Near-identical star formation rate densities from Hα and FUVat redshift zero

For the first time both Hα and far-ultraviolet (FUV) observations from an H I-selected sample are used to determine the dust-corrected star formation rate density (SFRD: \dot{ρ }) in the local Universe. Applying the two star formation rate indicators on 294 local galaxies, we determine log(\dot{ρ } _{ Hα }) = -1.68^{+0.13}_{-0.05} [M_⊙ yr^-1 Mpc^-3] and log(\dot{ρ }_{ FUV}) = -1.71^{+0.12}_{-0.13} [M_⊙ yr^-1 Mpc^-3]. These values are derived from scaling Hα and FUV observations to the H I mass function. Galaxies were selected to uniformly sample the full H I mass (M_{H I}) range of the H I Parkes All-Sky Survey (M_{H I} ∼ 10⁷ to ∼10^10.7 M_⊙). The approach leads to relatively larger sampling of dwarf galaxies compared to optically selected surveys. The low H I mass, low luminosity, and low surface brightness galaxy populations have, on average, lower Hα/FUV flux ratios than the remaining galaxy populations, consistent with the earlier results of Meurer. The near-identical Hα- and FUV-derived SFRD values arise with the low Hα/FUV flux ratios of some galaxies being offset by enhanced Hα from the brightest and high mass galaxy populations. Our findings confirm the necessity to fully sample the H I mass range for a complete census of local star formation to include lower stellar mass galaxies which dominate the local Universe.