Hubble constant and sound horizon from the late-time Universe

We measure the expansion rate of the recent Universe and the calibration scale of the baryon acoustic oscillation (BAO) from low-redshift data. BAO relies on the calibration scale, i. e. , the sound horizon at the end of drag epoch r₃, which often imposes a prior of the cosmic microwave background (CMB) measurement from the Planck satellite. In order to make really independent measurements of H₀, we leave r₃ completely free and use the BAO data sets combined with the 31 observational H (z) data, GW170817, and Pantheon sample of Type Ia supernovae. In lambda cold dark matter () model, we get H₀=68. 63-₁. ₇₇^+1. 75 km s^-1 Mpc^-1, r₃=146. 85-₃. ₇₇^+3. 29 Mpc. For the two model-independent reconstructions of H (z), we obtain H₀=68. 021. 82 km s^-1 Mpc^-1, r₃=148. 18-₃. ₇₈^+3. 36 Mpc in the cubic expansion, and H₀=68. 581. 76 km s^-1 Mpc^-1, r₃=148. 02-₃. ₆₀^+3. 63 Mpc in the polynomial expansion. The values of Hubble constant H₀ and sound horizon r₃ are consistent with the estimate derived from the Planck CMB data assuming a flat model, but H₀ is in 2. 42. 6 tension with SH0ES 2019, respectively.