2018MNRAS.480..119A

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.