2025ApJ...993..111W

To understand how massive galaxies are influenced by their surroundings, we present new Atacama Large Millimeter/submillimeter Array and Northern Extended Millimeter Array observations as part of A Multiwavelength Study of Enormous Lyα Nebula (ELAN) Environments (AMUSE²). These observations target submillimeter sources discovered in single-dish surveys around nine quasars hosting Lyα nebulae at z = 2 ∼3, including two enormous Lyα nebulae. Through detection of mid-J CO lines, we confirm physical associations of 15 SMGs, which are located outside the expected virial radii of the central dark-matter halos hosting the quasars. We find $7{3}_{-21}^{+29} \% $ of SMGs have line profiles better described by double-Gaussian models, with a median peak-to-peak separation of 350 ± 25 km s^–1, suggesting rotating disks or interacting pairs. Modified blackbody fits of the far-infrared photometry yield a median β of 2.0 ± 0.2 and T_dust of 34 ± 3 K. Overall, SMGs outside quasar halos share similar physical properties with those in the field, but combining data from other studies reveals depleted gas fractions within quasar halos. This suggests that dense environments significantly impact massive star-forming galaxies only within halo scales at cosmic noon. Additionally, spatial analyses of 15 SMGs indicate they trace large-scale structures, possibly filamentary or elongated pancake-like, with a scale height of 2-5 cMpc. Our measured distributions and densities of star formation rates align with models, although likely represent lower limits.