An observational pursuit for Pop III stars in a Lyα emitter at z>6 through He II emission

We report our on-going observational project to search for population III (Pop III) stars in high-z galaxies. We searched Lyα emitters (LAEs) with a large equivalent width (EW), by our new selection technique `NB921-depressed i′-dropout selection'. We found eight photometric candidates and spectroscopically identified five LAEs with EW₀(Lyα) > 100 Å. We then carried out a very deep near-infrared spectroscopy for a LAE among the above five, to search for the redshifted He IIλ1640 emission from Pop III stars in the galaxy, but obtained only an upper limit.