We made two new sensitive (rms noise sigma_n ~ 1 microJy/beam) high resolution (theta = 3.0″ and theta = 0.66″ FWHM) S–band (2 < nu < 4 GHz) images covering a single JVLA primary beam (FWHM ~ 14′) centered on J2000 RA = 10 46, Dec = 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 microJy at lambda = 4.5 micron. About 91% of the radio sources found in our previously published, comparably sensitive low resolution (theta = 8″ FWHM) image covering the same area were also detected at 0.66″ resolution, so most radio sources with S_3GHz >~ 5 microJy have angular structure phi <~ 0.66″. The ratios of peak brightness in the 0.66″ and 3″ images have a distribution indicating that most microJy radio sources are quite compact, with a median Gaussian angular diameter <phi> = 0.3″ +/- 0.1″ FWHM and an rms scatter sigma_phi <~ 0.3″ of individual sizes. Most of our microJy 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 <rho_e> ~ <phi>/2.43 ~ 0.12″, so the median effective radius of star-forming galaxies at redshifts z~1 is <r_e> ~ 1.0 kpc.
W. Cotton, J. Condon, K. Kellermann, et. al.
Tue, 13 Feb 18
Comments: 20 pages, 8 figures