Constraints on Hyperluminous QSO Lifetimes via Fluorescent Lyα Emitters at Z ~= 2.7

We present observations of a population of Lyα emitters (LAEs) exhibiting fluorescent emission via the reprocessing of ionizing radiation from nearby hyperluminous QSOs. These LAEs are part of a survey at redshifts 2.5 < z < 2.9 combining narrow-band photometric selection and spectroscopic follow-up to characterize the emission mechanisms, physical properties, and three-dimensional locations of the emitters with respect to their nearby hyperluminous QSOs. These data allow us to probe the radiation field, and thus the radiative history, of the QSOs, and we determine that most of the eight QSOs in our sample have been active and of comparable luminosity for a time 1 Myr <~ t _Q <~ 20 Myr. Furthermore, we find that the ionizing QSO emission must have an opening angle θ ~ 30° or larger relative to the line of sight.