Program: GN-2018A-FT-114

We request Gemini GNIRS observation of a newly discovered quasar at z=7.0, the third highest redshift quasar known to date. The existence of damping wing absorption in the two previously known z>7 quasars strongly suggests that we are witnessing the peak of cosmic reionization. Our low signal-to-noise spectrum of this new z=7 quasar also shows evidence of a damping wing profile. However, due to the limited signal-to-noise and spectral coverage, and a lack of accurate redshift determination, the absorption feature is poorly constrained. Therefore, we ask for FT observations to speed up analysis and publication of this important object and to timely plan JWST and other multiple-wavelength followup observations. The Gemini/GNIRS observations will provide accurate measurements of the quasar redshift from MgII emission line, allowing detailed modeling of quasar absorption spectra, including the profile of damping wing and the size of proximity zone in order to measure IGM neutral fraction and to constrain reionization at z~7. It will also measure BH mass, Eddington ratio and chemical abundances in the quasar broad line regions. In addition, the high quality Gemini spectra will detect weak high redshift intervening metal absorbers to probe the IGM chemical enrichment from early galaxies at z>6.5.