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Session 85 - Quasar Absorption Line Systems.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
Metal absorption lines in quasar spectra are important probes of galactic evolution and star formation at redshifts up to z \sim 5. We are engaged in a broad study of the absorption lines that form physically close to the QSOs. These ``intrinsic'' features are valuable probes of the kinematics, physical conditions and metal abundances in the gaseous environments of QSOs. The metal abundances, in particular, could yield valuable constraints on galactic nuclear evolution that will compliment studies of extended galactic structures (e.g. disks and halos) using the intervening lines.
Intrinsic QSO absorption lines include the broad absorption lines (BALs) and any of the so-called associated (\zaz ) metal line systems that are physically related to QSOs. Here we present a general theoretical reference for deriving metal abundances from the intrinsic absorption features, with a quantitative assessment of the uncertainties. The theoretical uncertainties can be large for intrinsic absorbers because the lines of low ionization metals are often absent and one is forced to compare highly ionized metals to H I. We use photoionization models to explore the effects of various physical conditions and ionizing continuum shapes consistent with QSO observations. We then apply the results to derive ionizations and metal abundances from new data obtained with HST and the Keck 10 m telescope. We also uniformly reanalyze the best published data to test the robustness of recent high-metallicity results.
This work is supported by NASA grants NAG5-1630, NAG5-1858 and AR-5292.02-93B.
Program listing for Wednesday