Illustration of the Δ_m correction (see Sect. 3.1.3 for details) for a galaxy at z = 3.3. For a galaxy of certain brightness m_UV, rest, we use this spectrum (Shapley et al. 2003) to estimate the expected brightness in the far UV part of the spectrum. The blue and orange shaded regions indicate spectral ranges for which m_FUV, rest and m_UV, rest are measured. The blue arrow indicates the spectral range that is simulated in the simulation when m_FUV, rest is estimated. For comparison, we also show the stacked spectrum of intermediate resolution by Rigby et al. (2018).