We propose to conduct two nights observation of Keck/MOSFIRE H-band spectroscopy for an overdense structure of quiescent galaxies at z=3.0, which is newly found in the COSMOS2020 catalog. Obtaining rest-frame optical spectra of nine quiescent galaxies and 31 star-forming galaxies inside the structure, we will confirm the existence of this unique structure, which will be located at a higher redshift than the protocluster previously cofirmed as an overdensity of quiescent galaxies at z=2.77 (Ito et al. 2023). We will determine the stellar velocity dispersion of six out of nine quiescent galaxies. Combining the high-resolution image of the James Webb Space Telescope (JWST), we then evaluate the environmental dependence of the velocity dispersion, size, and their scaling-relation. In addition, combining the obtained spectra and multi-wavelength photometry enables us to estimate their star formation history. This estimation at a higher redshift than before will more strongly constrain when this structure forms and what its progenitor is. This combination of JWST and Keck will make this structure an ideal laboratory for understanding quiescent protoclusters’ evolutionary history and revealing quiescent galaxies’ environmental dependence.
This document was translated from LATEX by HEVEA.