(Proposal ID) S15B-047

(PI) Kashikawa, Nobunari

(Proposal Title)
Mapping the most massive overdensity through HI

(Abstract)
We have undertaken a survey of the most massive and overdense galaxy 
structures in the early universe at z~2, traced by regions of the highest 
optical depth from IGM Lyalpha absorption over large scale of 20 Mpc. These 
structures represent the most biased regions in the universe at the peak of 
galaxy formation epoch. We propose Subaru/SCam deep narrowband imaging to 
probe the LAEs in five of the most extreme group of H{i} absorbers, where the 
effective optical depth over 20 h^{-1} Mpc is 4-6 x higher than the mean 
optical depth at z=2.3, in the quasar spectra drawn from the complete SDSS-III
/BOSS database over a 10,000 deg^2. Our survey volume is equivalent to ~1h^{-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. Our 
previous shallow KPNO-4m imaging observations have confirmed a significant 
overdensity of bright Lyalpha emitters associating with such a group of IGM 
H{i} absorbers. The main goal of the Subaru/Scam observation is to construct 
the first statistical sample of five large-scale structures traced by most 
extreme group of IGM Lyalpha absorption systems. Simultaneously, these 
observations should also detect extended LABs, probing their connection to 
galaxy overdensities.