Measuring the Hubble constant using localized and nonlocalized fast radio bursts

The Hubble constant ( H 0 ) 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 4 σ , 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 H 0 using localized and nonlocalized FRBs. We first used 108 localized FRBs to constrain H 0 using the probability distributions of DM host and DM IGM 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 H 0 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 H 0 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.