The impact of baryons on the sparsity of simulated galaxy clusters from THE THREE HUNDRED Project

Astrophysical and cosmological implications

¹ LUX, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 92190 Meudon, France
² Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France
³ Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián, Gipuzkoa, Spain
⁴ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, via Piero Gobetti 93/3, I-40129 Bologna, Italy
⁵ INFN, Sezione di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna, Italy
⁶ Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Rome, Italy
⁷ INAF-Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131 Trieste, Italy
⁸ IFPU-Institute for Fundamental Physics of the Universe, via Beirut 2, 34151 Trieste, Italy
⁹ Department of Physics, University of Michigan, 450 Church St, Ann Arbor, MI 48109, USA
¹⁰ Departamento de Física Teórica, Módulo 15, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
¹¹ Centro de Investigación Avanzada en Física Fundamental (CIAFF), Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
¹² INAF – Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, I-00133 Rome, Italy
¹³ Université Paris Cité, F-75006 Paris, France

^⋆ Corresponding authors: Pier-Stefano.Corasaniti@obspm.fr; tamara.richardson@dipc.org

Received: 27 January 2025
Accepted: 19 March 2025

Abstract

Context. Measurements of the sparsity of galaxy clusters can be used to probe the cosmological information encoded in the host dark matter halo profile, and infer constraints on the cosmological model parameters. Key to the success of these analyses is the control of potential sources of systematic uncertainties. As an example, the presence of baryons can alter the cluster sparsity with respect to predictions from N-body simulations. Similarly, a radial-dependent mass bias, as in the case of cluster masses inferred under the hydrostatic equilibrium (HE) hypothesis, can affect sparsity estimates.

Aims. First, we examined the imprint of baryonic processes on the sparsity statistics. Then, we investigated the relation between cluster sparsities and the gas mass fraction. Finally, we performed a study of the impact of HE mass bias on sparsity measurements and the implication on cosmological parameter inference analyses.

Methods. We used catalogues of simulated galaxy clusters from THE THREE HUNDRED project and ran a comparative analysis of the sparsity of clusters from hydrodynamical N-body simulations implementing different feedback model scenarios.

Results. Sparsities that probe the mass profile across a large radial range are affected by the presence of baryons in a way that is particularly sensitive to astrophysical feedback, whereas those exclusively probing external cluster regions are less affected. In the former case, we find the sparsities to be moderately correlated with measurements of the gas fraction in the inner cluster regions. We inferred constraints on S₈ using synthetic average sparsity measurements generated to evaluate the impact of baryons, selection effects and HE bias. In the case of multiple sparsities (s_200, 500, s_200, 2500, and s_500, 2500), these lead to highly biased results. Hence, we calibrated linear bias models that enabled us to correct for these effects and recover unbiased constraints that are significantly tighter than those inferred from the analysis of s_200, 500 only.