VIMOS 1D spectrum of ID3 (2h-exposure, pointing P1+P3; black line) and of the sky rescaled to arbitrary units (green line). The lower inset shows the sum of the 2D spectra ( h exposure, P1+P3). The 4h-stacked 2D spectra of each multiple image (ID2, ID3, and ID4) are shown in the insets on the top. A zoomed version of the 1D and 2D spectra around the Ly is shown in the central inset. The vertical blue dotted line marks the position of the peak of the line, which shows a clearly asymmetric profile. In the 2D spectrum, the green segments mark the position of the peak of the flux and that of the 20% flux level.