Cosmology With Low-Redshift Observations: No Signal For New Physics

TL;DR

The study investigates whether low-redshift observations require new physics beyond ΛCDM by fitting ΛCDM and several dark energy parameterizations to SN, BAO, strong-lensing time delays, cosmic chronometer measurements, and growth data, then assesses models via Bayesian evidence. It finds that ΛCDM with $H_{0} = 70.3^{+1.36}_{-1.35}$ km s$^{-1}$ Mpc$^{-1}$, $r_{d} = 144.68^{+2.9}_{-2.9}$ Mpc, and $S_{8} = 0.76^{+0.03}_{-0.03}$ provides the best fit, while alternative models (wCDM, CPL, Pade) are disfavored by Δ$\ln Z > 2.5$. The low-redshift constraints are consistent with Planck and other measurements within about $2\sigma$, and the independent $S_{8}$ estimate agrees with KiDS+DES; Cosmic Chronometers help align $H_{0}$ with Planck by increasing $r_d$. Overall, the results support ΛCDM as the simplest viable description of the late-time Universe and suggest no compelling reason to invoke new physics based on current low-redshift data.

Abstract

We analyse various low-redshift cosmological data from Type-Ia Supernova, Baryon Acoustic Oscillations, Time-Delay measurements using Strong-Lensing, $H(z)$ measurements using Cosmic Chronometers and growth measurements from large scale structure observations for $Λ$CDM and some different dark energy models. By calculating the Bayesian Evidence for different dark energy models, we find out that the $Λ$CDM still gives the best fit to the data with $H_{0}=70.3^{+1.36}_{-1.35}$ Km/s/Mpc (at $1σ$). This value is in $2σ$ or less tension with various low and high redshift measurements for $H_{0}$ including SH0ES, Planck-2018 and the recent results from H0LiCOW-XIII. The derived constraint on $S_{8}=σ_{8}\sqrt{Ω_{m0}/{0.3}}$ from our analysis is $S_{8} = 0.76^{+0.03}_{-0.03}$, fully consistent with direct measurement of $S_{8}$ by KiDS+VIKING-450+DES1 survey. We hence conclude that the $Λ$CDM model with parameter constraints obtained in this work is consistent with different early and late Universe observations within $2σ$. We therefore, do not find any compelling reason to go beyond concordance $Λ$CDM model.

Figures (5)

• Figure 1: Values of $H_{0}$ with $1$-$\sigma$ error for several models studied in the work. The results are shown for different combinations of data-sets studied.
• Figure 2: $1\sigma$ and $2\sigma$ constrained contours in $H_{0}-r_{d}$ parameter plane. The horizontal green band is $1\sigma$ constraints on $H_{0}$ by R19. The horizontal (vertical) grey band is constraint on $H_{0}$ (on $r_{d}$) from Planck-2018. Here the "BASE+CC+$f\sigma_{8}$" data sets is used.
• Figure 3: $H_{0}$ measurements with $1\sigma$ error bars from different observational data including the one reported in this work for $\Lambda$CDM model. We also show the tensions in our measurement with low-redshift observations compared to other observations. The DES+BBN+BAO, MIRAS, MCP and SBF measurements are taken from Verde:2019ivm. For the rest of the measurements, see the text.
• Figure 4: Values of $H_{0}r_{d}$ (in Km/s) for different dark energy model. The data set used "BASE+CC".
• Figure 5: $1\sigma$ and $2\sigma$ contours in ($H_{0},S_{8}$) plane (Left Figure) and in ($\Omega_{m0},S_{8}$) (Right Figure) for different dark energy models. The grey band is $1\sigma$ bound for $S_{8}$ from KiDS+VIKING-450+DES-Y1 survey results. The green band in the Left Figure is the $1\sigma$ bound on $H_{0}$ from R19.