Cold gas accretion along LSSs, towards proto-cluster cores, and to individual galaxies, plays critical roles in accelerating star forming activities at high redshifts. However mapping the cold gas is challenging as we can observe them only by absorptions. Recently, two prominent LSSs hosting super-clusters at z=3.3 have been identified, for which a pair narrow-band filters exists which can neatly capture Lyα and [OIII] emission lines from the structures. Taking this unique opportunity, we will map out the HI gas by comparing Lyα emitters and [OII] emitters embedded in the structures. [OIII] emission lines, which are known to be strong for high redshift star forming galaxies, can neatly trace the spatial distributions of normal star forming galaxies, while Lyα emission lines are scattered and attenuated if the galaxies are enshrouded by HI gas. Previous studies for the proto-clusters at the cosmic noon (z=2.2–2.5) have been revealing that, in younger proto-clusters, Lyα emitters tend to avoid the cores traced by Hα emitters, suggesting the existence of rich HI gas in these cores fed by cold gas accretion through the filaments. We will extend this study to higher redshifts beyond the cosmic noon to reveal even earlier phase of cold gas accretion along the LSSs and star forming activities in the structures.
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