The Angular Size Distribution of μJy Radio Sources
Bibliographic record
Abstract
Abstract We made two new sensitive (rms noise μJy beam−1) high-resolution (θ = 3.″0 and θ = 0.″66 FWHM) S-band (2 < ν < 4 GHz) images covering a single JVLA primary beam (FWHM ≈ 14′) centered on J2000 , δ = +59°01′ in the Lockman Hole. These images yielded a catalog of 792 radio sources, 97.7 ± 0.8% of which have infrared counterparts stronger than S ≈ 2 μJy at λ = 4.5 μm. About 91% of the radio sources found in our previously published, comparably sensitive low-resolution (θ = 8″ FWHM) image covering the same area were also detected at 0.″66 resolution, so most radio sources with S(3 GHz) ≳ 5 μJy have angular structure ϕ ≲ 0.″66. The ratios of peak brightness in the 0.″66 and 3″ images have a distribution indicating that most μJy radio sources are quite compact, with a median Gaussian angular diameter FWHM and an rms scatter σ ϕ ≲ 0.″3 of individual sizes. Most of our μJy radio sources obey the tight far-infrared/radio correlation, indicating that they are powered by star formation. The median effective angular radius enclosing half the light emitted by an exponential disk is , so the median effective radius of star-forming galaxies at redshifts z ∼ 1 is .
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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 | 0.002 | 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) | 0.003 | 0.001 |
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".