Brighter and More Massive Galaxies in the Vicinity of Lyα Nebulae

It has been well established in the local universe that galaxy properties differ based on the large-scale environment in which they reside. As luminous Ly α nebulae have been shown to trace overdense environments at z ∼ 2–3, comparing the properties of galaxies within Ly α nebulae systems to those in the field can provide insight into how and when locally observed trends between galaxy properties and environment emerged. Six Ly α nebulae were discovered at z ∼ 2.3 in a blind search of the GOODS-S extragalactic field, a region also covered by the 3D-HST spectroscopic survey. Utilizing 3D-HST data, we identified 86 galaxies in the vicinity of these nebulae and used statistical tests to compare their physical properties to galaxies elsewhere in the field. Galaxies lying within 320 proper kpc of a Ly α nebula are roughly half a magnitude brighter than those in the field, with higher stellar masses, higher star formation rates, and larger effective radii. Even when considering the effects of sample incompleteness, our study suggests that galaxies in overdensities at z ∼ 2.3 traced by Ly α nebulae are being influenced by their environment. Furthermore, Ly α -nebula-associated galaxies lie on the same main sequence of star formation as field galaxies but have a larger proportion of high-mass galaxies, consistent with the idea that galaxy evolution is accelerated in rich environments. Expanded surveys for Ly α nebulae in other deep extragalactic fields and galaxy spectroscopic follow-up with the James Webb Space Telescope (JWST) will better constrain the demographics of Ly α -nebula-associated galaxies.