The host galaxies of strong Ca II quasar absorption systems at z < 0.5
Bibliographic record
Abstract
We present new imaging and spectroscopic observations of the fields of five quasars with very strong intervening Ca ii absorption systems at redshifts zabs < 0.5 selected from the Sloan Digital Sky Survey. Recent studies of these very rare absorbers indicate that they may be related to damped Lyman α systems (DLAs). In all five cases, we identify a galaxy at the redshift of the Ca ii system with impact parameters up to ∼24 kpc. In four out of five cases the galaxies are luminous (L≃L*), metal-rich (Z≃ Z⊙), massive (velocity dispersion σ≃ 100 km s−1) spirals. Their star formation rates (SFRs), deduced from Hα emission, are high, in the range SFR = 0.3 –30 M⊙ yr−1. In our analysis, we paid particular attention to correcting the observed emission-line fluxes for stellar absorption and dust extinction. We show that these effects are important for a correct SFR estimate; the difficulties of incorporating such corrections in previous low-z studies of DLA-selected galaxies has probably led to an underestimate of the star formation activity in at least some DLA hosts. We discuss possible links between Ca ii-selected galaxies and DLAs and outline future observations which will help clarify the relationship between these different classes of quasar absorbers.
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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 | 0.002 | 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) | 0.002 | 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".