S21B0083
S21B0083
Lyα opacity, τeff, measured by the Gunn-Peterson (GP) trough at z>5.5, has a significant variation among different quasar lines of sight (LOS), indicating a spatially inhomogeneous reionizing process. A physical origin of such a significant variation has not yet been identified. Two contradictory models, incorporating additional fluctuations in either the ionizing background (Γ) or the relic temperature (T) fluctuation, have completely different predictions about the spatial distribution of the Lyα opacity, and it is thus possible to directly distinguish these two predictions through galaxy distributions at the same redshift. We have conducted HSC NB816 imaging to probe the Lyα emitters (LAEs) in three high-τeff regions. One field shows LAE underdensity around the quasar LOS, which is consistent with the previous study, while the other two fields show overdensity, though all three fields are high-τeff regions at z=5.7. One possible explanation is that observed overdensities are contaminated by the LAEs in the foreground and/or background low-τeff regions. We propose FOCAS spectroscopy to measure the redshifts of LAEs in these overdense regions to test whether τeff correlates positively or negatively or both with the galaxy density.
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