Nature and Origins of Rich Complexes of C iv Associated Absorption Lines

Abstract

Abstract Rich complexes of associated absorption lines (AALs) in quasar spectra provide unique information about gaseous infall, outflows, and feedback processes in quasar environments. We study five quasars at redshifts z ~ 3.1–4.4 with AAL complexes containing from 7 to 18 C iv λ1548, 1551 systems in high-resolution spectra. These complexes span velocity ranges ≲3600 km s−1 within ≲8200 km s−1 of the quasar redshifts. All are highly ionized with no measurable low-ionization ions like Si ii or C ii, and all appear to form in the quasar/host galaxy environments based on evidence for line locking, partial covering of the background light source, strong N v absorption, and/or roughly solar metallicities, and on the implausibility of such complexes forming in unrelated intervening galaxies. Most of the lines in all five complexes identify high-speed quasar-driven outflows at velocity shifts v ≲ − 1000 km s−1. Four of the complexes also have lines at smaller blueshifted velocities that might form in ambient interstellar clouds, low-speed outflows, or at feedback interfaces in the host galaxies where high-speed winds impact and shred interstellar clouds. The partial covering we measure in some of the high-speed outflow lines require small absorbing clouds with characteristic sizes ≲1 pc or ≲0.01 pc. The short survival times of these clouds require locations very close to the quasars, or cloud creation in situ at larger distances perhaps via feedback/cloud-shredding processes. The AAL complex in one quasar, J1008+3623, includes unusually narrow C iv systems at redshifted velocities 350 ≲ v ≲ 640 km s−1 that are excellent candidates for gaseous infall toward the quasar, e.g., “cold-mode” accretion or a gravitationally bound galactic fountain.