We propose spectroscopy for 20 dropout galaxy candidates at z∼7 found in the ∼400 deg2 Subaru strategic program with Hyper Suprime-Cam (HSC-SSP). 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. With our proposed observations, we will make a statistical sample of spectroscopically confirmed dropouts at the bright-end, and investigate whether the galaxy luminosity function shows the excess or not at the 5σ level. 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 spectroscopically confirmed bright galaxies for JWST follow-up observations to understand the physical origin of the bright end excess and massive galaxy formation in early universe.
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