2024/02/08 by Tang, Mengtao, Stark, Daniel P., Ellis, Richard S. +22
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2402.06070
JWST has recently sparked a new era of Lyα spectroscopy, delivering the first measurements of the Lyα escape fraction and velocity profile in typical galaxies at z≃6-10. These observations offer new prospects for insight into the earliest stages of reionization. But to realize this potential, we need robust models of Lyα properties in galaxies at z≃5-6 when the IGM is mostly ionized. Here we use new JWST observations from the JADES and FRESCO surveys combined with VLT/MUSE and Keck/DEIMOS data to characterize statistical distributions of Lyα velocity offsets, escape fractions, and EWs in z≃5-6 galaxies. We find that galaxies with large Lyα escape fractions (> 0.2) are common at z≃5-6, comprising 30 per cent of Lyman break selected samples. Comparing to literature studies, our census suggests that Lyα becomes more prevalent in the galaxy population toward higher redshift from z∼3 to z∼6, although we find that this evolution slows considerably between z∼5 and z∼6, consistent with modest attenuation from residual HI in the mostly ionized IGM at z≃5-6. We find significant evolution in Lyα velocity profiles between z≃2-3 and z≃5-6, likely reflecting the influence of resonant scattering from residual intergalactic HI on the escape of Lyα emission near line center. This effect will make it challenging to use Lyα peak offsets as a probe of Lyman continuum leakage at z≃5-6. We use our z≃5-6 Lyα distributions to make predictions for typical Lyα properties at z\gtrsim8 and discuss implications of a recently-discovered Lyα emitter at z≃8.5 with a small peak velocity offset (156 km s-1).