Average Properties of a Large Sample of<i>z</i><sub>abs</sub>∼<i>z</i><sub>em</sub>Associated Mg<scp>ii</scp>Absorption Line Systems
Bibliographic record
Abstract
We studied a sample of 415 associated ( z abs ∼ z em ; relative velocity with respect to QSO in units of c , β < 0.01) Mg II absorption systems with 1.0 ⩽ z abs ⩽ 1.86, in the spectra of SDSS DR3 QSOs, to determine the dust content and ionization state in the absorbers. We also compared these properties to those of a similarly selected sample of 809 intervening systems (β > 0.01), so as to understand their origin. Normalized, composite spectra were derived for absorption line measurements, for the full sample and for several subsamples, chosen on the basis of the line strengths and other absorber and QSO properties. From these, and from the equivalent widths in individual spectra, we conclude that the associated Mg II absorbers have higher ionization (higher ratios of the strengths of C IV and Mg II lines), than the intervening absorbers. The ionization decreases with increasing β. Average extinction curves were obtained for the subsamples by comparing their geometric mean QSO spectra with those of matching (in z em and i magnitude) samples of QSOs without absorption lines. There is clear evidence for SMC-like dust attenuation in these systems; the 2175 Å absorption feature is absent. The extinction is almost twice that observed in intervening systems. We reconfirm that QSOs with nonzero FIRST radio flux are intrinsically redder than the QSOs with no detection in the FIRST survey. The incidence of associated Mg II systems in radio-detected QSOs is 1.7 times that in radio-undetected QSOs. The associated absorbers in radio-detected QSOs cause 3 times more reddening than those in radio-undetected QSOs. This excess reddening is correlated with the strength of Mg II absorption, possibly suggesting an intrinsic nature for the associated absorbers in radio-detected QSOs.
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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".