Lyα emission from [O iii] emitters near reionization: the role of environment in galaxy Lyα detection

This is the authors' abstract. We don't add key points for this paper.

Using galaxy Lyα emission to probe reionization relies on establishing baseline expectations for its detectability in the absence of attenuation by neutral gas in the intergalactic medium (IGM). Towards this end, the growing numbers of z ~ 5–6 star-forming galaxies spectroscopically selected by James Webb Space Telescope (JWST) provide an ideal sample for determining how Lyα emission depends on galaxy properties and environment after reionization has largely completed. In this study, we use Keck Low-Resolution Imaging Spectrograph (LRIS) to measure the Lyα emission of 46 JWST-selected [O iii]-emitting galaxies over 5.3 z 6.2 in the foreground of the ultraluminous quasar J0100 + 2802. Overall, we find that the fraction of galaxies detected in Lyα emission is consistent with previous works; however, the fraction also varies with environment. Most notably, we find an apparent deficit of Lyα in the largest group in our sample, at z 6.19, which falls within the redshift range of the quasar’s highly ionized proximity zone. We speculate that the Lyα emission from this group may be partly scattered by a foreground neutral island. In contrast, we detect a high rate of Lyα emission in two groups at z 5.73 and 5.78. These groups may be part of a structure that is extended along the line of sight, enhancing the transmission of Lyα emission. While our sample size is limited, our results suggest that environment may play a significant role in the detectability of galaxy Lyα emission even as late as z ~ 6.