Program: GN-2018A-DD-103

We request Gemini DDT observation of a newly discovered extremely luminous quasar at z=6.50. It is the most luminous object that ever seen at z>6.0 and could host a twenty billion solar mass super-massive black hole (SMBH). This quasar is setting and can only be visible before middle March. Therefore, we ask for DDT observations to speed up analysis and publication of this important object and to prepare for followup observations with JWST and ALMA. In addition to hosting a monster BH, this quasar has a pretty small proximity zone compared with other quasars at similar redshift. The tiny proximity zone suggests that this quasar started to illuminate surrounding inter-galactic medium with less than hundred thousand years. The existence of twenty billion solar mass BH with such short life time would put the strongest constraints on the BH formation and growth history. However, we only have optical spectrum for this object and can not determine the MgII emission line based BH mass, which is the most accurate way to measure BH mass at high redshift. Thus we propose to use Gemini/GNIRS to obtain deep NIR spectroscopic observations of this new quasar. The GNIRS observations will also provide accurate measurements of the quasar redshift using MgII emission line, allowing detailed modeling of quasar absorption spectra and measure the size of proximity zone accurately. It will also enable us to measure Eddington ratio and chemical abundances in the quasar broad line regions. Remarkably, the high quality Gemini spectra will detect weak high redshift intervening metal absorbers to probe the IGM chemical enrichment from early galaxies at z>6.0.