2025A&A...698A.312G

The cosmic star formation rate density, molecular gas density, and active galactic nucleus (AGN) activity of the Universe peak at z∼2-3, demonstrating the Universe is most active at this epoch. The nature of the galaxies at these redshifts and their properties as a function of their environment are particularly interesting with respect to our understanding of the mechanisms driving their star formation and quenching. At z∼2.5, the massive (∼4.8×10¹⁵ M_⊙) proto-supercluster Hyperion, consisting of seven groups and peaks and extending over a co-moving volume of 60×60×150 Mpc³, is an excellent laboratory for probing the properties and evolution of galaxies as a function of their environments. We used a large compilation of photometric (optical to radio wavelengths, COSMOS2020, COSMOS-Super-deblended, and A³COSMOS), and spectroscopic (C3VO, HST-Hyperion, VUDS, zCOSMOS, DEIMOS10K, and MAGAZ3NE) data to assign membership and study the relation between the local environment and the molecular gas mass, the star-formation rate (SFR), gas depletion timescales, and quenching mechanisms. We find that the depletion timescales and the molecular gas fractions decrease and SFR increases in denser environments at the ∼2σ level, suggesting accelerated evolution in the densest regions of this proto-supercluster resulting from gas stripping, over-consumption, and/or cessation of cold flows. Dedicated observations at sub-millimeter (sub-mm) wavelengths will enable further spectroscopic confirmations and better coverage at these wavelengths, thereby offering more conclusive results on the environmental implications on gas reservoirs of galaxies in Hyperion.