The Atacama cosmology telescope : a census of bridges between galaxy clusters

Isopi, Giovanni (author), Fabjan, Dunja (author)

According to cosmic microwave background (CMB) measurements, baryonic matter constitutes about 5% of the mass-energy density of the universe. A significant population of these baryons, for a long time referred to as "missing", resides in a low density, warm-hot intergalactic medium (WHIM) outside galaxy clusters, tracing the "cosmic web", a network of large scale dark matter filaments. Various studies have detected this inter-cluster gas, both by stacking and by observing individual filaments in compact, massive systems. In this paper, we study short filaments (< 10 Mpc) connecting massive clusters (<M 500> ≈ 3 × 1014 M⊙) detected by the Atacama Cosmology Telescope (ACT) using the scattering of CMB light off the ionised gas, a phenomenon known as the thermal Sunyaev-Zeldovich (tSZ) effect. The first part of this work is a search for suitable candidates for high resolution follow-up tSZ observations. We identify four cluster pairs with an intercluster signal above the noise floor (S/N > 2), including two with a tentative > 2σ statistical significance for an intercluster bridge from the ACT data alone. In the second part of this work, starting from the same cluster sample, we directly stack on ∼100 cluster pairs and observe an excess SZ signal between the stacked clusters of y = (7.2+2.3 -2.5) × 10-7 with a significance of 3.3σ. It is the first tSZ measurement of hot gas between clusters in this range of masses at moderate redshift (<z> ≈ 0.5). We compare this to the signal from simulated cluster pairs with similar redshifts and separations in the THE300 and MAGNETICUM Pathfinder cosmological simulations and find broad consistency. Additionally, we show that our measurement is consistent with scaling relations between filament parameters and mass of the embedded halos identified in simulations.

• Language: English
• Keywords: cosmic web, cosmological simulations, galaxy clusters, Sunyaev-Zeldovich effect
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Publication date: 01.08.2025
• Year: 2025
• Number of pages: 43 str.
• Numbering: Vol. 2025, id. 78
• PID: 20.500.12556/RUL-171865
• UDC: 524.8
• ISSN on article: 1475-7516
• DOI: 10.1088/1475-7516/2025/08/078
• COBISS.SI-ID: 247580419
• Publication date in RUL: 03.09.2025

Record is a part of a journal

• Title: Journal of cosmology and astroparticle physics
• Publisher: Institute of Physics Pub.
• ISSN: 1475-7516
• COBISS.SI-ID: 389627

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P1-0188-2022
• Name: Astrofizika in fizika atmosfere