The emperor’s new arc: gigaparsec patterns abound in a ΛCDM universe

Sawala, Till; Teeriaho, Meri; Frenk, Carlos S; Helly, John; Jenkins, Adrian; Racz, Gabor; Schaller, Matthieu; Schaye, Joop

Abstract

Recent discoveries of apparent large-scale features in the structure of the Universe extending over many hundreds of megaparsecs, have been claimed to contradict the large-scale isotropy and homogeneity foundational to the standard (Lambda cold dark matter – CDM) cosmological model. We explicitly test and refute this conjecture using FLAMINGO-10K, a new and very large cosmological simulation of the growth of structure in a CDM context. Applying the same methods used in the observations, we show that patterns like the ‘Giant Arc’, supposedly in tension with the standard model, are, in fact, common and expected in a CDM universe. We also show that their reported significant overdensities are an algorithmic artefact and unlikely to reflect any underlying structure.

Citation

Sawala, T., Teeriaho, M., Frenk, C. S., Helly, J., Jenkins, A., Racz, G., Schaller, M., & Schaye, J. (2025). The emperor’s new arc: gigaparsec patterns abound in a ΛCDM universe. Monthly Notices of the Royal Astronomical Society: Letters, 541(1), L22-L27. https://doi.org/10.1093/mnrasl/slaf021

• Journal Article Type: Article
• Acceptance Date: Mar 7, 2025
• Online Publication Date: Mar 11, 2025
• Publication Date: 2025-07
• Deposit Date: May 28, 2025
• Publicly Available Date: May 28, 2025
• Journal: Monthly Notices of the Royal Astronomical Society: Letters
• Electronic ISSN: 1745-3933
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 541
• Issue: 1
• Pages: L22-L27
• DOI: https://doi.org/10.1093/mnrasl/slaf021
• Keywords: methods: statistical, large-scale structure of Universe, methods: numerical, cosmology: theory
• Public URL: https://durham-repository.worktribe.com/output/3963433