Elbers, W, Frenk, CS, Jenkins, A, Li, B, Helly, JC, Kugel, R, Schaller, M, Schaye, J, Braspenning, J, Kwan, J, McCarthy, IG, Salcido, J, van Daalen, MP, Vandenbroucke, B and Pascoli, S (2025) The FLAMINGO project: the coupling between baryonic feedback and cosmology in light of the S8 tension. Monthly Notices of the Royal Astronomical Society, 537 (2). pp. 2160-2178. ISSN 0035-8711

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Abstract

Large-scale structure surveys have reported measurements of the density of matter, Ωm, and the amplitude of clustering, σ8, that are in tension with the values inferred from observations of the cosmic microwave background. While this may be a sign of new physics that slows the growth of structure at late times, strong astrophysical feedback processes could also be responsible. In this work, we argue that astrophysical processes are not independent of cosmology and that their coupling naturally leads to stronger baryonic feedback in cosmological models with suppressed structure formation or when combined with a mechanism that removes dark matter from haloes. We illustrate this with two well-motivated extensions of the Standard Model known to suppress structure formation: massive neutrinos and decaying dark matter. Our results, based on the FLAMINGO suite of hydrodynamical simulations, show that the combined effect of baryonic and non-baryonic suppression mechanisms is greater than the sum of its parts, particularly for decaying dark matter. We also show that the dependence of baryonic feedback on cosmology can be modelled as a function of the ratio fb/c2v～ fb/(Ωmσ8)1/4 of the universal baryon fraction, fb, to a velocity-based definition of halo concentration, c2v, giving an accurate fitting formula for the baryonic suppression of the matter power spectrum. Although the combination of baryonic and non-baryonic suppression mechanisms can resolve the tension, the models with neutrinos and decaying dark matter are challenged by constraints on the expansion history.

Item Type:	Article
Uncontrolled Keywords:	5106 Nuclear and Plasma Physics; 5107 Particle and High Energy Physics; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press (OUP)
SWORD Depositor:	A Symplectic
Date Deposited:	12 Mar 2025 13:27
Last Modified:	12 Mar 2025 13:30
DOI or ID number:	10.1093/mnras/staf093
URI:	https://researchonline.ljmu.ac.uk/id/eprint/25864

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