Observed spectral regions at the position of BDF521 UV lines observed by X-shooter. The regions cover the range from -1000 to +1000 km/s around the Lyα redshift. The red vertical lines mark the expected positions of UV lines or doublet components, assuming no velocity shift with respect to the Lyα redshift. The top panels show the 2D S/N spectrum, while the bottom panels show the 1D spectrum and rms as black and grey lines, respectively. The shaded red regions are masked due to contamination from sky lines.