Quasar outflow energetics from broad absorption line variability

Abstract Quasar outflows have long been recognized as potential contributors to the co-evolution between supermassive black holes (SMBHs) and their host galaxies. The role of outflows in active galactic nucleus (AGN) feedback processes can be better understood by placing observational constraints on wind locations and kinetic energies. We utilize broad absorption line (BAL) variability to investigate the properties of a sample of 71 BAL quasars with P v broad absorption. The presence of P v BALs indicates that other BALs like C iv are saturated, such that variability in those lines favours clouds crossing the line of sight. We use these constraints with measurements of BAL variability to estimate outflow locations and energetics. Our data set consists of multiple-epoch spectra from the Sloan Digital Sky Survey and MDM Observatory. We detect significant (4σ) BAL variations from 10 quasars in our sample over rest-frame time-scales between ≤0.2–3.8 yr. Our derived distances for the 10 variable outflows are nominally ≲ 1–10 pc from the SMBH using the transverse-motion scenario, and ≲ 100–1000 pc from the central source using ionization-change considerations. These distances, in combination with the estimated high outflow column densities (i.e. NH ≳ 1022 cm−2), yield outflow kinetic luminosities between ∼ 0.001 and 1 times the bolometric luminosity of the quasar, indicating that many absorber energies within our sample are viable for AGN feedback.