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 $0.25\mu \mathrm{J}\mathrm{y}$ 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 $\approx 4.3\times {10}^3$ nearby SFGs, finding that it is very tight but distinctly sub-linear: $L_{\mathrm{F}\mathrm{I}\mathrm{R}}\propto L_{1.4\mathrm{G}\mathrm{H}\mathrm{z}}^{0.85}$. 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) $\psi (M_{\odot }{\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}^{-1}{\mathrm{M}\mathrm{p}\mathrm{c}}^{-3}$) 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 $t\approx 3\mathrm{G}\mathrm{y}\mathrm{r}$ and $z \approx 2$,andsubsequentlydecayswithan$e$-foldingtimescale$\tau = 3.2
$\mathrm{G}\mathrm{y}\mathrm{r}$$. This evolution is similar to, but somewhat stronger than, SFRD evolution estimated from UV and FIR data.