Incidence of H i 21-cm absorption in strong Fe ii systems at 0.5 <<i>z</i>< 1.5
Bibliographic record
Abstract
We present the results from our search for H i 21-cm absorption in a sample of 16 strong Fe ii systems [Wr(Mg ii λ2796) ≥ 1.0 Å and Wr(Fe ii λ2600) or |$W_{{\rm Fe\,\small {II}}}$| ≥ 1 Å] at 0.5 < z < 1.5 using the Giant Metrewave Radio Telescope and the Green Bank Telescope. We report six new H i 21-cm absorption detections from our sample, which have increased the known number of detections in strong Mg ii systems at this redshift range by ∼50 per cent. Combining our measurements with those in the literature, we find that the detection rate of H i 21-cm absorption increases with |$W_{{\rm Fe\,\small {II}}}$|, being four times higher in systems with |$W_{{\rm Fe\,\small {II}}}$| ≥ 1 Å compared to systems with |$W_{{\rm Fe\,\small {II}}}$| < 1 Å. The N(|${\rm H\,\small {I}}$|) associated with the H i 21-cm absorbers would be ≥2 × 1020 cm−2, assuming a spin temperature of ∼500 K (based on H i 21-cm absorption measurements of damped Lyman α systems at this redshift range) and unit covering factor. We find that H i 21-cm absorption arises on an average in systems with stronger metal absorption. We also find that quasars with H i 21-cm absorption detected towards them have systematically higher E(B − V) values than those which do not. Further, by comparing the velocity widths of H i 21-cm absorption lines detected in absorption- and galaxy-selected samples, we find that they show an increasing trend (significant at 3.8σ) with redshift at z < 3.5, which could imply that the absorption originates from more massive galaxy haloes at high z. Increasing the number of H i 21-cm absorption detections at these redshifts is important to confirm various trends noted here with higher statistical significance.
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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.009 | 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".