S21B0092
S21B0092
This is a resubmission of our approved S20B program, which was cancelled due to heavy snow on Maunakea. Our recent MOIRCS NB(Hα) observations of a Planck-selected, protocluster candidate at z=2.16 (PHzG237) successfully revealed a strong over-density of Hα emitters (HAEs). This is the first observational evidence reporting the physical association between “normal" SF galaxies and a Planck-selected dusty cluster in the early universe. We here propose Keck/MOSFIRE (H+K) follow-up spectroscopy to study the nature of these normal galaxies surviving in this cluster environment. By targeting all major rest-optical emission lines (Hβ/[Oiii]/Hα/[Nii]) of ∼30 HAEs, our science goals are: (1) to determine the 3-D structure and dynamical mass of the cluster, to quantify the cluster mass-normalized SFR (ΣSFR/Mcl); (2) to measure the dust attenuation levels of HAEs using the Hα/Hβ ratio, to reveal the reason behind the surprisingly large difference between the Hα- and IR-based cluster total SFRs; (3) to determine the gas-phase metallicity and the presence of AGNs among the protocluster galaxies. The proposed observations will provide a pioneering dataset to unveil the nature of young cluster galaxies experiencing a rapid mass growth at the peak epoch of galaxy formation.
This document was translated from LATEX by HEVEA.