Program: GN-2021B-FT-104

We propose a NIR spectroscopic observation with GNIRS for an optically invisible galaxy at z_phot ~ 2.7 discovered in the AKARI North Ecliptic Pole (NEP) field. The proposed target is not detected even by deep optical imaging with Subaru/HSC but is clearly detected by AKARI IR bands. These optically invisible galaxies are crucial to understanding the maximum phase of galaxy-SMBH co-evolution behind a large amount of gas and dust. However, a very large uncertainty of z_phot (~30%) prevented us from measuring accurate physical properties and understanding a full picture of the optically invisible galaxies. The purpose of this proposal is to determine its spectroscopic redshift. This proposal also has the potential of showing the most powerful ionized gas outflow ever known in its rest-frame optical spectrum. If this pilot study succeeds, we will start a spectroscopic follow-up campaign using 8m-class telescopes and JWST. This proposal will establish a benchmark for forthcoming studies of extremely-dusty SFGs/AGN missed by the previous optical surveys.