Testing decaying dark matter models as a solution to the S₈ tension with the thermal Sunyaev-Zel’dovich effect

¹ Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Bâtiment 121, 91405 Orsay, France
² Kavli IPMU (WPI), UTIAS, The University of Tokyo, Kashiwa, Chiba, 277-8583 Japan
e-mail: hideki.tanimura@ipmu.jp

Received: 10 January 2023
Accepted: 5 May 2023

Abstract

Considering possible solutions to the S₈ tension between the Planck cosmic microwave background (CMB) measurement and low-redshift probes, we extended the standard ΛCDM cosmological model by including decay of dark matter (DDM). We first tested the DDM model in which dark matter decays into a form of noninteracting dark radiation. Under this DDM model, we investigated the impacts of DDM on the Sunyaev Zel’dovich (SZ) effect by varying the decay lifetime, Γ⁻¹, including the background evolution in cosmology and the nonlinear prescription in the halo mass function. We performed a cosmological analysis under the assumption of this extended cosmological model by combining the latest high-redshift Planck CMB measurement and low-redshift measurements of the SZ power spectrum as well as the baryonic acoustic oscillations (BAO) and luminosity distances to type Ia supernovae (SNIa). Our result shows a preference for Γ⁻¹ ∼ 220 Gyr with a lower bound on the decay lifetime of ∼38 Gyr at 95% confidence level. Additionally, we tested the other DDM model in which dark matter decays into warm dark matter and dark radiation. This model supports Γ⁻¹ ∼ 137 Gyr to resolve the S₈ tension with a lower bound on the decay lifetime of ∼24 Gyr at 95% confidence level. Comparing these two models, we find that the second leads to slightly better reconciliation of the S₈ tension.