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Lyman-alpha emission from galaxies should be suppressed completely or partially at redshifts beyond reionization. Without knowing the instrinsic properties of galaxies at z = 6. 5, this attenuation is hard to infer in any one source, but can be infered from a comparison of luminosity functions of lyman-alpha emitters at redshifts just before and after reionization. We combine published surveys of widely varying depths and areas to construct luminosity functions at z=6. 5 and 5. 7, where the characteristic luminosity Lₛtar and density phiₛtar are well constrained while the faint-end slope of the luminosity function is essentially unconstrained. Excellent consistency is seen in all but one published result. We then calculate the likelihood of obtaining the z=6. 5 observations given the z=5. 7 luminosity function with (A) no evolution and (B) an attenuation of a factor of three. Hypothesis (A) gives an acceptable likelihood while (B) does not. This indicates that the z=6. 5 lyman-alpha lines are not strongly suppressed by a neutral intergalactic medium and that reionization was largely complete at z = 6. 5.
Malhotra et al. (Thu,) studied this question.