Spatially extended absorption around the<i>z</i>= 2.63 radio galaxy MRC 2025−218: outflow or infall?
Bibliographic record
Abstract
We present an investigation into the absorber in front of the z = 2.63 radio galaxy MRC 2025-218, using integral field spectroscopy obtained at the Very Large Telescope, and longslit spectroscopy obtained at the Keck II telescope.The properties of MRC 2025-218 are particularly conducive to study the nature of the absorbing gas, i.e. this galaxy shows bright and spatially extended Lyα emission, along with bright continuum emission from the active nucleus.Lyα absorption is detected across ∼40 × 30 kpc 2 , has a covering factor of ∼1, and shows remarkably little variation in its properties across its entire spatial extent.This absorber is kinematically detached from the extended emission line region (EELR).Its properties suggest that the absorber is outside of the EELR.We derive lower limits to the H I, H II and H column densities for this absorber of 3 × 10 16 , 7 × 10 17 and 2 × 10 18 cm -2 , respectively.Moreover, the relatively bright emission from the active nucleus has allowed us to measure a number of metal absorption lines: C I, C II, C IV, N V, O I, Si II, Si IV, Al II and Al III.The column density ratios are most naturally explained using photoionization by a hard continuum, with an ionization parameter U ∼ 0.0005-0.005.Shocks or photoionization by young stars cannot reproduce satisfactorily the measured column ratios.Using the ratio between the Si II * and Si II column densities, we derive a lower limit of ≥10 cm -3 for the electron density of the absorber.The data do not allow useful constraints to be placed on the metallicity of the absorber.We consider two possibilities for the nature of this absorber: the cosmological infall of gas, and an outflow driven by supernovae or the radio jets.We find it plausible that the absorber around 2025-218 is in outflow.We also find good agreement between the observed properties of the H I absorber and the properties of the H I absorption expected from the cosmological infall model of Barkana & Loeb.
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".