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

TL;DR

The paper develops a model-independent pipeline based on Bézier parametric interpolation to break the baryon–dark matter degeneracy using intermediate-redshift data. It reconstructs $H(z)$ from observational Hubble data to bound $h_0$, uses SZ-derived angular diameter distances to constrain curvature $Ω_k$, and employs multiple BAO observables, including a correlated acoustic parameter $A_2(z)$, to bound $ω_b$ and $ω_m$ via $ω_b=h_0^2Ω_b$ and $ω_m=h_0^2Ω_m$. Monte Carlo–Markov chain analyses show results consistent with flat ΛCDM at 1σ, though the Hubble constant tension remains at about 2σ, and non-flat models are allowed within larger uncertainties. The method demonstrates a viable, data-driven, model-independent route to constrain key cosmological parameters without relying on CMB or SNe Ia data, while highlighting the current limitations imposed by SZ data redshift coverage and pointing to future improvements with expanded intermediate-redshift catalogs.

Abstract

We propose a model-independent \textit{Bézier parametric interpolation} to alleviate the degeneracy between baryonic and dark matter abundances by means of intermediate-redshift data. To do so, we first interpolate the observational Hubble data to extract cosmic bounds over the (reduced) Hubble constant, $h_0$, and interpolate the angular diameter distances, $D(z)$, of the galaxy clusters, inferred from the Sunyaev-Zeldovich effect, constraining the spatial curvature, $Ω_k$. Through the so-determined Hubble points and $D(z)$, we interpolate uncorrelated data of baryonic acoustic oscillations bounding the baryon ($ω_b = h^2_0Ω_b$) and total matter ($ω_m = h^2_0Ω_m$) densities, reinforcing the constraints on $h_0$ and $Ω_k$ with the same technique. Instead of pursuing the usual treatment to fix $ω_b$ via the value obtained from the cosmic microwave background to remove the matter sector degeneracy, we here interpolate the acoustic parameter from correlated baryonic acoustic oscillations. The results of our Monte Carlo--Markov chain simulations turn out to agree at $1$--$σ$ confidence level with the flat $Λ$CDM model. While our findings are roughly suitable at $1$--$σ$ with its non-flat extension too, the Hubble constant appears in tension up to the $2$--$σ$ confidence level. Accordingly, we also reanalyze the Hubble tension with our treatment and find our expectations slightly match local constraints.

Figures (2)

• Figure 1: MCMC contour plots of the Bézier interpolation. Darker (lighter) areas exhibit $1$--$\sigma$ ($2$--$\sigma$) confidence regions.
• Figure 2: Plots of the best-fitting Bézier curves (blue lines) and $1$--$\sigma$ confidence bands for $H_2(z)$, $D_2(z)$, $\delta_2(z)$, and $\Delta_2(z)$ (gray bands), and $A_2(z)$ and $\Theta_2(z)$ (green bands), compared to the $\Lambda$CDM paradigm Planck2018 (dashed red curves).