Strong candidate for AGN feedback: VLT/X-shooter observations of BALQSO SDSS J0831+0354

We measure the location and energetics of a S IV BALQSO outflow. This outflow has a velocity of 10 800 km s(-1) and a kinetic luminosity of 10(45.7) erg s(-1), which is 5.2 per cent of the Eddington luminosity of the quasar. From collisional excitation models of the observed S IV/S IV* absorption troughs, we measure a hydrogen number density of n(H) = 10(4.3) cm(-3), which allows us to determine that the outflow is located 110 pc from the quasar. Since S IV is formed in the same ionization phase as C IV, our results can be generalized to the ubiquitous C IV broad absorption lines (BALs). Our accumulated distance measurements suggest that observed BAL outflows are located much farther away from the central source than is generally assumed (0.01-0.1 pc).