Ionizing photon production per unit UV luminosity, ξ_ion, as a function of the absolute UV magnitude (top panel) and the UV slope (bottom) of the five Lyman continuum leakers of I16a,b. Large red symbols show ξ_ion, large blue symbols after correction for UV attenuation (two blue triangles are indistinguishable). The cyan band illustrates canonical values for the intrinsic . Recent determinations of for LBGs at z = 3.8–5 and z = 5.1–5.4 from Bouwens et al. (2015) are shown by small black and magenta symbols with error bars, respectively.