(Proposal ID) S16B-030

(PI) Kashikawa, Nobunari

(Proposal Title)
Mapping the most massive overdensity through HI

(Abstract)
We are surveying the most massive and overdense structures in the early 
universe at z~2, identified by the group of strong intergalactic H {i} (Ly
alpha) absorption on ~sim15 co-Mpc.  These structures represent the most 
biased regions in the universe at the peak of galaxy formation epoch. We 
propose Subaru/HSC deep narrowband imaging to probe the Lyalpha emitters 
(LAEs) in five of the most extreme group of H {i} absorbers, where the 
effective optical depth over 15 h^{-1} Mpc is 4x higher than the mean optical 
depth at z=2.1, in the quasar spectra drawn from the complete SDSS-III/BOSS 
database over a 10,000 deg^2.  Our survey volume is equivalent to ~1 h^{-1} 
Gpc^3, which is one order of magnitude larger than any existing high-z galaxy 
survey, enabling the discovery of the rarest and most massive systems. The 
main goal of the observation are (1) to construct the first statistical sample 
of five large-scale structures traced by most extreme group of IGM Lyalpha 
absorption systems, and (2) to study the global correlation between optical 
depth of Lyalpha absorption (IGM gas) and the galaxy distribution with ~50 
quasar sight lines per field.  Simultaneously, these observations should also 
detect giant LABs, and probe their connection to galaxy overdensities.