(Proposal ID) S10B-021 (PI) Kashikawa, Nobunari (Proposal Title) The first QSOs at z~7: Spectroscopy (Abstract) We propose to take follow-up spectroscopy for our primising QSO candidates at z ~ 7. In S09A, we have obtained wide and deep z_B/z_R images with Subaru/Suprime-Cam for 7 deg^2 in total for three UKIDSS-DXS fields in order to select QSO candidates at z ~ 7. Using z_B - z_R and z_R - J color selection, we have carefully selected 15 promising QSO candidates. The colors and image shape of our candidates are exactly as expected for z ~ 7 QSOs. This project is a new search for the most distant QSOs at z ~ 7 utilizing unique capabilities of wide-field imaging of Suprime-Cam, its high-sensitivity CCDs at ~ 1 mu m, and z_B/z_R filters to effectively isolate high-z QSOs from L/T dwarfs. Our primary objective of this project is to determine the census of QSOs at z ~ 7. The constraint of QSO number density at the highest redshift is very important to revise formation and evolution models of early QSO/SMBH in a time scale as short as <1Gyr. The census of QSOs at z ~ 7 is also quite interesting in estimating the QSO contribution to the photon budget of cosmic reionization. The obtained QSO sample at z ~ 7 will give precious opportunities for the current and future observational facilities to follow-up. The discovery of even one QSO at z ~ 7 will have a great impact on astronomy.