High‐Resolution Keck Spectra of the Associated Absorption Lines in 3C 191

Associated absorption lines (AALs) are valuable probes of the gaseousenvironments near quasars. Here we discuss high-resolution (6.7 km/s) spectraof the AALs in the radio-loud quasar 3C 191 (redshift z=1.956). The measuredAALs have ionizations ranging from Mg I to N V, and multi-component profilesthat are blueshifted by ~400 to ~1400 km/s relative to the quasar's broademission lines. These data yield the following new results. 1) The densitybased on Si II*/Si II lines is ~300 cm-3, implying a distance of ~28 kpc fromthe quasar if the gas is photoionized. 2) The characteristic flow time is thus\~3 x 10^7 yr. 3) Strong Mg I AALs identify neutral gas with very lowionization parameter and high density. We estimate n_H > 5 x 10^4 cm-3 in thisregion, compared to ~15 cm-3 where the N V lines form. 4) The total columndensity is N_H < 4 x 10^18 cm-2 in the neutral gas and N_H ~ 2 x 10^20 cm-2 inthe moderately ionized regions. 5) The total mass in the AAL outflow is M ~ 2 x10^9 Mo, assuming a global covering factor (as viewed from the quasar) of ~10%>. 6) The absorbing gas only partially covers the background light source(s)along our line(s) of sight, requiring absorption in small clouds or filaments<0.01 pc across. The ratio N_H/n_H implies that the clouds have radial (line-of-sight) thicknesses <0.2 pc. These properties might characterize a sub-classof AALs that are physically related to quasars but form at large distances. Wepropose a model for the absorber in which pockets of dense neutral gas aresurrounded by larger clouds of generally lower density and higher ionization.This outflowing material might be leftover from a blowout associated with anuclear starburst, the onset of quasar activity or a past broad absorption line(BAL) wind phase.Comment: 15 pages text plus 6 figures, in press with Ap