2018ApJ...856...67C

We made two new sensitive (rms noise σ_n~1µJy 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 α=10^h46^m, 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 ph <= 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 <φ>=0′′ / . 3±0′′ / . 1 FWHM and an rms scatter σ_ph <= 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 <ρ_e>~<φ>/2.43~0′′ / . 12, so the median effective radius of star-forming galaxies at redshifts z ∼ 1 is <r_e>~1.0kpc.