Luminosity functions of lyα emitters at redshifts z = 6.5 and z = 5.7: Evidence against reionization at z ≤ 6.5

The visibility of Lyα emission from galaxies should be suppressed substantially by a neutral intergalactic medium before reionization. Even after taking into account a local H u region produced by the galaxy and a velocity offset of Lyα, a factor of 3 attenuation in the line is unavoidable. We rule out such a suppression by comparing line luminosity functions of Lyα emitters at z = 6.5 and 5.7. The luminosity functions at z = 5.7 and z = 6.5 were constructed using published surveys over a range of depths and volumes. They constrain both characteristic luminosity L* and density φ_x. The luminosity functions at the two redshifts are statistically consistent with one another, and only one survey lies substantially off the luminosity function. We conclude that reionization was largely complete at z ≈ 6.5.