically undetected in both and 12CO(J= 7 → 6) lines; we derive line luminosity limits for both C i and CO of L′≲ 2 × 1010 K km s−1 pc2. Assuming carbon excitation temperatures of Tex= 30 K (the galaxies' measured dust temperatures), we infer C i mass limits of MC i < 5.4 × 106 M⊙ (GN 20) and MC i < 6.8 × 106 M⊙ (GN 20.2). The derived C i abundance limits are <1.8 × 10−5 for GN 20 and <3.8 × 10−5 for GN 20.2, implying that the systems have Milky Way level carbon enrichment (X[C i]/X[H2]) or lower, similar to high-redshift carbon-detected systems (at 5 × 10−5) but about 50 times less than the carbon enrichment of local starburst galaxies. Observations of GN 20 and GN 20.2 in high-resolution MERLIN+VLA (Multi-Element Radio Linked Interferometer Network+Very Large Array) radio maps of GOODS-N (Great Observatories Origin Deep Survey-North) are used to further constrain the sizes and locations of active regions. We conclude that the physical gas properties of young rapidly evolving systems like GN 20 and GN 20.2 are likely significantly different than starburst/ULIRG (ultraluminous infrared galaxy) environments in the local Universe yet similar to z∼ 2 SMGs. Unless gravitationally amplified examples can be found, observations of galaxies like GN 20 will require the order of magnitude increase in sensitivity of the Atacama Large Millimetre Array (ALMA) to constrain their C i and high-J CO content, despite the fact that they are the brightest systems at z∼ 4.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.000 |
| 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".