Constraints on cosmological models from Hubble parameters measurements

Abstract

In this paper, we study the cosmological constraints from the measurements of Hubble parameters — H(z) data. Here, we consider two kinds of H(z) data: the direct H0 probe from the Hubble Space Telescope (HST) observations of Cepheid variables with H0 = 73.8 ± 2.4 km s-1 Mpc-1 and several measurements on the Hubble parameter at high redshifts H(z). Employing Markov Chain Monte Carlo (MCMC) method, we also combine the WMAP nine-year data (WMAP9), the baryon acoustic oscillations (BAO) and type Ia supernovae (SNIa) Union2.1 compilation to determine the cosmological parameters, such as the equation of state (EoS) of dark energy w, the curvature of the universe Ωk, the total neutrino mass ∑mν, the effective number of neutrinos N eff and the parameters associated with the power spectrum of primordial fluctuations. These H(z) data provide extra information on the accelerate rate of our universe at high redshifts. Therefore, adding these H(z) data significantly improves the constraints on cosmological parameters, such as the number of relativistic species. Moreover, we find that direct prior on H0 from HST can also give good constraints on some parameters, due to the degeneracies between these parameters and H0.