Measuring H0 from low-z datasets

The Hubble constant H0 represents the expansion rate of the Universe at present and is closely related to the age of the Universe. The accurate measurement of Hubble constant is crucial for modern cosmology. However, different cosmological observations give diverse values of Hubble constant in literature. Up to now, there are two methods to measure the Hubble constant. One is to directly measure the Hubble constant based on distance ladder estimates of Cepheids and so on. The other is to globally fit the Hubble constant under the assumption of a cosmological model, for example the “standard” ACDM model. Adopting the low-redshift observational datasets, including the Pantheon sample of Type Ia supernovae, baryon acoustic oscillation measurements, and the tomographic Alcock-Paczynski method, we determine the Hubble constant to be 67.95−1.03+0.78, 69.81−2.70+2.22 and 66.75−4.23+3.42 km s−1 Mpc−1 at 68% confidence level in the ACDM, wCDM and w0waCDM models, respectively. Compared to the Hubble constant given by Riess et al. in 2019, we conclude that the new physics beyond the standard ACDM model is needed if all of these datasets are reliable.