JADES: measuring reionization properties using Lyman-alpha emission

Ly αis the transition to the ground state from the first excited state of hydrogen (the most common element). Resonant scattering of this line by neutral hydrogen greatly impedes its emergence from galaxies, so the fraction of galaxies emitting Ly αis a tracer of the neutral fraction of the intergalactic medium (IGM), and thus the history of reionization. In previous works, we used early JWST /NIRSpec data from the JWST Advanced Deep Extragalactic Surv e y (JADES) to classify and characterize Ly αemitting galaxies (LAEs). This surv e y is approaching completion, and the current sample is nearly an order of magnitude larger. From a sample of 795 galaxies in JADES at 4 . 0 < z < 14 . 3, we find evidence for Ly αemission in 150 sources. We reproduce the previously found correlation between Ly αescape fraction ( f Ly αesc ) -Ly αrest-frame equi v alent width ( REW Ly α) and the ne gativ e correlation between Ly αvelocity offset -f Ly αesc . Both f Ly αesc and REW Ly αdecrease with redshift ( z _ 5 . 5), indicating the progression of reionization on a population scale. Our data are used to demonstrate an increasing IGM transmission of Ly αfrom z ∼14 -6. We measure the completeness-corrected fraction of LAEs ( X Ly α) from z = 4 -9 . 5. An application of these X Ly αvalues to the results of previously utilized semi-analytical models suggests a high neutral fraction at z = 7 ( X HI ∼0 . 8 -0 . 9). Using an updated fit to the intrinsic distribution of REW Ly αresults in a lower value in agreement with current works ( X HI = 0 . 64 + 0 . 13 -0 . 21 ). This sample of LAEs will be paramount for unbiased population studies of galaxies in the EoR.