S18B0083abst

S18B0083

We aim to understand the origin of the observed large-scale distribution of the effective Hi opacity (τ_eff, averaged on ∼70 cMpc scales) of the intergalactic medium at the end tail of cosmic reionization. The distribution of τ_eff is fully explained by the density variations at z<5. Interestingly, however, the variation in τ_eff dramatically increases at z>∼5.5, greatly exceeding the level expected from the density fluctuations alone. This must be reflecting the spatial dependence of reionization at its end, and should then be a key clue to understand the reionization processes at earlier epochs. In particular, we will examine three possibilities that have been suggested to account for the observed large variations in τ_eff, which predict different correlations between τ_eff and the cosmological density field, or the presence of rare luminous quasars near to low-τ regions. We propose HSC observations (using the r,i, z filters) of the fields of 5 quasars at z∼6 for which extremely high or low τ_eff have been measured in their Lyα forest. We search for Lyman Break Galaxies, which trace the large-scale density field, and luminous quasars within the large cylindrical regions across z=5.4–6.0 covered by the HSC field-of-view (100 cMpc in radius), whose size is well suited to our experiment.

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