ULTRAVIOLET QUASI-STELLAR OBJECTS
Bibliographic record
Abstract
We present a sample of spectroscopically confirmed quasi-stellar objects (QSOs) with FUV–NUV color (as measured by Galaxy Evolution Explorer ( GALEX ) photometry, FUV band: 1344–1786 Å, NUV band: 1771–2831 Å) bluer than canonical QSO templates and than the majority of known QSOs. We analyze their FUV to NIR colors, luminosities, and optical spectra. The sample includes a group of 150 objects at low redshift ( z < 0.5), and a group of 21 objects with redshift 1.7 < z < 2.6. For the low-redshift objects, the "blue" FUV–NUV color may be caused by enhanced Lyα emission, since Lyα transits the GALEX FUV band from z = 0.1 to z = 0.47. Synthetic QSO templates constructed with Lyα up to three times stronger than in standard templates match the observed UV colors of our low-redshift sample. Optical photometric and spectroscopic properties of these QSOs are not atypical. The Hα emission increases, and the optical spectra become bluer, with increasing absolute UV luminosity. The lack of selected objects at intermediate redshift is consistent with the fact that for z = 0.48–1.63, Lyα is included in the GALEX NUV band, making the observed FUV–NUV redder than the limit of our sample selection. The UV-blue QSOs at redshift ∼2, where the GALEX bands sample rest-frame ≈450–590 Å (FUV) and ≈590–940 Å (NUV), are fainter than the average of UV-normal QSOs at similar redshift in NUV, while they have comparable luminosities in other bands. Therefore, we speculate that their observed FUV–NUV color may be explained by a combination of steep flux rise toward short wavelengths and dust absorption below the Lyman limit, such as from small grains or crystalline carbon (nanodiamonds). The ratio of Lyα to C iv could be measured in 10 objects; it is higher (30% on average) than for UV-normal QSOs, and close to the value expected for shock or collisional ionization. However, optical spectra are taken at different times than the UV photometry, which may bias the comparison if lines are variable. These QSO groups are uniquely set apart by the GALEX photometry within larger samples, given that their optical properties are not unusual.
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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 | 0.001 | 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) | 0.006 | 0.002 |
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".