New cosmological constraints with extended-Baryon Oscillation Spectroscopic Survey DR14 quasar sample

TL;DR

This paper assesses cosmological parameters by combining Planck 2015 CMB data with BAO measurements, including the DR14 quasar BAO at $z=1.52$, to test the base $\Lambda$CDM model and several extensions. Using CosmoMC, it derives tight constraints: the dark-energy equation of state in $w$CDM is $w=-1.036\pm0.056$, the effective number of relativistic species $N_{\text{eff}}=3.09_{-0.20}^{+0.18}$, the spatial curvature $\Omega_k=(1.8\pm1.9)\times10^{-3}$, and the total neutrino mass bounds $\sum m_\nu<0.16$ eV (NH) and $<0.19$ eV (IH) at 95% C.L., with a slight preference for NH. The results favor a flat $\Lambda$CDM universe with $w$ near $-1$, and while DR14 improves some constraints, it does not resolve the tension in the Hubble constant with local measurements. Overall, the study finds no compelling evidence for physics beyond $\Lambda$CDM given current data.

Abstract

We update the constraints on the cosmological parameters by adopting the Planck data released in 2015 and Baryon Acoustic Oscillation (BAO) measurements including the new DR14 quasar sample measurement at redshift $z=1.52$, and we conclude that the based six-parameter $Λ$CDM model is preferred. Exploring some extensions to the $Λ$CDM models, we find that the equation of state of dark energy reads $w=-1.036\pm 0.056$ in the $w$CDM model, the effective relativistic degrees of freedom in the Universe is $N_\text{eff}=3.09_{-0.20}^{+0.18}$ in the $N_\text{eff}+Λ$CDM model and the spatial curvature parameter is $Ω_k=(1.8\pm1.9)\times 10^{-3}$ in the $Ω_k+Λ$CDM model at $68\%$ confidence level (C.L.), and the $95\%$ C.L. upper bounds on the sum of three active neutrinos masses are $\sum m_ν<0.16$ eV for the normal hierarchy (NH) and $\sum m_ν<0.19$ eV for the inverted hierarchy (IH) with $Δχ^2\equiv χ^2_\text{NH}-χ^2_\text{IH}=-1.25$.

Figures (5)

• Figure 1: The triangular plot of $H_0$, $w_0$ and $w_a$ in the $w_0 w_a$CDM model. The point ($w_0=-1$, $w_a=0$) locates in the $w_0 w_a$CDM 68$\%$ C.L. region.
• Figure 2: The normalized $H(z)$ plot in the $\Lambda$CDM model, $w$CDM model and $w_0 w_a$CDM model. The grey band represents the $68\%$ confidence range in the $\Lambda$CDM model allowed by P15+BAO. The ranges between the two blue dash-dotted lines and the two red dashed lines represent the $68\%$ confidence ranges of the $w$CDM model and $w_0 w_a$CDM model allowed by P15+BAO respectively. The black and orange error bars denote the Hubble parameters measured by HST (named R16) in Riess:2016jrr and the Ly$\alpha$ forest of BOSS DR11 quasars (named Ly$\alpha$ Forest) in Delubac:2014aqe.
• Figure 3: The likelihood distributions of $\sum m_{\nu}$ for the NH and IH neutrinos in the $\nu \Lambda$CDM model. The dashed lines donate the allowed minimums of $\sum m_{\nu}$, namely 0.059 eV for NH and 0.101 eV for IH.
• Figure 4: The 2D contour plot of $H_0$ and $N_\text{eff}$ in the $N_\text{eff}+\Lambda$CDM model. The rectangle shaded region represents the observational value $H_0=73.24\pm 1.74$ km s$^{-1}$ Mpc$^{-1}$. They are overlapped at the 95$\%$ C.L. region.
• Figure 5: The contour plot of $\Omega_m$ and $\Omega_{\Lambda}$ in the $\Omega_k+\Lambda$CDM model. The dashed line indicates $\Omega_m+\Omega_{\Lambda}=1$.