Radio Sources and Star Formation in the Local Universe

Galaxies from the entire Uppsala Galaxy Catalog (UGC) have been identified with 4583 radio sources stronger than 2.5 mJy at 1.4 GHz from the NRAO VLA Sky Survey (NVSS). The complete sample of 3398 galaxies brighter than mp = 14.5 in the area defined by δ > -2°30' and |b| > 20° yielded the UGC/NVSS sample of 1966 radio sources. Their dominant energy sources were classified as stars (85%) or active galactic nuclei (15%). The luminosity function of star-forming galaxies agrees well with the far-infrared (FIR) luminosity function converted to 1.4 GHz by the FIR/radio correlation. The spectral power density of star-forming galaxies is USF = (1.53 ± 0.07) × 1019 W Hz-1 Mpc-3 (statistical errors only) if H0 = 70 km s-1 Mpc-1. We used a model consistent with the observed FIR/radio correlation to estimate the corresponding star formation rate density within the past τ ∼ 3 × 108 yr; it is ρSF(M > 0.1 M⊙) ≈ 0.018 M⊙ yr-1 Mpc-3. The radio sources in star-forming galaxies may be evolving even at moderately low redshifts (z ∼ 0.1).