Lyman-$\alpha$ Visibility During the Epoch of Reionization: Combining JWST FRESCO Grism Data with Keck Archival Spectroscopy

Abstract

The visibility of Lyman-$\alpha$ emission at $z>7$ provides crucial insights into the reionization process and the role of galaxies in shaping the ionized intergalactic medium. Using JWST FRESCO data, we investigate the environments of Lyman-$\alpha$ emitters (LAEs) in the GOODS-N and GOODS-S fields by identifying [OIII] emitters and analyzing their large-scale distribution. Using the FRESCO redshifts, we recover eight new LAEs from archival Keck/MOSFIRE observations at $z=7.0-7.7$, including a potential AGN candidate at $z\sim 7.2$. Complemented by six literature LAEs, our sample consists of 14 LAEs in total, all of which are [OIII] emitters except for one very faint source not detected by FRESCO. We define seven groups of [OIII] emitters centered around the brightest LAEs and find that these bright LAEs do not reside in more overdense environments than the average galaxy population. The overdensity parameters for LAEs and [OIII] emitters without Lyman-$\alpha$, calculated for sources with ${\mathrm{M}}_{\mathrm{UV}}<-19.5$ to ensure completeness, are similar, indicating that overdensities alone cannot fully explain Lyman-$\alpha$ visibility. While LAEs have slightly higher recent star formation (SFR${}_{10}$/SFR${}_{50}\approx 1.3\times$) and [OIII] EW ($\approx 1.5\times$), they show no significant differences from [OIII] emitters in UV slope ($\beta$), UV magnitude (${\mathrm{M}}_{\mathrm{UV}}$), or stellar mass (${\log }_{{\mathrm{M}}_{\star }}$). Our results suggest that other factors may contribute to the observability of Lyman-$\alpha$ emission. Future spectroscopic surveys with broader wavelength coverage and more complete sampling will be crucial for refining our understanding of reionization.

22 pages, 12 figures, 8 tables, Submitted to MNRAS