2021ApJ...909..193M

Brightness-weighted differential source counts S²n(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 x 10⁴ discrete sources complete above S = 10 µJy over Ω = 1.04 deg². The brightness-weighted counts converge as S²n(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.