Program: GS-2018B-FT-202

Quasars at the epoch of reionization provide direct probes to the evolution of supermassive black holes (SMBHs), the cosmic reionization hisotry, and the build-up of the most massive galaxies at cosmic dawn. Although more than 150 quasars have been discovered at z>6, only two quasars previously known at z>7, because of a combination of their declining spatial density and limited sky coverage of near infrared photoemtry. Very recently, we discovered three z~7quasars with redshift from 6.85 to 7.03. Here, we propose to use Gemini/GMOS to obtain deep optical spectroscopic observations of these three newly discovered quasars. The proposed observations will allow detailed modeling of quasar absorption spectra, including the profile of damping wing and proximity zone, which will provide new constraints on the intergalactic medium (IGM) neutral fraction at the cosmic reionzation era and constrain the life time of these three quasars.