Gas properties as a function of environment in the proto-supercluster Hyperion at z ∼ 2.45

¹ University of Bologna – Department of Physics and Astronomy “Augusto Righi” (DIFA), Via Gobetti 93/2, I-40129, Bologna, Italy
² INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, I-40129, Bologna, Italy
³ Scuola Internazionale Superiore Studi Avanzati (SISSA), Physics Area, Via Bonomea 265, 34136 Trieste, Italy
⁴ IFPU-Institute for Fundamental Physics of the Universe, Via Beirut 2, 34014 Trieste, Italy
⁵ Department of Physics and Astronomy, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
⁶ Gemini Observatory, NSF NOIRLab, 670 N. A’ohoku Place, Hilo, HI 96720, USA
⁷ Department of Physics and Astronomy, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA
⁸ Department of Physics and Astronomy, Texas A&M University, College Station, TX, 77843-4242 USA
⁹ George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX, 77843-4242 USA
¹⁰ INAF – Astronomical Observatory of Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
¹¹ Department of Astronomy & Astrophysics, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093, USA
¹² INAF-IASF Milano, Via Alfonso Corti 12, 20133, Milano, Italy
¹³ INAF – Osservatorio astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy
¹⁴ Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
¹⁵ Astronomy Department, University of Massachusetts, Amherst, MA 01003, USA
¹⁶ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁷ Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France

^⋆ Corresponding author: ggururaj@sissa.it

Received: 27 January 2025
Accepted: 11 April 2025

Abstract

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.