SIMBAD references

We report a tight Hubble constant constraint 67.78^+1.21_–1.86 km s^–1 Mpc^–1 (2.26 per cent precision) derived from galaxy redshift surveys. We combine the baryon acoustic oscillation (BAO) measurements from 6dFGS, the SDSS DR7 main galaxies, the BOSS DR12 galaxies, and eBOSS DR14 quasars, and also apply the tomographic Alcock-Paczynski (AP) method to the BOSS DR12 galaxies, to place constraints on H₀. Although the AP method alone cannot constrain H₀, it assists the BAO method by tightening the constraint on Ω_m and breaks the degeneracy between the two parameters. Our result is fully consistent with the cosmic microwave background constraints from Planck, but in 2.58σ tension with local measurements. Compared with the BAO-alone constraint, the combined result reduces the error bar by 32 per cent, showing the strong power of the tomographic AP method in extracting cosmological information from galaxy surveys. In the analysis we adopt a prior of Ω_ b_ h^2 from the Planck experiment constraint and assume that the cosmology is the six-parameter flat lambda cold dark matter (ΛCDM). We find that the first assumption has little effect on the derived constraints, i.e. the constraint is less affected as long as the PlanckΩ_ b_ h^2 is not deviated from the true value by >4σ; the second assumption means that the results may alter in alternatives to ΛCDM, where the H₀ constraints from different experiments can become more consistent.