Studying reionization with the next generation of Lyα emitter surveys

We study the prospects for constraining the ionized fraction of the intergalactic medium (IGM) at z> 6 with the next generation of large Lyα emitter surveys. We make predic-tions for the upcoming Subaru Hyper Suprime-Cam (HSC) Lyα survey and a hypothetical spectroscopic survey performed with the James Webb Space Telescope (JWST). Consider-ing various scenarios where the observed evolution of the Lyα luminosity function of Lyα emitters at z> 6 is explained partly by an increasingly neutral IGM and partly by intrinsic galaxy evolution, we show how clustering measurements will be able to distinguish between these scenarios. We find that the HSC survey should be able to detect the additional cluster-ing induced by a neutral IGM if the global IGM neutral fraction is greater than ∼20 per cent at z = 6.5. If measurements of the Lyα equivalent widths (EWs) are also available, neutral fractions as small as 10 per cent may be detectable by looking for correlation between the EW and the local number density of objects. In this case, if it should turn out that the IGM is significantly neutral at z = 6.5 and the intrinsic EW distribution is relatively narrow, the observed EWs can also be used to construct a map of the locations and approximate sizes o