J. A. S. Lima, J. V. Cunha
We show that a joint analysis involving independent cosmological probes at intermediate redshifts provides a remarkable cross-checking for the Hubble constant Ho which is competitive with the existing measurements of the local Universe. Although dependent on the physics at z ~ 1, this result is fully independent on the calibrations involved in the cosmic distance ladder. The cosmological probes to be considered here are: (i) Angular diameter distances of galaxy clusters through SZE/X-ray technique (0.14 < z < 0.89), (ii) the ages of old galaxies at intermediate redshifts (0.62 < z < 1.70), (iii) measurements of the Hubble parameter H(z) (0.1 < z < 1.8), and (iv) the baryon acoustic oscillation (BAO) signature (z=0.35). By taking into account statistical plus systematic errors and assuming a flat LCDM cosmology (Ho and Omega_M as free parameters), our joint analysis provides Ho = 73.4 {+3.1}_{-3.1} km/s.Mpc (1sigma) when only the first three probes are combined. By adding the BAO scale, we obtain Ho = 74.1 {+2.2}_{-2.2} km/s.Mpc (1sigma) which is a 3% determination of the Hubble constant at intermediate redshifts. Due to this special combination of tests, the present value of Ho is competitive with the latest determinations based on nearby Cepheids and SNe Ia [Riess et al. ApJ 730, 119 (2001)]. This value can be much improved in the near future when more and larger samples (with smaller statistical and systematic uncertainties) become available. The present result also suggests that the method proposed here can be useful to achieve the wished theoretical and observational convergence on the value of Ho.
View original:
http://arxiv.org/abs/1206.0332
No comments:
Post a Comment