Measuring the Hubble constant using localized and nonlocalized fast radio bursts

The Hubble constant (H0) is one of the most important parameters in the standard ΛCDM model. The measurements given by the main two methods show a gap larger than 4σ, which is known as Hubble tension. Fast radio bursts (FRBs) are extragalactic pulses with durations of milliseconds. They can be used as cosmological probes. We constrain H0 using localized and nonlocalized FRBs. We first used 108 localized FRBs to constrain H0 using the probability distributions of DMhost and DMIGM from the IllustrisTNG simulation. Then, we used a Monte Carlo sampling to calculate the pseudo-redshift distributions of 527 nonlocalized FRBs from CHIME observations. The 108 localized FRBs yield a constraint of $ H_0 = 69.40_{-1.97}^{+2.14} $ km s−1 Mpc−1, which lies between the early- and late-time values. The constraint of H0 from nonlocalized FRBs yields $ H_0 = 68.81_{-0.68}^{+0.68} $ km s−1 Mpc−1. This result indicates that the uncertainty on the constraint of H0 drops to ∼1% when the number of localized FRBs is increased to ∼500. These uncertainties only include the statistical error. The systematic errors are also discussed and play a dominant role in the current sample.