ABSORPTION-LINES AND ION ABUNDANCES IN THE QSO-PKS0528-250

Spectra of the QSO PKS 0528 - 250 (ze = 2.765) have been obtained with the AAT at 2 A resolution from 3100 to 7180 A. Absorption line systems have been identified at zA1 = 2.81322, zA2 = 2.81100, zB = 2.53758 and zc = 2.14077. The ionization ranges from H i, Al n and Fe n to N v or O vi in system A, from Hi and possibly Si II to C iv in B and from Hi, Alii and Sin to Civ in C In system A the Siiv and higher stages are concentrated in A2. Broad La profiles in A and C correspond to 2 x 1021 and 5 x1020 atom cm-2 respectively. Column densities also have been estimated for several heavier elements at each redshift. In system A depletions by factors of 8 to 160 relative to solar abundances appear to be present in Sn, O i and N i as well as the typical factor 10 for Si n and Fe n similar to interstellar clouds in the plane of our galaxy. Longward of the La absorption in system A there are 44 lines of which only 27 have proposed identifications, whereas at the shorter wavelengths there are 112 lines of which 43 have plausible identifications due to one or more ions other than hydrogen. Thus caution is needed with the common assumption that most absorptions shortward of La emission in QSOs are due to La. © Royal Astronomical Society.