Program: GN-2011A-Q-106

As a direct consequence of the luminosity generated through accretion, quasars can eject energetic outflows at high velocities. These outflows are directly observed in Broad Absorption Line (BAL) quasars through their deep, blue-shifted absorption lines. To date, one of the main challenges in constraining the fundamental properties (covering fractions and column densities) of these outflows has been that these lines are typically heavily saturated, but non-black (because of partial covering of the continuum). However, we have recently demonstrated that HeI* observations at rest-frame 10830 and 3888 Angstroms are a particularly powerful means of circumventing this problem for the thickest outflows because of the relatively small population of atoms in the metastable state. This means that even at very large column densities, HeI* absorption lines are not saturated. We propose to exploit this feature of atomic physics to constrain, for the first time, the column density and covering fraction of a sample of 8 BAL quasars with 13 hours of GNIRS spectroscopy. These important observations are a crucial step towards measuring a fundamental parameter -- the kinetic luminosity of a quasar outflow -- required to investigate the accleration mechanism in quasar winds and the magnitude of quasar feedback.