Illustration of our stacked photometric measurements (solid circles) in the 3.6 μm and 4.5 μm bands for galaxies at 4.532 <  z <  4.955 in three different bins of UV luminosity M_UV −20.5 <  M_UV <  −19.5 (left), −19.5 <  M_UV <  −18.5 (center), and −18.5 <  M_UV <  −17.5 (right). The width of the 3.6 μm and 4.5 μm bands are shown with horizontal error bars, while the vertical error bars are 1σ. The lines show example model spectra using the line ratios assumed in our analysis (Sect. 4.2)