Breaking the baryon-dark matter degeneracy in a model-independent way through the Sunyaev-Zeldovich effect

¹ Scuola Superiore Meridionale, Largo S. Marcellino 10, 80138 Napoli, Italy
e-mail: annac.alfano@studenti.unina.it
² Università di Camerino, Divisione di Fisica, Via Madonna delle carceri 9, 62032 Camerino, Italy
e-mail: orlando.luongo@unicam.it; marco.muccino@lnf.infn.it
³ SUNY Polytechnic Institute, 13502 Utica, New York, USA
⁴ INFN, Sezione di Perugia, Perugia 06123, Italy
⁵ INAF – Osservatorio Astronomico di Brera, Milano, Italy
⁶ Al-Farabi Kazakh National University, Al-Farabi av. 71, 050040 Almaty, Kazakhstan

Received: 13 November 2023
Accepted: 15 February 2024

Abstract

Context. In cosmological fits, it is common to fix the baryon density ω_b via the cosmic microwave background. We here constrain ω_b by means of a model-independent interpolation of the acoustic parameter from correlated baryonic acoustic oscillations.

Aims. The proposed technique is used to alleviate the degeneracy between baryonic and dark matter abundances.

Methods. We propose a model-independent Bézier parametric interpolation and applied it to intermediate-redshift data. We first interpolated the observational Hubble data to extract cosmic bounds over the (reduced) Hubble constant h₀ and interpolated the angular diameter distances, D(z), of the galaxy clusters, inferred from the Sunyaev-Zeldovich effect, to constrain the spatial curvature, Ω_k. Through the Hubble points and D(z) determined in this way, we interpolated uncorrelated data of baryonic acoustic oscillations bounding the baryon ω_b and total matter ω_m densities, reinforcing the constraints on h₀ and Ω_k with the same technique. Finally, to remove the matter sector degeneracy, we obtained ω_b by interpolating the acoustic parameter from correlated baryonic acoustic oscillations.

Results. Monte Carlo Markov chain simulations agree at 1σ confidence level with the flat ΛCDM model and are roughly suitable at 1σ with its nonflat extension, while the Hubble constant appears in tension up to the 2σ confidence levels.

Conclusions. Our method excludes very small extensions of the standard cosmological model, and on the Hubble tension side, seems to match local constraints slightly.