(Proposal ID) S17A-105

(PI) Toshikawa, Jun

(Proposal Title)
Systematic Spectroscopy of HSC-SSP Protoclusters at z~4

(Abstract)
Large-scale structure formation and galaxy evolution in high-density 
environments are important open issues. Direct investigations into evolutionary
steps of galaxy clusters through protoclusters will enable us to address these 
questions. Furthermore, since galaxy clusters are growing into massive halo 
through the stochastic events of halo mergers, it is also necessary to make 
statistical sample of protoclusters to understand the diversity of 
protoclusters. Now, the unprecedented imaging data of the Hyper SuprimeCam 
Subaru Strategic Program, for the first time, allow us to make statistic study 
of protoclusters. A large sample of protocluster candidates were able to 
constructed in the ~170deg^2 HSC-Wide layer by using the same procedure, 
which is well established in our previous study. Then, we propose to take 
a systematic follow-up spectroscopy for the confirmation of ten the most 
plausible candidates at z ~4, which are expected to grow into > 5 x 10^{14} 
M_{sun} halos based on the theoretical model. From the proposed observation, 
we will investigate physical properties and internal structures of 
protoclusters by comparing with themselves as well as field galaxies. Based on 
these analysis from various directions, we will reveal general property and 
its variation of protoclusters on their growth phase.