Observed spectrum of PSZ1-ARC G311.6602−18.4624 (black solid curve). The dotted curve indicates the 1σ uncertainty of the spectrum. The most prominent absorption and emission lines, at a measured redshift of z = 2.369, are labelled on the figure and indicated with vertical dotted lines. Also plotted (orange curve) is a composite spectrum of ~1000 Lyman break galaxies at z ~ 3 from Shapley et al. (2003).