Five fast radio bursts ( FRBs ) , including three apparently non-repeating ones FRB 180924 , FRB 181112 , and FRB 190523 , and two repeaters , FRB 121102 and FRB 180916.J0158+65 , have already been localized so far .
We apply a method developed recently by us ( Li et al .
2019 ) to these five localized FRBs to give a cosmology-insensitive estimate of the fraction of baryon mass in the IGM , f _ { IGM } .
Using the measured dispersion measure ( DM ) and luminosity distance d _ { L } data ( inferred from the FRB redshifts and d _ { L } of type Ia supernovae at the same redshifts ) of the five FRBs , we constrain the local f _ { IGM } = 0.84 ^ { +0.16 } _ { -0.22 } with no evidence of redshift dependence .
This cosmology-insensitive estimate of f _ { IGM } from FRB observations is in excellent agreement with previous constraints using other probes .
Moreover , using the three apparently non-repeating FRBs only we get a little looser but consistent result f _ { IGM } = 0.74 ^ { +0.24 } _ { -0.18 } .
In these two cases , reasonable estimations for the host galaxy DM contribution ( { DM _ { host } } ) can be achieved by modelling it as a function of star formation rate .
The constraints on both f _ { IGM } and { DM _ { host } } are expected to be significantly improved with the rapid progress in localizing FRBs .