On metal abundances in QSO absorbers
  I review our recent results concerning the metal abundances in quasar absorption-line spectra obtained with the UVES/VLT, HIRES/ KECK, and STIS/HST spectrographs. The analysis is based on the Monte Carlo inversion procedure aimed at the restoring the physical parameters and the 1D distributions of the velocity and density fields in quasar absorbers. A functional dependence of the line-of-sight velocity dispersion, sigma_v, on the absorber linear size, L, was found which may indicate that the metal absorbers are associated with virialized systems like galaxies or their halos. A metal content enhancement (up to Z = 4Z_solar) was observed in small-size absorbers (L < 0.4 kpc), whereas decreasing metal abundances were found in systems with increasing L.The lowest metallicity ([C/H] = -3.0) was detected in the z = 2.917 Lymna-limit system (LLS) with N(HI) = 3.2 10^{17} cm^{-2} and L = 140 kpc. The relative abundance ratio of [Si/C] = 0.35, measured in this LLS, seems to indicate that the initial mass function for the stellar population, produced the observed metallicity pattern, was constrained to intermediate masses, M_up < 25M_solar. 
S. A. Levshakov