Cosmic Star Formation History Measured at 1.4 GHz

We matched the 1.4 GHz local luminosity functions of star-forming galaxies (SFGs) and active galactic nuclei to the 1.4 GHz differential source counts from 0.25 μJy to 25 Jy using combinations of luminosity and density evolution. We present the most robust and complete local far-infrared (FIR)/radio luminosity correlation to date in a volume-limited sample of ≈4.3 × 10³ nearby SFGs, finding that it is very tight but distinctly sublinear: $L_{FIR}\propto L_{1.4GHz}^{0.85}$. If the local FIR/radio correlation does not evolve, the evolving 1.4 GHz luminosity function of SFGs yields the evolving star formation rate density (SFRD) ψ(M _⊙ yr⁻¹ Mpc⁻³) as a function of time since the Big Bang. The SFRD measured at 1.4 GHz grows rapidly at early times, peaks at "cosmic noon" when t ≈ 3 Gyr and z ≈ 2, and subsequently decays with an e-folding timescale τ = 3.2 Gyr. This evolution is similar to, but somewhat stronger than, SFRD evolution estimated from UV and FIR data.