The Universe is at Most 88% Neutral at z=10.6

Understand

Recent observations of GN-z11 with JWST have revealed a Ly$\alpha$ emission line with an equivalent width of 18$\pm 2$ angstroms.

• At z=10.6, this galaxy is expected to lie in the heart of reionization.
• We use a series of inhomogeneous reionization simulations to derive the distribution of the Ly$\alpha$ EW after traveling through the neutral intergalactic medium with varying average neutral gas fraction, $x_{HI}$.
• We use these distribution to place an upper limit of $x_{HI} < $ 0.88 at z=10.6 at 95% confidence level.