Cosmic Star Formation History Measured at 1.4 GHz

Abstract

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 μ Jy 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 × 10 3 nearby SFGs, finding that it is very tight but distinctly sublinear: L FIR ∝ L 1.4 GHz 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.