QSO spectrum with the Lyα DLA feature. The blue line is the measured spectrum, with the emission feature at the bottom of the damped Lyα absorption trough. The Lyα forest lies on the blue side of the DLA Lyα absorption. The red curve shows the Voigt fit of the DLA. The green curve is the reconstructed “continuum”, actually the broad Lyα emission line of the QSO (see text). Note that the reconstructed QSO line is only an interpolated guess between ~ 4950 Å and ~ 4958 Å. The thin dashed magenta line is the SDSS QSO template of Vanden Berk et al. (2001) redshifted to z = 3.092 and normalized to match the green curve as well as possible.