Optical identification of<i>XMM</i>sources in the CanadaâFranceâHawaii Telescope Legacy Survey
Bibliographic record
Abstract
We present optical spectroscopic identifications of X-ray sources in ∼3 deg2 of the XMM–Large Scale Structure survey (XMM–LSS), also covered by the Canada–France–Hawaii Telescope Legacy Survey (CFHTLS), obtained with the AAOmega instrument at the Anglo-Australian Telescope. In a flux-limited sample of 829 point-like sources in the optical band with g′≤ 22 mag and the 0.5–2 keV flux (f0.5-2 keV) > 1 × 10−15 erg cm−2 s−1, we observed 693 objects and obtained reliable spectroscopic identification for 487 sources, approximately 59 per cent of the overall sample. We therefore increase the number of identifications in this field by a factor close to 5. Galactic stellar sources represent about 15 per cent of the total (74/487). About 54 per cent (265/487) are broad-line active galactic nuclei (AGN) spanning redshifts between 0.15 and 3.87 with a median value of 1.68. The optical-to-X-ray spectral index (αox) of the broad-line AGN is 1.47 ± 0.03, typical of optically selected type I quasars, and is found to correlate with the rest-frame X-ray and optical monochromatic luminosities at 2 keV and 2500 Å, respectively. Consistent with previous studies, we find αox not to be correlated with z. In addition, 32 and 116 X-ray sources are, respectively, absorption- and emission-line galaxies at z < 0.76. From a line ratio diagnostic diagram, it is found that in about 50 per cent of these emission-line galaxies, the emission lines are powered significantly by the AGN. 30 of the XMM sources are detected at one or more radio frequencies. In addition, 24 sources have ambiguous identification: in eight cases, two XMM sources have a single optical source within 6 arcsec of each of them, whereas two and 14 XMM sources have, respectively, three and two possible optical sources within 6 arcsec of each of them. Spectra of multiple possible counterparts were obtained in such ambiguous cases.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.004 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".