Source Counts Spanning Eight Decades of Flux Density at 1.4 GHz

Abstract

Brightness-weighted differential source counts S 2 n(S) spanning the eight decades of flux density between 0.25 μJy and 25 Jy at 1.4 GHz were measured from (1) the confusion brightness distribution in the MeerKAT DEEP2 image below 10 μJy, (2) counts of DEEP2 sources between 10 μJy and 2.5 mJy, and (3) counts of NVSS sources stronger than 2.5 mJy. We present our DEEP2 catalog of 1.7 × 104 discrete sources complete above S = 10 μJy over Ω = 1.04 deg2. The brightness-weighted counts converge as S 2 n(S) ∝ S 1/2 below S = 10 μJy, so >99% of the ΔT b ∼ 0.06 K sky brightness produced by active galactic nuclei and ≈96% of the ΔT b ∼ 0.04 K added by star-forming galaxies has been resolved into sources with S ≥ 0.25 μJy. The ΔT b ≈ 0.4 K excess brightness measured by ARCADE 2 cannot be produced by faint sources smaller than ≈50 kpc if they cluster like galaxies.