This is a resubmission of an approved proposal partly lost due to bad weather. We propose spectroscopy for 20 galaxy candidates at z∼7 found in the ∼400 deg2 Subaru Hyper Suprime-Cam (HSC) survey. Our targets are rare and remarkably luminous with LUV∼8× LUV*, distinct from previously studied z∼7 fainter galaxies found in smaller-area (<10 deg2) surveys such as REBELS. Interestingly, these targets show a possible excess of the number density from the Schechter form of the galaxy UV luminosity function, after subtraction of the contribution from AGN, indicating inefficient mass quenching or a significant number of merging galaxies at the bright end. However, due to the small number of spectroscopically-confirmed galaxies, the significance of the bright-end excess is only 2σ. In this program, we will make a statistical sample of spectroscopically confirmed galaxies at the bright-end, and investigate whether the galaxy luminosity function shows the excess or not at 5σ. Because the luminosity range of our targets is not covered by planned JWST observations at z>∼7, this program will also provide a unique sample of bright galaxies for JWST follow-ups to understand the physical origin of the bright end excess and massive galaxy formation in the early universe.
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