Integrated emission of the HFLS3 field, using the same illustrative wavelength ranges as in Fig. 1: redshifted Hα for z ∼ 6.34 for the R2700 cube (λ_obs = 4.79954  −  4.84467 μm, upper panel) and the approximate wavelength range of HST/WFC3 F160W for the R100 cube (λ_obs = 1.4  −  1.6 μm; lower panel). The colour scale has been adjusted to highlight weak emission. Low-level candidate galaxies are shown with cyan boundaries. North is up and east is to the left.