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

Abstract

Context. In cosmological fits, it is common to fix the baryon density ωb via the cosmic microwave background. We here constrain ωb 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, Ωk. Through the Hubble points and D(z) determined in this way, we interpolated uncorrelated data of baryonic acoustic oscillations bounding the baryon ωb and total matter ωm densities, reinforcing the constraints on h0 and Ωk with the same technique. Finally, to remove the matter sector degeneracy, we obtained ωb 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.