Program: GN-2011B-Q-56

Weak emission line quasars (WLQs) constitute a distinct population in the distributions of UV emission-line strengths in high-redshift quasars. We propose to extend our successful Gemini-N near-IR observations of two WLQs and obtain GNIRS H-band spectra of the Mg II emission line region in three additional WLQs at z~4.9. Our overall goal is to obtain virial black hole masses and accretion rate determinations for a statistically meaningful sample of WLQs. Such observations will distinguish between two competing scenarios for the origin of WLQs: 1) extremely high accretion rates, leading to softer ionizing spectra and the suppression of high-ionization lines, such as C IV, with respect to low-ionization lines, such as Mg II, or 2) a significant gas deficit in the broad-line region of WLQs. The proposed observations, coupled with detailed photoionization modeling, may therefore lead to new insights into the accretion process and emission-line formation in all quasars.