The Angular Size Distribution of μJy Radio Sources
Abstract
We made two new sensitive (rms noise {σ }{{n}}≈ 1 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 α ={10}{{h}} {46}{{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 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 < φ > =0\buildrel{\prime\prime}\over{.} 3+/- 0\buildrel{\prime\prime}\over{.} 1 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 < {ρ }{{e}}> ≈ < φ > /2.43≈ 0\buildrel{\prime\prime}\over{.} 12, so the median effective radius of star-forming galaxies at redshifts z ∼ 1 is < {r}{{e}}> ≈ 1.0 {kpc}.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2018
- DOI:
- 10.3847/1538-4357/aaaec4
- arXiv:
- arXiv:1802.04209
- Bibcode:
- 2018ApJ...856...67C
- Keywords:
-
- catalogs;
- galaxies: fundamental parameters;
- galaxies: star formation;
- infrared: galaxies;
- radio continuum: galaxies;
- surveys;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 20 pages, 8 figures