Metal Abundances and Ionization in Quasar Intrinsic Absorbers

This paper provides a general reference for deriving the ionizations and metal abundances for absorption-line clouds in photoionization equilibrium with a QSO spectrum. The results include a quantitative assessment of the theoretical uncertainties and Ðrm lower limits on the metallicities when no ionization constraints are available. The calculations applied to the best available column densities for QSO intrinsic absorbers support previous studies ; there is strong evidence for super-solar metallicities in broad absorption line (BAL) and at least some ““ associated ÏÏ absorption regions. Even in cases (z a B z e ) where the level of ionization is unknown (e.g., when only H I and C IV lines are measured), Ðrm lower limits on the metal abundances (C/H) imply for typical BALs and some absorbers. These ZZZ _ z a B z e results support the independent evidence for high metallicities in QSO broad emission line regions. I argue that high gas-phase abundances, up to D10 can be expected in QSOs because of the normal Z _ , enrichment by stars in the cores of young, massive galaxies. ( Z 1011 M _ ) The measured column densities in intrinsic absorbers also indicate that the gas is usually optically thin in the H I Lyman continuum out to energies above at least the C IV and N V ionization edges (i.e., Z100 eV). The column density ratios often require a range of ionization states in the same absorber. Neighboring systems (having similar redshifts and often blended spectroscopically) also usually require difz a B z e ferent ionizations or metal abundances. If the abundances are similar in neighboring systems, their ionization parameters must sometimes di†er by more than an order of magnitude, requiring a signiÐcant range of densities and/or distances from the ionizing QSO. These results, and the overall levels of ionization, are not consistent with single-zone models of the UV line and X-ray continuum (““ warm ÏÏ) absorbers. Subject headings : galaxies : abundances È galaxy : evolution È quasars : absorption lines È quasars : general